Here’s all the pertinent stuff for the 50 Amp hot air tester:
The brain is capable of driving the relay directly and has an internal protection diode, which simplifies things. The load is a pair of 350 watt 12VDC air heaters for cars. These use PTC heating elements so the temperature is self limiting and pretty much constant power. The fans are very quiet! If you want to put in three or four switches you can get a range of load currents very cheaply.
Note that the fans run all the time; you want to make sure the heaters get cooled off after the test.
Components:
- Brain and 50 Amp shunt, $28:
- Fuse, 75 Amp. $8 Something like these two, or get it from your local auto parts place. A breaker would work just as well too. Don’t go bigger than 75Amps or so.
- Two air heaters, $27
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- REALLY important: make sure your fans run the right direction. I got one defective one!
- Contactor (has an 80 Ohm coil), $13:
- Wire: use 6 AWG fine stranded. If you want to run lots of parallel wires to the heaters use 14 AWG or so; each one passes 15 Amps.
- SB50 connectors, you need one set with 6 pins. About $20.
- Three crimp lugs for 1/4" studs (2 for 6, one for small wire)
- Enclosure: plastic or wood; note that there will be air running through the heaters, so plan for in and out! The fans are open, so make sure you keep fingers and junk out of them.
About $130 plus wire and enclosure.
