How to determine maximum ratings of a Peltier Element?

Discussion in 'Electronics Resources' started by abhaymv, Dec 10, 2013.

  1. abhaymv

    Thread Starter Active Member

    Aug 6, 2011
    104
    4
    Hello,

    Recently I bought a Peltier element for use in a temperature controller application. They didn't provide any ratings for the peltier, and it doesn't have any ratings specified as a code either. The brand is "Supercool", with dimensions of 30 mm X 15 mm X 4 mm.

    The shopkeeper told me to 'try' 12 V, but I'd like to be sure about the ratings. So can someone please help me to identify the peltier? I've linked the pictures.

    http://i1322.photobucket.com/albums/u569/abhaymv/Photo1773_zps89ed85e0.jpg

    http://i1322.photobucket.com/albums/u569/abhaymv/Photo1770_zpsd60681d2.jpg

    http://i1322.photobucket.com/albums/u569/abhaymv/Photo1772_zps2a4f4e2b.jpg

    http://i1322.photobucket.com/albums/u569/abhaymv/Photo1771_zpsfb4103e9.jpg
     
  2. Metalmann

    Active Member

    Dec 8, 2012
    700
    223
    Good question, I just bought some also.

    I know they are used in car and truck coolers, so I'd say 12-24 Volts.
     
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  3. abhaymv

    Thread Starter Active Member

    Aug 6, 2011
    104
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    But won't the peltier break if I drive it at a voltage greater than maximum? How can I ensure that this won't happen?
     
  4. Duane P Wetick

    Active Member

    Apr 23, 2009
    408
    19
    You will need some type of control for this device; PID would be ideal, but can be expensive. A DC Burst (SCR) control; adj duty cycle ON---OFF; typically used in heating applications would be a possibility. You may not need a feedback element, if the environment can be controlled by other means. See KB Electronics, Coral Springs, FLA. for economical controls solutions.

    Cheers, DPW [Everything has limitations...and I hate limitations.]
     
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  5. MrChips

    Moderator

    Oct 2, 2009
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    What will damage a TEC is the maximum temperature on the hot side.
    Try running at 6 to 12VDC and monitor the current.
    Do not operate without proper heat sinks on both sides of the module.

    Edit: Judging by the size of that TEC I would suggest not exceeding a current of 3A.
     
    Last edited: Dec 10, 2013
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  6. abhaymv

    Thread Starter Active Member

    Aug 6, 2011
    104
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    Thank you for the reply. But why do I need a heat sink on both sides? I thought only the hot side would need a heat sink...

    EDIT: I was able to get the specs of the peltier after digging through the internet. Apparently I had to use the keyword 'TEC' instead of peltier. Thank you for giving me the idea!

    http://www.ge.infn.it/ATLAS/Electronics/Humidity/Peltier/peltier%20RS.pdf
    The specs are 3.4 A, 7.8 V and 16.5 W.


    So do I operate this at 7.8 V? Do I need heat sinks on both sides?
     
    Last edited: Dec 10, 2013
  7. MrChips

    Moderator

    Oct 2, 2009
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    Put heat sinks on both sides for testing the current/voltage/power/temperature characteristics.
    After that you are free to do as you wish, at the risk of killing the TEC.
     
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  8. abhaymv

    Thread Starter Active Member

    Aug 6, 2011
    104
    4
    :eek:
    I am planning to use a heat sink on the hot side, but how can I use the TEC at all if I need heat sinks on both sides?

    My application requires both heating and cooling. Would this be a problem if I reverse the polarity of the voltage and use the same peltier for both? While heating, my heat sink would be attached to the cold side of the peltier and I'd be heating an aluminium block. While cooling, the heat sink would be attached to the hot side, as it should be...
     
  9. MrChips

    Moderator

    Oct 2, 2009
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    In your actual application your load will take the place of heat sinks.

    I am suggesting putting heat sinks on both sides for testing purposes.
     
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  10. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Firstly they don;t run at "volts" as they are current operated devices.

    The max current for that package will be similar to any semiconductor, it depends on how big the heatsink is on the hot side vs how much work it is doing (how much heat it is transferring).

    You need to rate it within the final hardware structure. What I do is to assemble with the heatsink/fan etc, slowly increase current and measure the temperatures in many steps.

    Then do a quick chart, and you will see the cold temperature gets colder in proportion to current, but it soon gets to a point on the chart where more current does not give the expected increase in "coldness". That is showing that the limit of its heatsinking and/or current capability is being reached, and it is becoming much less efficient and risks damage.
     
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  11. #12

    Expert

    Nov 30, 2010
    16,298
    6,811
    I've never seen a Peltier, so correct me if I'm wrong. This is just basic thermodynamics:

    You have to think of heat as a flow. If you put a radiator (and I use the term loosely) on the hot side and apply power, the cold side will get cold. It doesn't have enough surface area to collect the heat that the Peltier might move, if it could. The cold side might even become coated with frost and frost is an insulator. As less heat can get into the cold side, the flow of heat to the hot side will be reduced. This will wreck your performance graph because you will be measuring the insulating ability of still air or frost, not the performance of the Peltier. That would be like trying to measure a hair dryer with your hand over the air intake holes.

    After you get done finding out what to expect, install it where you want to. If it doesn't live up to what you measured with good radiators on both sides, you will know where to look and adjust things to get it working well.
     
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  12. abhaymv

    Thread Starter Active Member

    Aug 6, 2011
    104
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    Thank you! I'll try this procedure ASAP!
    Again, thank you for this post. It helps understand peltiers a bit better. :D
     
  13. MrChips

    Moderator

    Oct 2, 2009
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    Believe me, you can kill these little things very quickly.

    With 24W being generated think of a 24W soldering iron. They get hot very quickly.
    My point is, while you are in the experimentation stage, use a very large heat sink.

    Why use heat sinks on both sides?
    Because you don't know which side is the hot side and which side is the cold side.

    And don't exceed 3A.
     
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  14. abhaymv

    Thread Starter Active Member

    Aug 6, 2011
    104
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    Right. Thanks. I'm planning to use CPU heat sinks, which should have a thermal resistance of 0.5W/K if the datasheets are to be believed...:)
     
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