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Constructing Power Supply

  1. Aug 15, 2009 #1
    Hi,

    I'm new here so I apologize if my question isn't composed appropriately.

    I’m currently designing water cooling unit, which is a component of a larger project, that utilizes peltier plates as a heat pump to displace the energy from the water. To cool the peltier plates themselves I want to employ heat sinks and CPU fans, as to prevent the plates from over heating and damaging themselves.

    The problem I’m encountering with this system is finding the appropriate power supply. I know all the components consume DC power but I was hoping to be able to plug this in to a standard US outlet. I lack the electrical skills to actually make an appropriate selection for this purpose, but I was thinking that I could use a computer Power Supply since that converts AC power to DC power but I’m unsure as how to connect the peltier coolers to those P-type connectors.

    Any suggestions or ideas regarding this? I’ve listed the specifications of the peltier coolers below but I haven’t made a decision on heat sinks and cooling fans.

    168 W Peltier Cooler 12V
    At 50 C
    Qmax = 120 W
    Imax = 10.9 A
    Vmax = 15.4

    Thanks
     
  2. jcsd
  3. Aug 15, 2009 #2

    dlgoff

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    Last edited by a moderator: Apr 24, 2017
  4. Aug 15, 2009 #3
    Hello Double-D,

    It sounds like a good time to visit Digikey.com. Type in power supplies and go from there. you should be looking at $100-$200.
    The computer switchers have very little output capability at 12 volts. They're designed to supply the vast majority of their power to the logic chips (3.3 volts?).

    Oh, one other thing. If your running your junction below the dew point, you need to seal it up to protect from condensate.


    - Mike
     
  5. Aug 16, 2009 #4
    You can buy fairly cheap ready-made peltier food coolers at your local department store or online. they run on 12V automobile supply, so you could replace that with a battery charger.
     
  6. Aug 16, 2009 #5
    Fleem's got a good point about the food coolers - They're sealed, and already have a heat sink. The only difficulty I can see is getting to the cooling side without tearing up the seal. The two heat sinks are most likely sealed together, and machining down one heat sink without dis assembly would be a hassle.

    I'd look for a better power supply though. I suspect you'll get much better efficiency from a steady DC source than a pulsating source like a battery charger.
     
  7. Aug 17, 2009 #6
    And, just as a general safety rule when beginning to work with high frequency switching power supples (which frequently are not fullly isolated from the mains), is an isolation transformer for your work bench. Not needed in the final system, but a safety item during the 'open' design and construction phases.
     
  8. Aug 18, 2009 #7
    I understand that it is pertinent to protect the peltier cooler from condensation if I am running it below the dew point, but how would you suggest I seal it. The reason I chose to use peltier coolers for this project specifically is due to the fact I already have some laying around, so I was hoping to employee those rather than purchasing new ones.
     
    Last edited: Aug 18, 2009
  9. Aug 18, 2009 #8
    Double-D,

    I've only had mixed results when attempting to make air-tight seals with RTV, but it seams to be the only game in town. I've seen military seals that used some tough, pink rubber, and then the everyday seals that they use for food coolers, which are a white rubber that's also tenacious.

    I guess I would attempt to clean the surface very-very thoroughly and stick with RTV. I think I might even go so far as to go after the surface with some heat-sink compound (or better yet, a water-based polish) and a rag before hitting it with some lighter fluid and then IPA. The heat sink compound is pretty good at polishing. You just need to clean the grease out afterwards... That should help with the porosity and scratches.
     
  10. Aug 18, 2009 #9
    http://www.overclock.net/faqs/112445-how-make-80-watt-peltier-beverage.html

    I acctually found this link to an older forum post that addresses the creation of a peltier beverage cooler. I understand that he didn't appropriatly account for condensation from operating below the due point, but my attention was drawn to the power set up he created using Molex connectors. Outside of constructing a computer, I haven't encountered this use for Molex connectors, and I believe he used them so that a computers power supply could power the peltier plates. Is that inference correct? Could anyone elaborate on implementing molex connectors in this manner with "loose" wires?

    Also what about using a wall wart? I'm disregarding efficiency.
     
    Last edited by a moderator: Apr 24, 2017
  11. Aug 21, 2009 #10
    If you're needing many amps at 12 volts, you're not gonna get it from the 12 volt supply on a computer PC or a wall wart. You could get considerable current (10's of amps) at lower voltages (3.3 or 5) using computer supplies.
    If you can run with lower voltages (lower temperature change), than the PC supply will work, otherwise you need something a little more dedicated - A 12V switcher
     
  12. Aug 21, 2009 #11
    there are a few projects about, that show you how to convert to high current winding and power supply components of a standard PC power supply, to change the high current supply part from the 5Volts for the digital logic, to the 12Volt supply for just such a purpose.

    look up "silicon chip" magazine or the like.

    "converting PC power supply for high current 12 volts".
     
  13. Aug 21, 2009 #12
    also if you need high current 12V, and it does not have to be super "clean", you can use a car battery and a bar battery float charger, then you can even claim "green" and put a solar panel on it.
     
  14. Aug 21, 2009 #13
    TORR SEAL is a polymer high vacuum sealant.
     
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