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Peltier modules???

Discussion in 'Boat Electronics' started by Glenn Ashmore, Jul 23, 2003.

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  1. Can someonr explain the idiosincracies I have observed in a peltier module?

    In scrounging parts for the watermaker I cam across an interesting
    surplus assembly. I was really after the 1 gpm flowmeter and stainless
    needle valve but it came with a really strange device. One of those
    things you just sense is to good to throw away. This thing is a pair of
    hollow black anodized aluminum blocks about 4.25"x1.75"x1" with pipe
    fittings on each end. They are bolted together with what appears to be
    a couple of 1.5" square Peltier modules separating them.

    Being a curious sort, I did the natural thing and took it apart to play
    with the Peltier modules. First I put them on the VOM to check
    resistance. They seems to float around between 19 and 22 ohms. Then I
    wired it to a DC power supply and slowly cranked up the voltage. While
    one side slowly got warm and the other cooler I could not get it higher
    than 3 volts and the current never got above .25 amps. Changing
    polarity did not make any difference.

    This does not seem to fit any of my perception of the rules of
    electricity. What is happening?

    --
    Glenn Ashmore

    I'm building a 45' cutter in strip/composite. Watch my progress (or lack
    there of) at: http://www.rutuonline.com
    Shameless Commercial Division: http://www.spade-anchor-us.com
     
  2. John Doe

    John Doe Guest

    Peltier modules are pretty neat. You can get more info from a company
    called MELCOR. They sell all kinds of Peltier devices, from individual
    chips to whole assemblies. http://www.melcor.com/teccover.htm also has
    some links to "handbooks" and product information. I'm not sure I can
    explain the phenomenom that you observed, but you might try emailing MELCOR
    and asking them. If you do get something back, please paste it back to this
    thread.

    I bought some modules from them a long time ago. At the time, a 1" unit
    cost around $25, and I was thinking of using them in a cacaded arrangement
    to replace the freon-driven system on my Norcold fridge. Then I learned how
    "efficient" they were. Oh well. I do use one of the larger cooler type
    units on many occcasions I have filled it with pop and beer and left it
    plugged in on my boat all week. When I go out the next weekend, I'm stocked
    up with a cooler full of COLD drinks! I have since fixed the Norcold, so
    now I just use the peltier cooler for "additional capacity" for parties.
     
  3. John Doe

    John Doe Guest

    An interesting snippet from this site about resistance measurements on
    Peltier modules:

    Can you test a TE module with an ohmmeter? No - the DC voltage that an
    standard
    ohmmeter applies will cause a temperature change (Peltier Effect) which will
    in
    turn cause a voltage to be generated (Seebeck Effect) which will cause the
    ohmmeter to read goofy (drifting, and even a 'negative' resistance. So, then
    use the "diode test" position on the ohmmeter? No - even though a TE module
    is
    constructed of an array of N and P doped semiconductors there isn't an
    actual
    diode junction. A resistance test can be made with an LCR meter which
    measures resistance using an AC voltage. Using a HP 4274A LCR meter I have
    measured a few ohms for small modules and a fraction of an ohm for larger
    ones.
    While one does not usually see the resistance parameter specified on
    manufacturer's data sheets it is probably not a bad of a check of a module's
    health, especially if more sophisticated test methods are not available.
     
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