Z wave relay to turn on computer by bridging pins on the motherboard?

Has anyone figured out how to start up a computer using a z wave relay? The power button on the outside of pc cases just shorts the two pins on the motherboard.

I have a media server running UnRAID and its hooked up to a ups, so if the power goes out for longer than about 45min then the server does a clean shut down, but will not restart itself. I dont want to change the bios to always turn on when power returns because it could make a boot loop where the ups tells it to shut down because its below the battery threshold, but once it shuts down the bios will tell it to kick back on.

They make the piKVM but they are pricey (like $300).

I'd first look at other options your BIOS might offer such as wake on LAN, etc. Could be something clever in software you could do without the soldering.

Or maybe use the option to start up on power restore, but put it on a smart plug that cuts the power when the UPS power drops.

However, any smart relay could do it. I'd consider a Zooz ZEN16 but that is overkill since it gives you three relays.


I'll look into the zooz zen16.

Id rather not do wake on lan, i did think about putting a smart plug in the mix but there's gotta be a better way.

that relay and something like this should work

How are you monitoring the UPS status? I use similar automation, but I'm only looking at the battery % of the UPS is the status is on battery and not mains. If it's on mains, then the battery level wouldn't matter. This prevents your concern.

I use Wake On LAN (WOL) to turn on my computer when I sit down in my office chair. It works very reliably. I have a pressure sensor under the seat cushion, which is hard-wired to a contact sensor. I removed the magnetic reed switch, and just soldered the pressure sensor leads to the board. WOL has been working very reliably. I also use the "Office Chair Contact Sensor" to make sure the office lights do not turn off when the PIR motion sensor does not see me move for a while.

In any event, WOL really is a decent solution assuming your motherboard supports it.


I can see on my server the ups stats, i dont have any way to view it through hubitat.

Which UPS do you use?

im using a cyberpower CP1350PFCLCD

Thats a pretty cool solution.

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You can setup NUT on your server and use this integration to get the UPS data in HE.


I don't understand that part:

If the computer shuts down, why would the bios tell it to kick back on before there is a power recovery?

My computer is setup to turn back on when power comes back. If I shut it down, it will stay off even if there is power on the circuit. I would need to toggle the power off and on to make it start again (instead of using the on button).

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You just need to set your BIOS to turn on when power is applied. I have been using this setting for decades. No need for any outside devices.

Im afraid it would make a boot loop, the ups would still provide power to the PSU in the server after it shut down, so it would boot back up....then the ups would tell it to shut down.....over and over.

If the UPS is turning the computer off via a usb/serial connection, can't it also turn it back on?

That doesn't happen unless there is an issue with the motherboard itself. I mean, lets suppose the UPS wasn't there and you were plugged into the cataleptic directly. You would never be able to shut down the pc for anything because power would always be applied. That is not how that setting works. It monitors for power change. So if there is no power to the unit and power is restored, the mainboard monitors the change. It doesn't shut down and then says, oh, I still have power, I need to start again! The ups tells windows/mac/linux to shutdown and the pc shuts down and then waits. So unless the UPS completely dies from running out of battery power the change never happens and the pc will remain as is. It will not go into a boot loop. Even in corporate enviroments I keep this setting turned on in case of power failures and not once when servicing a unit have I had a pc turn on after shutting it down while connected to power.

Thanks! I might give the bios change a try. Unclean shutdowns are pretty bad and trigger a 2 day process for my unraid server, so i'm really hesitant to mess around with it too much.

I guess i really need to look at my ups, and see if after it sends the command to preform a clean shut down, does it still provide power to the server. I could use a kill-a-watt and see.

They do. Kind of another reason to also have WOL implemented. Say your threshold is 15% battery. You hit that and the UPS commands the server to shutdown. It's still providing power to the server though, so if power is restored before the UPS battery is depleted, then the power cycle does not happen that triggers the BIOS to boot the server. In that case, you'll want something like WOL to automatically start the server back up.


:point_up: This is the way! :wink:


I'm not ultra familiar with WOL, but in my case being a media server....if someone other than myself tries to access the server remotely (via Plex) then it would fire up the server even if the power were not restored yet?

Thats my only worry with WOL.

I think i would rather have control to see if power is out when i'm away, i can control when the server starts up.

No, that is not how WOL works. True WOL requires a special WOL network packet to turn on or wake a system. The feature has to be supported in the BIOS of the device, to allow another system on the network to wake it up.

Here is thread where WOL was discussed years ago...