Scavenging a PC monitor auto-shutdown circuit?

[Ummon]

Originally, this was in Main but there was no response, so I'm trying here.

PC monitors have an auto-shutdown when out of sync or when no signal is being sent. Is this a simple circuit and could it be easily scavenged and incorporated into an arcade monitor set-up?

[SirPeale]

I would think it wouldn't be easy, if fact next to impossible to scavenge this from a VGA monitor.

[SavannahLion]

I would think it wouldn't be easy, if fact next to impossible to scavenge this from a VGA monitor.

In any case, the work extracting said circuit would probably be more than the work constructing and designing your own circuit.

There are dedicated IC's that can determine whether a signal exists ( but not if it's out of sync that I'm aware of ) and there are a couple of circuit designs using very small microcontrollers dedicated to monitoring for a signal which can probably be modified to search for out of sync signals as well.

[Nado]

it would probably be easier to use i signal from you source ie computer/psu to trigger a relay to switch the monitor power on/off
just a thought 

[richms]

That wont turn the screen off then the computer is idle however.

There is a sync detector on some of the VGA to jamma solutions, if you are using one of those then you may be able to start with that, and get the sync and run it into a timer (make sure its retriggerable) that has a greater then 1/50th of a second time. I would want a few seconds of holdup for when the vga card changes modes.

Anyway, take the output of the timer to a solid state relay thats able to switch the mains supply to the monitor. Job done.

If you don't have a sync detector already, then there are many circuits out there, you may not need one however if you have seperate horizontal and vertical sync signals going to the monitor, just have to watch the idle polarity of them when the PC has gone to powersave mode, I cant remember if they go high or low...

[payment_due]

Have you checked the wiki or the faq?

[Ummon]

Have you checked the wiki or the faq?

Not recently. I have no idea where in the wiki someone might put something like this....though I did a quick check in monitor/video and saw nothing. Nothing in the faq (no surprise as it's more about arcade monitors). Have you seen something on it somewhere in the wiki?

[MonMotha]

It is fairly trivial to program a small microcontroller to do this.  That's what many of the PC to JAMMA adapters do to handle "sync out of range" detection.  An output that could drive e.g. a relay or SSR to just shut the thing off wouldn't be hard.

I'd offer to whip something up, but given how busy I seem to be, it could easily be several months.

If you just want to determine if there's a sync signal present (but not if it's too fast and could pose a hazard to your monitor), you can just build a "leaky integrator" and comparator and drive your relay with the comparator output.  This is two op-amps and could possibly collapsed into one.  Personally, I find the digital solutions easier, but the analog methods don't require writing code and putting the program on the chip - just build and go.

[Ummon]

Actually, I think gatordad created an app recently that does this - I have it, I just don't remember if he made it.... - but I haven't put together a circuit. And then I thought maybe I could salvage something that's actually made for that.