Hi folks, I want to built myself a metalblock thermo-calibrator to calibrate precise pt-1000 elements. For this I want to use a couple of peltier element, which scream for lots of power.
With usual regulated power supplies this makes lots of heat, so I want to use a pulsed power supply. But somewhere I've read, the peltiers don't work very long then, because they need a constant voltage.
Does anbody have more information of this?
Thanks, Rainer
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Depending on the voltage and power requirements, you can buy switchmode modules off the shelf with output ratings up to 25 amps or so (I am sure they go higher, I have never had the occasion to look). Typical efficiencies (depending on Vin/Vout are around 80% for these modules.
You'll have to heatsink the Peltier modules, of course.
Try a search for 'switchmode power module' in Google.
Cheers
PeteS
Look for the TEC controllers freom Analog and TI(BB)
Bye
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If you have a spare computer power supply (AT preferably) one could drive most peltiers. But usually one peltier per power supply unless you have a nice 550+ watt supply. And with some, you may need to set up a feedback to trick the supply as if it's hooked to the motherboard.
Quick and dirty method would be to find a 120v or 240v (depending on where you live) to 12v transformer, a bridge or 2 (or 3, make sure the combined current is more than then max total current you need), some heat sink for the bridges, and several electrolytic caps to filter out the ripple. I said several because one even at suitable voltage can't handle the current requirement alone. I'd also suggest a fuse and double pole switch on the primary side.
This should work as peltier are usually designed to work well in a wide range of voltage so getting exactly 12v out of the transformer is not important. Just make sure the compoments used are rated higher than your peltiers.
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Alternate idea would be to use the MC34063 and precisely calibrate the current (you can set a trip point and voltage) this chip will go up to several A if its output transistor is bridged with a beefy FET.
-A
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