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A PC ATx switching power supply will give me the 12 volts DC I need to drive a Peltier unit but what about the Amps.
Does it matter of the Amps available from the PS exceed the Peltier's needs by a substantial amount?
An ATX supply? Not likely chemelec. He stated plainly that the supply was capable of much more current than the peltier unit, aside from that ATX supplies have something like 4 failsafes. They're over current protected, short circuit protected, thermally protected, and DI/DT protected, they're nearly impossible to hurt even if you do something stupid. They can be damaged by large inductive loads and that's about it.
There are loads of pages about using PC PSU's. I actually turned one into a grossly overdone bench supply for my first attempts with Peltiers. It was only because I had the bits laying around I did it, otherwise it would of been far to expensive for such a simple project.
All I have done is bundled and connected the different wires to posts....simples..as they say.
**broken link removed**
**broken link removed**
Note:- I now only use it for low power undervolting experiments with peltiers. I was a bit concerned about the current limits of the posts when using big units.
I have never seen an ATX power supply that has more than one 12V rail, and even if it did you'd still be able to put them in parallel safely. Simply popping the lid off the power supply and looking inside will tell you instantly. Every ATX I've seen or used has common connections for all the same voltage rails. I have heard of higher end power supplies that have multiple 12 volt rails but again there is nothing wrong with paralleling them.Crosh said:Sometimes you can parallel the outputs together to gain more current, other times you can't (depending on the design of the PSU). Since you don't have and can't get the needed information to know this (forget even trying), it will be a hit-n-miss operation;
zipdogso said:While PC PSU's can be used to power Peltiers they are not the best thing by any means.
Firstly I trust you know the modders trick to get the PSU working without a motherboard. You don't do this it wont work at all. Bear in mind if you power up the PSU with no load you will probably kill it.
2nd assuming it is a fairly modern PSU there will be several special coloured sense wires that will need to be grounded for it to work correctly.
3rd When installed correctly in a PC the PSU will use the 5v line for regulation so often to get it to work reliably you should have a load on the 5v (red) line you can provide this with a 10w resister.
finally both the molex connectors and the wires on a PC PSU are only rated at 8 amps, 7amps for safety. If your Peltier is say.... 15 amps you divide the current you want by the wire limit - 7amps so thus:- 15/7 =2.1 round it up to 3 for safety.
You can then use 3 yellow wires soldered together for the Peltier +ve and 3 Black wires soldered together for the ground. Make sure all the wires seperately trace back to the body of the PSU and of course cut off the molex.
Obviously you can see you you may be quickly limited to the Peltiers you can use due to the number of wires.
That's a pretty nice unit you've set up - got any more info on it, pictures of the inside?
I wish I knew of an easy way to make a PC supply adjustable, both for current and voltage - being able to have a preset and a cutoff would be really useful; right now I have a couple low-amperage ECI bench supplies; they were cheap, but they leave a bit to be desired in the amperage dept (the adjustable stage can go from 0-25VDC @ 0-1.25A)...
I'm not sure why you say this isn't the best way by any means, the bulk majority of peltier coolers are meant to be run off 12 volt supplies, for either automotive (portable coolers) or CPU heat pumps.
Grounding a sense line would very likely fry any device hooked up to line that required it, it's there for voltage feedback, if you ground it the supply is going to put out the maximum voltage it's capable of on that line thinking the voltage is low.
2nd assuming it is a fairly modern PSU there will be several special coloured sense wires that will need to be grounded for it to work correctly.
I might have some photos somewhere....it was years ago.
Generally I dont think its worth the hassle to make one adjustable, just buy a decent PSU (not PC one.)
They will have a variable voltage but few if any wil have variable current it just isn't neccessary. So long as the PSU can deliver more than the peltier/s will draw that's it. If you had variable current and accidently set it low you'd blow the fuse or worse.