Stepper Motor to control vehicle clutch

I’ve got a project where I’m building an electronic system to control a clutch on a classic mini. I’m a paraplegic (in a wheelchair) and want to make the clutch hand controlled.

I’m planning to use a stepper motor and controller. The control input will be a spring loaded potentiometer off a mobility scooter. The potentiometer will be used to control the rotational position of the stepper motor and not the speed.

I’ve been looking at this stepper motor tutorial (Stepper Motors and Arduino - The Ultimate Guide (

I’ve been looking at either of these stepper motors:

  1. Stepper Motor: Unipolar/Bipolar, 200 Steps/Rev, 57×76mm, 4.5V, 2 A/Phase or
  2. Bipolar Stepper Motor with Planet Gear Box ( stepper motor.

Design overview:
• Cable connected to clutch has a 4kg load with a 70mm travel length.
• Stepper motor load will be 1.17N-m (12kg-cm) total rotational position will be 0-135 degrees
• Cable to be pulled by a pulley (which I’ll get machined)
• Pulley to be controlled by either a direct stepper motor or a stepper motor through a gearbox
• Power source is the cars 12v battery.
• System controlled by a spring loaded throttle switch (either a jetski throttle or a throttle switch from an electric scoot).
• Design to have a switch at the end of the clutch travel. When engaged the stepper motor is to stop rotating and hold load.

I’m looking at using an Adriano UNO R3 and maybe the A4988


  • Which motor would you recommend
  • If using the motor with planet gearbox:
    • What is the weight
    • Is there a bracket for the motor? Does it match one of the NEMA sizes
  • Which controller would you use? Is this A4988 suitable (A4988 Stepper Motor Driver Carrier, Black Edition (Header Pins Soldered))
  • Do you need a fuse between the car battery and the controller
  • What else would I need for the build
  • Is there any example codes for using stepper motors to control position and not speed.
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Hi Neil,

I’ve never looked into what the process is for modifying the controls of a vehicle and having it remain road legal but might be able to assist with the stepper questions directly.

Both of those steppers will produce more or less the same result in terms of torque at the output shaft but the consequence of one using a planetary gearbox will mean the stepper motor itself needs to rotate further and faster to give the same output speed.

It looks like the A4988 would have enough current capacity to continuously drive the geared stepper, but would be undersized for the larger stepper motor. So you’d either need to keep current limiting on and have the stepper give less than it’s full power output, or find a larger driver.

It certainly wouldn’t hurt, accidents happen and it’s usually worth the trouble of installing.

The larger motor shouldn’t be too hard to mount since it’s just a standard Nema 23. The stepper with the gearmotor is Nema 17 sized, but will need a mount to match the gearmotor’s faceplate which is smaller still. Nema sizes correspond to the outside of the square faceplate so the gearmotor appears to be using a different mounting standard, but it may not be too hard to match by drilling some correctly sized and spaced holes in another bracket with a cutoutt large enough for the motor shaft.

My own experience with geared steppers is limited so perhaps someone else in the community will have more insight regarding the tradeoffs you can expect in terms of maximum speed, blacklash, mounting options.

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Welcome Neil!!

Sounds like an awesome project :smiley:

Is there any reason why you’ve opted to use a stepper instead of a large high-torque servo?
Some pros and cons for each:

  • Setup should be far simpler - inbuild position control
  • Programming the servo is very easy - lots of libraries are available for different microcontrollers


  • More limited voltage input - you’ll most likely need a regulator
  • The motor itself is likely to cost more
  • If it fails it may enter a lot of different modes - frozen, free spinning

Stepper motor:

  • Wide input voltage, just set the current limit to make sure the motor doesn’t burn out
  • Also easy to program


  • Out of the box you are only able to input a velocity and even still you aren’t certain that the motor is moving (You’ll need a form of position control programmed into the Arduino)
  • More parts to use the stepper


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HiTrent and Liam,

Thankyou for the response. I’mnowlookinginto servo’s need to find one that has the required torque requirements. Will post again if I don’t find what I need.


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