Can I use 2 separate power supply to power a computer? - Page 1
Forum section: electronics / beginners

author: sam1275
author_rank: Frequent Contributor
timestamp: December 24, 2015, 05:18:39 pm
content: Hi everyone, I got a industrial embedded single board computer, the power connector is same as the old IDE HDD, a 4-pin, 12v+5v connector, I tried power it by a PC power supply and it works, but it's not good to have power supply twice bigger than the little computer, with tons of unused lines, I knew I can just buy a dual-volt power supply, but I find I have a 5v and another 12v power adapter (just like normal cellphone charger), SO: Can I connect the negative line from 2 different adapter together, then use them like a dual-volt PSU?Thanks!

author: Macbeth
author_rank: Super Contributor
timestamp: December 24, 2015, 05:42:56 pm
content: Pretty much yes. Keep the grounds connected and you should be fine. Just make sure they can supply the required amps.

author: Simon
author_rank: Unknown
timestamp: December 24, 2015, 05:51:56 pm
content: but don't be tempted to use two adapters of the same voltage to power different parts at that voltage.I once ran my hard drives off one power supply and my main board off another. I was not hugely surprised to find the main board power connector a bit burnt when I took the computer apart time later. It was because the 5V from the hard drive power was finding it's way to the mainboard over the ATA signal lines and there was a little bit of a mismatch it would seem.

author: Jeroen3
author_rank: Super Contributor
timestamp: December 24, 2015, 06:25:48 pm
content: No you can not. Unless you have a load sharing unit. (Board of diodes)

author: Simon
author_rank: Unknown
timestamp: December 24, 2015, 06:36:14 pm
content: Quote from: Jeroen3 on December 24, 2015, 06:25:48 pmthe OP is using two different PSU's for two different power rails.

author: IanB
author_rank: Super Contributor
timestamp: December 24, 2015, 06:38:27 pm
content: I don't see why not, unless for whatever reason the 12 V loads try to return power to the 5 V rail. With two independent supplies that wouldn't work. Do PC's ever do that?

author: aaronwiz
author_rank: Contributor
timestamp: December 25, 2015, 03:23:17 am
content: I think it will be fine, as long as you do not hook it up in a way that the power supplies will be directly connected in parallel right out of the power supplies. Since it is impossible to make two power supplies have the exact same voltage one will inevitably take more of the load.I don't think this is really a problem due to the fact they will probably be connected in parallel after having to travel through the PSU's cables. The cable resistance should naturally mitigate the problem.The power cables coming out of the PSU will act as a small resistor, and if one power supply takes significantly more of the load than the other one, the voltage drop across the cables will be larger and the other PSU will be forced to take up more of the load.

author: cs.dk
author_rank: Unknown
timestamp: December 25, 2015, 06:39:17 am
content: Quote from: dave_finch on December 24, 2015, 11:47:34 pmDid you just create a profile for spaming 95 topics??

author: Simon
author_rank: Unknown
timestamp: December 25, 2015, 06:07:40 pm
content: Quote from: cs.dk on December 25, 2015, 06:39:17 amYes he did duh! please do not quote troll/spammers post particularly containing potential personal information, just gives us more work to do.

author: Monkeh
author_rank: Super Contributor
timestamp: December 25, 2015, 06:38:55 pm
content: Quote from: Simon on December 24, 2015, 05:51:56 pmI really doubt that had anything to do with it. It's far more likely you just had a high resistance connection.

author: Simon
author_rank: Unknown
timestamp: December 25, 2015, 07:09:22 pm
content: Well all the 5V pins were toasty, and only the 5V pins, the only link I could find was the fact that the ATA ports would be switching 5V between disks and motherboard, and each end of that line was powered from a slightly different 5V. PC worked fine though until it blew a long time after I put it back to one supply.