Amplify current from function generator to drive motor

Discussion in 'General Electronics Chat' started by dustynrobots, Aug 11, 2015.

  1. dustynrobots

    Thread Starter New Member

    Dec 12, 2013
    I've seen a couple similar posts - but nothing that gets at what I'm trying to do. I have a function generator/oscilloscope (an Analog Discovery unit from Digilent) and want to use it to drive a small motor with a square wave, say 0-5V, 2 Hz. The motor I'm using is a Pololu low power 75:1 gear ratio DC motor that runs from about 2-12V and draws from 200-900mA or so. The square wave from the function gen can only source 50mA, so it's not enough to drive the motor, even unloaded. What are some ways I can boost the current from the function generator without changing the voltage? The objective is to use the function generator and oscilloscope to see the open loop behavior of the motor, then create a controller (in hardware with op-amps and/or in software) and see the difference in performance.

    Thanks for any tips!
  2. ScottWang


    Aug 23, 2012
    You can see the similar request as from #14, I also uploaded the circuit.
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    An amplifier which works down to 2Hz is what you need. An op-amp plus a P-MOSFET should do the job.
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    They make power opamps that will source/sink up to a couple of Amps. Get one, operate it on split +- supplies, and wire it as a voltage-follower. Here is a list of those in stock at Digikey
    Last edited: Aug 11, 2015
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    Here's the sort of thing I had in mind: