An On/Off Motor Controller with BrakeA relay-based on/off controller on the other hand can be very efficient. A typical relay has a contact resistance of 3 milliOhm. At 20A, this translates to a voltage drop of 0.06 volts, with a power loss of 1.2W. The relay itself typically consumes around 0.4W. And, by using a double throw relay, one gets a brake for free.

An On/Off Motor Controller with Brake
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An On/Off Motor Controller with Brake