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Cool down Roland wired piezo head and rim with 100k pot

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  • Cool down Roland wired piezo head and rim with 100k pot

    Hi!

    I know reducing piezo sensitivity has been discussed several times, but I'm not sure how to wire the pot to the jack and piezo to keep the Roland wiring intact and not change the polarity. It's important since I need the positional sensing to work. Can someone help me draw the necessary connections on my picture I would be very glad?

    I've seen Hellfires wiring to pots but also that a few people thought that it would be better and make more sense to prevent shorting out the piezo when set at the minimum value which would change the impedance of the piezo and its electrical response characteristics.
    Last edited by rockdude; 07-07-19, 05:32 AM.

  • #2
    Ok here痴 my own take on this

    This way the output trs jack is connected to the center slot of the pot which to my limited understanding would avoid shorting out the piezos or change any of the electric characteristics.

    I知 using terminal A and B of the variable pot, leaving terminal C empty which would make this act as a rheostat and by that a variable resistor if I知 correct.

    Will this connection allow me to control the signal strength of the piezos and keep the Roland wiring intact? Or did i mess something up? I知 a little bit confused about how to think of the head piezo ceramic part which goes to the sleeve when doing Roland wiring.
    Last edited by rockdude; 07-07-19, 07:05 AM.

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    • #3
      Sleeve is common ground - you'll need to connect the ground pin on your trimpots for them to function.

      I've connected these in opposite ways for the sake of making the diagram easier to understand - which you shouldn't do irl - or you'll be turning one counter-clockwise and the other clockwise to increase/decrease resistance.

      But otherwise it will work and it doesn't matter which side you use. Set and forget.

      The middle pin is typically the wiper and the resistance between pins 1 and 3 (or 3 and 1) is the max of your chosen trimpot, i.e. 100k.

      I don't think trimpots can even affect polarity, you'll need a precision rectifier to do that.

      This should be configured as a 2-zone (Roland) pad with a 27mm head pizeo, 35mm rim piezo.

      voltagedivider.jpg
      Last edited by Kabonfaiba; 07-07-19, 10:54 AM.
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      • #4
        Thanks Kabonfaiba, but to get positional sensing to work, Roland wiring requires the ceramic part of the head piezo to go to the sleeve on the jack and the brass part of the piezo to the tip of the jack. Your drawing would change polarity making it non Roland compatible for positional sensing and mess up the first half wave?

        I thought the pot would work as a rheostat (variable resistor) instead of a potentiometer (voltage divider) if I skip terminal c?

        Maybe I知 just not getting it. My head spins trying to understand what exactly I知 doing.
        Last edited by rockdude; 07-07-19, 02:21 PM.

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        • #5
          Wire it as a voltage divider, it will work. Here's my version of how to wire it with the piezo polarity that Roland needs for PS.
          image_34190.jpg
          MegaDrum module, DIY A2E pads, DIY hall effect 3 zone hi hat, DIY 1, 2 & 3 zone cymbals, DIY kick beater triggers on DIY modded longboard, direct drive pedals, DIY triple driver IEMs, El Cheapo Buttkicker. Various VSTs running in a tweaked Linux Mint. Kit pics thread

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          • #6
            Thanks Ignotus! I値l give it a try
            A question...the black cable going from terminal A on the right pot to terminal A on the left pot and then to sleeve on the jack...It wouldn稚 change anything letting the black cable go from the terminal A on the right pot directly to the jack sleeve? Like below?

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            • #7
              Same difference, it's up to you - as long as the grounds are all connected together it doesn't matter.
              BTW, ceramic = positive and brass = negative isn't always the case. It's often taken as given but lacking an oscilloscope if you see that PS doesn't work, try reversing the polarity of the piezos one by one and then both (swap the leads going to the outer pins on the pots).
              MegaDrum module, DIY A2E pads, DIY hall effect 3 zone hi hat, DIY 1, 2 & 3 zone cymbals, DIY kick beater triggers on DIY modded longboard, direct drive pedals, DIY triple driver IEMs, El Cheapo Buttkicker. Various VSTs running in a tweaked Linux Mint. Kit pics thread

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              • #8
                Still curious though, what would happen if I wire it like a rheostat, only using center terminal + 1 of the other terminals, making it a variable resistor like in my second post? What痴 the difference having a variable resistor compared to a voltage divider on a piezo? Benefits, drawbacks, differences...

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                • #9
                  It will also work. From what I understand with a variable resistor of, say 100K, you can adjust the resistance from 0 to 100K, with the corresponding variation in voltage limited to what that range produces (I can't say as it depends on the current). With a voltage divider, what you do is split the voltage depending on the ratio of the two resistors (the graphite on each side of the pot's wiper). This means that you can go from no voltage change, to 0 volts, with everything in between. Thus, (and unless I'm mistaken), a voltage divider potentially gives you a wider range of possibilities.
                  MegaDrum module, DIY A2E pads, DIY hall effect 3 zone hi hat, DIY 1, 2 & 3 zone cymbals, DIY kick beater triggers on DIY modded longboard, direct drive pedals, DIY triple driver IEMs, El Cheapo Buttkicker. Various VSTs running in a tweaked Linux Mint. Kit pics thread

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                  • #10
                    I went for your solution Ignotus and so far it`s doing its job nicely as a voltage divider Thanks!

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