timed dc start/stop circuit

Discussion in 'The Projects Forum' started by daltman1967, Feb 25, 2011.

  1. daltman1967

    Thread Starter New Member

    Feb 25, 2011
    2
    0
    I have a small dc motor I'm buying. When I push the button one way, I want it to start (forward), then stop after x seconds. When I push the button the other way, I want it to start (reverse), then stop after x seconds. The x seconds will have to be adjusted, according to how long it takes to perform its function.

    I have absolutely no idea where to begin. A 555 timer? Any help is greatly appreciated. I need this circuit ASAP. Thanks!
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,792
    948
    You are on the right track with a 555. I would recommend the 'One Shot' configuration. You could include a pot to vary the duration of the pulse.

    For reversing a DC motor you would first make sure it is capable of reversal by reversing the input polarity, then attach the motor to a relay center contact and use it select direction. One switch position activates, and the other deactivates the relay, and either position triggers the one shot timer.

    Edit: You will need two relays. a double pole double throw (DPDT) and a single pole single throw.

    The one shot will need to also drive the single pole relay. It will prevent the motor from running until the button is pressed

    If you need a simple diagram let me know.
     
  3. bio88

    Member

    Feb 17, 2011
    34
    0
    Interesting - I have a very similar motor driving need myself. My application does the same exact thing as the OP but has a pause for X seconds in the middle before motor spins other direction.

    I've been reading that the timing of the on state and off state can be done by an RC timer? Assume cap and resistor? That would be ideal to keep costs down and for simplicity.

    Any diagrams would be very helpful!
     
  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,792
    948
    circuit minus the 555 timer.

    [​IMG]

    Sorry Bio88, this isn't for you, but maybe will give you ideas.
     
  5. daltman1967

    Thread Starter New Member

    Feb 25, 2011
    2
    0
    I found a circuit which might work... the momentary pushbutton would be pressed by a lever on the motor; when the motor turns so far, it hits the pushbutton, turning itself off. The same type of pushbutton is on the other line for reverse.

    This totally eliminates the 555 timer idea. What do you think?
     
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