Help- Trigger ATX psu via USB on another device

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Dreamerbydesign

Supreme [H]ardness
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Feb 3, 2008
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as the title states. Looking to trigger/ activate a ATX psu from the usb port of another pc when it turns on.

Reason:
I have a Mini PC connected to an array of hard drives. A external ATX PSU powers the array. The mini pc of course runs on its own 19V power brick.

I’d like to turn the atx power supply on automatically once the Mini PC powers up.

I know the green wore (PSU_on) needs to be tired to ground to activate the ATX psu. I’ve tested and it works fine.

I have looked at USB relays such as this: USB 1 Channel Relay

If I bought one of those, would it be possible to program it to just trigger the relay when the pc is powered on? If so I think should do the trick?

I have a smart plug connected if I need to disconnect power remotely to the array.

Can someone chime in, if I’m going the right direction or if there is a easier method? I can’t be the only person to try to power an array with a separate psu, using a laptop/mini pc/ non atx psu to trigger the ATX powered array.
 
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Might have to make sure your usb ports are actually un-powered when it is off. The 5V rail still runs when powered down to provide usb power. But your method should work provided this condition isnt in the way.
 
I verified the usb port I want to use to trigger is completely off when the mini pc is powered off.

As far as that USB relay I linked above… I have no problem figuring out how to program it, but once programmed it should stay in the same state correct? Just program it once and plug it in?

I am assuming since all it’s doing is connecting a ground, there is no real worry about amperage correct?

Thanks guys for the help. It seems simple but I want to be sure.
 
Dreamerbydesign said:
...once programmed it should stay in the same state correct? Just program it once and plug it in?..
Click to expand...
The description for the first item you linked to says "Use serial port assistant to send 0xAA, the relay keeps opening; Send 0xBB, the relay keeps closing". Interpreting the poor English, it sounds like after you send one of those commandst, it will stay in that state indefinitely. It doesn't say if it keeps that state after being turned off; it will probably lose its state and default to being open when powered-up, but you'll have to verify that yourself.

Dreamerbydesign said:
...I am assuming since all it’s doing is connecting a ground, there is no real worry about amperage correct?..
Click to expand...
Indeed. Approximately 0 current.
 
Im sorry i missed that in the page. That one is command driven. So like you would be able to run a script to turn it on or off. You might want something dumb for the route you are explaining. Just a 5v relay with opto isolater would be fine. Just might have to pull apart a usb cable to wire it up.
 
Mr Evil said:
The description for the first item you linked to says "Use serial port assistant to send 0xAA, the relay keeps opening; Send 0xBB, the relay keeps closing". Interpreting the poor English, it sounds like after you send one of those commandst, it will stay in that state indefinitely. It doesn't say if it keeps that state after being turned off; it will probably lose its state and default to being open when powered-up, but you'll have to verify that yourself.


Indeed. Approximately 0 current.
Click to expand...
Yea I should have just stated no current 😆 I appreciate the help.

without testing yet, I believe the PSU_ON being grounded just needs to be triggered once to turn on the psu, and does not need to remain connected for the atx psu to stay powered on? I could be wrong. Do you know if it powers down if the ground is removed aka the relay turns off?
 
Darunion said:
Im sorry i missed that in the page. That one is command driven. So like you would be able to run a script to turn it on or off. You might want something dumb for the route you are explaining. Just a 5v relay with opto isolater would be fine. Just might have to pull apart a usb cable to wire it up.
Click to expand...
Yea I was wondering that. Windows needs to boot and execute the script before the relay will trigger on the one I linked?

Actually it might end up running promox on bare metal. So the triggering USB device would basically need to be script agnostic. Power on port triggers relay kind of thing.
 
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Dreamerbydesign said:
Yea I should have just stated no current 😆 I appreciate the help.

without testing yet, I believe the PSU_ON being grounded just needs to be triggered once to turn on the psu, and does not need to remain connected for the atx psu to stay powered on? I could be wrong. Do you know if it powers down if the ground is removed aka the relay turns off?
Click to expand...
See section 3.3.3 (PDF) and the figure shortly following. tl;dr, yes, if you open the connection, the supply turns off.

Screenshot_2024-04-11-11-10-05-94_e2d5b3f32b79de1d45acd1fad96fbb0f.jpg
 
Darunion said:
Correct.

This might be a better solution IMO

https://www.amazon.com/SainSmart-2-Channel-Duemilanove-MEGA2560-MEGA1280/dp/B0079WI2ZC/

2 Channels if you want to do something else with it. I like solid state better personally.
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Something else I read suggested a solid state relay would easier on the port long term. Makes sense. I checked out the relay I’d just have to figure out the usb part.

Honestly I’m not afraid of a soldering iron. And if I knew it wouldn’t hurt the motherboard, I’d just cut off a male usb cable and solder the 5v and ground to trigger the relay. It seems too simple to be correct though?
 
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Nobu said:
See section 3.3.3 (PDF) and the figure shortly following. tl;dr, yes, if you open the connection, the supply turns off.

View attachment 647027
Click to expand...
One quick question- I am not at home to test at the moment.

When I tested motherboards in the past that I suspected I had a faulty switch, I would short the motherboard header pins to turn it on, and that was momentary.

Must be the motherboard power header is momentary, and then whatever it does keeps a constant signal to the PSU_ON line on the 24 pin ATX plug. Hmm.

I like a fun challenge! Hopefully I can do some testing.

I think I am going to try the solid state 5v relay posted above, along with a male USB 5V cable. They arrive tomorrow and I’ll do some testing on an old pc before I use it on the mini pc.
 
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