Motor polarity reversing

Discussion in 'General Electronics Chat' started by ducky_bass, Apr 14, 2010.

  1. ducky_bass

    Thread Starter New Member

    Apr 12, 2010
    Hi, i need to know how to reverse the polarity on a motor. I'm planning on building a robot with a pushbutton switch in front a when it runs into something the switch is pressed and reverses the motor polarity. I'm hooking the switch up to a 555 timer and somehow plan to use the output to reverse polarity of the motor, but I don't know how. If anyone can help me, please do.

  2. beenthere

    Retired Moderator

    Apr 20, 2004
    For your given purpose, a DPDT relay would probably work. Using a latching relay lets you get away from the 555 (not sure how you were planning to use one).

    If you want something snazzy like speed control too, then you will want a PWM circuit.
    ducky_bass likes this.
  3. retched

    AAC Fanatic!

    Dec 5, 2009
    SgtWookie has posted a schematic to this problem from other members. The DPDT relay could be triggered by the impact bumper button. The + and - to the motor are simply swapped on the other side of the relay.. And using a latching relay, you can do without the timer. However, if you only wanted to reverse for a set amount of time, you could trigger a 555 as well as the relay to de-energize the reversing relay after a set delay. This is how the robots that use the 90deg reversing wheels work. (The wheel drives straight while forward, but when reversing, it mechanically turns)
  4. SgtWookie


    Jul 17, 2007
    I was looking for the image, but I'd given it a different name from all the other motor reversing schematics I'd done, so it took me awhile to track it down.

    It's a pretty simple idea. It would be best to use a resistor between the switch and motor, or switch and power supply, as if the motor is reversed at full speed with no current limiting, it will be hard on the motor.