VGA/SCART/Audio Automatic Switch
This circuit is designed to go between the video card and computer monitor. Everything will work as normal until TV freq video detected - then the audio and video are switched to the TV. Primarily for watching (divx,xvid,etc) video but it's also good for games, emulation and annoying anyone watching TV..
PCB Layout - at 600dpi
PCB Component Overlay
Autotrax PCB file
Hex for the PIC µC and the asm
source
The PCB is 102*57mm and should (just) fit into one of those 130x68x42 plastic boxes. The circuit uses pretty standard parts that should be available at any decent electronics shop. The relays have a "mini fujitsu" footprint - the closest thing I could find to a standard. Most shops have 'em, if not in 12v then in 5v (or 6v).
If using video resolutions higher than 1024x768 there may be some ghosting on the VGA monitor. Maybe this can be reduced by using thin coax (like the type inside a monitor cable) to connect the VGA out socket to the PCB.
I've changed the board layout slightly since this one was made. The audio coupling caps are bent over IC4, there's not much room for them otherwise.
SOTWARE
The best software to run Windows at TV frequencies is EnTech's PowerStrip. There's a couple of guides to
using power strip for this purpose here
and here. It's written for ATi Radeon cards but the info applies to almost all modern video cards.
The ideal setup is two PowerStrip shortcuts, one to switch into into a TV mode and one to
switch out of it.
For DOS or Linux drivers have a look at Tomi Engdahl's VGA to TV converter page.
3/7/04