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Pulse (One-Shot) Timer

Discussion in 'General Electronics Chat' started by Kal_B, Mar 12, 2017.

  1. Kal_B

    Kal_B Member

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    And here's a video of it. The oscillation starts at 0.31 seconds when I switch on SW2.
    SW1 is just me touching the two wires.
     
  2. Kal_B

    Kal_B Member

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    I like it. I read alittle about what a snubber is and it just may be the solution.
     
  3. Kal_B

    Kal_B Member

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    So the snubber would go across R2? I don't understand how it affects the circuit by simply passing through the contacts of R1!
    R2 in the real life application is a 220VAC Contactors.
     
  4. dave

    Dave New Member

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  5. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    The snubber goes across the contacts handling the AC. The idea being to surpress (snub) the AC contact arc.

    Ron
     
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  6. kinarfi

    kinarfi Well-Known Member

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    I was tired and headed for bed, AND MIS READ SCHEMATIC, POST DELETED
     
    Last edited: Mar 21, 2017
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  7. Kal_B

    Kal_B Member

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    Hello guys,

    I tired a PLC and a commercially bought pulse timer in place of the one I built and they both worked fine without a snubber, why were they able to do that and not the one I built?
     
  8. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    While the data sheet is informative less an actual schematic it is hard to guess what the commercial circuit has that your circuit doesn't. That leaves it open for guesses and speculation. :(

    Ron
     
  9. Kal_B

    Kal_B Member

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    Sorry, wrong thread...sort of.
     
  10. Kal_B

    Kal_B Member

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    Hello everyone,

    So I finally got back to this circuit again and trying to make it work for learning purpose as I already bought a commercial pulse timer to do what I wanted to.
    I didn't buy nor make an RC snubber due to lack of time and knowledge but I needed a contactor and a surge suppressor for another application and had them at hand so I thought I would try them out but first a reminder of what the problem was.

    The circuit as in the attachment works fantastic without R2 in it. Everything works as intended but when R2 is wired as in the attached drawing both relays oscillate On and Off for as long as switch S1 is closed and when it opens they oscillate a couple of times then turns off.

    Now when I am using Sprecher+Schuh Contactor CA7-9E-10 with surge suppressor in CRV7 (in the same .pdf) place of R2 and it worked perfect so I figured the surge suppressor made the difference but to confirm that conclusion I removed the surge suppressor and to my surprise the circuit still worked perfect.
    The question is why does the contactor work and not the relay, both are VDC?

    And what's the difference between an RC snubber and a surge suppressor?

    Thanks
    Kal
     

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    Last edited: Sep 10, 2017

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