I have a refrigerator that broke, some cheap Chinese PC board went out and its $40 for a new one. Its got an interface and a thermal control unit, but I figure if I can power the thermoelectric cooling unit and the fan to the heat sink, I can still make it certain level of cold at steady state.
I have an 18.5 V 3.5 Amp DC power converter for a laptop that I want to use to power the 12V 2-2.5 Amp (50-77W) Peltier plate, and the fan which works just fine at the full 18.5V, 3.5 amp and will be fine with less. What kind of circuit do I need to build to make sure I don't fry the fan/Peltier unit? If I put them in parallel do you think I'll be fine? I don't even know how to calculate values for this kind of circuit, as I have very little experience with electronics (just resistors/capacitors/inductors in school). Any help would be appreciated, and please don't tell me I'm an idiot and should buy a new PC board, because I already know that's the best solution to my problem.A fan, a peltier board and an 18v DC power converter = my refrigerator works again?
If the peltier module is in fact 12V and 50-77W, it draws 50W/12V = 4.17A to 77W/12V = 6.4A. If you connect 18V to it it will try to draw much more current than this, overloading both the peltier unit and the power supply.
No good. Just smoke or blown fuse.
The power supply has a total power of 18.5V x 3.5A = 65W, so insufficient to convert to a lower voltage using a relevant switch-mode supply, especially considering losses of 10-20%.
You could connect a 12V supply with at least 7A continuous rating across the peltier unit and the fan and that would work, just cooling to the minimum temperature the insulation vs heat-sink allows.
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