# DC Motor reversing relays using a micro switch [closed]

I'm looking to use relays and 1 micro switch to reverse the polarity of the circuit. I will need a simple ON/OFF switch to have the motor turning in one direction and then when the micro switch is activated for it to reverse polarity and stay it to stay that way.

• It is really not at all clear what you are asking here. This question will require a lot more detail. Jan 19, 2015 at 13:31

What you want is a double-pole double-throw (DPDT) switch. These can be arranged to appear as a box that has two inputs, and the outputs are the inputs but possibly flipped depending on the state of the switch. Hook up the DPDT switch like this:

Follow this circuit and see that when the switch is in the right position, as show, OUT is directly connected to IN with the same polarity. When the switch is in the left position, OUT is flipped from in.

If IN is connected to a power supply and OUT to a DC motor, then the switch sets the direction the motor is driven by the applied voltage.

This switch can just as well be the output of a DPDT mechanical relay. Energizing or not energizing the coil then controls the motor polarity. Your microswitch can drive this relay on/off, or it can be the input to a microcontroller. The micro can then perform more complicated logic and timing on the microswitch signal and drive the DPDT relay accordingly.

It sounds like you ought to have a 3 pole double throw relay. Two of the poles are wired as Olin points out like this (motor reversing circuit): -

The 3rd pole is used to latch the relay into the opposite direction: -

(source: the12volt.com)

The diagram above shows a switch called "push start" - ignore the name and use the micro switch in this position. When this switch is activated, the 3rd relay contact closes and shorts out the micro switch thus latching; the other two contacts are used for motor reversing.

A simplification is made if you look at the A-B contact on the 1st diagram - point A can wire back to the relay coil thus you only really need a DPDT relay.

Shown below is a simple arrangement that forces a train on a track to reverse back and forth when it hit buffers: -