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need help finding the right part for a mini fridge/cooler

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johnathon007

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Im trying to build a TEC powered mini fridge/cooler and so far all has gone well but the TEC empties my battery to fast and gets colder then needed. What i want to do to fix it is put a thermosister in to limit the power when it is cold enough [around 40F] and raise power when it gets warmer. the battery im working with is a 6V like the ones found in kids cars its a 9Ah battery and i would like it to idle down to around 1-2 amps when its at ~40F [i think it runs about 6 amps just on the TECs internal resistance but cant measure because my multimeter is crap] on a side note the battery also powers a 80mm computer fan for the heatsink and a 40mm vga fan for the cold air circulation. I get around an hour if im lucky right now but id like to be able to bump that to around 2-3 or more if possible.
 
I use a commercially available programmable thermostat that has front panel controls and an LDC readout. It's not cheap at about 35USD, but you'll be up and running in about 15 minutes. I buy it from a local retailer. If you trying to cheap out, then you're probably looking at a homebrew controller. There are a few threads, so if you tell me how much you want to spend, I'll try to find the appropriate thread.
 
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I could try to salvage an old thermostat from somewhere but i was going to try to spend under $40 for the whole thing and im at 35 right now, so maybe an analog thermostat would better fit my budget.
 
that all looks a bit over done for what im doing, i dont need anything really complex more of a high low is what im looking for. Just a simple full power and then a second setting to stablize the temp. i cant really find one but a thermosister that is ~0Ω at 40F and 1-2 at above that [if my calculations are right which they probably arent]
 
You can eliminate the feedback resistor, and make one of the resistors connected to the "+" input (R16 in the final drawing -- post #93) a variable one, to dial in the desired temperature. It doesn't get much simplier than that.
 
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i bookmarking that page but i think im going to look for a prebuild thermostat just becuase im trying to keep this very professional looking, im not sure why i want it to look so nice but thats how i like to do everything.
 
Ir you use a simple mercury switch t-stat, you have to mount it exactly as it would be used in house. It's proper operation depends on the way it's mounted. If you use a digital one, you can mount it any way you please.
 
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