Using just the 12v rail from a PSU

[Headcase_Fargone]

I have an Intel Atom-based board and an InWin case here that only has an input for a 4pin 12v connector on the board. Trouble is of course the power supply won't power up without the 20pin ATX connector plugged in.

What would happen if I shorted the two pins like so and plugged the 12v connector into the motherboard.

Would that work? Would I still be able to turn the motherboard on and off with the chassis power button? I know the PSU would always be turned on, but this system will always be on anyway.

 

[Stefan Payne]

Won't work on a classic PSU (non DC-DC design).
They need at least a load on +5V.

 

[Headcase_Fargone]

Frak. Why in the help is that 12v plug there on this board if there aren't any power supplies out there that'll use it?

One of the gentlemen over on another forum suggested I use an exrernal 102w ac adapter as this board supports an external power supply. Would it be safe to use a 12v 8.5a adapter if the board's spec sheet recommends a 12v 5a adapter?

 

[HOOfan 1]

pico PSU sounds like what you want....the unit will only pull as much current as it needs...the adapter is rated for up to 8.5A...doesn't mean it is always putting out 8.5A

 

[Headcase_Fargone]

So I should be good with this adapter? I'm not risking damaging the board with a higher amperage than is recommended?

 

[heymrdj]

You won't risk anything by having a higher amperage. The amperage rating means it can supply *up to* that much power. The power will only be used when needed. You can only damage a device by using one with too low an amperage rating, where the device your powering becomes starved for power when load becomes max.

The main thing to check is that the barrel connector matches your main board's barrel connector (the specs of the one you linked shows it's a 5mm/2.5mm barrel). It's 5mm of outside diameter, and 2.5mm on the inside pin receiver.

 

[Headcase_Fargone]

Looks like the adapter I linked meets those standards so I guess I'm good to go.