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how do I determine characteristics of unknown peltier module?

Discussion in 'Electronic Components' started by Eric Braunhauffer, Sep 24, 2007.

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  1. I have an unknown (unmarked) peltier module. I'd like to determine the
    characteristics of the peltier itself. The only things I know about it are
    its size and the fact that it is drawing 6 amps at 12 volts. I'd like to
    determine it's output wattage if possible. Anyone have ideas as to how I
    could do this?

  2. A TEC made for 12V is probably set to be efficient at that voltage. Such
    TEC's usually have a Vmax of about 14.5V, so assuming 2 ohms as a basis for
    assuming 7.25 amps as Imax (you can test that briefly to see if it's true)
    then consumed power will be 105 watts. Qmax will be about half of that.
  3. Should say in case unclear, Qmax IS maximum 'output power', it's the most
    heat you can pump, such that cold side temperature matches hot side, when
    hot side is on the best heatsink possible.
  4. Guest

    Pelteriers get hot on one side and cld one the other. They cannot go
    below 0C. You need to heatsink them well and maybe cool the hot
    side )with fan and heatsink)., Maybe having a fan runnning over it,
    and the other side of the Peltier gets cold.They change polarity (heat
    and cold) depending on the way you wire then up. I used 4mm perspex tp
    make a decent heat exchanger. It is worth the effort.
  5. Hal Murray

    Hal Murray Guest

    What's magic about 0C?

    I'm reasonably sure astronomers use peltiers to cool CCDs
    much colder than that.
  6. (Hal Murray) wrote in
    Yes, they do.

    TEC's can have delta T of 67°C with a hot side clamped at 25°C, some as
    much as 71°C, so around -45°C is usually possible with a tiny load, like a
    sensor. The main reason to avoid going below 0°C is ice, if water vapour
    gets in there, the expansion on freezing will easily break a TEC, but water
    will damage the thermocouples anyway, so it should always be excluded.
  7. Peltier devices, are effectively electrical heat pumps. They only get cold
    on one side, if the heat being generated on the other is removed. This
    heat comprises the heat being pumped, and the heat generated by the
    Peltier itself. They can go way below 0C. There is a balance between how
    much heat they can move, and the temperature difference between the two
    sides of the module. Typically modules can achieve up to about 70C delta,
    but at this, they are able to move almost no heat. Conversely, depending
    on the size of the module, there will be a point where the temperature
    difference reaches zero, for a given amount of heat to move (Qmax).
    Typically a Peltier will draw about double the power, that they can move.
    So, in the example, the element is drawing about 72W. This would be
    typical of a module able to move perhaps 40W of heat at a 0C delta. Add a
    heatsink, with a temperature rise of perhape 0.1C/W, fan cooled to the
    'hot' side, and this will need to dissipate about 112W of heat in this
    'worst case'. It'll then run up to about 11C above ambient. If you have
    something that only generates 15W of heat, and attach this to the 'cold'
    side, expect the delta C to be perhaps 45C, and the component to cool to
    about 34C below the ambient. The actual delta will depend on the module,
    but this would be a typical value for a module this size. The 'lowside'
    temperature can be well below zero. There is nothing 'magic' for a Peltier
    module about 0C. For even higher delta's, cascade two modules. Remember
    though, that the 'hot' module, has to pump not only the original heat, but
    the heat being added by the first module...
    I have one sitting here on the bench, which is currently holding a couple
    of semiconductor junctions at -40C. They are only generating about 1W of
    heat, but to maintain this temperature (currently 62C below ambient), with
    the two stage cooler attached, over 100W of power is being fed into the
    cooler module, and the heatsink size reflects this...
    The best way to 'characterise' the module, would be to measure the
    temperatures on both sides of the junction, with known amount of heat
    being applied to the cold side (resistor fed from a controlled voltage
    source). You can then measure the delta T, for different power inputs, and
    build your own graph for the behaviour of the module.

    Best Wishes
  8. Guest


    Look at this...

    It looks to be what you are looking for.

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