How do I reverse polarity on a DC motor

Discussion in 'The Projects Forum' started by PMB917, Mar 27, 2006.

  1. PMB917

    Thread Starter New Member

    Mar 7, 2006
    I need a design that will allow me to switch polarity back and forth on a DC motor.
    I am designing a tiny vehicle that will go forward, backwards left and right. I've been reading up on the "H bridge", but woundering if theres a more simple way.

    Many thanks
  2. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    You could just use relays.
  3. alim

    AAC Fanatic!

    Dec 27, 2005
    Hi. do you want to do this manually? if yes a double pole single throw switch will do .
  4. Gadget

    Distinguished Member

    Jan 10, 2006
    Like Windoze says. a Double pole double throw relay or switch is needed.

  5. Spoggles

    Well-Known Member

    Dec 2, 2005

    If you use the same idea, but use two relays and connect the load (moter) to the common side, and use two N.O pushbuttons for foward and the other for reverse, you get the added benifit of having the motor stop when you want it to..

    You could also go really crazy and add another motor and two more relays (right and left) and two more push buttons (say a joy stick) and go any direction you want with the benifit of having the thing stop when all switches are off.

  6. ttennis

    New Member

    Aug 16, 2006
    Or you can use four transistors that are in bridge formation and the motor is across the null points. When you switch the bottom transistor of one pair on, the top transistor must go off. At the same time, the top transistor of the other pair must go on while the bottom one goes off. To make the motor go in reverse, turn the top transistor of the first pair on while turning on the bottom one of the second pair. Do the reverse of making the motor go forward.
  7. someoddthing

    New Member

    Dec 21, 2010
    I've been trying to do the same with the same idea listed above with the 4 transistor bridge. I just can't get it to work. I've tried different transistors (2N3904,2N2222,TP120-Darlington,etc.) and the main problem is getting the top transistor into saturation so that there is no major voltage drop across it. I need the majority of the voltage drop across the motor in order for it to turn on. I can get the bottom transistor in saturation, but not the top.
    So far, i don't think this is a viable set-up. :(
  8. thatoneguy


    Feb 19, 2009
    Have you tried an H-Bridge IC ? That IC provides 2 full H-Bridges to control 2 motors fwd/rev/stop/brake with logic signals. Though not at very high currents.

    A DPDT relay is simply a mechanical H-Bridge.

    What are the power requirements of your motor?
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    What is with this thread.. :confused:

    I think I am going nuts!!!
  10. Chris15

    Active Member

    Apr 15, 2009
    Dont use relays, Just use a Switch. Double pole single throw, some have a centre position which is off. wire it like this:

    Unless your car is Radio Controlled, then im not sure, yes maybe relays are better for that, but if its manual than this switch is the best way
  11. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Oh ..for the love of...

    this thread is 4 years old the date for Pete's sake
  12. Chris15

    Active Member

    Apr 15, 2009
    HAHAHAHAHA OHK omg, LOL nice point R!f@@