Power Peltier Device from Laptop Power Supply

Discussion in 'The Projects Forum' started by justin_ca, Oct 3, 2009.

  1. justin_ca

    Thread Starter New Member

    Oct 3, 2009
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    I'm trying to build an aquarium chiller using a Peltier device, large computer heat sink, and a laptop power supply to drive the system. I'm using this device:
    http://auspicious-e.com/index.php?main_page=product_info&cPath=30&products_id=263

    The stats say it has a 1.3 to 1.5 Ohms resistance.

    The laptop power supply I'm using outputs 20V and 3.5A.

    I first tried a 12V 1A wall wart to run the device. This worked, but got the wall wart very hot (as expected) and couldn't drive the cooler to full power.

    I tried just hooking the laptop power supply to the peltier device and the power supply would just cut out. It obviously has a short circuit protection and was detecting way to many amps drawn.

    My calcs would tell me that at 20V into 1.5 Ohms of resistance I'd have 20/1.5 Amps (ohm's law, right?). So that's way over the rated 3.5A. So I went and picked up some Radio Shack resistors. They are 10Ohm 10W ceramic resistors. So my idea was that I put all 3 in parallel. So that gives me 10/3 = 3.3 Ohms of combined resistance. I then put this in series with the peltier device. So that would give me 3.3 + 1.5 = 4.8 Ohms of resistance total, right? So that should draw 4.2A. Still over the rated limit, but it works to not trigger the protection circuit in the power supply.

    PROBLEMS:
    1) The resistors get really hot. My IR temp probe is reading 230F even when they are connected to a heat sink.
    2) The peltier is not transferring much more heat than with the 12V, 1A supply. My guess is that all my extra power is going to heating up the resistors....

    Any ideas on how I can power the peltier properly??
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    A car battery:)

    The spec sheet says 12V @ 9A, which is 108W. Simply put, you need a power supply which will put out >9A @ 12V. You can buy one on ebay, or build one from scratch.
     
  3. justin_ca

    Thread Starter New Member

    Oct 3, 2009
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    0
    Would an alternative be to get a power supply that could supply amps that 1.5 Ohms would draw at 12V, or 9A? Do they even make a 12V, 9A supply that would be affordable?
     
  4. justin_ca

    Thread Starter New Member

    Oct 3, 2009
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    Thanks for the reply, yeah I was just arriving at the same conclusion. Could I just use 5 2A wall warts in parallel?
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Sure. Look at this, for example. I recently bought some used 12V 60A Meanwells off ebay.
     
  6. t06afre

    AAC Fanatic!

    May 11, 2009
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    Perhaps a desktop PC power can supply that kind of power and the correct voltage. I think this is the cheapest alternative.
     
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