Hi, I want to built a pretty simple project with one peltier element where I can regulate the heat/cold with a pwm signal. which is so far pretty easy with one n channel mosfet and a 10k resistor. (http://garagelab.com/profiles/blogs/how-to-use-a-peltier-with-arduino) I tried it and it worked perfectly. My problem is I want to be able to change from heating to cooling on the same side. I found something which looks pretty similar to the thing I want but unfortunatly it's only a picture from fritzing without any explanation or part list. (http://www.arduino-tutorial.de/2010/08/peltier-element/) has anyone done it before? and can share a simple schematic.
You might want to use a DPDT relay controlled by the Arduino. It would reverse the current to the element and is relatively easy to use.
I think you can use a 'MotorDriver' IC for this - or build your H-Bridge with discrete components...
I have never used an H-Bridge. can you do pwm with it? and do you need anything other than the h bridge?
I have never used an H-Bridge. can you do pwm with it?
Yes, that is one of their most important functions.
and do you need anything other than the h bridge?
Yes, a power supply and something to control the H-bridge, like an Arduino.
KOR: I have never used an H-Bridge. can you do pwm with it? and do you need anything other than the h bridge?
Also, be sure to get an h-bridge that can handle the current needs of your peltier - for most (probably all?) peltiers, any simple L293 or L298 based h-bridge driver circuits will -not- be able to handle the current needs (even an L298 wired in parallel for 4 amps of output current).
You'll likely need something with 5 or more amps of current output capability (10 amps to be safe). That's not a small h-bridge, but it won't be horrendously expensive to purchase; you might even be able to build one (simplest would be to use a DPDT relay with contacts rated for 10 amps (easy to get).
You likely won't need any diodes on the output of the relay, since a peltier is not an inductive device (it won't hurt if they are already a part of the device, should you purchase the an appropriate h-bridge controller).