Adding reverse function to a DC speed control.

Discussion in 'The Projects Forum' started by duey101, Feb 2, 2014.

  1. duey101

    Thread Starter New Member

    Feb 2, 2014
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    0
    Hi,

    I would like to ask a question about a speed controller I want to use for a camera slider. The controller I want to use is one directional as far as I can tell, but I would like to know if it is possible to make it reversible by maybe adding a DPDT switch or some other option so the motor will move in both directions. Can someone take a look at the attached images and let me know if it is possible to make the controller reversible. If it could be done how would I go about wiring it to the switch? I am just getting started learning electronics wiring so any help would be appreciated.

    The one I want to use is here...

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  2. crutschow

    Expert

    Mar 14, 2008
    12,977
    3,221
    If the motor can be reversed by just reversing the voltage polarity then a 2PDT switch can do that as shown here.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    One thing to watch when using a simple change over SW is that the motor should be at zero rpm when the reverse is made, otherwise you can overtax the switching semi.
    Max.
     
  4. duey101

    Thread Starter New Member

    Feb 2, 2014
    4
    0
    Thanks for your replies. I figured it could be done. What I was worried about is whether or not adding a switch would damage the board in any way. Apparently not, is that correct?

    So I guess I would end up with something looking like this then? I saw a post on some DSLR forum somewhere that had a similar situation but I can't find it.

    [​IMG]


    In that case, would I wire the other one like this?

    [​IMG]

    What I would really like is a way to modify the potentiometer so that it worked in two directions where the middle position stops the motor and moving it left or right controls the direction of the motor.

    Oh... it's fun when you learn new stuff.
     
  5. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
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    No, did you look at crutschow link?

    Only the leads to motor go thru switch.
     
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    Nope, not like that. That doesn't even make sense.

    If you want direction and speed controlled by the pot, you're going to need a different controller.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    As mentioned, do not connect like that, the power in does not go through the switch, just the motor leads are reversed.
    If you notice, the example you posted has extra terminals on the board in order to allow the switch to be connected correctly.
    Max.
     
  8. duey101

    Thread Starter New Member

    Feb 2, 2014
    4
    0
    Thank for your help. I will just buy the other one since it is already reversible.
     
  9. duey101

    Thread Starter New Member

    Feb 2, 2014
    4
    0
    But just out of curiosity, would this be correct? So in the off position the motor is of and then by switching the toggle to either on position would make the motor go left or right?

    [​IMG]
     
  10. inwo

    Well-Known Member

    Nov 7, 2013
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    Yes, motor to 1&2 or 5&6......................

    And another one may be no better. Unless it has safety features to prevent reversing under power.
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    There are special toggle switches that are used on these types of reversing situations such as used on the simple uni-directional SCR drives, the switch prevents the operator moving from left to right in one motion, the internal mechanism causes the toggle to stop at mid point until you relieve the pressure, they then allow the switch to be moved to the alternate position, they also have a section for placing a braking resistor across the motor.
    If you were interested, you may be able to pick one up if you have a local motor rep for Baldor or KB drives.
    Probably not cheap though?
    Max.
     
  12. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    A switch with a third pole helps too. Use it to open the latched stop function. (start-stop) It looks like your board may have one. Although it may be NO. which won't work directly.

    Motor will then have to be restarted.
     
  13. burger2227

    Member

    Feb 3, 2014
    190
    24
    You could add a nonpolar capacitor or make one to go across the two center switch contacts. Solder 2 large electrolytic capacitor negatives together and put the plus to each lug. That should absorb some of the reverse current.
     
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