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Interfacing with machine counter

Discussion in 'General Electronics Discussion' started by getya, Dec 6, 2012.

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  1. getya


    Dec 6, 2012
    I'm trying to use the counter signal from a pad printing machine to trigger a small 24v relay.

    The machine has a pnp output that signals the end of cycle to an omron h7ec.

    When I try to hook a relay directly to the output and +24v the relay latches at the end of the cycle and stays latched.

    My understanding is I need a diode between the inputs on the coil of the relay but I'm not sure what type and rating to use and if this actually the proper way to do this.

    Any help you fine gentlemen could offer would be greatly appreciated.
  2. davenn

    davenn Moderator

    Sep 5, 2009
    hi there
    welcome to the forums :)

    The diode across the relay coil is there to stop the back EMF spike. Its not likely to stop the latching.
    The latching will be caused by one of 2 likely reasons ...
    1) you are accidentally using a latching relay ??
    2) there is still signal from the machine that is holding the relay on
    that will need to be determined and if so find a way to reset the output from the machine.

    the other question is... why are you using a relay between the machine and the counter module anyway ?

  3. getya


    Dec 6, 2012
    I need the relay to momentarily supply 120v ac to actuate a pneumatic solenoid that controls an indexing table. Basically the machine is designed to run 1 part at a time but I've got a 6 position indexing table with an ejector mounted in front of the machine so an operator can easily run twice as fast.

    Currently it works well but I'm using a mechanical switch that gets struck by a part of the machine during operation to control the indexing table. If I can use the counter signal the machine will run much faster and I won't have to run the table as fast which will reduce wear.

    I've got another machine with the exact same setup except it runs a mechanical counter triggered by 24v so it was childs play to convert it to use the relay.

    The relay I'm using is definitely not a latching relay as it's the same model I used on the other machine

    The conversion boosted the output of the machine by 43% and I was able to reduce the indexing tables air pressure to 50 psi from 90.
  4. getya


    Dec 6, 2012
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