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I am a novice looking for as simple a device / circuit as possible to automatically reverse a small gearmotor ( stall torque max .5 A, 12 V DC) powered by a 2A 12V source, wherein the motor is to come on and runs 2 minutes (based on a timer that powers the AC to 12 DC converter) in one direction. After a period of several hours the timer powers up the DC and motor for another 2 minute run. What do I put between the +,- DC supply wires and the 2 wires to the motor, such that with no intervention by a person, the direction of the motor reverses on each next activation? Pretend you are talking to someone educated to High school physics. I have been told a Finder 20.23 relay would do this. No idea at all how to connect the 4 wires described above to make that relay do what I said. Thanks in advance for suggestions or a solution. This answer could be useful for many applications where someone wants to run a motor for x amount of time to do something, and the next activation run the same amount of time in the other direction to undo the previous run.

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  • \$\begingroup\$ You have to decide how the "thing" knows which direction to send the motor after it has lost power because without some kind of simple memory, powering up after a couple of hours it's not going to retain any knowledge of the previous event direction. It needs intelligence (of a sort) and memory. Or, maybe you can you provide the knowledge of which direction it needs to go? Maybe you should explain the set-up. \$\endgroup\$ – Andy aka Dec 15 '15 at 18:26
  • \$\begingroup\$ An impulse relay would do this kind of trick. \$\endgroup\$ – Marko Buršič Dec 15 '15 at 18:49
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The Finder 20 Series are step relays with plenty of power for your application but they only have two contacts.

schematic

simulate this circuit – Schematic created using CircuitLab

A DPDT (double-pole, double-throw) impulse relay should do what you need.

  • The sketch shows the relay with V+ connected to the left side of the motor.
  • The next time the 12V turns on the relay will change state (managed by some internal contacts not shown on the diagram). This will cause the motor to run the other direction.
  • And so on ...
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