How to draw power from PSU when system is off

[eiriklade]

I have a microcontroller (Arduino) that I want to permanently place inside my PC to run at all times, even if the system is off (OS shut down, but PSU still active). It needs around 6-12 volts and <100mA.

Is it possible to tap this power from the PSU when the system is off, or is USB Charging the only solution?

Thanks in advance.

 

[4745454b]

To my knowledge there is only a 5V "constant on" in a PSU. If you need 6-12V you'll need to leave the PC running/in idle to power it.

 

[eiriklade]

To my knowledge there is only a 5V "constant on" in a PSU. If you need 6-12V you'll need to leave the PC running/in idle to power it.

5V might work with the controller, though I'm not certain. Could you elaborate or give me some references as to what rail this is?

 

[4745454b]

It is it's own rail. 5V standby. That one is on all the time. You'll need to check the specs of your controller if it will work on a 5V feed, and make sure it won't overload the rail as it normally only supplies 2-3A.

Looking online I found this pic, the 5V stand by looks to be the purple plug in the 24pin bundle. You'll need to find a way to wire it into that.