At 01:26 PM 4/11/2010, Troy wrote: >Just a quick question about switches: I need a switch that when >toggled in one position will operates one appliance, and when >toggled in the other position will operates a second, different >appliance. Do I need a single pole double throw switch, or a double >pole, double throw switch? I'm guessing the latter, but wanted to >doublecheck. The SPDT If you're operating both appliances from the same circuit then an SPDT will do nicely; connect the supply to the center terminal. If you're operating from different circuits or voltages then you need a DPDT; connect each supply to one of the two center terminals. Note that most switches don't have DC ratings unless they're intended specifically for automotive use. A decent rule of thumb is that the switch should handle about the same number of amps at 12 v DC as it's rated for at 110 v AC. If you don't want to run heavy wiring to the switch, use a small SPST switch to activate an SPDT (or DPDT) relay which will do the power switching for you. If you need a "both off" position it gets a bit more complicated as the relay will have the NC contacts closed when it's not activated. Yours, David |
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