Brief contact switch?

Discussion in 'The Projects Forum' started by Subvertz, Sep 2, 2012.

  1. Subvertz

    Thread Starter New Member

    Sep 2, 2012
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    Got a friend building magnetic pulsers for new age health stuff, supposed to stimulate blood circulation, healing, blah blah.

    His customers are burning up their pulser machines by holding down the momentary push button switches. He needs a small push button switch that activates for only a split second even if held down. I know I've seen them before, but can't remember for the life of me what its called. I spend a day searching but even my google-fu is too weak.

    Any ideas? Thanks ya'll!
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,094
    3,033
    Lookup a 555 timer based monostable multivibrator circuit. Don't google vibrator. ;)
     
  3. Subvertz

    Thread Starter New Member

    Sep 2, 2012
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    Yeah, this application is a little space limited, and I was trying to avoid a circuit if there is a simple switch that could do it.
    I could even build a switch to do it, but it would simpler to buy for "mass" production.
    Thanks though!
     
  4. #12

    Expert

    Nov 30, 2010
    16,261
    6,768
    This page has an explanation about retriggering the monostable and blah blah blah.
    It's enough information to design a lockout period.

    http://www.allaboutcircuits.com/vol_6/chpt_8/4.html

    If we could see inside the pulser design, we could probably sneak in a capacitor and a resistor using very little space.
     
  5. Subvertz

    Thread Starter New Member

    Sep 2, 2012
    3
    0
    OK, I asked him and its called a Beck Pulser. The picture isnt my friends, but very similar. He's got one trigger push button DPST on the unit, and one on the handle of the coil.
    So the one on the unit has plenty of space, but the one in the handle (about 6" of 1" of PVC pipe) is cramped already.
    It only takes about a millisecond to discharge the capacitors throught the wand coil (design purpose). Leaving the button depressed has been burning up SCRs. Yeah, user error, but he's trying to design it out.
    [​IMG]
    Circuit below:
    [​IMG]
     
  6. #12

    Expert

    Nov 30, 2010
    16,261
    6,768
    Here is a simplified circuit of a switch that can not keep the triac conducting if it is held "on". In addition, it will take several seconds to build up enough charge to fire the triac again.
     
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