adjustable momentary switch

Discussion in 'The Projects Forum' started by pscook, Mar 25, 2006.

  1. pscook

    Thread Starter New Member

    Mar 25, 2006
    2
    0
    Hi-
    I'm working on a small little project for my racing motorcycle. I am looking to make an adjustable momentary switch to interrupt the ignition circuit, to allow me to make full throttle upshifts while on the track.
    A couple of examples-
    Powershifter2
    Techtronics Quick shifter
    TECHTRONICS PQS3
    I know that I can buy these, but why not make my own?
    I have tried to use a carefully adjusted mechanical momentary switch on a bracket, directly inline with the ignition circuit, but I couldn't control the duration (or exact location) of the switch activation. So, my thoughts are that I just need to get a trigger to send a signal to a programmable/adjustable momentary, which would then interrupt the ignition for a predetermined length of time.
    What parts would be needed to produce this in the smallest space possible? It needs to run off of 12v DC (+/- 1v).
    Oh, the ignition circuit is normally closed, so I would need to open the circuit for 20ms to 120ms.
    And, if this isn't feasible for a shade-tree mechanic, tell me. Or don't.
    Thanks,
    phil
    pscook@att.net
     
  2. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    4
    You need an adjustable monostable circuit to provide duration control. This can be build using 555 timer IC. If you need to control/delay the trigger signal, you could use a timed RC delay or another 555. You need to use a mechanical relay or better a solid state relay to interrupt the ignition. This has to be rated above the ignition voltage and current. Relay is cheap and robust but might introduce contact bounce and delay (more difficult to adjust), solid state relay is more expensive and not so robust but has predictable timing (delay/reaction time).

    Google for 555 monostable and you should get plenty info.
     
  3. pscook

    Thread Starter New Member

    Mar 25, 2006
    2
    0
    That looks like just the ticket. When I hvae more time, I will fully investigate.
    Thanks,
    phil
     
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