# Reversing the direction of a 1-3v DC motor using a limit switch

#### MrJSmith

Joined Mar 23, 2021
4
Hi guys, new to electronics, just wondering if I wanted to reverse the polarity of a circuit using a single limit switch, for example upon being activated the current would be reversed, what would be a good approach? Ideally I want to do this without the use of an arduino or anything like that.

crutschow gave a good looking diagram in this thread here http://forum.allaboutcircuits.com/threads/reversing-dc-motor-using-relay-and-limit-switches.144963 but this was in regards to a belt that would continuously move back and forth when it came into contact with a limit switch either end. Also this circuit was for a 12v DC motor but I am currently working with a 1-3V DC motor.

Many thanks.

#### Ya’akov

Joined Jan 27, 2019
8,180
It would be very helpful if you could explain the application for the motor.

#### LesJones

Joined Jan 8, 2017
4,013
You need to better define how you want the motor to behave. At the moment you have only defined what happens at one end of the motors travel. What happens at the other end of it's travel ? (Or does it just continues rotating in the same direction once it has reversed at the limit switch position ?)

Les.

#### MrJSmith

Joined Mar 23, 2021
4
Hi apologies, I should've described it better, I wanted to replicate the motion of a 3d printer belt.
As the motor is moving the belt, the aim is to reverse the direction of the motor when the limit switch is activated. The belt will continue to move in this direction and the direction will not reverse again.

#### MrJSmith

Joined Mar 23, 2021
4
You need to better define how you want the motor to behave. At the moment you have only defined what happens at one end of the motors travel. What happens at the other end of it's travel ? (Or does it just continues rotating in the same direction once it has reversed at the limit switch position ?)

Les.
Yes exactly, the motor will continually rotate in the same direction.
Edit: once it has been reversed as you said, just to clarify.

#### LesJones

Joined Jan 8, 2017
4,013
You will just need a DPDT relay with a 3 volt coil and an normally open limit switch. Here is a suggested schematic.

When power is applied the relay will be de energised and drive the motor in the direction of the limit switch. When the limit switch is triggered the relay will pull in causing the motor to reverse. When the limit switch opens again the coil will remain energised via the left hand NO contact and will continue in that direction until power is removed.

Edit. I have missed a diode out on the above schematic.. There should be a diode connected between the left hand motor connection and the bottom end of the relay coil. The cathode of the diode to the left hand motor connection.
Schematic now corrected.

Les.

Last edited:

#### MrJSmith

Joined Mar 23, 2021
4
You will just need a DPDT relay with a 3 volt coil and an normally open limit switch. Here is a suggested schematic.
View attachment 233460When power is applied the relay will be de energised and drive the motor in the direction of the limit switch. When the limit switch is triggered the relay will pull in causing the motor to reverse. When the limit switch opens again the coil will remain energised via the left hand NO contact and will continue in that direction until power is removed.

Edit. I have missed a diode out on the above schematic.. There should be a diode connected between the left hand motor connection and the bottom end of the relay coil. The cathode of the diode to the left hand motor connection.

Les.
That's really helpful, thanks, im just wondering if I was to put another motor directly in series with that motor in the diagram, would that also have its direction change when the limit switch is activated? I am assuming it does but just wanted to check.

#### LesJones

Joined Jan 8, 2017
4,013
It would work but the motors would rotate at about half speed. Also they would try to produce the same torque so if you put more load on one motor it would slow down and the other motor would speed up.

Les