24VDC Motor Control Question from a Novice

I will admit I am a novice at motor controllers. I am a Chemical Engineer and an avid woodworker for 15+ years now.

I have a power wheelchair motor that I would like to drive with a 24VDC power source. I already tested and the power source and motor are operational.

The goal is to use the motor to operate a threaded shaft that will drive a carriage (holding a router) back and forth in between 2 contacts.

I was thinking of using a latching type relay with a DPDT that would change the polarity of power feeding the motor. But now I think a Pololu simple motor controller might work. Being a ChemEng I don’t want to have to learn programming in order to get this functional. The more simple the better, something I can diagnose and fix easily.

For contacts I was thinking simple push buttons to act as momentary switches, but I’m not sure how I would get the controller to interpret that as reversing directions (polarity). Would I have to have one contact be a latching relay type of connection and the other would break that latch?

Really any help would be appreciated.


Hello, Ivan.

I am not entirely sure how you are proposing to use the relays and switches you mentioned together, but a DPDT switch will allow you to reverse the polarity of your power supply to switch motor direction. If you post a diagram that shows how you intend to connect everything, I might be able to make suggestions.

As you already mentioned, you could also use the Simple Motor Controller to switch motor direction. However, you would probably have to write a program to get it to change motor directions after encountering a limit switch.

In general, wheelchair motors are pretty powerful, and it sounds like you might be switching from full speed forward to full speed reverse, which could cause the current draw to be twice the stall current. So, you should make sure the Simple Motor Controller you choose can handle that current.

Also, please note that we do not recommend our products be used in applications where their failure might result in injury or significant property damage.


Latching Relay Schematic - 041814.pdf (171 KB)Jonathan,

My apologies for not getting back to you sooner. Please see attached schematic of what I was thinking. Essentially I am looking for a way to change the direction of a motor with a relay and a pair of contacts.

My question is, how do I select the Relay if I want it to drive a 24VDC motor and what control voltage do I need? I think the control voltage will define my selection of contacts and may be dictated by the Relay latching voltage.

Any help would be appreciated. I understand the liability and am aware of the potential risks involved.


Unfortunately, I am not sure if your circuit will work and do not have any advice on how to select an appropriate relay; maybe someone else on the forum can help. If you decide to use our Simple Motor Controller for this, and have additional questions about using it, let me know.


I’m not sure how to proceed, I’m know the circuit as drawn might not be 100% but I don’t have the time or inclination to learn programming.

If there is anyone that would know how to select the parts and program the Simple Motor Control then I would appreciate the help or point me in the right direction.


I am not sure what your preferred method of control would be, but the Simple Motor Controller supports analog voltages as input, so you might consider using a potentiometer to adjust the position of the router carriage along its two contacts. This approach does not need any programming. You would only need to connect the SMC directly to your computer to configure it to accept analog voltages. You can read more about this inside the “Connecting a Potentiometer or Analog Joystick” section of the SMC’s user’s guide, which can be found under the Resources tab of its product page. Also, if you tell me the intended operating voltage and stall current of your motor (or link to the datasheet or product page for it), I might be able to help you pick out an appropriate SMC.



I wanted this to be automated oscillation, not manual direction change.

If there is a way to set up a 24VDC motor control with alternating polarity (changing rotation) and I can find someone that would be able to program that would be OK.

Any hardware needs to be robust as it will be subject to life in a woodshop with sawdust and vibration.


In general, programming is required to automate hand tools like that. You might be able to find more information and help with that kind of thing on a website dedicated to DIY CNC, like BuildYourCNC.