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Advice on finding a rotary knob

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    Advice on finding a rotary knob

    Hello all, long time no see! Haven't been active here in some time due to a job change, still in the electronics field but not doing board level work anymore. Good to see some familiar names still around, and some new blood as well!

    Anyway, I'm hoping that you guys (and gals) can offer me some advice. I am trying to find a rotary knob, not a potentiometer, for a personal project and after browsing some offerings on Mouser I quickly realized that I don't know the correct terminology for what I'm looking for. I am trying to replace two separate momentary push buttons that function as 'up' and 'down' with a rotary knob. What I'm thinking of is a knob like you'd find in many cars for use with the entertainment systems, or on some home audio equipment, where you can feel clicks or detents as your turn it. Basically each click in one direction moves a selector, or volume, up by one notch, and vice versa in the other direction. In my head, this would have either one input (which goes to ground) attached to two switched outputs, where a click in one direction makes momentary contact between the ground input and one output, and likewise for a click in the opposite direction and the second output. Two inputs and two outputs would also work, if input and output A were linked and isolated from input and output B which are also linked to each other.

    Most of the rotary switches I've seen have several contacts, which I'm thinking would be each position or "click" of the knob as a different output. For that matter, maybe what I'm envisioning doesn't even exist, maybe there has to be an associated controller that says something like "if input changes from contact 'x' to contact 'x'+1, then output 'up' signal; if input changes from contact 'x' to 'x'-1, then output 'down' signal." Dunno, but hopefully someone does!

    Thanks in advance for any help!

    #2
    Re: Advice on finding a rotary knob

    It is called ROTARY ENCODER SWITCH. You do need the decoder circuit.
    http://electronicdesign.com/analog/s...otary-encoders
    http://www.edn.com/design/systems-de...ne-from-coarse

    ENCODER I.E.:
    https://cdn.badcaps-static.com/pdfs/...060ac37d37.pdf
    Last edited by budm; 12-19-2014, 01:11 PM.
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      #3
      Re: Advice on finding a rotary knob

      yep, rotary encoder.
      you also need a bit of logic to do what your after.

      one output will pulse for each step, the other will either be on or off at the start of the signal on the first depending on direction.
      it's called "quadrature encoding"

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        #4
        Re: Advice on finding a rotary knob

        Not sure how a rotary switch would work as when you went from 0+3 when you click it down it would not be down - only less up?? well I know what I mean. Presumably if you are replacing buttons the required circuit is in place.
        Easiest would be to replace the buttons??.
        Next - could you use a 3-WAY ON/OFF/ON ROCKER SWITCH or an onoffon toggle type switch. That could be connected with the on/off1 to the circuit for one press button and the off/on2 to the other button circuit.
        Does it really have to be a rotary switch? and what voltage are you talking about switching? and is there a size factor?
        Please upload pictures using attachment function when ask for help on the repair
        http://www.badcaps.net/forum/showthread.php?t=39740

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          #5
          Re: Advice on finding a rotary knob

          I think you are looking for a selector switch with momentary contacts center off
          http://www.digikey.com/product-searc...itches/1114766

          when turned to the right it would go up when released it would be off when turned to the left it would go down. Something like this?
          Attached Files
          Last edited by R_J; 12-19-2014, 04:38 PM.

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