Component list
C1 22 uF 10V electrolytic
C2 22 uF 10V electrolytic
R1 2.2 kohm
R2 2.2 kohm
U1 74LS86 or 74HCT86
Connecting VGA to Sync-on-Green monitor
Some monitors use sync-on-green syncronization instead of separate sync. In that case you can't used my circuits
directly. You have to modify those circuits to add Sync-on-Green capability. Generating sync signals to screen
picture component is quite easy. I have not had any need for such a circuit, so I haven't designed such option.
Check this article to get the idea what to add to my circuits. For more complete explanation how to deal with sync
on green monitors, check the Sync on Green FAQ.
Building the circuit
The circuit is quite simple to built if you have basic skills in building electronic circuits. The electronics of the circuits
can be easily built to a small piece of veroboard so no special circuit board is necessarily needed (I used this
approach in my prototype). I have designed a circuit board for my VGA to TV converter and this same PCB design
(GIF picture scanned at 300x300 dots/inc resolution, also available in zipped postscript file format) and component
layout can be used with this project also. Note that there are some differences in connection of the IC U1 pins in
PCB compared to the schematic, but the circuit built to this PCB fuctions in the same way.
The circuit need well-stabilized power +5V power source (+/- 5%). The circuit takes less than 150 mA current, so
you don't need a large power supply. If you don't have anythign suitable avalable, you can always use a small
general purpose wall transformer and a small +5V voltage regulation circuit. Another option is to take the +5V
power from PC using methods explained in my How to get power from PC to your circuits document.
The wiring should be made carefully and 75 ohm coaxial cabling for picture signals should be used everywhere,
especially if you are going to use this circuit with a high resolution monitor. Signals reclections caused by bad
wiring can really mess up your picture quality. I would recommend using metal box, shielded cables and shielded
connectors for circuit to keep noise and radio interference minimum.
VGA to RGBS converter component list
U1 74LS86
C1,C2 22 microfarads, 16V
R1,R2 2.2 kohm, 1/4 W
R3,R4 1.8 kohm, 1/4 W
R5 2.7 kohm, 1/4 W
R6,R7,R9 47 ohm, 1/2 W
R8 120 ohm, 1/2 W
T1,T2 BC547B
P1 15 pin SUB-D connector
(20 Seiten)
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