555(?) circuit to detect double pulse?

Discussion in 'The Projects Forum' started by mbabayan, Mar 21, 2011.

  1. mbabayan

    Thread Starter Member

    Jul 12, 2010
    30
    1
    Hello,

    I'm trying to design a circuit that would produce an output pulse (.5-1 seconds) when double pulse on the input is detected with a time gap of <=.5 seconds.
    It looks to me like something that could be done with 555s, but I don't have enough experience to produce it myself and google did not reveal anything :)
    This is supposed to be a gadget that activates a garage opener on the double-tap of the "flash-to-pass" switch on the motorcycle. Devices like this are available commercially, but I'm not paying $100 or so when I can build it :)
    Thank you very much in advance for suggestions.
     
  2. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
    2,831
    89
    You can use 4017 with 555 ic, set how many pulse you want to detect with the help of 4017, have a look of 4017 ic in Google. the reset pin should be used if you want 2 pulse then connect the reset pin to 4th output of decade counter (4017) and take output from 3rd serial output. the timing you want can be set by 555.
     
  3. mbabayan

    Thread Starter Member

    Jul 12, 2010
    30
    1
    Thanks!
    Now if I could only find an LTSpice model for that counter :)
     
  4. mbabayan

    Thread Starter Member

    Jul 12, 2010
    30
    1
    Well, it appears to be working (in LTSpice)
    Not sure if this has a chance in real world, so would really appreciate an input.
     
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  5. mbabayan

    Thread Starter Member

    Jul 12, 2010
    30
    1
    Given that the pulse will be produced by closing a switch ( no pulse = 0v, pulse = 12v), and final output should follow the same logic, here are updated schematic and plot.

    Feedback would be greatly appreciated.
     
  6. mbabayan

    Thread Starter Member

    Jul 12, 2010
    30
    1
    Bump ?:) Please?
     
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