Driving two peltiers in a low amp circuit

Discussion in 'The Projects Forum' started by simondavidkelly, Aug 5, 2010.

  1. simondavidkelly

    Thread Starter New Member

    Nov 12, 2009

    I'm trying to create a cooler curcuit using a couple of peltiers and a CPU cooling setup. It's for a meter cubed temperature controlled environment, not a PC.

    I have a confirmation question about increasing the current in the curcuit for the peltiers that require 9A at 12V. My supply will go from 3 to 24V and I'm not sure if the 200mA is constant across all voltage values.

    I have made an educated guess that if I want 9A for the peltiers, it has to be in the curcuit to start with and the 200mA will not be able to be magically amplified but I'd like confirmation. I was reading up on a Darlington Pair, but I think that this is more for switching amps than creating them.


  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Peltier coolers are current operated devices. Changing an applied voltage is not a good way to control them, if I read your method correctly.

    We have had any number of threads dealing with Peltier coolers. Here is a link to one of them - http://forum.allaboutcircuits.com/showthread.php?t=13676
  3. simondavidkelly

    Thread Starter New Member

    Nov 12, 2009
    Thanks BeenThere.
  4. JDT

    Well-Known Member

    Feb 12, 2009
    How are you cooling the hot side of the Peltiers? this is very important. Peltiers are only useful if you want to cool something below ambient.

    The heatsink on the hot side not only has to remove the heat from the device you are cooling but also has to remove the heat generated by the Peltier itself. To be effective it must do this without raising its own temperature more than a few degrees above ambient.

    This is because while the Peltier is pumping heat from the cold side to the hot side, the heat is conducting back through the Peltier. Bit like pumping water up into a tank which has a fairly large leak! It is very hard to get more than 15 - 20 degrees C difference across the Peltier.

    So to do this, the heatsink will have to be MUCH MUCH larger that the original CPU heatsink.