12v AC PSU + 50w Pelt = HOT!!!!

Before you guys ask, No I wasn't using the pelt on my computer... It was in a mini-fridge I bought, the sold to my neighbor for $5. (The same fridge list for $110, and this one had NEVER been used).

Basically, He wanted the fridge in his room, but it was designed to go in a car and ran on 12vdc. At first I rigged my ghetto computer PSU up to it and it worked. The problem was the PSU I had looked like a fire hazard and he didn't want his parents to freak out if they found it. So to remedy this, I bought a 12v "Malibu Intermatic LV134T Low Voltage Transformer" rated @ 12v@88w. When I wired the transformer to the fridge, it heated the inside up, no matter which way the I wired it... Wired huh? Come to find out, the transformer outputs 12v AC, not 12v DC. Anyway, the AC current would heat BOTH sides of the pelt up, so be careful the PSU you buy isn't ouputting AC...

BTW, the AC did not destroy the pelt! It's nowrunning fine on a computer PSU.

ive wondered what that would do...

Dude, just get a bridge rectifier and some capacitors. A transformer by itself won't work to power a peltier.

mateo88 said:

Dude, just get a bridge rectifier and some capacitors. A transformer by itself won't work to power a peltier.

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Cool. I didn't even know what a bridge rectifier was until I googled it... One question. Why would I need caps? Is it so that the pelt is powered when the phase reverses?

Cyrix_2k said:

Cool. I didn't even know what a bridge rectifier was until I googled it... One question. Why would I need caps? Is it so that the pelt is powered when the phase reverses?

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The power coming out of the rectifier isn't very smooth. The caps smooth it out.

squeakygeek said:

The power coming out of the rectifier isn't very smooth. The caps smooth it out.

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Ok, thanks Just learned alot... What size caps should I use? Think something like 200uf @ 24v will do?

Ithought someone already linked to this, but I guess not. Here's a guide on how to make your own power supply: http://www.overclockers.com/tips1054/

That will explain what you will need for caps. One thing about the guide that really pissed me off though is how he says that 25 amp transformer is enough for a 226 watt pelt, which has a Umax (or is it Imax?) of 24 amps. The parts downstream of the transformer are NOT 100% efficient, so you will draw more current than just what your pelt draws. I ended up burning out the transformer, and wasting my money. I ended up getting an FSP-550 psu that is enough to power my computer and my pelt both. Anyway, you're only experimenting with a 50watt pelt, so you should be able to make one pretty easily, or just use a computer psu, but don't expect to be able to cool anything with it.