Changing state to pulse trigger timer

Discussion in 'The Projects Forum' started by squawker, Jun 26, 2014.

  1. squawker

    Thread Starter New Member

    Jun 26, 2014
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    0
    I need an idea of what approach to use for interfacing an electronic skin conditioner to a timer/stopwatch to measure time of cycles. The device is a very low current source that runs up to + or - 12VDC depending on the cycle. I need to start a stopwatch timer with a change in output state when the unit starts a cycle and stop the timer a few minutes later at the end of a cycle when the output state changes back to to 0V. Unless there is a better timer, the only one I could find with an external trigger requires a momentary contact to start and to stop the count. So far, the only thing that comes to mind is 2 short pulses to a relay module. The best way to automatically turn both a +12VDC and a -12VDC long duration pulse (minutes/done separately) to 2 short pulses at the rising/falling edges is what has me thinking. or is there a better overall strategy (without an MCU).
     
  2. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Sounds like you need a free running clock with an enable input.

    Then a rectified signal to the enable pin would allow clock to run during cycle.

    Reset is another issue.

    Search for time counter or timer

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    Last edited: Jun 26, 2014
  3. squawker

    Thread Starter New Member

    Jun 26, 2014
    3
    0
    So far, this is the only timer I can find with any kind of external trigger (momentary contact between green and black is equivalent to pushing the start/stop button)
     
  4. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    The omron H7ET series of timers are self powered displays.
    Bottom picture.

    http://elcodis.com/parts/479137/H7ET-BM_p2.html#datasheet

    Enable and reset input can be ac, dc, or contact closure.
    Models from seconds to days.

    The low level output from your device should be easy to use for enable signal. This will cause clock to run only while your device is in operation.

    A reset signal can be manual or ?

    http://www.ebay.com/itm/Omron-Time-...236?pt=LH_DefaultDomain_0&hash=item565d258c14

    Or seconds
    http://www.ebay.com/itm/H7ET-B1-Omr...294?pt=LH_DefaultDomain_0&hash=item1c3b41bd26
     
  5. squawker

    Thread Starter New Member

    Jun 26, 2014
    3
    0
    yes, timer start with 8-12VDC positive rising edge and stop with falling edge, then manual reset - and the same with a single negative pulse (up to 5 minutes) This model looks like it might work but it is difficult to tell for sure from reading the spec sheets.

    Thanks
     
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