VGA pinout. How to make a long VGA cable from a Category 5 network cable? VGA-SCART pin assignments

I built a gazebo in the yard. There is a place to sit with friends, but there is an inconvenience: I want to watch TV in the fresh air. I don’t have a portable TV, the system unit has a TV tuner, but I won’t carry the system unit and monitor back and forth. The obvious solution is to buy a VGA cable extension, but the maximum length of such a cable is 5 meters, and 15 meters to the gazebo. After rummaging around on the Internet, I found a simple solution. Since in a VGA cable with 15 contacts, it is enough to use only 8 for signal transmission, just the number of conductors in the “twisted pair”.

Here is a wiring diagram for the extension cord for the monitor:

The patch cord (cable) for connection is used direct (not cross) categories 5E or 6. On the Internet there is a version of printed circuit boards for this device, but it did not fit my parts, so in the archive on the forum there is my version of printed circuit boards in the format * .lay.

To minimize the size of the board, I used SMD resistors with a nominal value of 0 Ohm, that is, jumpers. Photo of finished extension boards.

I use these adapters with an Ethernet cable 15 meters long at a monitor resolution of 800*600, frequency 85 Hz, without visible distortion. I attach a screenshot of the desktop shown through the extension cable for the monitor above. The material was sent by R. Alexander.

— an adapter that allows you to connect the video output of your computer to a regular color TV. Below we will look at several options for such an adapter, describe the pros and cons of each design, and provide tips on making a VGA SCART adapter with your own hands.

Before we begin, one important clarification: all advice and instructions in this manual are provided “as is” and are used at your own risk.

VGA-SCART pin assignments

To understand the functioning of the following VGA SCART adapter circuits, let's look at the different types of signals that need to be transmitted from the computer to the TV.

RGB signal

The main signal that is transmitted via cable from the computer to the TV is an RGB signal divided into three components (R-red, G-green, B-blue). Fortunately, in this case, the standard and SCART connector are fully compatible (outputs: amplitude 0 .7V, resistance 75 Ohm). Therefore, you can directly connect the corresponding contacts without resorting to the use of special circuits or devices (we will consider this option later).

Common wire

VGA and SCART connectors have several pins connected to a common wire (ground), which are often connected to each other inside the cable. Their common connection makes it possible to eliminate various interferences (especially in relation to the three RGB lines). The same applies to shielded cable.

Note: there is essentially only one common wire, so it is normal that all contacts marked with ground are connected together.

Signal Audio

In order to output sound to the TV, you need to take a cable with a standard 3.5 mm connector for a PC and connect it directly to the SCART connector. You can output both mono and stereo sound without resorting to the use of special devices and circuits. Just be careful not to confuse the audio output with the audio input, since SCART has them next to each other.

Switching signals

As mentioned earlier, the SCART input can accept different types of signals. In order for the TV to understand what type of signal is supplied to the input, there is a special “RGB Blanking” contact (pin 16). If a voltage of 0...0.4V is applied to this contact, then the TV will expect a “Composite signal”; if 1...3V, then the signal will be “RGB”. The use of this type of signal is extremely important for the functioning of the VGA-SCART adapter, and as we will see later, there are various ways to obtain it.

Another pin that might interest us is “Swtch” (pin 8). This pin is intended for switching TV/AV mode. Also on some TVs, this pin allows you to set the aspect ratio of the image:

• TV mode - from 0 to 2 V.
• AV mode with 16:9 ratio – 5 to 8V.
• AV mode with 4:3 ratio - 9.5 to 12V.

If we do not send a signal to this pin, the TV will remain in its default state (TV mode), and then to switch to AV mode we will need to use the remote control.

Synchronization signals

This is where the most difficult part about building a VGA-SCART adapter begins. The synchronization of signals on a computer's video card is very different from the synchronization system that is used in a regular TV, so you need to resort to some tricks to make them compatible. The difference between most VGA-SCART adapter circuits is based on ways to solve this problem.

In a computer, standard VGA uses two different signals for synchronization, one vertical (60 Hz) and one horizontal (31 kHz). Both signals operate according to TTL logic and hence have a peak value of 5V. Finally, the signals can be either positive or negative depending on the video operating mode used.

However, the TV only needs one composite sync signal with a peak value of about 1...3V. Also, the horizontal frequency is much lower, about 15 kHz (vertical, but 50...60 Hz is almost the same). Finally, the signal should always be negative.

The main problem we face is horizontal synchronization. Assembling a circuit for this transformation is quite a difficult task. In this case, as a rule, changes are made to the signal source itself (video card), using special software or even a modified VGA (like the famous ArcadeVGA) to directly obtain 15 kHz at the VGA output. We will consider this question further.

Receiving a 15 kHz clock signal using software

As mentioned in the previous section, the solution to the main task when building a VGA SCART adapter is to obtain a horizontal sync signal at 15 kHz. As a rule, the solution is achieved by changing, mainly in the field of software, the settings of the video card of the personal computer. In addition, the synchronization signals must be negative, i.e. with a constant level of up to + 5V, which goes to zero during the pulse itself.

Soft-15kHz program

This interesting software for Windows XP/Vista, created by a German programmer, allows you to obtain a negative 15 kHz clock signal in a very simple way. It is compatible with most video cards and is very easy to use.

Its only drawback is that while the operating system is starting, the signal from the video card remains at 31khz, so you cannot see anything until the end of Windows loading. Using the Soft15khz program is quite simple: after downloading, simply unpack the rar archive with the program and run it (no installation required), then click on “Install 15kHz” and restart your computer.

(1.4 Mb, downloaded: 2,317)

This is powerful software for editing all video card parameters, including obtaining a 15 kHz clock signal. The program is not free, although it can be successfully used in the shareware version (the only drawback in this case is the presence of a splash screen that lasts about six seconds upon startup). You can download the PowerStrip program from the official website.

Receiving a 15kHz clock signal in hardware

Let us now turn to the study of various VGA SCART adapter circuits, ranging from the simplest to the most complex. Let's start with the pinout of the VGA and SCART connectors:

Basic circuit with composite timing (ATI RADEON video cards only)

• pros: Easy to implement, does not require any special components.
• Minuses: Requires external 5V and 12V power supply, only works with certain ATI Radeon video cards.

Basically, three RGB lines are used (VGA pins 1, 2, 3) connected to the corresponding SCART pins (pins 15, 11, 7). It is also necessary to connect the common wires of each channel (of course, one common wire is enough, but for high-quality shielding it is better to use all of them). To do this, the VGA pins (6,7,8) must be connected to 13, 9, 5 SCART.

Note: these connections are always the same in all adapter circuits. The dotted brown wire that connects pins 10 VGA and 17 SCART is the common sync signal wire. The black wire connects the shielded cable sheaths of both connectors. And finally, the brown wire that goes from VGA pin 13 to SCART pin 20 transmits the composite clock signal.

ATTENTION: In order for this VGA SCART adapter circuit to work, it is very important that the video card supports the clock signal mode on pin 13, which is usually absent in most video cards and only some video cards belonging to the ATI RADEON family can support this mode of operation.

Receiving a clock signal using diodes and resistors

• pros: Works with any video cards, the function is turned on by an external signal.
• Minuses: Requires external 12V power supply.

Let's look at the first adapter circuit. In this case, the connections of the lines R, G, B and ground are the same as in the previous diagram. The circuit allows you to use a regular video card (not generating a composite video signal). The clock signals from VGA pins 13 and 14 are mixed in a circuit of diodes and a 330 ohm resistor, and then sent to a regular 20-pin Scart.

Using a bipolar transistor to mix the two clock signals ensures good image quality.

Instead of using an external power supply, the 5V voltage is taken from VGA pin 9. True, not all video cards are capable of providing this voltage, especially older generation cards. In any case, all the latest VESA 2.0 compatible models should be fine. In this circuit, pin 8 is supplied not with 12V (to enable AV mode), but with 5V. If the TV supports aspect ratio switching mode at 5V, the aspect ratio will be 16:9 instead of 4:3.

Adapter based on 74HC86 chip

• Pros: Excellent quality and compatibility (works with any video cards)
• Minuses: Definitely one of the most complex schemes.

The VGA SCART adapter circuit is based on the 74HC86 integrated circuit (four XOR gates). An external 5V power supply is also required. The signals are mixed using exclusive OR elements, the output of which is a composite signal of excellent quality. The adapter works with any TV and provides a negative signal at a frequency of 15 kHz.

Those who own a significant amount of audio and video equipment are faced with a choice: make it yourself or purchase an adapter from the store that will convert signals of different types. Needless to say, factory devices cost a lot, but you can often do without them. And within the article we will talk about how to make a VGA to RCA adapter. Frequently asked questions will also be answered.

What is a VGA RCA adapter

The circuit of this device may seem complicated, but only until you understand it. What is this device? This is an adapter from tulips (RCA connectors) of analog video output to VGA D-Sub for 15 pins. The device reviewed here can be used to connect a DVD player or satellite tuner to a multimedia projector. Of course, provided that it is not possible to work directly using the same type of cable, which is usually common in cheap or outdated devices.

What is the idea?

How to implement such an idea? You need a computer cable (twisted pair type CAT5/CAT5e) designed to transmit video signals. We will use it because the transmission is carried out over a distance of fifty meters without loss of quality.

First, we need to acquire three RCA connectors and one D-Sub15 pin (this is a plug), as well as a twisted pair cable. The last part is better to use shielded STP than UTP. But this one is more difficult to get, which affects the price. Therefore, the issue of possibilities and desires is considered here. There is no particular difference between the elements, but there is one nuance: it is better to use UTP if the cable length is less than 10 meters. If the distance is greater, then it would still be better to find STP.

Pinout

How to pinout a 15 pin D-Sub connector? The numbers go from left to right:

1 - R-Y (Pr).
2 - Y.
3 - B-Y (Pb).
4 - Ground - Brown.
5 - Ground - Wht\Brown.
6 - Ground R-Y (Pr) - Wht\Red.
7 - Ground Y - Wht\Green.
8 - Ground B-Y (Pb) - Wht\Blue.
9 - Not needed.
10 - Ground.
11 - Not needed.
12 - DDC DAT.
13 - Horizontal Synchronization.
14 - Vertical Synchronization.
15 - DDC Clock.

For the VGA RCA adapter cable we need six pins out of the fifteen presented. How to properly wire connectors and contacts? Check out this picture and you will understand how and what to do.

So let's see what happened. If everything was soldered correctly, then you now have an adapter that can supply a video signal to VGA D-Sub on the 15 pins of the projector. You can see approximately what the final product should look like in the photographs presented in the article.

Examination

Wire pairs with RCA plugs soldered at the ends can be usefully compressed with heat shrink to obtain greater rigidity. In general, now you can connect the result of your work and enjoy it (if everything was soldered together as needed). Paired wires, at the ends of which RCA plugs are attached, can be crimped with heat shrink to obtain greater rigidity.

In this case, we used a satellite tuner with a 3 RCA component video output as a signal source and a Sanyo multimedia projector, which did not have a separate video input of the same type. If at the moment it is not possible to verify the functionality of the resulting adapter, then you can only carefully inspect the entire structure and make sure that there were no omissions, and everything is soldered as indicated in the article.

What you need to understand

You should be aware that the adapter in question can ensure the operation and full functioning of a device that has a VGA video input only if it can automatically detect the type of incoming video signal. An indicator of this will be the ability to select the mode in which data will be transmitted to RGB/YPbPr. Usage will be positively impacted by sending these types of signals. Why is that?

The fact is that RGB and HV.sync (for example, data coming from the output of a personal computer’s video card) are converted to RGB, which has sync pulses in the green channel (Y). It, in turn, turns into the color-difference YPbPr. And as a result, we can conclude that these signals are not the same thing, although they can convey the same information. Therefore, carefully study what a VGA RCA adapter looks like.

FAQ

Based on the data presented in the article, it can be assumed that readers have some questions. However, this is not the first time such a topic has been raised, so such information can be found without difficulty. We found out how to make a VGA RCA adapter with your own hands. Now let's look at its possible improvements.

What adapters can be made using twisted pair?

• VGA extenders are special cables that have D-Sub 15 pin connectors on both ends, while their input and output use the same technology.
• RCA (3xRCA) is used to transmit component video signals. There are three connectors at each end. Used when working with a DVD player and TV.
• RCA (D-Sub15pin) was discussed a little higher. Here are the components Y, Pr, Pb in VGA.
• To transmit analog audio, two pairs of stereo signals can be used simultaneously (4 RCA connectors at each end).

Why is a free Brown-Brown/Wht pair needed?

It can be used to transmit mono audio from a DVD player when there is an audio input on a multimedia projector (assuming it has speakers). Otherwise, it would be better to cut this pair and insulate it. Therefore, you should carefully consider the aspects and how the VGA RCA adapter will be used.

How can I make a Scart VGA adapter?

If the video source has a full Scart video output, then such a device can be made without problems. To do this, pinout the contacts is carried out as follows (outputs first):

• 7 - blue;
• 11 - green;
• 15 - red.

Now the ground:

• 5 - blue;
• 9 - green;
• 13 - red.

Otherwise, everything is done as previously described in the article.

Conclusion

Any final words? Carefully study the presented drawings and mentally imagine in detail what and how you will do. During work, exercise extreme caution and attentiveness - after all, if you miss the grounding, the consequences will be quite sad and very negative. The result is not VGA RCA for equipment, but the need to buy a new device for video playback. But if everything works out, then connecting a computer, projector, TV and many other devices will not be a problem now. The main thing is to make sure that all the pins are connected to the required outputs, and no incidents will happen.

But at the same time, we can raise the question of the profitability of assembling this adapter. The fact is that you can buy it for 100-150 rubles, which is not a high price. Time spent creating an adapter on your own will end up costing more in the long run. The only acceptable option is if everything is already there, and you just need to make this device. From a purely amateur point of view, such experience can be valuable if one has an eye on work closely related to the restoration and creation of similar devices in the future.