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Peltier

Discussion in 'General Electronics Discussion' started by Karthik rajagopal, Jul 23, 2016.

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  1. Karthik rajagopal

    Karthik rajagopal

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    May 9, 2016
    Hi guys
    Can someone tell me how a peltier works , it's uses and how to connect it in circuits? Thank you in advance.
     
  2. BobK

    BobK

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    This kind of question is what Google is for.

    Bob
     
    hevans1944 likes this.
  3. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    Instructions usually come with it. Not knowing specifically what you have advice is difficult. Mine is pretty straight forward. Red and black wires are positive and negative. Draws about 6 Amps. Be sure to use a heat sink on the hot side. Fans on both sides are a good idea. For power I used an old PC power supply.
     
  4. donkey

    donkey

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    1 http://www.marlow.com/resources/general-faq/6-how-do-thermoelectric-coolers-tecs-work.html
    very simply a peltier moves heat from one place to another using semiconductors

    2 uses are for cooling and heating (its odd but yes heating) and if you make one side hot and other cold it could theoretically generate power too... but not efficiently. peltiers can be found inside computers on the cpu (not standard but it is fun to do) to help cool it. this is the most widely used peltier, however there are peltier fridges, air cons etc

    3 to connect a peltier up connect it like a motor. one wire black-, 1 wire red +. if you hook these up the other way around then the hot and cold sides will reverse. this can be beneficial if you want to make a cup holder, keep some drinks cold, other warm

    now having said all of this peltiers are currently a great idea for non-mechanical/moving parts cooling. unfortunately they suck amps like fish suck water.....

    ok lastly a peltier works on 2 key aspects... number 1 if they get too cold or hot they no worky
    2 the best thing to look at is a temperature difference. what I mean from this is that lets say 30 degrees is the temp dif(TD) that means the cold side will only ever be 30 degrees colder than the hot side. so if you don't take away the heat (heat sink, water, fan(not so effective without heatsink) then the hot side will slowly get hotter when this happens the cold side gets hotter too.... so then you actually start warming it.
    2a having said this if you want a 60 degree TD the easiest way is to plug a heat sink on the hot side of one, the plug the cold side to the hot side of another..... this will give you colder temps... but more amps
     
    hevans1944 likes this.
  5. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    You got a good one. Mine never got hot enough to cook with or cold enough to make ice but it kept my coffee cup warm or my sodas cool.
     
  6. Chemelec

    Chemelec

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    Jul 12, 2016
    Ideally you also create a Control Circuit to Monitor Both the Cold and Hot Side Temperatures.
    So the Module turns On/Off as needed to better control the temperature.

    Here are some Small Coolers I built and the control circuits I designed.
    Lucky I have a Metal Lathe and Mill Machine, to Custom Size and shape my Heat and Cold Sinks.

    http://chemelec.com/Projects/Peltier/Peltier.htm

    Building Large Coolers, Requires LOTS OF INSULATION, if you actually want it to Cool.
    And Even More Difficult to do, If the Outside Air Temperature is Hot.
     
  7. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    Liquid cooling interests me. Would antifreeze or liquid silicone be better than water? I got a glimpse of a liquid cooling system used in military aircraft for a RADAR jamming gear. It felt like liquid silicon was used to keep the VERY high power transmitters cool. Not efficient energy wise but very effective.
    This replaced the older CO2 spray that was not so reliable.
     
  8. Chemelec

    Chemelec

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    Jul 12, 2016
    It is Not so much about the Medium (Water, Liquid Silicone, Air or Antifreeze), It is How can you keep those Medium's Cool?

    Water is Good, If it is coming from a TAP, so Constantly Cool.
    But NOT Portable.

    Ultimately your Cooler is Surrounded by AIR and if the Air is HOT.
    LOT OF LUCK in Cooling!
     
  9. hevans1944

    hevans1944 Hop - AC8NS

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    Peltier cooler: an inefficient solid-state heat pump invented by the French in retaliation for some perceived slight, probably by the Germans, who came up with the Thompson effect which is mostly identical to the Peltier effect. Doesn't hold a candle to mechanical refrigeration, but does have the advantage of no moving parts. Neat toy. I have one in a "cooler" for use while vacation camping that runs off a car battery. Best to leave the car engine running though, because as @donkey said, it sucks a lot of current. It can warm or cool the contents depending on battery polarity. Decided it was more convenient to just dump a few pounds of ice (or dry ice) into an insulated container and to heat food with a propane gas grill. At one time Peltier cryogenic coolers, mounted in series stages in a vacuum, were hyped as useful for cooling infrared detectors. The final stage, on which the detector chip was mounted, was smaller than a postage stamp and radiation shields between stages complicated things. Liquid nitrogen was more convenient and reached a lower temperature of 70 K without as much fuss.
     
  10. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    I was thinking more in terms of cooling a tank of some liquid and using it to keep an electronics circuit cool.. Something non-corrosive and non-conductive that transferred heat well. Maybe keep the whole circuit board in the tank not just the heat sink of the circuit. With a fan or pump keeping the fluid in circulation. Can I run a fan in a tank of antifreeze? Not all antifreeze seems suitable.
     
  11. Chemelec

    Chemelec

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    Jul 12, 2016
    Not sure I understand your comment.
    But you Can't put the Peltier Device in a Coolant.
    That would be counter productive.

    You can create a water cooled heat sink and Yes you can use a Tank of Fluid and a Pump to Circulate it, But it still needs to LOSE the acquired heat into the surrounding air.
     
  12. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    I have a Peltier junction with a heat sink on both sides. I was going to put the cool side in a tank. A fan or pump circulates the coolant. The objective being to cool a heat sink of an electronics assembly. A fan on the hor side heat sink blows the heat away.
    Would the whole be any more effective than just having a heat sink? We have the advantage of the whole board being in the cooled fluid. The objective might be kilowatts of cooling in a cubic foot. maybe.
     
  13. Chemelec

    Chemelec

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    Jul 12, 2016
    A Fan on the Hot side is normal.
    USUALLY the Object is to keep the Hot Side Cool, so the Cold side can keep your FOOD Cool.

    So Why put the Cold side in a Tank?
     
  14. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    Cool the fluid which cools the electronics.
     
  15. davenn

    davenn Moderator

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    u need to clarify how you are going to do that
     
  16. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    Where are we missing each other. Cooling side of the junction cools the liquid. electronics package to be cooled is in the liquid.
    I don't know why it wouldn't work to keep my cans of soda cool also. I'll try building something next week and let you know how it comes out. Does water transfer heat better than air? In air the soda can just about has to be in touch with the heat sink before it gets very cold. If the heat sink cools the water that cools the soda can would it be more efficient?
     
  17. Chemelec

    Chemelec

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    Jul 12, 2016
    OK, I Understand what your saying now.

    BUT How are you going to INSULATE This TANK of Water so it doesn't ABSORB HEAT FROM THE AIR?
     
    davenn likes this.
  18. Herschel Peeler

    Herschel Peeler

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    Feb 21, 2016
    Ah, I see. Should I be worried about that? Plastic "shoe box" tank. Styrofoam top. Top mounted junction.. If it made a difference I guess I could make a Styrofoam box to put it in. First version will just use water and see how cold it gets.
     
  19. Chemelec

    Chemelec

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    Jul 12, 2016
    Just like your Fridge or Freezer, Insulation is VERY IMPORTANT.

    And Peltier Modules are Very Low Efficiency, compared to compressor types of refrigeration.
    I would recommend at LEAST 1 or 2 inches of Styrofoam over ALL Exterior Surfaces.

    Try it your way and you will find it Does Not work very good.
    You Might get 5 degrees lower.

    And If you fan does Not keep the Hot Side COOL, than the Cold side will Get WARMER
     
    davenn likes this.
  20. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Two grocery stores where I shop have a small cooler on a stand filled with circulating chilled water that you can drop a bottle into to chill the bottle while you shop. Takes about seven minutes or so to chill contents of bottle to same temperature as the water. The cooler top is open to air, and the bottle is not totally submerged, so there is significant heat loss to ambient air whether a bottle is present or not. The chiller runs 24/7/365 at one of the stores, which is open the same hours for business. This would seem to be an ideal application for a Peltier cooler: only moving parts are the pump that circulates the water and the fan that exhausts the heat to ambient air. These could be driven from the same motor shaft. A little pricey for home use.

    [​IMG]
     
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