• 12-11-2005, 09:49 AM
    jordan314
    Piezo switches for MIDI glove
    Hey All,
    I'm not sure if this is the place to talk about MIDI / circuits but I'll give it a shot. I'm trying to make a MIDI glove - a glove with triggers in the fingertips and palm so that I can make music with them. I've bought a Logitec USB Dual Action Gamepad that works with Junxion, a Mac OS X program that can convert gamepad controls into MIDI signals, so when you press a button on the gamepad, it sends an assignable midi signal.
    Now, I'm going to take the buttons out from the gamepad and attach wires to the circuits so that shorting the wires will be the same as pushing the button, and run them into the glove. The question I have is, what switches would be good to work with? I've heard great things about piezo discs being good drum triggers, but those are transducers that generate electricity when bent, and I need a switch. Would there be some way to attach a relay to the piezo disc to get what I want? Or do you know of any switches that are fast acting and thin, similar to the piezo?
    Thanks,
    Jordan
  • 12-11-2005, 10:53 AM
    FLZapped
    Quote:

    Originally Posted by jordan314
    Hey All,
    I'm not sure if this is the place to talk about MIDI / circuits but I'll give it a shot. I'm trying to make a MIDI glove - a glove with triggers in the fingertips and palm so that I can make music with them. I've bought a Logitec USB Dual Action Gamepad that works with Junxion, a Mac OS X program that can convert gamepad controls into MIDI signals, so when you press a button on the gamepad, it sends an assignable midi signal.
    Now, I'm going to take the buttons out from the gamepad and attach wires to the circuits so that shorting the wires will be the same as pushing the button, and run them into the glove. The question I have is, what switches would be good to work with? I've heard great things about piezo discs being good drum triggers, but those are transducers that generate electricity when bent, and I need a switch. Would there be some way to attach a relay to the piezo disc to get what I want? Or do you know of any switches that are fast acting and thin, similar to the piezo?
    Thanks,
    Jordan

    Piezos are EXTREMELY high impedance. you would have to smooth out the pulses with a schmidt trigger and then be able to drive a logic circuit capable of whatever current you need. You could try and group some microswitches around your wrist with lines attached through guides to the fingertips so that when you moved your finger downward, it would trigger the switch, but then you would be force to keep your hand in a given position all the time.....there are also "tape" switches that you could put in the finger tips and when you tap them on a surface would be activated.

    Relays in general are probably too slow for what you want.....

    -Bruce
  • 12-16-2005, 11:28 AM
    jordan314
    Thanks for your reply, you've convinced me not to go with piezos. I won't go with relays either. Your tipoffs to tape switches and microswitches were especially helpful, though I have not yet found the right kind. I'm wondering if I could just rig a dome membrane switch ripped from the gamepad or a calculator or keyboard or something to each fingertip and if that would work, or if I would have to aim too hard or if their action is too slow.
    Thanks for your help!
    Jordan
  • 12-16-2005, 11:53 AM
    FLZapped
    Quote:

    Originally Posted by jordan314
    Thanks for your reply, you've convinced me not to go with piezos. I won't go with relays either. Your tipoffs to tape switches and microswitches were especially helpful, though I have not yet found the right kind. I'm wondering if I could just rig a dome membrane switch ripped from the gamepad or a calculator or keyboard or something to each fingertip and if that would work, or if I would have to aim too hard or if their action is too slow.
    Thanks for your help!
    Jordan


    Yeah, you could. they are cheap, but have a fair amount of travel to them without mechanical amplification. A real pain if they get out of alignment. Another method is to use a conductive pad across a grid.

    The later would need an electronic interface since you would essentially be hanging a resistor across the wires in the grid. Actually, almost any method would need some sort of interface, if for nothing else than to filter out contact bounce.

    -Bruce
  • 12-16-2005, 12:45 PM
    jordan314
    I thought that's what dome switches were, a conductive pad inside a rubber dome that touches a grid when squished. I'm still learning about this--just read up on contact bounce, I didn't know about that--I'm hoping that by attaching my switch to the contacts in the gamepad it will already correct for contact bounce, and serve as my interface.

    Thanks,
    Jordan