Power on computer after mains power restoration

[roeften]

Hello,

I have a computer connected to a UPS in my closet

The computer is turned off properly on power failure (via the UPS software). However the only way to power it up after power restoration is to press the power on button.

Please note that the computer is turned off before the UPS battery gets empty. So UPS power may or may not fail (that rules out the use of BIOS settings to power up computer).

I would like to know if there is a device (relay?) that I can connect to the mains (directly, not the UPS) and signal the power on. The device should short circuit the motherboard's power switch pins momentarily when AC is restored, simulating the push-to-make switch.

Is there such a solution? If you can suggest alternatives please do.

Cheers

 

[Softus]

Which OS are you using - could you utilise the Wake-on-LAN feature?

 

[roeften]

Which OS are you using - could you utilise the Wake-on-LAN feature?

I am using Linux, and yes both the hardware & the software allows me to use WOL. I will use this solution if I have no alternatives. I was looking for something completely automated.

Thanks for your input.

 

[Softus]

I was looking for omething completely automated.

OK - so just schedule a task on some remote computer and run a script that sends the magic packet.

 

[roeften]

I was looking for omething completely automated.

OK - so just schedule a task on some remote computer and run a script that sends the magic packet.

This is not a bad idea, I could use diskless computer running a live cd so that the file system will not get corrupted. And use power up after failure option in the bios.

If I do not find the relay thingy I will probably follow your advice.

Cheers.

 

[Softus]

I could use diskless computer running a live cd so that the file system will not get corrupted. And use power up after failure option in the bios.

I like that idea, and it sounds like fun, but I was thinking of something with far less effort, which is any computer anywhere that's capable of running a script at a pre-defined interval of, say, 30 minutes. The script sends the packet over t'Internet and a router sticks it to the slumbering machine's NIC.

 

[plugwash]

you could just use a small relay with its coil connected to a cheap wall wart, make sure the voltage of the relays coil matches the wall wart and your good to go.

there is one problem with this however. It will cause problems if the mains goes away and comes back before the ups initiated shutdown finishes so you need a second relay which monitors the PCs 5V line and inhibits the output of the first relay when the system is already on.

make sure you use protection diodes (use a shotkey rectifier diode) connected in paralell with the relay and connected so they will be reverse biased (off) when supplied by the incoming power (theese diodes are to protect against negative voltage surges when the supply turns off)

 

[roeften]

you could just use a small relay with its coil connected to a cheap wall wart, make sure the voltage of the relays coil matches the wall wart and your good to go.

there is one problem with this however. It will cause problems if the mains goes away and comes back before the ups initiated shutdown finishes so you need a second relay which monitors the PCs 5V line and inhibits the output of the first relay when the system is already on.

make sure you use protection diodes (use a shotkey rectifier diode) connected in paralell with the relay and connected so they will be reverse biased (off) when supplied by the incoming power (theese diodes are to protect against negative voltage surges when the supply turns off)

Excellent idea, thank you!

 

[Softus]

Strange use of the word excellent.

Mind you, why use existing technology when you can whip out the soldering iron? Better still, couldn't you rig up a mobile phone connected to a robotic arm that presses the power button when you phone it up?

 

[roeften]

Strange use of the word excellent.

Mind you, why use existing technology when you can whip out the soldering iron? Better still, couldn't you rig up a mobile phone connected to a robotic arm that presses the power button when you phone it up?

Well his idea was exactly what I was looking for from the beginning. Of course I was looking for a commercial product but after emailing RS the expectation kind of faded away.

And I think that by getting an extra input voltage into the circuit from the mb I may even monitor if the PC is on or off and close the circuit or not.

And it will cost a few euros compared to an existing technology solution (using a sacrificial lamp PC... otherwise how will it turn on to send the WOL packet?)

The mobile phone with arm idea sounds also appealing

 

[Softus]

Well his idea was exactly what I was looking for from the beginning.

Eh? I thought you were looking for a solution to a problem, not just a specific solution because you wanted to fiddle around with some components.

And it will cost a few euros compared to an existing technology solution (using a sacrificial lamp PC... otherwise how will it turn on to send the WOL packet?)

I think you're now way off kilter. Why can't you use any computer (cost=nothing), anywhere you like in the entire world, to send the WOL packet? And why would the machine need to be "turned on" - that's the whole point of WOL.

The mobile phone with arm idea sounds also appealing

Well I hope that's a joke.

 

[roeften]

Eh? I thought you were looking for a solution to a problem, not just a specific solution because you wanted to fiddle around with some components.

Well I did also say I was looking for a commercial one like a relay.

Why can't you use any computer (cost=nothing), anywhere you like in the entire world, to send the WOL packet? And why would the machine need to be "turned on" - that's the whole point of WOL.

I agree here. I am not aware if my modem (which does the Natting) will forward a directed (to my public IP) UDP packet as a broadcast packet to the internal LAN. I will try and tell you if it works.

Have you accomplished such a thing?

 

[Softus]

Well I did also say I was looking for a commercial one like a relay.

You're quite right - I apologise and retract.

I am not aware if my modem (which does the Natting) will forward a directed (to my public IP) UDP packet as a broadcast packet to the internal LAN.

There aren't many NAT routers that won't do this reliably, although BT are good at providing some sh*te ones.

I will try and tell you if it works.

Have you accomplished such a thing?

Of course.

 

[Lantash]

Wake on Lan will only work if the computer is in standby. It will not switch the computer on from cold.

The majority of UPS's are designed to stay powered-down once the battery is exhausted, requiring human intervention to restart - this is a sensible policy, as the mains might fluctuate repeatedly during the outage, causing disk corruption if the PC repeatedly powered on/off as a result.

However, some UPS's have the option to instead restore power on the return of mains; this may be configurable by software, or might need a small internal mod. You'd need to check with the manufacturer to see if this is possible.

As for the PC, the majority of mobos have a BIOS setting which will cause powerup as soon as juice is applied. Some don't have this option, however. If it's a special purpose setup then finding a mobo that does do this is probably easier than homebrew methods.