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Putting a monitor to sleep when no video signal
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soldar:
I have two 22" Philips 22PFL2807H TV/monitors. They are primarily supposed to be TV receivers but I use them mainly as FHD computer monitors. One I use with VGA and the other with HDMI.

The problem is that when the computer goes to sleep after no activity, I expect a monitor to go to sleep when it receives no video input but it does not do that, instead it just displays "No signal from PC" and I have to turn it off manually.

I do not imagine any easy solution that would turn off the monitor when the computer sends no video signal. And any possible solution cannot involve just cutting the power because when it comes back the monitor goes to standby mode and has to be turned on anyway.

To make matters worse the monitor has no easily accessible buttons so it would have to be turned on and off using IR remote.

So I am thinking if there is an easy way to

(1) detect video (or perhaps I could detect mouse/kb activity)

And then have a timer that would

(2) send IR code to monitor to turn it off.

Initially, to me, it sounds like too complicated to be worth the effort. It might be easier to just live with it and turn them off with the remote, which is what I do. But sometimes I forget.

ataradov:
The cleanest solution would be to make a simple USB device that implements low power mode. When the OS goes to sleep, it would send the device into low power mode, which in turn would activate the IR remote.

It is not a huge project, but still a project.
soldar:

--- Quote from: ataradov on February 05, 2024, 09:01:39 pm ---The cleanest solution would be to make a simple USB device that implements low power mode. When the OS goes to sleep, it would send the device into low power mode, which in turn would activate the IR remote.

It is not a huge project, but still a project.
--- End quote ---
I had not thought of that but after thinking about it I do not think it would do what I need because my computer is not really "going to sleep" but rather just turns off the video to the screen after a programmed amount of time. It was a good idea though.

If there was a way to enable or disable a USB device when the video was turned off I think that would work but I think the only practical way to detect when video is off would be via software and that is way over my head.

In VGA I believe the sync signal is dead when there is no video and that would not be too difficult to detect but it would require tapping into the vga cable. I think a high impedance tap into the V_Sync wire would work to detect no video state. The next part would be to simulate the IR pulses or to physically press the remote control button.

I don't understand why or how Philips would make a monitor that would not go to sleep on its own.
EPAIII:
With VGA, video detection is fairly simple. The sync signals are available on the VGA connector and you can use a CMOS inverting buffer with feedback to establish an amplifier with 5X - 10X gain to bring them up to logic levels. The high impedance of the CMOS chip will not degrade the sync signal(s). Then a pulse detector and you have it. Dare I suggest a 555?

HDMI, being digital, is a bigger challenge. But a quick search shows HDMI to VGA converters are available a dirt cheap prices. You don't need super quality for video detection, just a way to access that sync signal mentioned above.

If you need to go the IR remote way, there are universal IR remote transmitters that can learn the codes needed for any device. Again, they are dirt cheap. But a simple power relay would probably be OK to turn them off and it appears you are turning them back on again manually anyway.
ebastler:
Most TVs have a "auto-off timeout" feature. It does not do quite what you need -- just switches the TV off if no button has been pressed (or remote control command received) for a time you can set.

If you just want to ensure that the monitor does not run overnight or even over the weekend, simply setting a long timeout of several hours might be good enough. Or you could flip the remote-control scheme around: Set a relatively short auto-off timeout, and let your computer send "keep-alive" IR commands regularly via a background task. Or build a microcontroller gadget which monitors activity of an external keyboard or mouse and sends IR commands to the monitor.
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