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How can I reverse polarity using 2 switches? Answered

I am trying to reverse polarity on a small 12 v pump. I currently have 2 SPDT switches and have them hooked up like a DPDT. I am getting voltage feedback when they are in the off position. I need to have t switches any help?



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10 years ago

Using a pair of spdt switches, we define the three connections for each

1) NO or normally open
2) NC or normally closed
3) COM, or common terminal

Connect the pump (-) to COM on one of the switches. Call this S1
Connect the pump(+) to the COM terminal on the second switch S2
Connect PWR(+) to the NO contact on S1and the NC contact on S2
Connect PWR(-) to the NC contact on S1 and the NO contact on S2

You will require a third switch to enable disable power to the circuit, UNLESS the spdt switches are of the form On-OFF-ON, which empirically can be determined by answering this question:

Do the switches have a center position? (that is, are there three detent positions for the switches?)

Presuming the answer is yes, then the center position will be "power off", and as long as the two switches are switched the same each to NO or each to NC, the voltage will reverse and engage the pump accordingly.