Power/Ground Switching

Discussion in 'General Electronics Chat' started by Kalcorp, Oct 22, 2014.

  1. Kalcorp

    Thread Starter New Member

    Aug 15, 2014
    5
    0
    I am looking to build a circuit that will allow me to switch the power and ground at any time. Meaning I need to design something that can switch its positive and negative output at any time. i.e. if I have a fan hooked up with positive and negative and the fan spins clockwise, I need to design something that can switch the positive and negative at will and then the fan would spin counter-clockwise (for example). Any and all help is greatly appreciated!!!! :D
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    use a dpdt, double pole double throw switch. the simplest way to do it.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,512
    2,369
  4. Kalcorp

    Thread Starter New Member

    Aug 15, 2014
    5
    0
    You guys are both awesome, thank you!
     
  5. crutschow

    Expert

    Mar 14, 2008
    12,993
    3,227
    The presumes the fan motor will rotate in the opposite direction when the leads are reversed. Most won't.
     
  6. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
    304
    And, if you need it, your switch should have a "center off" position
     
  7. wayneh

    Expert

    Sep 9, 2010
    12,094
    3,033
    True for the ubiquitous PC fans that the OP is likely using. We know that old-fashioned two-wire brushed DC motors will reverse, but that's not likely what the OP has on his fan.
     
  8. Kalcorp

    Thread Starter New Member

    Aug 15, 2014
    5
    0
    The fan was just an example fellas, to better illustrate what needs to be taking place
     
  9. wayneh

    Expert

    Sep 9, 2010
    12,094
    3,033
    Do you want manual switching as suggested? There are other ways to accomplish the switching electronically. Whatever you choose, be sure the switch is rated for the load you are switching.
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,512
    2,369
    Sounds like it may not even be a fan, but if it is many are blade designed for maximum efficiency in one direction!,
    Max.
     
  11. Kalcorp

    Thread Starter New Member

    Aug 15, 2014
    5
    0
    What ways are there to do this electronically?
     
  12. wayneh

    Expert

    Sep 9, 2010
    12,094
    3,033
    There are too many to list, without some detail about your specifications.
    I've used a 4017 counter IC to get reversing polarity. You put the load between two of the outputs, such as the "0" and the "1". Both are never on at the same time, and are pulled to ground when off. So current goes one way on "0" and reverses on "1", and then you can reset on "2" if you like. This will handle only a few mA. A 555 timer can handle up to ~200mA. Beyond that you need an H-bridge.
     
Loading...