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Trying to create a cooler that plugs on the mains. How should I make it Answered

I want to use this item (peltier module) to create a cooler. It will use a fan + heatsink to blow cool air. I dont have much knowledge in circuitry (only highschool level) so I wanted to know what I would need to create this and how the design should be. Thanks

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Jack A Lopez

9 months ago

I think a typical peltier module is going to be hard to break by overpowering it, provided it has somewhere to dump the heat. Or in other words, it should be happy provided it has a big heatsink, and maybe a fan too, on its hot side.

Regarding the electric power supply, ideally it wants to be driven by a stiff, constant, 12.0 volts DC. However you might be able to err by like %20, high or low, (i.e. from 9.6 to 14.4) and still not hurt the thing.

The actual current that flows, depends strongly on the applied voltage. In fact you could approximate the peltier module's I-V curve as a resistor, and calculate its value just by dividing 12 volts by the rated current. E.g.

R = (12 volts)/(5 amperes) = 2.4 ohm

So, using this logic, the current seen when underdriving it, with only 10 volts, would be:

I = 10V/(2.4 ohm) = 4.17 A

Overdriving it, with 14 volts, gives,

I =14V/(2.4 ohm) = 5.83 A

With dissipated power, V*I =V^2/R =I^2*R, at 50.04 W, and 81.6.2 W, for the underdriving and overdriving case, respectively. It was just 12*5 = 60 W, for the nominal case of 12 volts at 5 A.

Basically when you go shopping for a an adapter, or power converter, for to change your mains power into 12 volts DC, you want to pick one with a current rating greater than the expected current draw from your device, which in this case is 5 amperes (5A). So, for example, 12 volt power supplies rated at 6A, 8A, 10A, etc, are all good.

If you are wondering how I know the expected current draw is 5A, the answer to that question is in the URL you provided,

"Thermoelectric-Cooler-Peltier-12705-12V-5A"

and also in the part number itself. The trailing "05", is the current rating in amperes. The "127" refers to the number of semiconductor junctions, and there were some other numbers encoded in the part number. This link, to a page titled "What TEC do I have?", explains what they all are:

https://customthermoelectric.com/tech-info/te-ency...

By the way, the problem of powering one of these peltier modules, from mains power, is similar to the problem of powering your old cordless drill, or other battery powered tool, from mains power. I mean the power converter is roughly the same spec, roughly 12 volts, with max current in the range of 5 to 10 A, approximately.

There are some power converters other things, like the old Microsoft Xbox 360(r). I think its power brick supplied 12 volts DC, at a max current of around 10 A, or so. The exact number was printed on the name plate, and varied slightly from one version to another.

Also the old, unregulated, battery chargers, for lead acid starting battery, for car or motorcycle. I have used these as, approximately 12 volt, DC power supplies, for loads that don't care about exact voltage. For these I added a large electrolytic capacitor, for to reduce ripple voltage.

I can share some pictures of these, if anyone is interested. I mean these pics already exist in my image library. I'd just have to find the links to them.

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Jack A LopezJack A Lopez

Reply 9 months ago

As promised: some links into my image library, showing old, dumb, 12 volt battery chargers, plus big filter capacitor for each, powering some DC loads, like a formerly cordless drill, and one of these peltier mini-fridge things.

The LO-MED-HI switch on the battery charger can still be used roughly for its original purpose; i.e. to crudely vary the amount of power flowing to the load.

The last pic shows what one of this style of battery charger looks like, before completely taking it apart. Typically these have a built-in ammeter, plus some kind of LO-HI, or LO-MED-HI, switch for different levels of power output.

https://www.instructables.com/file/FXRNIPRH0KKFXYP...

https://www.instructables.com/file/FGVV8KEH0KKFXYN...

https://www.instructables.com/file/FKHIHH6H0KL0KOF...

https://www.instructables.com/file/F2KKB6MH0KKJ61S...

https://www.instructables.com/file/F51PZFDH0KKW71H...

https://www.instructables.com/file/FNBPFAAH0KKW71I...