Capacitance touch killswitch

Discussion in 'Pickups, Electronics & General Tech' started by morbideddie, Apr 18, 2010.

  1. morbideddie

    morbideddie Member

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    hey. i was looking for a simple kill switch design on my guitar and dont want a flick switch or big red button on my guitar top. i want a fast use killswitch for buckethead style use. could i use one of my pickguard screws as a capacitance switch. either that or two as a resistance switch? anyone ever done this?
     
  2. peskywinnets

    peskywinnets Member

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    Have you been watching on of my videos by any chance?!

    http://www.tinyurl.com/y3g5cdd (that's my youtube link)


    Truthfully though, a capacitance touch switch would be no good for a kill switch - they're not good for dependable rapidfire switching (they need a set length of time to 'settle' between each toggle) - ideal for simnply on/off without having to drill your guitar though (which is why I came up with that method)
     
  3. morbideddie

    morbideddie Member

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    yeah. those lamps arent the most reliable in the world. thinking of a resistance switch so the current runs through my finger to the earth. thatd require one extra hole but would be discrete and hopefully responsive. and no i hadn't seen you video but its nice to know someone else has the idea
     
  4. lateralus819

    lateralus819 Mr. legacy

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    How exactly did you do that? I've love to do that on my carvin so i didnt have to drill any holes.
     
  5. peskywinnets

    peskywinnets Member

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    It was quite involved & not for the faint of heart. Basically I used a PIC...but I had to learn about PIC programming & then specifically relaxation oscillators.

    At a very high level ....

    you set part of the PIC up to run as an oscillator, the residual capacitance of your touch sensor affects the frequency that the PIC oscillator runs at.

    Ok, when you actually touch the touch sensor, this affects the overall capacitance of the oscillator circuit ...& therefore the frqeuecny of the oscillator changes - all simple enough, but then you have to get the PIC to count how many cycles of oscillator frequency it receives in a specified time frame.

    So for example, lets say your oscillator is free running at 250,000Hz....you set up the pic to sample every 1ms ...it would would expect to count 2,500 cycles in that time frame. So you set up an if condition (if cycle count >2,500, then do nothing

    When you touch the touch sensor the oscillator capcitance rises, the frequency drops & less pulses will be received in that 1ms timeframe, so your PIC then is programmed to do something....eg if cyclecount < 2500 then goto etc.....

    I was in (for me at least) pioneering territory, becuase at the time of doing it, there were only a few PICs out there capaable of doing capactitance touch ...but alas, the one I chose ...nobody on the net had done it on that PIC yet, so I had to figure out all the register settings on my jacksy - and like I say I'm new to PICS!

    There are many other ways to implement touch sensing....but it just so happened I was dabbling with PICs for my DIY sustainers anyway....which is why I went that route.

    Hope that helps!
     
  6. OwenD

    OwenD SS.org Regular

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    What about using an LDR? so when you cover it with your finger it would cut the signal.. It'd fit in the spot where a pot was if you didn't want to permanently modify your guitar.
     

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