Motor Controllers and Potentiometers

Discussion in 'General Electronics Chat' started by hacksign23, Sep 26, 2010.

  1. hacksign23

    Thread Starter New Member

    Sep 20, 2010
    Hi. Quick question.
    What exactly does a motor controller do? I know it obviously controls the motor, but how exactly does it work?

    Would it work if i just put a pot in place the motor controller?

    oh, and does a pot work by analog or digital?
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    A potentiometer is an analog device, although digital pots are available. However, you haven't made it clear if the motor is AC or DC.
  3. Wendy


    Mar 24, 2008
    Most pots don't handle current well, which most motors use in plenty.

    Pots are used to control electronics that control the motor because of this.

    As beenthere said, we need more info.
  4. majsyd2010


    Aug 29, 2010
    Saying in a sample way, for small DC motor a pot can be use to speed down or up the motor, But when we are talking about the motor controller, it will be a pot plus few other dry contact inputs and outputs that control other applications like fire alarms, timers and etc.

    For large AC motors, the VSD (Variable Speed Drive) or/and VFD (Variable Frequency Drive) are used as controller and speed driver such us soft start, Speed control based on Frequency or as sample as percentage. It also has Inputs and outputs for fire alarms and circuit board indicators and BMS (Building management system) input and etc.

    Hope you get the basic idea and if you want more info about it, the best website is

  5. hacksign23

    Thread Starter New Member

    Sep 20, 2010
    hi sorry :p it's a dc brushed motor
  6. DangerousBill

    Active Member

    Jul 21, 2010
    Using a pot works in some cases, especially if startup torque isn't an issue, and if the motor draws little current. The pot should be wirewound and rated for the max power dissipation.

    The simplest practical motor control produces a rectangular wave at full voltage. The duty cycle determines motor speed. The wider the ON pulse, the faster the motor runs. Frequencies of 50-200 Hz are ok with small motors.

    By doing it this way, you maintain torque (especially the startup torque), you use less power, and the motor can be run at a lower speed before it stalls.

    Dangerous Bill