Op-Amp to vary speed of motor

Discussion in 'The Projects Forum' started by Adam D 1, Mar 7, 2016.

  1. Adam D 1

    Thread Starter New Member

    Mar 7, 2016
    I'm looking to build an electric go kart, but I'm having trouble figuring out how to vary the voltage going into the motor in order to vary the speed.

    Would a voltage divider with a variable resistor connected to a non-inverting amplifier, which is then connected to the motor work?

    I want around 36v to the motor, so at 85% of the input I would want to supply the op-amp with around 48v and not have it go much higher than the 36v.

    If anyone has any advice or alternative methods that'd be great. Thanks.
  2. #12


    Nov 30, 2010
    There is no such thing as a kilowatt op-amp. Your start ideas are fair, but you will need a lot more beef to control that amount of current.
    ps, How much current does the motor use? We need both the start surge and the running amps.
  3. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    How much current does your motor draw?
    Do you know what an op-amp is and do you have one that can deliver the current your motor needs?

    Investigate PWM motor speed control.
    MaxHeadRoom and #12 like this.
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
  5. adio9182

    New Member

    Mar 7, 2016
    It has been a while since I've looked at this project, found this (http://www.ebay.co.uk/itm/12V-24V-4...788102?hash=item4188c99b46:g:LNoAAOSwU9xUPQ29) PWM on eBay, would it be suitable to control say a 24v motor and allow for varied speed for a small vehicle?

    I would look into replacing the dimmer mechanism of this set up with either a lever or pedal set up, any ideas on equipment required to achieve this?
    Thanks for your help, appreciate it.
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    If your motor draws less than 20 amps it should work just fine..
  7. adio9182

    New Member

    Mar 7, 2016
    Any ideas on the lever/pedal set up?