I've got a Peltier element rated at 12V / 2.5A (30W), but I'd like some clarification on how I should power it. I'm familiar with building power supplies with LM78xx linear regulators, and I've had a little experience with the LM317, but I've never tried to power anything beyond about 500mW. I'll also be powering two small 12V fans to cool the hot side of the device.
I found the LM350, which seems like a good bet - 3A rated, voltage up to 33V.
I'd be powering this off a UK mains socket (230V AC), so I'd probably set it up the same way I would an LM78xx regulator - run the mains into a transformer's primary, run the secondary into a diode bridge to half-rectify, use a 1mF electrolytic cap to smooth it, then run that source into the regulator.
I have a few questions about this, though.
- What voltage should I aim for on the transformer's secondary coil? Somewhere around 15V (e.g. this) seems about right to me, but I'm not entirely sure. As far as I can tell from Farnell and RS, there don't seem to be many transformers around that have low voltage secondaries.
- Do I need to use a heatsink on the regulator? If so, are there any resources that would help me select an appropriate one?
- Can/should I run the two fans off the same regulator as the element, or should I use a second regulator to power them? I figure an inductive load in parallel with the element might complicate things.
- Would I need to do this on a PCB due to higher currents, or could I get away with using stripboard?
- Are there any special safety considerations I should take into consideration for this build, aside from the usual ones when playing with mains electricity?