The two-tone bell circuit on microcircuits is assembled on two microcircuits and one transistor.

Device diagram

Logic elements D1.1—D1.3, resistor R1 and capacitor C1 form a switching generator. When the power is turned on, capacitor C1 begins to charge through resistor R1.

As the capacitor charges, the voltage on its plate connected to pins 1 and 2 of logic element DL2 increases. When it reaches 1.2... 1.5 V, a logical “1” signal (“4 V”) will appear at output 6 of element D1.3, and a logical “0” signal (“0” will appear at output 11 of element D1.1). ,4 V).

After this, capacitor C1 begins to discharge through resistor R1 and element DLL. As a result, rectangular voltage pulses will be formed at output 6 of element D1.3. The same pulses, but shifted in phase by 180°, will be at pin 11 of element D1.1, which acts as an inverter.

The duration of charge and discharge of capacitor C1, and therefore the frequency of the switching generator, depends on the capacitance of capacitor C1 and the resistance of resistor R1. With the ratings of these elements indicated in the diagram, the frequency of the switching generator is 0.7...0.8 Hz.

Rice. 1. Schematic diagram two-tone call on two K155LA3 microcircuits.

The switching generator pulses are fed to the tone generators. One of them is made on elements D1.4, D2.2, D2.3, the other - on elements D2.4, D2.3. The frequency of the first generator is 600 Hz (it can be changed by selecting elements C2, R2), the frequency of the second is 1000 Hz (this frequency can be changed by selecting elements SZ, R3).

When the switching generator is running, at the output of the tone generators (pin 6 of element D2.3), either the signal of one generator or the signal of another will periodically appear. These signals are then sent to a power amplifier (transistor VI) and converted by head B1 into sound. Resistor R4 is necessary to limit the base current of the transistor.

Setup and details

By adjusting resistor R5 you can select the desired sound volume.

Fixed resistors - MLT-0.125, trimmer - SPZ-1B, capacitors S1-SZ - K50-6. The K155LAZ logic chips can be replaced with KIZZLAZ, K158LAZ, the KT603V transistor can be replaced with KT608 with any letter index. The power source is four D-0.1 batteries connected in series, a 3336L battery or a stabilized 5 V rectifier.

Melodious call for a landline phone. Call pattern

Call on MC34017 for phone, door, devices...

Not all landline telephones have beautiful and melodious calls. If your phone has a sharp and loud ring, and some copies still have mechanical ones with cups, then you can fix this. Using the simple scheme below, assemble a beautiful melodic bell on one MC34017.

A loud and sharp telephone call that occurs without any warning greatly distracts from the train of our thoughts, and can generally frighten us :) A very quiet call is also bad - you can’t always hear it.

The circuit diagram shown below phone call on the MC34017 chip allows you to get out of this situation!

A beautiful melodic and moderately loud call - a sequence of melody from two mixed frequencies will invite you to the phone :)

There are three types of microcircuits:

• MS34017 -1 (1000 kHz) C2 - 1000 pf;
• MS34017 -2 (2000 kHz) C2 - 500 pf;
• MS34017 -3 (0.5 kHz) C2 - 2000 pf.

Sample printed circuit board and the arrangement of elements on it

Block diagram of the MC34017 chip

To connect the bell-trill circuit, you first need to disassemble the telephone set and disconnect the electric bell. It can be separate or built into the main board.

In the first case, we unsolder or unscrew the connecting wires suitable for the electric bell coil.

In the second case, we unsolder the two wires going to the piezoelectric element from the board and solder them to our board.

Please note that the circuit is compact and can easily be placed anywhere on the telephone in the place where the electric bell is normally located.

By changing the capacitance of capacitors C2 (high-frequency tone) and C3 (low-frequency tone), you can adjust the desired timbre of the ringing melody. And by changing the capacitance of capacitor C4 - the duration of the call.

This circuit can be used not only for a telephone call, but also for a bell installed at the entrance doors of your house, apartment or maybe room, and also as an indicator for a malfunction, warning, or accident of any electronic devices. To carry out this action, power is required for the circuit - an alternating voltage of 40 - 60V. Disconnect the power supply with a button installed at the door (if used as a doorbell). If you reduce the capacity of C1, you can connect it to a ~220V network. BUT IN THIS CASE BE CAREFUL - THE CIRCUIT AND THE BUTTON WILL BE UNDER LIFE-DANGEROUS VOLTAGE!

Zotov A. Volgograd region.

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Scheme of a simple melodic bell for an apartment

September 16, 2012 by admin Comment »

A simple melodic call for an apartment, the diagram of which is shown in Fig. 16.3.0, contains a minimum number of parts and can be assembled by any radio amateur with a little knowledge of a soldering iron. The sound (frequency of generated oscillations) of the bell is selected by rotating the axis of the variable resistor Rl and changing the capacitance of the capacitor C1. Instead of the transistors indicated in the diagram, you can use similar low-power germanium or silicon transistors.

Rice. 16.3. Schematic diagrams of electronic calls:

a) a simple melodic call;

b) touch call;

c) design of a touch bell based on a variable resistor

The dynamic head BA1 can be anything. The call can be powered from the network or a galvanic battery. The bell parts are assembled on a mounting plate secured in a suitable sized plastic box. The dimensions of the box must be such that it can accommodate the power source and the electrodynamic head available to the amateur. You can turn on the call either from a regular button or from touch contacts. The diagram of the touch version of the call is shown in Fig. 16.3.5. The multivibrator starts to work, that is, the bell rings when the touch contacts E1 and E2 are touched with a finger. At this moment, between the collector of transistor VT2 and the base of transistor VT1, the resistance of the skin of the finger turns on, and positive feedback appears between the cascades.

Touch contacts are two metal rings of different diameters, which are located one inside the other. The rings are cut out of a sheet of thin copper or brass foil and glued in a certain way onto a small plastic plate. After this, the wires going to the bell are soldered to the metal rings, and the plate is secured in a convenient place near the door. An unusable variable resistor, for example, type SP-1, can be used as touch contacts. The resistor cover and the axis with the slider are removed, and the remaining part is fixed in place of the bell button, Fig. 16.3.v.

Literature: V.M. Pestrikov. Encyclopedia of amateur radio.

nauchebe.net

E-call | Electrician in the house

To call, attract attention, or ring the doorbell, various sound and light signals are used. Previously, these were ordinary bells, then electric bells, electromagnetic bells. Nowadays, melodious electronic bells or electronic bells that play melodies, imitate the voices of birds, etc. are increasingly installed for calling and as doorbells. In this article we will look at several simple electronic calling schemes that you can make yourself.

Single tone electronic calls

The diagram shows:

• R1 - resistor MLT-0.5, 10 kOhm
• R2, R4 - resistors MLT-0.5, 2.2 kOhm
• R3 - resistor MLT-0.5, 91 kOhm
• S1 - button A1 0.4-127
• VT1, VT2 - transistors GT109Zh
• VT3 - transistor GT402I

The diagram shows a call using a multivibrator using bipolar transistors. Bipolar transistors (in the diagram VT1 and VT2) are components electronic circuit multivibrator. After the S1 button is pressed, the transistor pair (multivibrator) becomes a source electrical vibrations audio frequency, which are then transmitted to the playback device - the speaker. The frequency of the reproduced sound vibrations in the speaker is equal to the frequency of the multivibrator.

Doorbell of one tone with the ability to adjust the audio frequency of the signal

The diagram shows:

• R1, R4 - resistors MLT-0.5, 5.6 kOhm
• R2, R3 - resistors MLT-0.5, 62 kOhm
• R5 - trimming resistor SP3-38B, 47 kOhm
• C1, C2 - capacitors K50-35, 10 µF, 25 V
• S1- button A1 0.4-127
• VT1, VT2 - transistors GT109Zh
• VT3 - transistor GT402I
• B1 - speaker 0.5GD-17 (8 Ohm)

The figure shows a similar circuit of an electronic bell based on an oscillation modulation circuit consisting of two bipolar transistors VT1 and VT2, which is activated after pressing the button. The circuit is powered by a voltage of 9 V. The fundamental difference with the previous circuit is that thanks to a resistor with variable resistance (potentiometer), you can manually set the frequency of reproduced oscillations through an audio speaker connected to the collector of the VT3 transistor. The disadvantage of this circuit is the monotony of the frequencies of sound vibrations induced by the multivibrator.

Electronic bell operating at different voltages

The diagram shows:

• R1, R3 - resistors MLT-0.5, 2.4 kOhm
• R2 - resistor MLT-0.5, 100 kOhm
• C1, C2 - capacitors K73-17, 4.7 µF, 63 V
• VT1, VT2 - transistors GT109Zh
• VT3 - transistor GT402I
• B1 - speaker MRP 28N-A, 100 Ohm

The figure shows a diagram of an electronic bell, the operating principle of which is based on the use of different voltage values. The basis of the electronic bell multivibrator circuit consists of two bipolar transistors (in the circuit VT1 and VT2), this is structurally similar to the circuits presented earlier. While the potential difference is insufficient, the transistor is closed, as soon as the voltage is within the desired value at the XT1 terminals, then the transistor opens to allow current to flow and the speaker turns on.

Circuits of electronic doorbells with a complex sound signal

Bim-bom doorbell

If you are not satisfied with the monophonic sound of the doorbell, then you can install the electronic circuit shown in the diagram below, creating a “bim-bom” type sound of the bell. The operating principle of this circuit is based on the operation of a transistor multivibrator. Unlike previous schemes, this one allows you not only to create sound vibrations of various frequencies, but also to set the rhythm and pause time between the sound signals of the electronic call.

The diagram shows:

• T1 - step-down transformer TA-2-127/220-50 (pins 3 and 4 (~7V))
• S1 - button A1 0.4-127
• D1-D5 - diodes D226
• C1 - capacitor K50-16, 1000 µF, 16V
• C2, C3 - capacitor K50-16, 10 µF, 16V
• R1, R2 - trimming resistors SP3-38B, 470 kOhm
• R3, R6 - resistors MLT-0.5, 10 kOhm
• R4, R5 - resistors MLT-0.5, 33 kOhm
• R7 - resistor MLT-0.5, 1 kOhm
• R8 - resistor MLT-0.5, 470 Ohm
• VT1, VT2, VT3 - KT630D transistors
• VT4 - transistor KT630G

In the circuit diagram, the multivibrator circuit is formed using bipolar transistors VT1 and VT2. The frequency of formation of rectangular pulses is set using resistors with variable resistance (potentiometers) R1 and R2. Also by changing the resistance of adjustment resistors R1 and R2, you can set the pause time and sound duration of the signal transmitted to the playback speaker; in our case, the sound duration can reach from three seconds to creating a continuous sound of the outgoing audio signal.

This circuit is based on a multivibrator using bipolar transistors, in which rectangular pulses of audio frequency are generated. The resulting pulses passing through the repeater on the emitter of the bipolar transistor VT3 enter the cascade of the transistor VT4 and at this moment the circuit is closed and the bell makes a sound - “bim-bom”. In more detail, the principle of creating a sound signal of different tonality and sound can be described in this way: after pressing the button S1, transistor VT3 is open to allow current to flow to transistor VT4. This creates the basis for the occurrence of electrical impulses in the multivibrator, which are transmitted to the reproducing speaker and create audio frequency oscillations in it. Let's call this signal primary. If transistor VT2 is open, then transistors VTZ and VT4 are locked accordingly. This creates a situation where the bell circuit is broken, at which point the multivibrator generates a sound signal of a different frequency and tone. The duration of pressing the bell button also affects the frequency of the generated sound vibrations. To avoid excessive potential differences in the circuit, as well as inductive amplitude voltage fluctuations, the circuit built-in diode D5, which also provides safe work transistor VT4.

Electronic doorbell with triple tone alarm

The diagram shows:

• S1, S2, S3 - buttons A1 0.4-127
• D1 - zener diode D814V
• D2 - zener diode D816A
• D3 - zener diode KS468A
• D4 - diode D226G
• R1 - resistor MLT-0.5, 5.1 kOhm
• R2, R4, R7 - resistors MLT-0.5, 4.7 kOhm
• R3 - resistor MLT-0.5, 2.4 kOhm
• R5, R6 - resistors MLT-0.5, 120 kOhm
• R8 - resistor MLT-0.5, 820 Ohm
• R9 - resistor MLT-0.5, 560 Ohm
• C1, C2 - capacitors K73-17, 4.7 µF, 63 V
• VT1, VT2 - transistors KT630G
• VT3, VT4 - transistors GT402I

Schematic diagram of an electronic doorbell, which simulates oscillations of sound frequencies of several tones, using a multivibrator assembled on bipolar transistors. By varying the pressing of the S1, S2 and S3 buttons in the multivibrator, current pulses are generated, which, when transmitted to the playback speaker, create oscillations with a frequency of 2.0, 1.0 and 0.3 kHz.

These circuits are fundamentally simple to design and install, and therefore will not cause any difficulties even for novice radio amateurs. An item assembled with your own hands is always valued higher than something bought in a store, so create, invent, try. In addition, by selecting ohmic resistance or parameters of bipolar transistors, you can achieve a unique sound for electronic doorbell models.

elektricvdome.ru

Notes for the master - Electronic doorbells

Code call

In the circuit in Fig. 1, a two-tone generator is used as a code call. Now loved ones who know the bell code announce their arrival with a melodic sound, and those who do not know the code - with a single-tone signal.

The bell consists of four multi-contact buttons (the author used a P2K switch with a remote lock), which are fixed near front door.

The position of the contacts of the button block corresponds to code 1010. In standby mode, the bell is de-energized, and the base of the transistor VT1 is connected to the collector through the closed contacts SB1.1, SB3.1 of the SB1 and SB3 buttons.

When these buttons are pressed simultaneously, power is supplied to the bell through the closed contacts SB1.2 and SB3.2, and the open contacts SB1.1 and SB3.1 break the circuit connecting the collector and the base of transistor VT1. As a result, this transistor periodically (with the pulse repetition rate of a low-frequency oscillator assembled on elements DD1.1 - DD1.3) opens and supplies power to the second generator - a tone generator on elements DD2.1 - DD2.4. In this case, the dynamic head BA1 emits a frequency-modulated signal.

When other buttons are pressed in any combination, the base and collector circuits of transistor VT1 are closed and the dynamic head reproduces a single-tone signal, since frequency modulation does not occur.

It is not necessary to code the SB1 and SB3 buttons. You can code three or one button. It is important that their first contacts work to open.

Sinkov D.

Lugansk

Two-tone electronic call

It can be assembled on just one chip and one transistor (Fig. 2), and use a capsule as the BF1 emitter

TA-4. The peculiarity of this capsule is that it has a resonant frequency at which the sound volume increases sharply. Therefore, even when summing up weak signal you can achieve a clearly audible sound.

A two-tone generator is assembled on the K176IE5 chip. Its fundamental frequency depends on the resistance of resistor R3 and its capacitance of capacitor C1, and the modulation depth depends on the resistance of resistor R1. The transistor stage acts as a power amplifier, necessary to match the high-resistance output of the microcircuit with a relatively low-resistance load - the BF1 capsule.

The bell is powered by a somewhat unusual rectifier, which includes a limiting resistor R4, a rectifying diode VD1, a zener diode VD2, an LED HL1, and a capacitor C1. Until the SB1 bell button is pressed, the capacitor is charged to a voltage equal to the sum of the stabilization voltage of the zener diode and the voltage drop across the lit LED. In this case, the capacitor becomes a battery of electricity.

When the SB1 button is pressed, the voltage from the capacitor is supplied to the two-tone generator and power amplifier. A sound is heard from the capsule, the duration of which depends on the capacitance of capacitor C2. After releasing the button, the capacitor begins to charge again, which takes a few seconds. Moreover, the LED is switched off at the initial moment and begins to glow only when the voltage on the capacitor reaches the stabilization voltage of the zener diode and current flows through it.

When setting up a call, first turn off resistor R1 and select resistor R3 (for this purpose, it is advisable to temporarily replace it with a variable resistor with a resistance of 510 kOhm) to achieve the highest volume of the capsule sound (of course, with the contacts of the SB1 button closed). After this, connect resistor R1 and select it (if necessary) to set the desired modulation depth, in other words, the sound of the second tone.

Both during setup and final installation of the bell, ensure that the phasing of the connection of the bell wires to the lighting network is observed.

Zarubin A.

Karatau

Intermittent Signal Generator

The intermittent sound signal generator (Fig. 3) consists of two interconnected multivibrators in which all four logical elements of the K155LA3 microcircuit operate.

The multivibrator on elements DD1.3 and DD1.4 generates oscillations with a frequency of about 1000 Hz, which are converted by the telephone capsule BA1 into sound. But the sound is intermittent, because the operation of this multivibrator is controlled by another one - on logic elements DD1.1 and DD1.2. It generates clock pulses with a repetition rate of about 1 Hz. The telephone capsule sounds only during those periods of time when a high voltage level appears at the output of the clock generator. The duration of sound signals can be changed by selecting capacitor C1 and resistor R1, and the pitch of the sound by selecting capacitor C2 and resistor R2. Such a device can completely replace a regular apartment bell.

Borisov V.G.

The simplest touch call

The touch device can be used for a regular electric bell, Fig. 4.

In this case, there is no need for an electric button. When entering an apartment, a sound signal is heard at the moment a finger touches a sensor contact electrically isolated from the “ground”. The alarm is powered from the mains and does not consume any current in standby mode. It contains an amplifier using transistors VT1...VT3, a diode bridge VD2...VD5 and a bell HA1. When you touch the sensor contact E1, a weak leakage current flows through the base circuit of transistor VT1, and the transistors open at negative half-cycles of the network. In this case, the HA1 bell beeps. Diode VD1 conducts positive half-cycles of the leakage current.

The signaling device can only use high-voltage transistors with a permissible voltage between the collector and emitter of at least 300 V. The static current transfer coefficient of the transistors must be at least 25. The VT3 transistor can be of medium power, but provided that it is installed on a radiator that allows dissipation power 3…4 W. Bridge diodes must be designed for reverse voltage not less than 400 V, for example, D226B. Call NA1 is a network call, for a voltage of 127...220 V, for example, EP 127-220 V. To ensure safe operation of the device, resistor R1 must have a resistance of at least 2.2 Megohms and a power of at least 1 W. With such resistance, the leakage current passing through the human body is not felt at all.

When setting up the alarm device, you must remember that its elements are under mains voltage. By selecting the resistance of resistor R2, the required sensitivity of the device is established. Resistor R2 should not be selected with a resistance of more than 2.4 MΩ, since this will cause the device to operate intermittently.

Pestrikov V.M.

"Radio-electronic devices,

useful in everyday life"

Touch call

When you touch the E1 sensor, which consists of two metal plates, with your finger, the HL1 LED begins to blink and the B1 alarm beeper sounds intermittently, Fig. 5.

Transistors VT1 and VT2 form composite transistor. The input resistance (base) of such a transistor is high. While transistor VT1-VT2 is closed, the voltage on R2 is low, and transistor VT3 is also closed. In order for the composite transistor VT1-VT2 to open, voltage must arise at the base of VT1. When you touch the E1 sensor plates with your finger, an opening voltage is sent to the base through the conductivity of the skin of your finger. The composite transistor VT1-VT2 opens and discharges capacitor C1. The voltage on R2 increases and VT3 opens.

The collector circuit VT3 includes a sequentially flashing LED HL1 and a “beeper” B1 (a sound emitter with a built-in generator). The flashing LED HL1 flashes and B1 makes a sound each time the LED flashes.

After you remove your finger from the E1 touch plates, the composite transistor VT1-VT2 will close, but the touch bell will still blink and sound for some time while the capacitor C1 is charging through R2.

Resistor R1 can have a resistance from 3 to 10 megaohms. The capacitance of capacitor C1 can be from 220 µF to 1000 µF. The flashing LED HL1 type L-7986SRC-8 can be replaced with any other flashing one without a built-in current-limiting resistor.

You can also use a regular indicator LED, but then the lighting and sound will be without interruption.

Electronic touch bell

Figure 6 shows a diagram of an electronic call, or rather a tone signal which, moreover, does not require a button.

Instead, a sensor is used - a touch pad consisting of two metal plates separated from each other. If you touch it, a pleasant tone will be heard in the apartment, and the pitch of the tone depends on how hard you press your hand against the sensor. The stronger the pressure, the less resistance there will be between the power plus and the base of transistor T1. The latter causes a change in the frequency of oscillations produced by the generator on transistors T3, T4.

Power is supplied to the generator through transistor T2, controlled by transistor T1 with a sensor input. As soon as you lightly touch the sensor, transistors T1, T2 will immediately open, transistors T3, T4 will receive power through them, and further generation of the signal will depend on the degree of pressure on the touch pad.

Transistors are used like KT315, KT306, KT301 and others. Any small-sized one is suitable as a dynamic head, for example, type 0.5GD-14, 0.25GD-1. The circuit is placed in any compact case and is connected by two wires to the contacts of the touch pad.

Spot welding diagram

Connection diagram differential circuit breaker

Do-it-yourself chicken coop diagram for 10-20 chickens, photo drawings

I present to your attention a doorbell circuit that was assembled many years ago and has been in use for the same amount of time. It would be more correct to call this device: “Waste into income!” Because what it was made from was literally lying underfoot. This was during Soviet times. I was working at a small PBX at the time and had a lot of free time that I wanted to convert into money... Then I began collecting electronic calls based on this scheme and inserting them into . The installer of the city automatic telephone exchange willingly helped me with the implementation, making his own profit from it. The device imitates the sound of a bouncing ball. All characteristics are adjusted by selecting the capacitance of the capacitors and adjusting the variable resistor.

Electrical circuit diagram

Once assembled without errors, it starts working immediately. Power supply is possible from a 12 volt DC source (then diodes D1-D4 and capacitor C4 are excluded). PBX ringing impulses alternating current 110 volts 25 hertz - in this case, the capacitance of capacitor C4 should be 1 microfarad per 400 volts.

AC voltage 220 volts 50 hertz, when used as an apartment bell (in this case, the capacitance of capacitor C4 should be 0.5 microfarads at 400 volts). The device was assembled using pieces of foil getinax, which were cut on a machine (Skillful hands) with a small circular cutter. I used one board as a conductor for drilling holes, but it can also be assembled using wall mounting.

Parts used

Transistor T1 - mp25-26, T2 - kt605 or p307-309, but p605 works better, diodes D1-D4 - D226, but others are possible, although D226 was given top scores. Capacitors C1-0.1 C2-0.05, trimming resistor - 47k, C3 - 100 microfarads at 100 volts. The telephone capsule was used as an emitter, but only very old ones (large diameter).

The use of a Czech capsule with a resistance of 50 ohms gave very good results, but it has one feature - to achieve good volume, you need to remove the plastic plug from the side of the contact screws, under which there is an adjustment screw and, having turned on the device, use a small screwdriver to make adjustments, unscrewing and tightening screw to achieve maximum sound volume.

Warning! If you are going to use this device as a doorbell, do not set it up by connecting it to a 220 volt network! You may be exposed to high voltage! Set it up by connecting 12 volts to DC, and then connect the mains voltage.

Simple logic probe

A simple logic probe consists of two independent threshold devices, one of which is triggered by an input voltage corresponding to a logical "1", and the second - by a logical "O".

When the voltage at the probe input is between 0 and +0.4 V, transistors V7 and V8 are off, transistor V9 is off and V10 is on, the green LED V6 is on, indicating "0".

When the input voltage is from +0.4 to +2.3 V, transistors V7 and V8 are still closed, V9 is open, V10 is closed. LEDs do not light up. At a voltage above +2.3 V, transistors V8, V9 open and the red LED V5 lights up, indicating “1”. Diodes V1-V4 serve to increase the voltage at which the threshold device is activated, indicating “1”.

The current transfer coefficient of the transistors must be at least 400. The adjustment is made by selecting R5* and R7* according to the clear response of threshold devices at a voltage from +0.4 V to +2.4 V.

Network "CONTROL"

Typically, finder probes with neon bulbs are used to detect mains voltage. Alas, nowadays even such a sample is not easy to acquire. But it is quite simple to assemble a control device, the diagram of which is shown in the figure.

Simple transistor tester

A simple transistor tester allows you to check the performance of bipolar transistors of n-p-n- and p-n-p-structures.

The transistor being tested, together with one of the V1 or V2 installed in the device (depending on the structure of the transistor being tested, determined by the position of switch S1), forms a multivibrator that generates low-frequency oscillations. Indicators of the presence of oscillations, and therefore the health of the transistor being tested, are the LEDs V3 and V4, which flash at the frequency generated by the multivibrator.

This device can test transistors of low, medium and, in some cases, high power. Using resistor R1, the amplification properties of the low-power transistor being tested are assessed (approximately) - the greater the resistance of the introduced part of the resistor, at which the multivibrator is still operating, the higher the current transfer coefficient of this transistor. The device is powered by one 3336L battery.

Automatic light switch

The machine consists of a light sensor - a photoresistor and a photorelay made on transistors VI, V2, an actuator circuit on thyristors V4, V10 and a full-wave rectifier on diodes V6, V7. The machine works as follows. With decreasing illumination, the resistance of photoresistor R3 increases from 1...2 kOhm to 3...5 MOhm, which leads to an increase in the collector current of transistors VI and V2. As a result of this, thyristor V4 opens, the chain R7, SZ, V9 generates a pulse that opens thyristor V10, and the lighting lamps turn on. As the illumination of the photoresistor increases, its resistance decreases, and the collector current of transistor V2 also decreases, which leads to the blocking of thyristors V4 and V10. The lighting lamps go out, and the capacitor SZ is discharged through the diode V8 and resistors R5, R6 and R7. The switching threshold of the machine is set by resistor R1.

Details .

Variable resistor R1 type SPO-0.5, resistors type MLT-0.5; photoresistors of types SF2-2, SF2-5 or FSK-1; transistors - any low-frequency p-p-p structures with B>50; capacitor C2 type MBM, MBGC, MBGP for a voltage of 400 V.

When setting up, it is necessary to select resistors R5-R7, achieving reliable opening of thyristor V10 at the photorelay operating threshold specified (by resistor R1).

Transformerless power supply To power devices with a current consumption of up to 30 mA, you can use simple network power supplies, in which, instead of step-down transformers, two capacitors with an operating voltage of at least 300 V are used. VD3, VD4 C1=C2=1 µF x 400V C1=C2=2 µF x 400V D814B Iн=5mA Un=8B Ii=20mA Ui=7.6B Iн=5mA Un=8.1V Ii=20mA Ui=7.8V D814V Iн=5mA Un=9.2V Ii=20mA Ui=8.9V -

Power supply for analog and digital circuits

The power supply for analog and digital microcircuits consists of three stabilized rectifiers, two of which form a bipolar 12.6 V voltage source with separate regulation.

The adjustment is made using trimming resistors R6 and R9. The lower (according to the circuit) stabilizer provides a voltage of 5 V, which can also be adjusted with resistor R10.

The unified power transformer TAN 59-127/220-50 can be replaced with a homemade one with a magnetic core Ш 12 X 20. Network winding I at 220 V should have 3000 turns of PEV-2 wire - 0.12, winding II - 180 turns PEV-2 - ODZ , winding III - 220 turns of PEV-2 - 0.38 and winding IV - 70 turns of wire PEV-2 0.41. The different number of turns in windings II and III at the same voltage at the output of the stabilizer arms in this power supply design is explained by the fact that a current of 60 mA is consumed from the upper (according to the circuit) arm, and 350 mA from the lower arm. If, according to operating conditions, these currents must be equal, an equal number of turns of wire of the same diameter should be wound.

Instead of "neon"

Capacitor C1 is used as a wattless resistance; diodes VD1-VD4 protect speaker BA1 from sudden surges of current during on-off moments; resistor R1 serves to discharge C1 after turning on the device.
Capacitor C1 must have a voltage of at least 400 V and a capacity of 1-2 μF. Speaker - 0.25GD19 or any other, with a power of more than 0.25 W with an internal resistance of 6-10 Ohms. Instead of a speaker, you can use a telephone capsule, for example, "TON-1", while the capacitance C1 is reduced to 0.01 μF. The device is mounted mounted in a housing made of dielectric material.

High precision thermostat

A high-precision thermostat with a pulsed master-control circuit was proposed by I. Boeris and A. Titov. It has a high stability of maintaining a constant temperature (up to ±0.05°C in the range from 20 to 80°C). It can be used in thermostats, calorimeters and other devices with power consumption up to 1 kW.

The regulating circuit consists of a thermistor R6 type MMT-1 with diode V6, a variable resistor R7 with diode V7 with capacitor C4. The control circuit is powered by a stabilizer using zener diodes V3 and V4, connected to the secondary winding of the step-down transformer T1.

The amount of current through thyristors VI and V2, and therefore through the heater, depends on the charge and discharge time constants of capacitor C4, which are determined by the ratio of the resistances of resistors R6 and R7. As the temperature increases, the resistance of the thermistor decreases, as a result of which the discharge current of capacitor C4 through the thermistor and diode V6 increases and the voltage on capacitor C4 decreases. The control voltage supplied to the thyristors through the current amplifier contains direct and alternating components. The variable component is formed using a phase shifter (R3C1) and goes through capacitor C2 to the base of transistor V8. This ensures a smooth change in the cutoff angle of the thyristor current, and therefore the current through the load.

Details. Transformer T1 is made on a magnetic circuit Ш12 X 15: winding I contains 4000 turns of PEV-1 0.1 wire, winding II contains 300 turns of PEV-1 0.29 wire.

The setup comes down to selecting resistors R1 and R4. The voltages at the anodes of the thyristors must be in phase, otherwise the terminals of winding II of the transformer should be swapped.

Diode generator

The property of germanium diodes to have a negative section on the reverse branch of the current-voltage characteristic is used in a generator-relaxator.

This generator can be used as a probe, a source of sound vibrations when voicing toys, etc. The voltage amplitude at the output of the generator is about 14 V. Its disadvantage is that a lot of power is released at the diode, exceeding the maximum permissible. It is advisable to install the diode on the radiator and operate the generator for a short time. It is impossible to reduce the capacitance of capacitor C1 to a value less than 0.15 µF.

Replacing the electret microphone

When repeating some foreign designs, the problem of replacing an electret (condenser) microphone with a conventional dynamic one often arises. As can be seen from the diagram, a cascade on one transistor allows you to successfully cope with this.

temperature sensor

The temperature sensor can be used as a protective device for powerful transistors from overheating.

Such a sensor turns off power from the protected block or node as soon as the temperature of the powerful transistor case exceeds the permissible one. The temperature sensor in the device is transistor V2, glued through an insulating gasket to the body of the protected transistor. A threshold device is assembled on transistors V2 and V4, which operates at a certain temperature of the body V2 due to an increase in the collector current of the transistor with increasing temperature.

Due to the presence of positive feedback through resistor R7, the process of opening transistors V2 and V4 proceeds like an avalanche, while relay K1 is activated and, with its contacts, turns off the power to the protected unit. When the temperature drops, the device returns to its original state. The response threshold can be adjusted within +30...+80°C using variable resistor R2.

Details. Transistor V2 type MP40-MP42, V4 types KT605, KT608B, KT503; for higher temperatures, use a silicon transistor MP116, KT361 with any letter index; resistors type MLT-0.25; R6 - type MLT-0.5; relay type RES-22.

Liquid level sensor

This device differs from all known water level sensors in its simplicity, efficiency, small overall dimensions and, most importantly, the absence of contact bounce. The advantage of this sensor is that even a novice radio amateur can repeat and configure it.
The level sensor is indispensable when automating water towers, irrigation systems on farms, and in any other cases where it is necessary to control the level of liquids.

By changing the distance AB, you can configure the sensor for any
working conditions. The author’s design uses a metal tank, but if the tank is made of dielectric, it is necessary to install a third electrode, which should be connected to the negative bus of the power source and located at the bottom of the tank.

The parts in the circuit must be used with a margin of safety. For example, it is better to use a transformer 1.5 - 2 times the calculated power. Capacitors C1 - K60-6, K50-35, C2 - MBM, SZ - KSO, resistors - MLT 0.125. Installation is carried out using a “hinged” method. Resistor values ​​can change when configuring: for R1 - from 75k to 150k, for R2 - 820 to 2.2k. Relay - any low-power, small-sized one, the author has a REN-18, but you can also use the RES-9 type. The KTs405 diode bridge can be replaced with D226 diodes. If the level sensor is used in cold regions, it is better to use frost-resistant oxide semiconductor capacitors (type K53). Electrodes E1 and E2 are made in the form of rods 100 mm and 500 mm long, respectively, although these dimensions are not critical and may be different, depending on the dimensions of the container used.

Two tone call

The two-tone call contains a control generator assembled on elements D1.1-D1.3 of the K155LAZ microcircuit and generating control pulses, the frequency of which depends on the capacitance of capacitor C1 and the resistance of resistor R1.

With the ratings indicated in the diagram, the generator switching frequency is 0.7...0.8 Hz. The control generator pulses are fed to the tone generators and alternately connect them to an audio amplifier assembled on a transistor, VI. The first generator is made on microcircuit elements D1.4, D2.2, D2.3 and produces pulses with a frequency of 600 Hz (regulated by selecting elements C2, R2), the second generator is made on elements D2.1, D2.4, D2.3 and works with a frequency of 1000 Hz (regulated by the selection of elements SZ, R3). The sound volume is controlled by resistor R5.

Details. Resistors type MLT-0.125, trimming resistor type SPZ-16; capacitors S1-SZ type K50-6; microcircuit K155LAZ, K133LAZ, K131LAZ, K158LAZ; transistors KT603V, KT608, KT503 with any letter index.

Two-tone call on microcircuits

A two-tone call on microcircuits is assembled on two microcircuits and one transistor.

Logic elements D1.1-D1.3, resistor R1 and capacitor C1 form a switching generator.

When the power is turned on, capacitor C1 begins to charge through resistor R1. As the capacitor charges, the voltage on its plate connected to pins 1 and 2 of logic element D1.2 increases. When it reaches 1.2...1.5 V, a logical “1” signal (4 V) will appear at output 6 of element D1.3, and a logical “0” signal (0.4 V) will appear at output 11 of element D1.1. IN). After this, capacitor C1 begins to discharge through resistor R1 and element D1.1. As a result, rectangular voltage pulses will be formed at output 6 of element D1.3. The same pulses, but shifted in phase by 180°, will be at pin 11 of element D1.1, which acts as an inverter.

The duration of charge and discharge of capacitor C1, and therefore the frequency of the switching generator, depends on the capacitance of capacitor C1 and the resistance of resistor R1. With the ratings of these elements indicated in the diagram, the frequency of the switching generator is 0.7...0.8 Hz.

The switching generator pulses are fed to the tone generators. One of them is made on elements D1.4, D2.2, D2 3, the other - on elements D2.1, D2.4, D2.3. The frequency of the first generator is 600 Hz (it can be changed by selecting elements C2, R2), the frequency of the second is 1000 Hz (this frequency can be changed by selecting elements SZ, R3). When the switching generator is running, at the output of the tone generators (pin 6 of element D2.3), either the signal of one generator or the signal of another will periodically appear. These signals are then sent to a power amplifier (transistor V1) and converted by head B1 into sound. Resistor R4 is necessary to limit the base current of the transistor. By adjusting resistor R5 you can select the desired sound volume.

Fixed resistors - MLT-0.125, tuning resistors - SPZ-1B, capacitors S1-SZ - K50-6. Logic chips K155LAZ can be replaced with K133LAZ, K158LAZ, transistor KT603V - with KT608 with any letter index. The power source is four D-0.1 batteries connected in series, a 3336L battery or a stabilized 5 V rectifier.

Is there a simpler amplifier?

Gone are the days when radio amateurs assembled tube audio frequency amplifiers (AFAs) as one of the first designs. Bulky weekends and power transformers determined the final weight and dimensions of the device, high levels of supply voltages, required the use of high-voltage smoothing capacitors in anode and screen power filters, and created the danger of electric shock. A significant filament current of the lamps was also required, which reduced the efficiency of the amplifier and created additional (unjustified) heating. To bring it into a state of readiness after switching on, it took some time (to warm up the cathodes of the lamps) or it was necessary to keep the cathodes of the lamps heated. Let us pay tribute to the lamps and note that transistor and integrated ultrasonic frequencies are free from all of the listed shortcomings. But some transistor amplifiers are more complex in manufacturing than tube amplifiers, and integrated ones require a large number of additional “add-on” elements, which negates their advantages from the use of microcircuits.
But nothing stands still, and, in my opinion, the last difficulty has also been overcome. True, such a convenient circuit suddenly turned out to be part of a more complex combined analog integrated circuit (IC) K174XA10, although it would be useful to have such a “chip” separately.

As can be seen from the circuit diagram (see figure), the ultrasonic sounder contains a minimum of parts and can find very wide application. The advantage of this IC is also the prospect for a novice radio amateur, after “breaking in” the ultrasonic frequency and studying the capabilities of the IC, to assemble an AM receiver on the same chip, and then a combined one - AM-FM.
Let's imagine a typical everyday picture: after connecting the "Dandy" game console to the TV (as usual - with one cord into the antenna socket) and turning on the power supply of the console, the neighbors suddenly begin to behave like children - knocking on the walls, on the radiators, coming as uninvited guests to express their their attitude towards you for the interference that appeared on their TVs! The mood for the game, as a rule, deteriorates greatly after this. But many TVs have a “video input”, and “Dandy” has a video output, they need to be connected to each other, but at the same time, with a high-quality “picture” on the TV screen, the game becomes “silent”. To return the “voice”, you need to connect the “Dandy” output to the ultrasonic input of the TV, but this, as a rule, is not available and you need to “climb” into the TV. To avoid this, you can make the proposed AF, connect it to the AF output of the set-top box - and the problem is solved.
The AF input signal, having passed through the isolation (direct current) capacitor C1, goes to the volume control R1, and from its slider to the input of the IC, is amplified by it and through the isolation capacitor C4 goes to the loudspeaker (dynamic head) BA1. The gain of the IC depends on the capacitance of the SZ capacitor; it is not recommended to greatly reduce it. C2 ensures decoupling of the ultrasonic amplifier cascades (inside the IC) for power supply, and also contributes to the stability of the ultrasonic amplifier when powered by discharged batteries. C5 and C6 increase the amplifier's resistance to self-excitation, and C5 also affects the frequency response. Ultrasound C5 and C6 are optional and are installed only if necessary. Oxide capacitors can be used of any brand, resistor R1 of the volume control - if possible, group B, which provides smoother adjustment of the sound level. Dynamic head BA1 - any type with a resistance of 8... 16 Ohms, it is important that the connecting wires are as short as possible, since with long wires they lose part of the output power, since these wires are part of the load resistance of the ultrasonic sounder;
The amplifier can serve as a separate unit wherever it is necessary to raise the level of the AF signal for perception by the human ear: in a tape recorder, player, as part of various probes, loud-speaking toys, apartment calls, as an ultrasound frequency for detector receivers, for example in the country, etc. The ultrasonic amplifier is not critical to the supply voltage and consumes little current, but provides high-quality sound reproduction. Those expecting higher gain should use a higher supply voltage.
The author deliberately does not provide the technical data of the amplifier: they fully correspond to those given in and do not need any comments.

Literature
1. Microcircuits for household equipment/Handbook. - M. Radio and Communications, 1989. - P. 169 - 173.
2. Brodsky Yu. “Selga-309” - superheterodyne on one chip // Radio. - 1986. - N1. - P.43 - 45.

Sounding key fob on one chip

This version of the “responsive” key fob is the result of a creative reworking of a similar design published in the magazine “Radio” N1/1991. The previously described key fob is only good for that. if it uses K564 series microcircuits. However, working with these microcircuits requires certain skills, and they are much more difficult to acquire than other microcircuits of a similar CMOS series.

The new key fob is much simpler than the previous one, since it can use not two, but one microcircuit and, of course, almost without changing the dimensions of the device, select it from the K176, K561 series. True, the key fob produces a continuous signal instead of an intermittent one, nevertheless, it copes with its “responsibilities” quite well.

The key fob circuit diagram consists of a single-shot trigger (DD1.1, DD1.2), an audio generator (DD1.3, DD1.4), a transistor amplifier (VT1, VT2) and an audio signal receiver-emitter (BA1). The scheme works like this. In the “standby” state, there is a low level signal at pin 4 of element DD1.1, and a high level signal at pin 3 of element DD1.2. When an audio signal is received from the amplifier, the trigger switches. A signal appears at pin 4 of element DD1.1 high level, allowing the sound generator to operate. At the same time, capacitor C2 is charged through resistor R7. At the end of time t - 1/2R7C2, the voltage at input 1 of element DD1.2 drops to the trigger switching level, and the key fob goes silent.

Setting up the circuit comes down to setting the acceptable sensitivity of the key fob. To do this, during setup, a tuning resistor with a resistance of 500 k is connected instead of R4. By reducing R4, one finds such a critical value of its resistance at which the key fob sounds non-stop. After this, R4 is increased slightly. The closer R4 is to critical, the more sensitive the key fob. After adjustment, the tuning resistor is replaced with a constant one.
Resistors and capacitors of the circuit are selected for reasons of small size. Diode VD1 - with the lowest forward resistance.
Transistors VT1, VT2 - with the highest gain. The piezoceramic emitter ZP-3 can be replaced with ZP-1, but this will slightly increase the dimensions of the device and the current it consumes in sound mode. Batteries from three miniature disk batteries or three watch batteries can be used as a power source. The printed circuit board and the arrangement of elements in the device may be different, depending on the dimensions and design of the housing used for the key fob.

Logic chip capacitance meter

The capacitance meter consists of a pulse generator (D1.1-D1.3), a frequency divider (D2-D4), an electronic switch (V1) and a measuring circuit (V2, R7 and P1).

The operating principle of the device is based on measuring the average discharge current of the measured capacitor charged from a square-wave voltage source. The generator produces pulses with a frequency of 100 kHz. Depending on the selected range, switch S1 changes the division coefficient. Capacitor C2 serves to calibrate the device.

The device is powered from a stabilized 5 V source.

Electrolytic capacitor capacitance meter

Electrolytic capacitors change their capacitance during operation and storage, so sometimes it becomes necessary to measure their capacitance.

The operating principle of the capacitance meter for capacitors from 3000 pF - 300 µF is based on measuring the pulsating current flowing through the capacitor. The alternating component of this current is proportional to the capacitance of the capacitor.

The lower limit of the capacitance of the measured capacitors is limited by the sensitivity of the current meter; the upper one is the time constant of the discharge circuit of the capacitor under study and the resistor connected in series with it.

Capacitor Co - calibration. Before measurement, the contacts of switch S3 are closed and resistor R7 is used to set the arrow of the device to the mark corresponding to the capacitance of the model capacitor.

Alternating current is obtained by half-wave rectification of reduced mains voltage. Transformer T1 - network, from any tube broadcast receiver. It must have a filament winding with a voltage of 6.3 V and a current of at least 1 A. The power dissipation of resistor R1 is at least 5 W. Two fuses are required - one in the power circuit, the second protects the pointer device in the event of a short circuit in the terminals to which the capacitor Cx is connected, or in the event of a breakdown of the capacitor being tested.

Surf noise simulator

The surf noise simulator can be made according to the scheme shown in the figure.

The simulator is made in the form of a set-top box connected to an audio amplifier. The source of the noise signal is a silicon zener diode VI, operating in avalanche breakdown mode at low reverse current. An amplifier with variable gain is made on transistors V2-V4, which serves to amplify the noise signal. The gain is changed by transistor V5, connected to the emitter circuit of transistor V4, by applying control voltage to the base of V5 through the integrating circuit R8C4. This voltage is generated by a symmetrical multivibrator on transistors V6 and V7. Thus, at the output the noise signal will periodically rise and fall, simulating the noise of the surf. High-impedance headphones can be connected to the "Output" sockets. The simulator uses transistors of the KT351D type.

Rain noise simulator

According to the principle of operation, such a simulator corresponds to the previously described “surf” noise simulator.

The noise generator is made of transistor V2 and zener diode VI. The pulse generator, made on transistors V5 and V6, generates pulses with a frequency of 1...3 Hz, which arrive at the base of transistor V4 and change the gain of transistor V3, as a result of which rising and falling noise appears at the output, the level of which is adjustable variable resistor R3, and the timbre - by selecting capacitor C2.

Details. The circuit uses transistors V3-V6 type KT315, V2 types KT602A-KT602G, KT603A-KT603D. The zener diode is selected based on the highest noise level at the output of the simulator.

Power supply for IC meter

Power supply for simple measuring instruments (avometers, generators, etc.) can be done from a simple power source.

The peculiarity of this power supply is that the mains transformer, together with the ballast circuits R3C1 and R1C2, operates in current generator mode, i.e., it has high internal resistance. This made it possible to turn on the zener diode V1 directly after the rectifier (V2-V5) and thus implement the first stage of voltage stabilization. Further stabilization occurs in the electronic stabilizer on transistors V6-V9. The emitter junction of transistor V8 was used as a reference source. The control cascade is assembled using transistors V6, V7, V9, connected according to a composite emitter follower circuit. Ceramic capacitor C6 is designed to reduce the output resistance of the stabilizer at high frequencies.

Transformer T1 has a magnetic circuit Ш10 X 15. Winding I contains 2600 turns, and winding II contains 1300 turns of PEL-2-0.08 wire.

Power supply for measuring instruments

Modern measuring instruments can be assembled using transistors, operational amplifiers and digital microcircuits. To power such devices, it is necessary to have a voltage source that provides at least three voltages: 5; 12 and 20 V. One of the options for such a power source provides voltages close to the mentioned values.

The stabilizers on transistors V5 and VII are equipped with short circuit protection by means of zener diodes V2 and V7. During a short circuit, the zener diodes open and limit the collector current of the transistors. After the short circuit is eliminated, the device automatically returns to operating mode.

The circuit uses a ready-made transformer TVK-110LM-K (frame scan output transformer from TVs). Diode matrices VI and V6 can be replaced with diodes D226, D237, etc.

The power supply is adjusted by selecting resistors RI and R4 until the rated current in the load is obtained.

Small size rectifier

A small-sized rectifier is designed to power a transistor receiver.

The rectifier stabilizer is protected from overloads during a short circuit at the output or in the load. To reduce its dimensions, the T1 transformer is made on a core made of Ш6 plates with a set thickness of 40 mm. Winding I contains 3200 turns of PEV-1 - 0.1 wire with capacitor paper gaskets every 500 turns, winding II has 150 turns of PEV-1 -0.2. Between windings I and II, one layer of wire PEV-1 - 0.1 is wound, serving as a screen. The maximum load current (up to 120 mA) can be increased if instead of the transistor MP16 (V5) P213 is installed, resistors R1, R2 and R3 are replaced respectively with resistors with a resistance of 220 Ohm, 2.2 kOhm and 820 Ohm, and the TI transformer is replaced with a more powerful one with voltage in winding II 12…14 V (TVK from TV).

Low power power supply

The low-power power supply is designed to power portable transistor receivers, measuring instruments and other low-power devices from the network.

Transformer T1 has a transformation ratio of 1 and serves only as an isolation transformer to create safety for using the power supply. The R1C1 chain served as a mains voltage limiter. The table shows data for two versions of the power supply.

Designation	Option 1	Option 2
T1	Core 6.5x10, window 25x11 mm. The windings contain 850 turns of PEL wire with a diameter of 0.22 mm.	Core Ш6х8, window 6х15 mm. the windings contain 1100 turns of PEL wire with a diameter of 0.12 mm.
C1	2.0x300 V	0.5x300 V
V1	D815G	D814G
V2	D815G	D814G
R2	51 Ohm 0.5 W	150 Ohm 0.25 W
C2	400.0x15 V	80.0x15 V

In the first of them, at the output of the block at a voltage of 9 V, you can power a load that consumes 50 mA; in the second option, with the same output voltage, you can get a current of up to 20 mA. In the first version of the block, the transformer core is rod-shaped; it is assembled from L-shaped plates. The windings are placed on opposite rods. If you can hear the background of alternating current when receiving powerful stations, you should turn over the XI plug in the power outlet or ground the common positive wire of the unit.

Melodious call

A melodious bell is installed instead of a regular residential electric bell. The bell sounds with trills, which can be changed by simply altering it.

The melodic bell uses two logic chips and three transistors. The oscillation frequency of the generator (transistors V6 and V7) is determined by the capacitance of capacitor C2 and the total resistance of the circuit consisting of resistors R2-R6 and R10. The control unit (elements D2.1 and D2 2) is a serial counter with a division factor of 4, assembled on a double D-flip-flop. When the bell is operating (the S1 button is pressed), logical zero levels alternately appear on the cathodes of diodes VI-V5, which leads to the opening of the diodes and the connection of the corresponding resistors to the common power wire (minus battery GB1). Alternate connection is ensured by supplying pulses to the control unit from a clock generator made on 2I-NOT logic elements (D1.1, D1.2) according to a multivibrator circuit. Element D1.3 acts as a buffer (matching) cascade between the clock generator and the control unit.

From resistor R11, oscillations of the current generator are supplied through a matching stage made on element D1.4 and resistor R12 to the base of transistor V8 of the low-frequency amplifier. The load of the amplifier is the dynamic head B1, connected to the collector circuit of the transistor through the output transformer T1.

Transistors K315G can be replaced with any transistors of the KT312, KT315, KT301 series, and MP40 with MP25, MP26, MP42B. Instead of D9K diodes, you can use any germanium diodes.

Transformer T1 - TV-12 (from small-sized transistor receivers), which uses half of the primary winding. Dynamic head B1 - power up to 2 W, voice coil DC resistance 4...10 Ohms. Capacitors C1, SZ - K50-6, C2 - MBM. Power source - battery 3336L.

With serviceable parts and error-free installation, the bell starts working immediately after pressing the button. It’s easy to set the desired melody by selecting resistors R2*-R6*. During setup, it is more convenient to replace them with variable resistors with a resistance of 22 kOhm, select a melody, and then measure the resulting resistances and solder fixed resistors with the same resistance into the device.

If necessary, the tone of the melody is changed by selecting capacitor C2 and resistor R10. Stable operation of the tone generator is achieved by selecting resistor R7* (resistance from 6.8 to 22 kOhm).

The speed of the melody depends on the frequency of the clock generator, and it can be changed roughly by selecting capacitor C1, and smoothly by selecting resistor R1* within the range of 300...470 Ohms.

Multi-input touch device

Multi-input circuit touch device on thyristors, proposed by Yu. Sboev, can be used to switch television channels, receiver ranges, etc.

The diagram shows four identical sensor cells, each containing an SCR, a transistor, a switching capacitor and an indicator. When you touch any of the four pairs of contacts E1...E4 with your finger in the base circuit of the corresponding transistor (VI, V3, V5 or V7), a current will flow, opening the transistor, which in turn will open the corresponding thyristor. Capacitors C1...C4 are used to turn off a previously working cell when the sensor touches another cell, since in this case the voltage of these capacitors is applied to the working thyristor with reverse polarity, which leads to its turning off. To indicate the state of the cells, lamps H1...H4 are used.

Details: transistors type KT315, P307...P308); MBM type capacitors; indicator lamps CM37 or any others corresponding to the supply voltage of the touch device. The maximum permissible current through an open thyristor KU101A is 75 mA, so the load resistance is selected based on the specified current. The device supply voltage is 10...30 V. The capacitance of capacitors C1...C4 is selected when setting up the circuit. The capacitance value must be at least C = 36t/R, where t is the turn-off time of the thyristor, R is the load resistance.

Garland switch on one SCR

A garland switch on one SCR for one garland can be assembled according to the following scheme (Fig. IX.4, a).

Resistors, an electrolytic capacitor and a thyristor make up a closed cell that works “for itself”.

Elements R1C1 form a timing circuit. At the initial moment after turning on the device to the network, the thyristor is closed and the HI garland does not light up. Capacitor C1 is charged through resistor R1, and at a certain voltage across it, the thyristor opens. The garland lights up, and at the same time the capacitor is discharged through a resistor and an open thyristor. The SCR closes and the garland goes out again. The process is repeated.

The garland is made up of series-connected lamps with a current consumption of no more than 0.4 A. For higher currents, a more powerful diode V2 should be installed, for example D242B, and also SCRs KU202L (M, N) should be used.

With a slight improvement in the circuit, you can use a switch for two garlands with adjustable glow duration (see Fig. IX 4, b).

Complete extinguishing of each garland during a pause can be achieved if the HI garland is selected with a significantly higher current consumption.

Garland switch with smooth activation

The principle of operation of the device (Fig. IX. 1) is based on the interaction of two voltages close in frequency - the electric lighting network (50 Hz) and pulses received from the multivibrator to control transistor switches in the power circuits of the garlands.

The luminous flux and brightness of the lamps change with a frequency equal to the difference in the frequencies of these electrical signals. The moments of smooth lighting and extinguishing of lamps in garlands are shifted in time relative to each other, the interval between successive lighting and extinguishing of lamps can be smoothly adjusted over a wide range - up to 10 s or more. Control pulses are generated by a three-phase multivibrator (transistors VI-V6), powered by voltage from a full-wave rectifier (diodes V12-V15). The rectified voltage is stabilized by zener diode V7. Pulses from the multivibrator are supplied to power transistor switches V8, V9, V10, the collector circuits of which include strings of HI-H2 lamps. Alternately, for 1/3 of the control pulse period, groups of transistors VI, V2 and V8, V3, V4 and V9, V5, V6 and V10 are switched from open to closed. Variable resistor R10 sets the desired repetition rate of control pulses. To reliably start the multivibrator, the S1 Start button has been introduced.

Incandescent lamps in garlands are connected in parallel or in series, depending on their rated voltages and filament current. Power circuits consisting of transistor switches V8-V10 and their loads - garlands - are powered by pulsating voltage from a rectifier on diode V11. Current flows through the garland lamps only when the supply voltages of the power circuits and the control current pulses in the base circuits of transistors V8, V9, V10 coincide. Due to the difference in their frequencies, there is a time shift in the moments when the lamps come on and go out and a smooth change in the brightness of their glow.

The desired frequency of lighting and extinguishing of the garlands is set with a variable resistor R10 of the control device. If the pulsation frequency of the light flux is greater than required, select resistors R5*, R7* and R9*.

The power supply uses a transformer TA 163-127/220-50 (power 86 W), made on a magnetic core ШЛ20 X 40. According to the passport data, in the rated load mode, the voltage of windings 11-12 and 13-14 at a current of 0.68 A and windings 15-16 and 17-18 at a current of 0.71 A are equal to 28 V, and windings 19-20 and 21-22 at a current of 0.71 A are 6 V. Each of the garlands is made up of 10 lamps МН30-0.1 (on voltage 30 V and current 0.1 A). P210B transistors and D232 diodes operate without heat sinks.

P210B transistors can be replaced with similar ones in terms of maximum collector current, voltage between collector and base, reverse collector current and static base current transfer coefficient. The permissible voltage between the emitter and the base of transistors V2, V4 and V6 of the control device must be at least 10 V.

Using in power circuit silicon transistors, resistor R17 can be eliminated, while the resistances of resistors R15, R16, R18 can be twice as large.

Power supply

The power supply is a combination of a full-wave rectifier and a parametric voltage regulator using a zener diode.

The output voltage of the device is 9 V at a current of 25-30 mA. Quenching capacitors C1 and C2 determine the amount of current consumed by the device from the network. Capacitor SZ serves as a filter to smooth out ripples), and resistor R2 and zener diode V5 form a parametric voltage stabilizer.

Details. Diodes type D226; Zener diode D814B or D809; capacitors C1, C2 types KBG, BMT.

Device for testing field-effect transistors

The device allows you to check the performance of field-effect transistors with a p-n junction, with an insulated gate and a built-in channel (depleted type), as well as single- and double-gate transistors with insulated gates and an induced channel (enriched type).

Switch S3 is used to set, depending on the type of transistor under test, the required polarity of the drain voltage. To test transistors with a gate in the form of a p-n junction and transistors with an insulated gate and a built-in channel, switch S1 is set to the Depletion position, and S2 to the Substrate position.

To test transistors with insulated gates and an induced channel, switch S1 is set to the Enrichment position, and S2 is set to the Substrate position for single-gate and Gate 2 for dual-gate transistors.

After installing the switches in the required positions, connect the transistor being tested to the sockets of connector XI, turn on the power and, by adjusting the voltages on the gates with variable resistors R1 and R2, observe the change in the drain current.

Resistors R3 and R4 limit the gate current in case of breakdown or in case of incorrect polarity of the gate voltage (for transistors with a p-n junction gate). Resistors R5 and R6 eliminate the possibility of accumulation of static charges on the sockets of connector XI for connecting gates. Resistor R8 limits the current flowing through milliammeter P1. The bridge (diodes VI-V4) provides the required current polarity through measuring device at any polarity of the supply voltage.

Setting up the device comes down to selecting resistor R8*, which ensures that the milliammeter needle deflects to the last scale mark when the Drain and Source sockets are closed.

The device can use a milliammeter with a total deviation current of 10 mA or a microammeter with the corresponding resistance of the shunt resistor R7*. Diodes V1-V4 - any, low-power, germanium. The nominal resistance of resistors R1 and R2 is in the range of 5.1...47 kOhm.

The device is powered by two Krona batteries or two 7D-0.1 batteries.

This device can also measure the cutoff voltage (device P1 must have a current of 100 μA). To do this, additional sockets are installed parallel to the Gate 1 and Source sockets, to which a voltmeter is connected.

A button is connected in series with resistor R7*, and when pressed, the shunt resistor is turned off. When the button is pressed, the drain current is set to 10 μA and the cutoff voltage is determined using an external voltmeter.

Prefix - howler

This security device is also significantly different from previously published ones. The sensor is a piezoelectric element from a pickup (or a ceramic emitter ZP-1), pressed or glued (preferably not completely, but only at one end) to the lock body, door, car body or other protected object.

There can be several sensors connected in parallel. If the device is turned on and is in standby mode, then the first light blow to an object with a metal object (an attempt to open a lock with a key or master key, unscrew a wheel, etc.) will cause a package of voltage pulses on sensor D. Amplified by transistors VT1, VT2, passing through the regulator sensitivity R5 and inverter D3.3, the first pulse of the package triggers the one-shot on Dl.l, D1.2. At pin 11 of D1.1, a log “O” appears, which starts the second pulse generator on elements D1.3, D1.4. These pulses arrive at input “C” of D5. The counter switches, and logs appear alternately at outputs 1-9. "1".

If the second strike occurs during the second when the log. "1" is at output 4, then log. "O" from pin 11 of D3.1 will overturn the RS trigger on elements D4.1, D4.2. A log "1" will appear at the counter's input E, prohibiting counting for the entire duration of the one-shot pulse (about 1 minute). During this time, the owner will open the lock and turn off the signaling device. If the second strike occurs at a different time, the trigger will overturn on elements D4.3, D4.4, the counter will also stop, and at the same time the siren on elements D2.3, D2.4, D6 and VT3 - VT6 will turn on.The main tone of the siren changes under the influence of second pulses.

When the one-shot pulse ends, the siren will turn off, and a log will be sent to the “R” input of the counter. "1" which will reset the counter to initial state. At the same time log. “O” from pin 10 of D1.2 through diode VD4 will also set both RS triggers to their initial state and the device will go into standby mode.
A one-shot on elements D2.1, D2.2, triggered by pressing the KN button, blocks the operation of the counter and makes it impossible to turn on the siren for a little more than a minute. This is necessary for “silent” closing of the door. Secondary pulses arriving through the VD10 diode to the siren amplifier cause clicks in the loudspeaker, making it easier for the owner to turn off the siren. Element D3.4 switches it in standby mode to the off state, reducing the current consumption to 0.5 -1 mA.

The security device is mounted on printed circuit board. The location of the parts is given Here. During installation, the microcircuits should be protected from static electricity. Pin 9 of the D3.1 chip can be connected to any of the 9 outputs of D5, specifying your own version of the “key”. All other outputs must be connected through diodes, as shown in the diagram. The finished board, along with batteries, is installed in a suitable-sized case. The KN button and the power switch are mounted on top of the case.
If the set-top box is used to protect an apartment, then several dozen holes (3-6 mm) are drilled into the door, covered with a metal mesh (or a plate with the same holes), and a dynamic head is attached to it. The device body is attached to the door near the emitting head. The piezoelement is connected to the structure with a shielded or twisted wire.

Instead of the K561PU4 microcircuit, you can use the K176PUZ, and instead of the others from the 561 series, you can use the same ones from the 176, 164 or 564 series. The device, assembled from serviceable parts, does not require adjustment. You just need to set the required sensitivity with resistor R5. When you lightly hit the lock with a key or try to insert it into the hole, the pulse generator should turn on and clicks should begin to be heard with a frequency of 2 Hz. This means that the device has switched to the standby mode for the second strike. If everything is done as in the diagram , then you can turn off the siren by hitting the lock after the 8th click, that is, after 4 seconds. A strike at another time will turn on the siren. To make the thief’s “work” even more difficult, you can remove the clicks by removing the VD10 diode, but then the owner will need to withstand second rhythm yourself.
The sensitivity should not be set to high to avoid false alarms of the device.

The operating procedure of the device is as follows.
TURN ON THE STB AND PRESS THE BUTTON.
LEAVE THE HOUSE AND CLOSE THE DOOR (You only have one minute!).
WHEN YOU RETURN, HIT THE LOCK WITH THE KEY, COUNT THE REQUIRED NUMBER OF CLICKS AND HIT THE LOCK AGAIN.
OPEN THE DOOR AND GO INTO THE HOUSE(You only have 1 minute to turn off the alarm bell).

You don’t have to turn off the security device, then you will be protected at home, and the battery power will last for several months.

A simple color music console, proposed by A. Polozov, can be installed on the front panel of a stereo tape recorder, electrophone or radio.

The set-top box is made of two transistors, one logical chip and four miniature incandescent lamps. The signals supplied through resistors R1, R7 and capacitors C1, C2 to the input of the device are amplified by transistors VI and V2 and supplied to the inputs of inverters D1.1 and D1.3, the output circuit of which includes incandescent lamps HI and NC. The outputs of these inverters are connected through resistors R4, R10 to the outputs of inverters D1.2 and D1.4, loaded with incandescent lamps H2 and H4. When the HI lamp is ignited, the H2 lamp goes out, when the NC lamp is ignited, H4 goes out and vice versa. Thus, when a signal is received at the input, lamps HI, H2, NC, H4 seem to blink at the frequency of the sound signal. The lamps are installed behind a light-diffusing screen measuring 650 X 50 mm and painted red, blue, yellow and green, respectively.

Details: incandescent lamps SMN-6.3-20; constant resistors MLT-0.25, tuning resistors - SPO-0.5 or SP-0.4; capacitors C1 and C2 - KM or MBM. The setting comes down to adjusting resistors R2 and R8 so that without a signal, the HI and NC lamps are at the ignition threshold. Resistors R4 and R10 are used to extinguish lamps H2 and H4 when HI and NC are fully illuminated.

Simple color music console

A simple color music console is designed to work with a tube radio or tape recorder. Connect it to the secondary winding of the output transformer. For power supply, the alternating voltage of the lamp filament winding rectified by diode V4 (6.3 V) is used.

The set-top box is three-channel. The channel on transistor V1 amplifies the components higher frequencies, on transistor V2 - medium, on transistor V3 - low. The frequency spectrum of the input signal is divided by the simplest filters R3C1, R5C2C4 and R7C3C5. The transistor loads are miniature incandescent lamps МН6.3-0.28, painted blue, green and red.

Variable resistors R5 and R7 balance the brightness of the light, taking into account the spectrum of the real music signal; variable resistor R1 regulates the minimum brightness of all lamps at the selected sound reproduction volume.

The setup begins with the selection of resistors R2*, R4* and R6* (at this time it is advisable to replace them with variable resistors with a resistance of 6.8... 10 kOhm). The resistance of the resistors should be such that in the absence of a signal from the filament of the HI-H6 lamps barely glowed noticeably. Having achieved this, the resistor motors R5 and R7 are set to the middle position and a signal from the secondary winding of the output transformer is supplied to the input. Having set the receiver or tape recorder controls to the normal sound volume and the maximum rise in higher frequencies, move the resistor R1 slider until the HI and H2 lamps begin to flash in time with the music. Lastly, variable resistors R5 and R7 achieve the same bright glow of lamps NZ, H4 and H5, H6.

Simple voltage stabilizer

Power supply for modern equipment using transistors and especially microcircuits requires a stabilized source. In one of the stabilizer options (Figure VIII 22), the output voltage is regulated by resistor R2 in the range from 1 to 14 V at a current of up to 1 A.

The output resistance of the stabilizer is about 0.3 Ohm, the stabilization coefficient is approximately 40, and the ripple voltage (with full-wave rectification of the primary voltage) does not exceed 0.028 V. The stabilizer is protected from overload, automatically returning to operating mode when the latter is removed. The limiting threshold is set by resistor R3.

The static current transfer coefficient of the control transistor must be at least 70, and this transistor must be installed on a radiator with an effective surface area of ​​at least 150 cm 2.

Micromotor shaft speed controller

The shaft speed controller for a DC microelectric motor allows you to regulate and stabilize the motor shaft speed when the load changes.

The microelectric motor is included in the emitter circuit of transistor V2. The feedback signal is removed from the low-resistance resistor R4 and enters the base circuit of transistor VI. As the load increases, the motor current increases and the voltage across resistor R4 increases. This leads to an increase in the current of transistor V2 and an increase in the base current of transistor VI, which increases the voltage on the electric motor and the power on its shaft increases. When the load decreases, the described processes are repeated in reverse order. The rotational speed of the electric motor is set in idle mode with a variable resistor R1, changing the bias at the base of the transistor V2. Resistor R4 sets the limits within which the power on the shaft can change while maintaining the speed.

Details. Transistor VI type KT315B, the choice of transistor V2 (for example, KT814V) depends on the magnitude of the supply voltage and operating current of the microelectric motor; diode V3 type KD510A.

Touch sensor

Touch switches allow switching devices to be significantly closer to the switched circuits. This significantly simplifies obtaining a low background level, provides high noise immunity and provides the designer with greater freedom in the layout of the designed device. The figure shows the touch sensor circuit proposed by A. Sobolev.

To control the sensor, an alternating voltage induced on the human body is used, supplied to the base of transistor VI, operating in signal detection mode. The rectified pickup voltage is supplied to a current amplifier assembled on transistors V2 and V3. The relay winding K1 is used as the collector load of transistor V3, which is activated by touching the terminal of capacitor C1. The current consumption of the device in standby mode is 0.2 mA.

Details: transistors of the types indicated in the diagram with a static current transfer coefficient of 80...100; relay - RES-10 (passport RS4, 524.303) or RES-9 (passport RS4.524.202); capacitors S1-K10-7V, S2-MB; resistors - MLT-0.125.

When removing the touch sensor from the device, it should be connected with a shielded or double-bundled wire. The braid of the shielded wire is grounded.

Hearing aid

The hearing aid is intended for people with hearing loss.
It has the following parameters:

gain 5000,
operating frequency band 300-7000 Hz,
output voltage at load resistance 60 Ohm 0.5 V,
maximum current consumption 20 mA.

The amplifier of the device is made of three transistors. To stabilize the gain, the first two stages are covered by a negative feedback by direct current. From resistor R7, which acts as a gain regulator, the signal through separating capacitor C6 is supplied to the base of transistor V3, on which an amplifier stage with a floating operating point is assembled. This reduces current consumption in silent mode to 7 mA

Details .

Resistors type MLT-0.125 (R5 type SPZ-Za); electrolytic capacitors type K50-6; capacitors SZ type KLS or KM-4a; C1, C7, C8 type KM-6a or electrolytic K50-6 of the same rating, diodes type D9 or D2, electromagnetic microphone BK-2 (601); telephone type TN-3 or TN-4; power source - 9V Krona battery.

Establishment comes down to setting modes; for direct current for transistors V1 and V2 by resistors R4 and R6, respectively. The quiescent current of the final stage is 2-2.5 mA set with resistor R8 (with the microphone turned off); resistor R9 achieves undistorted signal amplification; The sound timbre is selected by the capacitance of the capacitor SZ.

DIY handset

This push-button telephone is made entirely of domestic radio elements. The basis is a circuit composed of several types of circuits for push-button telephone sets manufactured in Japan, Korea, Taiwan, and the USA.

The handset phone is assembled using seven transistors. Power to the circuit is removed from the diode bridge VD4 - VD7 through a reed switch (or other type) switch SA1. Transistors VT1, VT2, VT3 assemble a differential circuit and an electronic key for dialing a number. The power for the conversational part of the circuit is removed from the divider R5, R8 and depends on the value of the resistor R8 (150 - 200 Ohms). An amplifier for a dynamic microphone is assembled on transistor VT4, from the load resistor (R6) of which the amplified voltage is supplied through capacitor C1 to the base of transistor VT2. A telephone amplifier is assembled using transistors VT5, VT6, to the input of which low-frequency signals from the line are received from the divider R1, R4 through capacitor C2. The load of the telephone amplifier is resistor R11, from which the amplified low-frequency voltage from the line is supplied to the telephone capsule HA1.

An electronic bell is assembled on transistor VT7, which can be disconnected using switch SA2. The DEMSH-1A microphone capsule is used as a bell emitter.

For push-button dialing of a subscriber number, a D1 chip of type KR1008VZh1 is used. Power is supplied to the microcircuit from capacitor C6 (to pins 3,6 and 14). The power supply minus is common and is removed from diodes VD5, VD7. While the phone is operating, capacitor C6 is charged through resistor R5 and diode VD2, and in the initial state - through divider R13, R14 and diode VD1 (this is necessary to store the last dialed subscriber number in memory).
When dialing a number from pin 12 of microcircuit D1, positive pulses are sent through limiting resistor R3 to the base of transistor VT1 (electronic key), thereby opening and closing transistor VT1. The latter closes and opens transistors VT2, VT3. To adjust the dialing frequency, resistor R20 is used. The HL1 LED is necessary to monitor the functionality of the device circuit.

The device circuit is assembled on a single-sided printed circuit board (Fig. 3, 4) measuring 110 x 32 mm.

Thermostat

The thermostat can be used in thermostats, calorimeters and other devices with a heater power not exceeding 1 kW. If you need to increase the power of the heating installation, you should replace thyristor VI with a more powerful one, leaving the regulating part the same. If a suitable thyristor is not available, an intermediate contactor can be used.

The range of adjustable temperatures when using the MMT-1 thermistor is from 20 to 80 °C.

The regulating circuit of the thermostat consists of thermistor R6 with diode V6, variable resistor R7 with diode V7 and capacitor C4. The circuit is connected through a voltage stabilizer on zener diodes V3 and V4 to the secondary winding of step-down transformer T1. The value and polarity of the voltage on capacitor C4 are determined by the ratio of the resistances of resistors R6 and R7. When R6 > R7, the voltage on the upper plate of capacitor C4 in relation to the bottom (according to the diagram) will be positive and at a certain value it is sufficient to open the low-power thyristor V2, connected to the control circuit of the powerful thyristor VI. The emitter follower on transistors V8, V9 increases the input impedance of the amplifier and provides a large current transfer coefficient for controlling the thyristors.

The flow of current through the SCRs and through the heater at a given resistance of resistor R7 is determined by the resistance of thermistor R6. As the temperature rises, the resistance of the thermistor decreases, the discharge current of capacitor C4 through the thermistor and diode V6 increases, and the voltage across the capacitor decreases.

To ensure a smooth change in the cut-off angle of the current of the thyristors and, therefore, smooth regulation of the current through the heater, the control voltage supplied to the thyristors contains, along with a constant component, an alternating component. In relation to the phase of the mains voltage, it is shifted in phase by 90° by the chain R3C1. The alternating voltage of capacitor C1 is supplied through capacitor C2 to the base of transistor V8. When the control voltage supplied to the thyristors changes, the current through them changes over a wide range.

Transformer T1 is wound on a magnetic circuit Ш12 X 15. Winding I contains 4000 turns of PEV-1 wire - 0.1, II - 300 turns of PEV-1 wire - 0.29.

Setting up a thermostat comes down to selecting resistors R1 and R4, since the minimum starting current of SCRs has a large spread. It should be noted that for proper operation of the thermostat, the voltages at the anodes of thyristors VI and V2 must be in phase, which is achieved by switching the terminals of winding II of the transformer.

Three-phase electric motor in a single-phase network

In amateur radio practice, there is often a need to use three-phase electric motors for various purposes. However, to power them it is not necessary to have a three-phase network. Most effective method starting an electric motor involves connecting the third winding through a phase-shifting capacitor.

For a capacitor-start motor to operate properly, the capacitance of the capacitor must vary depending on the speed. Since this condition is difficult to fulfill, in practice the engine is controlled in two stages. Turn on the engine with the design (starting) capacity, leaving the working one. The starting capacitor is turned off manually with switch B2.

The operating capacitance of a capacitor (in microfarads) for a three-phase motor is determined by the formula

Cp=28001/U,
if the windings are connected in a star configuration (Fig. 1),

or Ср=48001/U,

if the windings are connected in a triangle pattern (Fig. 2).

With a known electric motor power, the current (in amperes) can be determined from the expression:

I=P/1.73 U?cos?,

Where P is the engine power indicated in the passport (on the dashboard), W;
U - network voltage, V; cos? - Power factor; ? -Efficiency.
The starting capacitor Sp should be 1.5 - 2 times larger than the operating capacitor Av.
The operating voltage of the capacitors must be 1.5 times greater than the network voltage, and the capacitor must be paper, for example, such as MBGO, MBGP, etc.

For a capacitor start electric motor there is a very simple circuit reversal. When switch B1 is switched, the engine changes direction of rotation. The operation of capacitor-started motors has some peculiarities. When the electric motor is running idle, a current flows through the winding fed through a capacitor by 20-40% more than the rated one. Therefore, when the engine is running. load, it is necessary to reduce the working capacity accordingly.

If the motor is overloaded, it may stop; in order to start it, the starting capacitor must be turned on again.

You need to know that with this switching on, the power developed by the electric motor is 50% of the rated value.

Any three-phase electric motors can be connected to a single-phase network. But some of them work poorly in a single-phase network, for example, motors with a double cage squirrel-cage rotor of the MA series, while others, with the correct choice of switching circuit and capacitor parameters, work well (asynchronous electric motors of the A, AO, AO2, D, AOL, APN, UAD series ).

Phone amplifier

This amplifier is intended for those who have difficulty hearing; it is also effective when the signal on the line is weakened for some reason.

The amplifier is mounted on a board measuring 20 x 25 mm and is placed in the handset under the telephone capsule if the device is an old type, or in the middle of the handset if the device is TAI 320, TA11322, etc. The leads of the amplifier circuit, marked with the appropriate color, are connected to the contacts on the microphone holder. Diodes such as KD102, D226, D223 can be used as VD1 - VD4. Instead of VT1, you can use transistors MP40A, MP26, capacitor C1 - type KM, resistor R2 can be either variable or constant. The value of the latter is selected based on the disappearance of the acoustic connection between the microphone and the telephone.

Advanced LED mains voltage indicator

I propose for repetition by radio amateurs an improved LED indicator of mains voltage, which differs from all previously published ones in being more noise-resistant. For example, the indicators shown in Fig. 1 and Fig. 2 are capable of giving false readings when the presence of voltage in a long cable is checked, and the cable has a broken phase wire. These indicators also give false readings when they are used to check the presence of voltage in network wiring with poor insulation - in basements, damp rooms, i.e. where there is low insulation resistance.

The proposed indicator (Fig. 3) is easy to manufacture and reliable in operation, free of false readings under any operating conditions. They can check both linear voltage 380 V and phase voltage. And it differs from all previous ones by using the KN102D dinistor in the circuit. Thanks to the latter, the indicator registers only the pure phase and does not respond to interference. The indicator uses a capacitor C1 - MBM 0.1 μF at 400 V and a resistor R1 - MLT 0.5.

Installation “FALLING SNOW”

Among New Year's decorations, many are familiar with the “Falling Snow” installation, which is a rotating ball with pieces of broken mirror glued to it and illuminated by a lamp. But such an installation tires the eyes, and the “falling snow” effect is not very diverse and quickly becomes boring.
I offer an improved installation, combined with a color and music device. Its design is clear from the figure.

The drum is easy to make from tin; it is coated with Moment glue and pasted over with pieces of broken mirror. Changing melodies change the lighting, and the effect of “falling snow” also changes.

Mosquito repellent device

The mosquito repellent device produces vibrations with a frequency of more than 10 kHz, repelling mosquitoes and even mice.

The generator is made on a single K155LAZ microcircuit loaded with a high-impedance TON-2 telephone. The generator frequency can be adjusted by resistors Rl, R2 and capacitor C1.

Long duration pulse former

The former contains an RC trigger assembled on 2I-NOT logic elements, an integrating circuit R1, R2, C1 and an inverter on transistor V1.

If the logic level is high at the input of the shaper, a high logic level will appear at output 1, and a low logic level will appear at output 2. When a negative trigger pulse is received at the input, the trigger switches to another state: a high logical level appears at the output of element D1.2, and a low logical level appears at the output of element D1.1. Through resistors R1 and R2, capacitor C1 begins to charge. As soon as the voltage across it reaches the opening voltage of transistor V1, the voltage at the collector of this transistor decreases, the trigger returns to its original state, and capacitor C1 is discharged.

Diode V2 accelerates the discharge of capacitor C1, and resistor R1 limits the discharge current.

Approximately, the duration of the pulses (in seconds) is equal to the product of the capacitance of capacitor C7 (in microfarads) and the resistance of resistor R2 (in megaohms). When using elements with ratings indicated on the circuit diagram, the pulse duration is about 5 s.

Function generator on a chip

A logic chip based on MOS transistors with additional symmetry allows you to build a generator that produces rectangular, triangular and sinusoidal oscillations.

Depending on the capacitance of the SZ capacitor, the frequency of the generated oscillations can be changed in the range from 35 to 3500 Hz. The generator is based on a comparator based on elements D1.1 and D1.2. From the output of the comparator, the signal goes to the integrator (SZ, R6, D1.3). Element D1.4 is used as a nonlinear amplifier. By adjusting the input voltage level with resistor R7 at the input of element D1.4, we achieve sinusoidal oscillations at its output. Potentiometer R1 is used to obtain symmetrical oscillations; the pulse frequency is changed by resistor R6.

Economical speed stabilization circuit

The circuit is a pulse stabilizer consisting of a tachometer bridge formed by resistors R4-R7 and the armature winding of the motor M1, a reference voltage source (V7, V8, R3), a controlled multivibrator on transistors V5, V6 and a trigger circuit (diodes VI-V4 and resistor R1).

When the bridge is balanced, the voltage between the points depends only on the engine speed. This voltage is compared with a reference, and the difference signal is used to control the rotation speed. When the circuit is turned on, the potential of point a is higher than point b, and the diode is open. Thanks to this, transistor V5 opens, followed by transistor V6. The tachometer bridge is connected to a power source, which causes the motor shaft to rotate.

Due to the presence of positive feedback through capacitor C1, the cascade on transistors V5, V6 is self-excited. The voltage on the tachometer bridge depends on the frequency and duration of the generated oscillations, which in turn depend on the difference control voltage based on transistor V5. In steady state, the motor shaft speed is determined by the bridge parameters and the reference voltage. In this case, the potential of point a is lower than the potential of point b, diode V4 closes, and the trigger circuit (VI-V4, R1) does not participate in the operation of the stabilizer. An increase in the load on the shaft causes a decrease in engine speed, which causes a decrease in voltage on the diagonal of the tachometer bridge. In this case, the voltage at the base of transistor V5 increases, which causes an increase in its collector current and a corresponding increase in the frequency and duration of pulses of the collector current of transistor V6. At the same time, the average voltage on the electric motor increases, due to which the rotational speed of its shaft is restored. Reducing the load on the shaft causes phenomena of the opposite nature in the circuit.

The instability of the rotation speed of the stabilizer with the DPM-25 engine under normal conditions is 0.5... 1%, and in the temperature range from -30 to +50°C 2...3%. When capacitor C1 is removed, the stabilizer goes into linear control mode.

Electronic gas lighter

An electronic gas lighter is a high-voltage pulse generator.

The generator pulses create spark discharges near the burner when the gas is turned on. To do this, a cam mechanism is installed on the axis of the gas handle, which closes the contacts S1 located near the handle. Relay K turns on, blocking the contacts of the S1 button and including capacitor C1 in the charging circuit. This starts the blocking generator, made on transistor V2. The open state of transistor VI is maintained during the charging time of capacitor C1, after which the transistor is turned off and the relay turns off the power from the circuit, returning it to its original state.

Details. The blocking generator transformer T1 is made on a ferrite magnetic core with a diameter of 20 mm; winding I contains 140, winding II - 70 turns of wire PEV 0.47; transformer T2 - ignition coil of a motorcycle or boat engine; power supply - four elements 373 or 343 connected in series.

Electronic canary.

Using a relatively simple device, you can imitate the singing of a canary.

A complex oscillation generator is used here. The repetition period of the trills is regulated by variable resistor R2, and the sound frequency by resistor R4.

Transformer T1 is output from any transistor portable receiver; dynamic head - also from a small-sized receiver. Current consumption is 5 mA, so you can use a battery for power supply

"Electronic nanny"

The alarm device (Fig. 6.37) provides a signal as soon as the baby's diapers become wet.

The sensor of the device is a plate 20 X 30 mm, cut from one-sided foil fiberglass 1 mm thick, along which a groove 1.5-2 mm wide is cut in the center, dividing the foil into two electrodes isolated from each other. The surface of the electrodes must be silvered or tinned. While the sensor resistance is high (the diapers are dry), transistor V4 is closed, and the current consumed by the alarm is a few microamps. With such a low current consumption, the alarm does not have a power switch. As soon as the resistance of the sensor decreases (the diapers are wet), transistor V4 opens and supplies power to the generator, simulating the sound of “meow”, made on transistors V2, V3. The duration of the “meow” sound depends on the resistance value of resistor R4 and the capacitance of capacitor C2. The repetition frequency of sounds depends on resistance R2 and capacitance C2, timbre - on capacitance C1.

Details. Transistors V2, V3 type MP40-MP42 with any letter index with h21e > 30, V4 types KT104, KT2OZ, KT361 with any letter index and h21e > 30; telephone capsule TK-67N with a DC winding resistance of 50 Ohms.

Electric thermometer for measuring grain temperature

The sensor of the device is a measuring needle with a diameter of 4 mm, with which a bag of grain is pierced.

The device is built on the principle of an unbalanced bridge, to one diagonal of which the supply voltage is supplied from battery(via button S1 and limiting resistors R7 and R8), and the other includes a measuring device - a microammeter with a scale of 0-50 μA, type M494. One of the arms of the bridge is a thermistor R3 type MT-54 with a resistance of 1.3 kOhm at 20 °C, installed at the end of the measuring needle. Calibrate the device using a reference mercury thermometer, starting with the lowest temperature (-10°C). Resistor R2 sets the microammeter needle to the initial scale division. To calibrate at the highest measured temperature, switch S2 is set to position “K” (control) and, by adjusting resistor R4, set the instrument needle to the final scale value (+70 °C). Before measuring temperature, the scale is calibrated in the “I” position of switch S2. By adjusting potentiometer R8, set the instrument needle to the final scale value.

Details. Resistor R4 is wound bifilarly with manganin wire PEMM-0.1; The wiring inside the needle is made with fluoroplastic insulated wire of type MGTFL-0.2.

AUTOMATIC WATERING PLANT

A schematic diagram of a simple automatic machine that turns on the supply of water to a controlled area of ​​soil (for example, in a greenhouse) when its humidity decreases below a certain level is shown in the figure. The device consists of an emitter follower on transistor V1 and a Schmitt trigger (transistors V2 and V4). The actuator is controlled by electromagnetic relay K1. Humidity sensors are two metal or carbon electrodes. immersed in the ground.

If the soil is sufficiently moist, the resistance between the electrodes is small and therefore transistor V2 will be open, transistor V4 will be closed, and relay K1 will be de-energized.

As the soil dries, the soil resistance between the electrodes increases, the bias voltage at the base of transistors V1 and V3 decreases. Finally, at a certain voltage at the base of transistor V1, transistor V4 opens and relay K1 is activated. Its contacts (not shown in the figure) close the circuit for turning on the damper or electric pump, which supplies water for watering the controlled area of ​​soil. As humidity increases, the soil resistance between the electrodes decreases; after reaching the required level, transistor V2 opens, transistor V4 closes and the relay is de-energized. Watering stops. The variable resistor R2 sets the operating threshold of the device, which ultimately determines the soil moisture in the controlled area. Transistor V4 is protected from voltage surges of negative polarity when relay K1 is turned off by diode V3.

Note. The device can use transistors KT316G (V1, V2), KT602A (V4) and diodes D226 (V3).

Source: "Elecronique pratique" (France), N 1461

Automatic feeding of aquarium fish

Yes, aquarium fish lovers, you can easily entrust the care of regular feeding of your charges to the automatic machine described here. It provides a daily one-time morning feeding for the fish.

The electronic part of such a device (Fig. 1) is formed by a photosensitive element, the function of which is performed by the photoresistor R1, a Schmitt trigger assembled on elements DD1.1 and DD1.2, a pulse shaper with a normalized duration of feed supply, made on elements DD1.3, DD1.4 , and an electronic switch on transistors VT1,VT2. The role of the feed dispenser is performed by an electromagnet controlled by a transistor switch.

The power source of the machine is the commercially produced PM-1 rectifier device, intended for powering the engines of electrified self-propelled models and toys, or any other mains power supply with an output voltage of 9 V and a load current of up to 300 mA. To increase the stability of the machine, its photocell and microcircuit are powered by a parametric voltage stabilizer R7, VD2, C2.

In the dark, when the resistance of the photosensor R1 is high, a low level voltage operates at the input and output of the Schmitt trigger, as well as at the input of element DD1.3 and the output of element DD1.4. Transistors VT1 and VT2 are closed. In this “standby” mode, the device consumes a small current - only a few milliamps. With dawn, the resistance of the photoresistor begins to gradually decrease, and the voltage drop across resistor R2 begins to increase. When this voltage reaches the threshold of the trigger, a high-level signal appears at the output of its element DD1.2, which is fed through resistor R5 and capacitor C3 to the input of element DD1.3. As a result, elements DD1.3 and DD1.4 of the pulse shaper of normalized duration are switched to the opposite logical state. Now the high-level signal at the output of element DD1.4 opens transistors VT1 and VT2, and electromagnet Y1, when triggered, activates the fish feed dispenser.

As evening approaches, the resistance of the photoresistor increases, and the voltage across resistor R2 and, consequently, at the trigger input decreases. At the threshold voltage, the trigger switches to its original state and capacitor C3 is quickly discharged through diode VD1, resistor R5 and element DD1.2. At dawn, the entire process of the machine’s operation is repeated.

Rice. 1

The duration of operation of the dispenser is determined by the charging time of capacitor C3 through resistor R6. By changing the resistance of this resistor, the amount of food poured into the aquarium is regulated. To prevent the device from triggering when the mains voltage disappears and then reappears, or various light interferences, capacitor C1 is connected in parallel with resistor R2.

DD1 chip can be K561LA7, transistor VT1 - KT315A-KT315I, KT312A-KG315V, KT3102A-KT3102E,/T2 - KT603A, KT603B, KT608A, KT608B, KT815A-KT815G, KT817A - KT817 G. We will replace the KS156A zener diode with KS168A, KS162V, KS168V. Diodes KD522B - on KD521A, KD102A, KD102B, KD103A, KD103B, D219A, D220. Capacitor S1-KM; C2 and C3-K50-6, K50-16; C4 - K50-16 or K50-6. Trimmer resistors R2 and R6 - SP3-3, other resistors - BC, MLT. Photoresistor R1 -SF2-2, SF2-5, SF2-6, SF2-12, SF2-16; You can also use the FT-1 phototransistor.

The circuit board along with the photoresistor is placed in a plastic case of suitable dimensions. A hole is drilled in the housing wall opposite the photoresistor. The device is placed on the windowsill in such a way that diffused daylight falls on the photoresistor through the hole in the housing and does not expose it to direct sunlight or light from artificial lighting sources. To connect to the power supply and dispenser, connectors of any design can be installed on the case.

A possible design of a dispenser installed on an aquarium is shown in Fig. 2. To simplify, the function of the electromagnet in it is performed by a slightly modified electromagnetic relay REN-18 (passport RX4.564.706), which operates at a voltage of 6 V and provides sufficient force for the dispenser to operate.

The dispenser itself consists of a cone-shaped hopper 2 made of thin metal (you can use the body of an aerosol drug), glued to a cylindrical base 1 with a thickness of 5...7 mm and a diameter of 15...20 mm. At the base there is a through hole with a diameter of 5...7 mm, in which you can freely move a thin-walled tube 3 with a dosing hole in the wall. A spring 9 is placed on the bottom of the tube, fixed with a washer 10 and a flared (or melted - for a plastic tube) end. The upper end of the tube is connected by a steel wire rod 4 to a lever 5, attached to the armature 6 of relay 7. All contact groups of the relay are removed. The hopper and relay are rigidly attached to the base 8 of the dispenser.
Dry food is poured into the hopper. At this time, the dosing hole in the tube, the diameter of which is equal to the stroke length of the tube, must be blocked by the base of the hopper under the action of the relay armature. When the relay is activated, its armature, through lever 5 and rod 4, moves the tube upward, the dosing hole in the tube opens and through it the food enters the aquarium.

The machine is set up in this order. The resistor R2 slider is set to the upper (according to the diagram) position and the device is placed in the selected location. In the morning, with little lighting, slowly increasing the resistance of this resistor, the dispenser is activated. Next, feed is poured into the hopper and, periodically shading the photoresistor, the tuning resistor R6 is used to regulate the duration of the dispenser operation.

The operation of the device in automatic mode is monitored for two or three minutes and additional necessary adjustments are made.

Rice. 2

Source: Radio No. 5, 1993, p. 33

AUTOMATIC LIGHT CONTROL

The regulators (Fig. 1.2) allow you to perform two functions: automatically maintain a given level of illumination regardless of changes in the level of external illumination and smoothly adjust the specified level of illumination. The noted properties of the regulators make it possible to use them to maintain constant illumination of corridor areas, for photo printing, to set the thermal (light) regime in production and household use(incubators, aquariums, greenhouses, thermo- and photostats, etc. devices).

A light-emitting element (incandescent lamp) with a power of up to 200 W can be connected to the thyristor load circuit by direct current (Fig. 1, 2) or by alternating current - in a break in the network wire.

The operation of the thyristor is controlled from a relaxation RC generator made on an avalanche transistor VT2 (K101KT1). At the initial moment of time, the charge of capacitor C1 is carried out from the positive half-cycle of the voltage removed from the anode of thyristor VS1 through resistor R2 and transistor VT1 (Fig. 1) or resistors R2 and R4 and diode VD1 (Fig. 2). A potassium sulfide photoresistor of the FSK-2 type is connected in parallel to capacitor C1, the resistance of which in the dark exceeds 3 MOhm. Thus, if the photoresistor is in a darkened area (in the absence of optical communication between the light emitter EL1 and the photoresistor R3), the latter almost does not bypass capacitor C 1. When the voltage on the capacitor plates exceeds 8 V, an avalanche breakdown of transistor VT2 occurs and the capacitor discharges to the control electrode thyristor VS 1. The thyristor opens for the current half-cycle of the mains voltage and the mains voltage is supplied to the incandescent lamp. For each subsequent half-cycle of the mains voltage, the process is repeated. Up to 95% of the supplied power is released on the lamp, which is typical for all types of thyristor and triac regulators. If the illumination of the photoresistor is increased, its resistance decreases to 200 kOhm or less. Since the photoresistor is connected in parallel with the storage capacitor C1 of the generator, its shunting leads to a decrease in the charging rate of the capacitor and a delay in turning on the thyristor. As a result, the incandescent lamp begins to turn on in each half-cycle with a delay proportional to the level of illumination at the point where the photoresistor is located. Accordingly, the total illumination is stabilized at a certain (specified) level. Potentiometer R1, included in the emitter circuit of transistor VT1 (Fig. 1) or R2, connected in parallel to the collector-emitter section of transistor VT1 (Fig. 2), are designed to set the maximum level of illumination and allow smooth adjustment of the specified level.

If necessary, the device can be converted into a thermostat operating on a similar principle. When installing the device, the photoresistor should be positioned in such a way that the light from the incandescent lamp does not directly hit the working area of ​​the photoresistor, because otherwise, the generation of flashes of light may occur, the frequency of which the phenomenon (optical feedback) can be used to generate light pulses, determine the distance between the reflective coating and the light emitter/receiver, in various radio-electronic devices.

Source: RL 5/95

IR light switch

Dignity remote control on IR rays (hereinafter simply referred to as IR) we have already experienced everything from our own experience. Remote control has invaded our daily life and saves our time to a sufficient extent. But at the moment, unfortunately, not all electrical appliances have remote control installed. This also applies to light switches. Our industry, however, is currently producing such a switch, but it costs a lot of money, and it is very, very difficult to find. This article proposes a fairly simple circuit for such a switch. Unlike the industrial one, which includes one BISK, it is mainly assembled on discrete elements, which, of course, increases the dimensions, but can be easily repaired if necessary. But if you are chasing dimensions, then in this case you can use planar parts. This circuit also has a built-in transmitter (industrial ones do not have one), which saves you from the need to carry the remote control with you all the time or look for it. It is enough to bring your hand to the switch at a distance of up to ten centimeters and it will work. Another advantage is that the remote control is suitable for any remote control from any imported or domestic radio equipment.

Transmitter.

Figure 1 shows a diagram of a short pulse emitter. This allows you to reduce the current consumed by the transmitter from the power source, and therefore extend the service life on a single battery. The elements DD1.1, DD1.2 are used to assemble a pulse generator with a frequency of 30...35 Hz. Short pulses with a duration of 13...15 μs are generated by the differentiating circuit C2R3. Elements DD1.4-DD1.6 and a normally closed transistor VT1 form a pulse amplifier with an IR diode VD1 on the load.

The dependence of the main parameters of such a generator on the supply voltage Upit is shown in the table.

Upit, V Iimp, A Ipot, mA

4.5 0.24 0.4

5 0.43 0.57

6 0.56 0.96

7 0.73 1.5

8 0.88 2.1

9 1.00 2.8

Here: Iimp is the amplitude of the current in the IR diode, Ipot is the current consumed by the generator from the power source (with the value of resistors R5 and R6 indicated on the diagram).

Any remote control from domestic or imported equipment (TV, VCR, music center) can also serve as a transmitter.

The printed circuit board is shown in Fig. 3. It is proposed to be made from double-sided foil fiberglass laminate with a thickness of 1.5 mm. The foil on the part side (not shown in the figure) serves as the common (negative) wire of the power source. Around the holes for passing the leads of the parts in the foil, areas with a diameter of 1.5...2 mm are etched. The leads of the parts connected to the common wire are soldered directly to the foil of this side of the board. Transistor VT1 is attached to the board with an M3 screw, without any heat sink. The optical axis of the IR diode VD1 should be parallel to the board and spaced 5 mm from it.

Receiver (with built-in transmitter).

The receiver is assembled according to the classical scheme adopted in Russian industry (in particular in TVs Rubin, Temp, etc.). Its diagram is shown in Figure 2. IR radiation pulses enter the IR photodiode VD1 and are converted into electrical signals and are amplified by transistors VT3, VT4, connected in a circuit with a common emitter. An emitter follower is assembled on transistor VT2, matching the dynamic load resistance of photodiode VD1 and transistor VT1 with the input resistance of the amplifier stage on transistor VT3. Diodes VD2, VD3 protect the pulse amplifier on transistor VT4 from overloads. All input amplification stages receiver are covered by deep current feedback. This ensures a constant position of the operating point of the transistors regardless of the external illumination level - a kind of automatic gain control, which is especially important when the receiver is operating in rooms with artificial lighting or outdoors in bright daylight, when the level of extraneous IR radiation is very high.

Next, the signal passes through an active filter with a double T-bridge, assembled on transistor VT5, resistors R12-R14 and capacitors C7-C9. Transistor VT5 must have a current transfer coefficient H21e = 30, otherwise the filter may begin to be excited. The filter cleans the transmitter signal from interference from the AC network, which is emitted by electric lamps. The lamps create a modulated radiation flux with a frequency of 100 Hz and not only in the visible part of the spectrum, but also in the IR region. The filtered code message signal is generated on transistor VT6. As a result, short pulses are obtained at its collector (if they came from an external transmitter) or proportional with a frequency of 30...35 Hz (if they came from a built-in transmitter).

Pulses arriving from the receiver are supplied to the buffer element DD1.1, and from it to the rectifier circuit. The rectifier circuit VD4, R19, C12 works like this: When the output of the element is logical 0, the diode VD4 is closed and capacitor C12 is discharged. As soon as pulses appear at the output of the element, the capacitor begins to charge, but gradually (not from the first pulse), and the diode prevents its discharge. Resistor R19 is selected in such a way that the capacitor has time to charge to a voltage equal to logical 1 only with 3...6 pulses arriving from the receiver. This is another protection against interference, short IR flashes (for example, from a camera flash, lightning, etc.). The capacitor discharges through resistor R19 and takes 1...2 s. This prevents fragmentation and random turning on and off of the light. Next, an amplifier DD1.2, DD1.3 with capacitive feedback (C3) is installed to obtain sharp rectangular drops at its output (when turned on and off). These drops are supplied to the input of the divider by 2 trigger assembled on the DD2 chip. Its non-inverted output is connected to an amplifier on transistor VT10, which controls thyristor VD11, and transistor VT9. The invert one is supplied to transistor VT8. Both of these transistors (VT8, Vt9) serve to light the corresponding color on the VD6 LED when the light is turned on and off. It also performs the function of a “beacon” when the lights are off. An RC circuit is connected to the R input of the divider trigger, which performs a reset. It is needed so that if the voltage in the apartment is turned off, then after turning on the light does not accidentally turn on.

The built-in transmitter is used to turn on the light without a remote control (by placing your palm on the switch). It is assembled on elements DD1.4-DD1.6, R20-R23, C14, VT7, VD5. The built-in transmitter is a pulse generator with a repetition frequency of 30...35 Hz and the amplifier includes an IR LED in the load. The IR LED is installed next to the IR photodiode and should be pointed in the same direction as it, and they should be separated by a light-proof partition. Resistor R20 is selected in such a way that the response distance, when the palm is raised, is equal to 50...200 mm. In the built-in transmitter, you can use an IR diode of the AL147A type or any other. (For example, I used an IR diode from an old disk drive, but with resistor R20=68 Ohm).

The power supply is assembled according to the classical circuit on KREN9B and the output voltage is 9V. It includes DA1, C15-C18, VS1, T1. Capacitor C19 serves to protect the device from power surges. The load in the diagram is shown as an incandescent lamp.

The receiver's printed circuit board (Fig. 4) is made of single-sided foil fiberglass laminate with dimensions of 100X52 mm and a thickness of 1.5 mm. All parts, with the exception of the diode VD1, VD5, VD8, are installed as usual, the same diodes are installed on the installation side. The VS1 diode bridge is assembled on discrete rectifier diodes, often used in imported equipment. The diode bridge (VD8-VD11) is assembled on diodes of the KD213 series (others are indicated in the diagram), when soldered, the diodes are located one above the other (column), this method is used to save space.

Literature:
1. Radio No. 7 1996 p.42-44. "IR sensor in a security alarm."

DOOR TOUCH BELL

The anode circuit of the thyratron includes relay K1 (RES6 passport RFO.452.103), a group of normally open contacts of which is connected in parallel with the self-locking contacts of the music bell relay (or through these contacts they power a regular apartment bell). To eliminate false triggering of the sensor device and spontaneous ignition of the thyratron, a parametric voltage stabilizer was introduced, made on the VD1 zener diode and the short-circuit ballast resistor. The constant supply voltage of 170 V remains unchanged when the mains voltage fluctuates from 180 to 250 V.

Sensor E1 in the form of an aluminum rivet, resistor R1 (it can have a resistance of 1 to 10 MOhm) and a thyratron are placed in a small housing mounted on the outside of the front door. To control the response of the sensor, a hole is drilled in the housing opposite the thyratron. The moment you touch the rivet button, the thyratron flashes brightly.

Setting up a sensor device comes down to setting the variable resistor R5 to a voltage of 170 V on the oxide capacitor at a minimum mains voltage (180 V) - such voltage can be supplied, for example, from an autotransformer.

The established device should be connected to the network in strict accordance with the diagram after identifying the neutral and phase wires.

Source: RADIO No. 6-90, p.77.

Capacitive relay

Security alarms, switches for household devices, control sensors on a production line - these are just a small part of the scope of application of this capacitive relay. It can be used, for example, in the simplest household automation: sat down in a chair - the floor lamp turned on, music started playing, the fan started working, etc. In a word, the scope of application of this relay will be suggested by the imagination and creative thought of the radio amateurs themselves.

The range of the relay depends on the accuracy of the setting of capacitor C1, as well as on the design of the sensor. The author’s maximum distance to which the relay reacts is 50 cm.

The schematic diagram of a capacitive relay is shown in Fig. 1, and the design of the inductive coil with its placement and the sensor on the board is shown in Fig. 3.

Coil L1 is wound on a multi-section polystyrene frame from the circuits of transistor radios and contains 500 turns (250 + 250) with a tap from the middle of the PEL-0.12mm wire. Winding - in bulk.

The sensor is installed perpendicular to the plane of the printed circuit board. It is a piece of insulated mounting wire from 15 to 100 cm long, or a square made of the same wire, with sides from 15 cm to 1 m.

Capacitive relay

The automatic device can be used in various models, toys, which will change their movement when encountering obstacles, as well as in everyday life (for example, when I sat down in a chair, the light in the floor lamp came on, music started playing, the fan started working); to turn on the light in rooms (corridor, room, pantry); for car alarms.
This device within a radius of 4-5 m it does not create interference, has small dimensions (85x30 mm), is powered by a DC source with a voltage of 9-12 V, consuming a current in the initial state of about 7 mA, and when the relay is activated - up to 45 mA.
The schematic diagram of a capacitive relay is shown in Fig. 1. A low-power generator with an operating frequency of 465 kHz is assembled on transistor VT1, and on triode VT2 there is an electronic switch for turning on relay K1, the contact system of which connects the actuator. Diode VD1 protects the device from accidental changes in the polarity of the connected power source.
The range of the capacitive relay, that is, its sensitivity, depends on the setting of capacitor C1 and the design of the sensor, and reaches up to 50 cm.

Rice. 1

A piece of insulated wire 1.5-2 mm long, 15 to 100 cm long, or a square or square grid made of wire with a side of 15 to 100 cm is used as a sensor.

The sensor and the printed circuit board are located in close proximity to each other, and the wire or antenna plane is installed perpendicular to the printed circuit board area. The “minus” of the power source must be connected to the housing (metal) of the structure in which this capacitive relay will be used.

Resistors, diode and coil L1 are installed vertically on the printed circuit board.

The parameters of the radioelements used in the device are not critical. The tuning capacitor is KPK-M, but another type can be used with a capacitance variation interval from 3 to 30 pF. Oxide capacitors C2-C4 are used grade K50-6, but other types can be used, you just have to modify the topology of the printed circuit board for them. Capacitances C2, C3 - from 20 to 30, C4 - from 50 to 1000 µF.

Diode D226 can be with any letter index. You can also use another semiconductor device designed for forward current up to 100 mA. Transistors: VT1 - field-effect, brand KP303, VT2 - bipolar p-n-p type MP40 brand with any letter indices. Instead of the latter, the P13, P14, P15, P16, MP39, MP41, MP42 series with any letter indices are also suitable.

K1-relay RES10 (passport RS4.524.303). Instead, you can connect a small-sized electric motor for toys.

Resistor R1 - any type with a resistance from 6.8 to 7.5 MOhm. R2 - from 820 kOhm to 1.1 MOhm. The value of resistor R3 is selected in the range from 0 to 30 Ohms, depending on the operating current of the relay or electric motor.

It is best to power the device in stationary conditions from a 9 V mains rectifier rated for a current of up to 100 mA.

Setting up. Connect the sensor and a 9-12 V DC source to the board, observing the polarity. Using an insulated screwdriver, set the rotor of capacitor C1 to the minimum capacitance position (6 pF) - the relay will operate. Then slowly rotate the C1 rotor in the direction of increasing capacity until K1 turns off (when setting C1, try to stay as far as possible from the sensor).

By bringing your hand to the sensor, test the sensitivity of the capacitive relay until it triggers itself (the smaller the capacitance C1, the greater the sensitivity of the device).

The bell (Fig. 8.1) consists of two generators: a tone generator made on transistors VT3 and VT4, and a symmetrical multivibrator on transistors VT1 nVT2. The output of the multivibrator is connected to the tone generator through resistor R5, so it will periodically be connected to the common wire (minus of the power supply), that is, in parallel with resistor R7. In this case, the frequency of the generator will change abruptly: when transistor VT2 is closed, the sound of one tone will be heard from head BA1, and when closed, another tone will be heard. The SZ capacitor smoothes out the steep edges of the multivibrator pulses, which lead to unpleasant tones in the ringing sound.

Rice. 8.1. Two tone call

Rice. 8.2. Printed circuit board of a two-tone ringer with placement of elements

The tone of the sound is affected by resistors R7 and R5 and capacitor C4. For the tone switching frequency - resistors R2, R3 and capacitors C1, C2.

In Fig. Figure 8.2 shows the topology of the printed circuit board and the placement of elements. The resistors and capacitors used in the design can be of any type, small-sized. For example, you can install polar capacitors K50-35, the rest K10-17, resistors MLT-0.125.

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