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Controlling/limiting a 6v DC motor with polarity module

Discussion in 'Sensors and Actuators' started by Lord Drek, Jul 19, 2021 at 1:24 AM.

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  1. Lord Drek

    Lord Drek

    I am trying to control both the direction and limits of a small DC motor with threaded shaft using components and modules readily available online.

    I have a very small DC 6v motor with gear reduction (500rpm) and a 2” threaded shaft. Upon receiving signal (LED on)I need this motor to turn until the threaded object nears the end of shaft then have motor stop until a second signal (LED off) then it will reverse and threaded object on shaft goes all the way back to start position ready to repeat the cycle again.

    The first trigger event is a 5v LED turning on and the second is it turning off. I am having a problem translating that into a usable signal for a reverse polarity module I am using.

    I have a NO switch I am using to test and every click triggers the module to reverse direction as intended but I need my signal to be activated by both the presence of voltage and then the absence of it.

    Then I also need power to motor to be cut off when the threaded object reaches the limits of the shaft in both directions. I had intended to use micro switches but if I do this then motor has no power when module reverses.

    For the signal could I use a relay module hooking both up both NO and NC to the trigger side of polarity module? Would that end up making a signal (switch on) during both states? If so that would solve the trigger signal problem.

    Then I have the limit switches. If a switch cuts off power to motor at end of travel how can I get it to reverse direction when it is time to do so?

    It seems like such an easy problem and with all these modules readily available I just have such limited knowledge at this point. I do however suspect that will change…

    This is the module I am using for this but am not married to it if a better solution surfaces.
  2. Bluejets


    Oct 5, 2014
    Probably quite a few ways to do this
    This part doesn't make sense to me though.
    Following your first requirements, wire the common and normally open of a limit switch to the trigger contacts.
    When the drive reaches the end of the first run, the limit switch first closes, and as the motor drives in reverse, it will open again, hense your pulse requirement. This will need to be closed less than the 2 second upper range for the trigger as in the specs.
    For your shut down at the end of the two cycles, wire a start stop latch to the power input with a normally closed limit switch at the start end (open when in limit)
    I'll do you up a quick sketch later.

    Also, don't know why it is but take note of spec requirement No.3
  3. Lord Drek

    Lord Drek

    I think spec 3 refers to the trigger signal making the motor instantly reverse direction and to stop the motor would require switches. I have this module and this is how it operates. The spec that confuses me is requiring 3x motor load power to properly operate. Not sure how to achieve this without a voltage regulator.

    If this helps I’m trying to make a device that opens to a certain point when the LED light is sensed and then closes to the original closed point when LED goes off. I really can’t pull much if any power from the LED and was hoping to use a photo optic sensor originally. It worked well but I needed a second signal for the polarity module to reverse.
  4. Bluejets


    Oct 5, 2014
    No, what the spec says is whatever power supply you use with a motor, it must have at least 3 times the power.
    Meaning if your motor draws say 30W, then the supply must be able to deliver at least 90W.

    Then down a bit further is this.........
    The maximum load current is 2A. If it is a load motor, the maximum load current is 1A.

    So I'd be inclined to treat it as 1A and be done with it, forget the wattage.
  5. Lord Drek

    Lord Drek

    Thank you I now understand. The motor is the size of my thumbnail so this is not an issue. Between your post and another forum I am starting to see the solution by adding diodes and a relay without tapping into pinball machines LED for power. These new machines use “node” boards that are fragile and not easily serviceable. That is the appeal of using a photo sensor.
  6. Minder


    Apr 24, 2015
    It is simple to use two N/C. L.S. in the two motor conductors, A diode rectifier is wired across each, connected so they only conduct if the switch is open and the correct polarity is supplied to reverse.
    I can post a pic if needed. One show the L.S. Diode method.

    Attached Files:

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