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Pinball switch closure timing problem

Discussion in 'General Electronics' started by frenchy, Mar 22, 2005.

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  1. frenchy

    frenchy Guest

    For years the pinball companies used a small .047 uf capacitor across
    some switch terminals for switches that could be closed and reopened
    very quickly like a target getting slammed particularly hard. The
    capacitor would increase the 'closure time' that the CPU would read the

    switch as closed, long enough to help it pick up the switch closure.
    These switches are just simple two blades and contacts, with one wire
    to the cpu, the other wire thru a diode to isolate it within the matrix

    of switches in the game, and the capacitor may or may not be across the

    terminals also.


    I'm having a problem with a particular swtich that the cap fix is
    working, but not completely. Some hardhits will still not register.
    Tried putting bigger cap on it with improved results but I've read that

    too big of a cap can cause 'ghosting' where it might start causing
    false closure reading on other switches in the matrix. So my question
    is....


    Is there a simple formula where one could increase the size of the .047

    cap or .1 cap or whatever is being used, but put in in series with a
    resistor, to lengthen the time that it is doing it's thing of
    lengthening of the closure to the cpu? I.e if I wanted to use a cap
    10x bigger, what resistor could I put in series with it to be sort of
    like the smaller cap without the resistor, but length of discharge
    would be stretched out? Or is this possible? I am pretty good at
    fixing pinballs, but electronics theory is not my calling. thanks for
    any assistance anybody can give me. Thanks!
     
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