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Question How do I make my spare desktop PSU turn on with my laptop?

S

s355

Junior Member
I want to power desktop peripherals but I've switched to a laptop. The laptop's power-on signal should actuate a relay which will then ground the green wire. When the laptop sends the power-down command to its own PSU board, the relay should reset and unground the green wire.
 
Sounds overly complicated and "hackish" to me.

Why not get an "ECO" power strip, with a "Master" outlet that the laptop can be plugged into, and then plug your peripherals into the other switched outlets.

Or get a docking bay or self-powered USB hub for USB peripherals or displays?

Edit: Something like this unit:
 
agree with larry.

Or put the PSU on a smart switch so you can tell alexa/google to turn it on/off for you.

The only way i can see this working is for you to take a usb cable somehow and butcher it up and attach it to a relay of some sort.
Any other way would most likely void your warrenty, as you would need to open the laptop and cut something to tap into a live line.
 
Yes this is easily accomplished using a 5V coil rated relay powered by a USB socket. I'm left wondering how much detail you need to make this work, as there are no surprises doing it, just USB +/- to relay coil, and PS_On and PSU Gnd to the normally open relay contacts.

There are ready made widgets that can do this via software too, then you'd issue the on/off command on startup and shutdown, or jumper around the control chip to make it come on/off with USB power.


Keep in mind that your ATX PSU would always have the 5VSB live so wasting a slight bit of power when not in use. I like Larry's idea more to just use a switched mains AC power outlet and then a powered hub or whatever.
 
mindless1 said:
Yes this is easily accomplished using a 5V coil rated relay powered by a USB socket. I'm left wondering how much detail you need to make this work, as there are no surprises doing it, just USB +/- to relay coil, and PS_On and PSU Gnd to the normally open relay contacts.

There are ready made widgets that can do this via software too, then you'd issue the on/off command on startup and shutdown, or jumper around the control chip to make it come on/off with USB power.


Keep in mind that your ATX PSU would always have the 5VSB live so wasting a slight bit of power when not in use. I like Larry's idea more to just use a switched mains AC power outlet and then a powered hub or whatever.
Click to expand...
Nothing's connected to 5VSB, so off is really off.
 
^ No, with nothing connected to 5VSB, it is still powering that subcircuit and using a little power to do so. Otherwise it would be impossible to turn it on shorting PS_On to ground, and really, there is no need to devote an entire ATX PSU to what you are doing at all.

You can take some other PSU with only the voltage rails you need, use the same setup to trigger a relay to turn it on at the connection to mains AC, -OR- you can do that with the ATX PSU, leave PS_On always connected to ground and use the relay to turn the mains AC input on, then it really is using no power and is really off until the laptop USB port goes live, but this makes it all the more wasteful to devote a perfectly good desktop ATX PSU to a PSU function that a less expensive, less complex PSU can do instead and then have the ATX PSU to reuse for something else (or sell).
 
mindless1 said:
^ No, with nothing connected to 5VSB, it is still powering that subcircuit and using a little power to do so. Otherwise it would be impossible to turn it on shorting PS_On to ground, and really, there is no need to devote an entire ATX PSU to what you are doing at all.

You can take some other PSU with only the voltage rails you need, use the same setup to trigger a relay to turn it on at the connection to mains AC, -OR- you can do that with the ATX PSU, leave PS_On always connected to ground and use the relay to turn the mains AC input on, then it really is using no power and is really off until the laptop USB port goes live, but this makes it all the more wasteful to devote a perfectly good desktop ATX PSU to a PSU function that a less expensive, less complex PSU can do instead and then have the ATX PSU to reuse for something else (or sell).
Click to expand...
Can I cheap out and get a $19 CoolMax 400W PSU to do so? My 1 kW PSU died. My peripherals have Molex, which only an ATX PSU has.
 
Yes a cheap PSU will "usually" power a light load reasonably (I have never used a Coolmax 400W so can't be that specific), though a really trashy one may have the fan or capacitors fail prematurely, though with the light load and not always fully on, odds are that the 5VSB capacitor(s) will fail before the rest.

I mean that this is a reasonable mid-term strategy but if you want long term, past 2-3 years, higher quality components are warranted.
 
Last edited:
VirtualLarry said:
Sounds overly complicated and "hackish" to me.

Why not get an "ECO" power strip, with a "Master" outlet that the laptop can be plugged into, and then plug your peripherals into the other switched outlets.

Or get a docking bay or self-powered USB hub for USB peripherals or displays?

Edit: Something like this unit:
Click to expand...

Agreed the simple solution is always the best solution in these matters unless someone is shopping for a nerd project like setting up a raid 0 on 96 cheap ssd’s.
 
When I've been in similar situations from time to time, I've used these kinds of things. Just flip the switch before you power up your laptop, and don't forget to turn it off again when done.

Not totally elegant, but cheap and doesn't expose any potential risk or modding of your laptop itself

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