reverse polarity motor help!

Thread Starter


Joined May 12, 2009
Hi all,

I am currently undertaking a personal project that is stretching the memory a bit in terms of circuit design / basic electronics.

Essentially this is what I need to happen. Designed to work on 12VDC, with a +12V constant supply, and a +12V switched supply - this will be the one to activate / deactivate the circuit.

When power is applied to constantly to the trigger wire, the motor in the will spin clockwise to open a monitor unit.
When the unit reaches a limit switch, the motor is stopped.

When the trigger power is disconnected (but still powered by constant 12v), the motor will turn in the opposite direction (reverses the polarity), until it reaches a second limit switch on the other side, then the motor will stop, in preparation for the power to be applied again (repeat of cycle).

Ideally, I would like a manual control switch to move the unit back or forth, depending on what position it is in. But this is optional to my needs.

The frame already has limit micro-switches installed, and they are normally open switched (completes the circuit when limit is reached). Ideally I would like to keep them this way, but please let me know your suggestions.

I have trolled through the site and found quite a few sample circuit designs, but I cant seem to adapt any to this specific application.

thanks you all.


Joined Mar 14, 2008
Here's a circuit I believe will do want you want. It requires two SPDT relays and one DPDT relay.

Motor Limit Ckt.gif

Edit: I didn't show a manual control. For that you could place a SPDT switch with center off between the Trigger switch and K3. Connect the common to K1, one contact to the Trigger switch output, and the other contact to V1.
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