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?
### Please remove all numbers in email address for reply ###
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.
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.
When you hear the toilet flush, and hear the words "uh oh", it's already
too late. - by anonymous Mother in Austin, TX
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.