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RE: [SeattleRobotics] advice on appropriate (mechanical) switches ...?

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  • Robert Dyer
    I lost some of the details in the flurry of replies, but I believe you said you don t need to know direction; just that the whisker isn t at the neutral point.
    Message 1 of 24 , Dec 6, 2012
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      I lost some of the details in the flurry of replies, but I believe you said you don't need to know direction; just that the whisker isn't at the neutral point. I think a switch is a good idea, but I'd do it the opposite of what I believe has been suggested so far. 

      How about your spring-centered gimbal idea (as in many R/C model transmitters) that pivots near the "creature" end of the whisker, but an inch or two before the end. Mount a switch just beyond the end so it is closed only when the whisker is in it's centered "neutral" position. When the "human" end of the whisker is pushed, the "creature" end moves away from neutral in the opposite direction, and the switch opens no matter which direction it moves. (I hope that's described clearly!)

      You could also attach a small disk at the end perpendicular to the axis of the whisker. The size of the disk will set the "sensitivity" of the switch. You could shape the disk into a dome to allow for return to center w/o damaging the switch.


      From: "Dick Curtiss" <rcurtiss@...>
      Sent: Thursday, December 06, 2012 11:21 AM
      To: SeattleRobotics@yahoogroups.com
      Subject: RE: [SeattleRobotics] advice on appropriate (mechanical) switches ...?


       

      For on/off switches, consider reed switches

      - Magnet gets close - switch closes with little or no key bounce

      - Pull magnet away - switch opens (after the position hysteresis zone is passed)

      - Hysteresis may or may not be good, depending on the application

      - Very little force is necessary to operate (add springs to adjust to the force desired)

       

      Imagine a magnet surrounded by a ring of reed switches (number determines position resolution)

       

      Reading possibilities:

      Digital input pin for each reed switch

      Multiplexer to scan switches (time multiplexing) to be read on a single digital input pin

      Carefully weighted resistor network produces a "position unique" analog voltage to be read on a single input pin

       


      From: SeattleRobotics@yahoogroups.com [mailto: SeattleRobotics@yahoogroups.com ] On Behalf Of twcarroll@...
      Sent: Wednesday, December 05, 2012 5:09 PM
      To: SeattleRobotics@yahoogroups.com
      Subject: Re: [SeattleRobotics] advice on appropriate (mechanical) switches ...?

       

       

      Hi, Pat,

           For simplicity's sake, you could mount each whisker or a group of whiskers in a group and mount them to a flexible conductive pin that could bend in any direction.  That could be a rubber rod with a metal sleeve connecting the whisker and the rod.  One small wire will be connected to the conductive sleeve and another wire to a metal ring surrounding the metal sleeve.  When the whisker is tweaked in any direction, because of the flexible rubber rod to which it is connected, the metal sleeve will contact the metal ring and complete a circuit like a switch. Instead of a bunch of metal rings for a lot of whiskers, try using a large mesh metal screen and place each whicker in each of the screen's mesh holes.

           Experiment.  I think this will be easier than a bunch of small micro switches.

           Good luck,

           Tom C.

       

      How big (diameter) are you thinking you need the whiskers to be? What material (nylon, steel, etc)? 

       

      If you're going to mount the whisker between momentary switches, you could always put the whisker on a cam, so that rocking it one way toggles one switch while rocking it another way toggles the other switch. A couple of small springs to keep it returning to center, and you'd be set.

       

      I'm kinda surprised that I couldn't find anything immediately in digikey (jameson, etc). You'd think more people would want products like that!

       


      From: Pat Tressel <ptressel@...>
      To: SeattleRobotics@yahoogroups.com
      Sent: Wednesday, December 5, 2012 4:37 PM
      Subject: [SeattleRobotics] advice on appropriate (mechanical) switches ...?

       

       

      Hi, all!

      I'm looking for advice on what sort of switch or other sensor might be appropriate:  I'm going to be helping build a robot that reacts to touch -- think of a cat being petted or whose whiskers are touched.  Won't be a literal cat -- more a fantasy creature, but we want to have it respond when its whiskers / quills / ruff / fronds are stroked.  Kids are involved, so it'll have to be fairly sturdy.  It'll be on the order of 4-6 feet long, and the "whiskers" might be 1 - 1.5 feet long, so not really tiny switches, but not something that needs a solid shove, as the whiskers will be flexible (for safety).

      I was thinking of something like the switch in a return to center joystick, but I'm only finding actual human-hand-sized joysticks, not bare switches.  Could probably do with some sort of return to center bidirectional switch, or maybe mount the "whisker" shaft between some bumper switches.  For bumper switches, I suppose one could surround the shaft with four bumper switches.

      Any ideas or suggestions?  Got favorite places for buying this sort of thing?  Any local retailers where I might be able to get some for trying out?  (Does Vetco carry bumper switches or joystick-like switches?)

      Thanks!!!

      -- Pat

      P.S.  Hmm, found this list on the UW Dxarts site:
      http://wiki.dxarts.washington.edu/groups/general/wiki/1d4c7/Where_to_Shop_for_Fabrication_Supplies.html


       


    • robotMaker
      Maybe this might help a little bit. http://www.youtube.com/watch?feature=player_embedded&v=rO2TR_8jXPc ________________________________ From: Pat Tressel
      Message 2 of 24 , Dec 7, 2012
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        Maybe this might help a little bit.

        http://www.youtube.com/watch?feature=player_embedded&v=rO2TR_8jXPc



        From: Pat Tressel <ptressel@...>
        To: SeattleRobotics@yahoogroups.com
        Sent: Wednesday, December 5, 2012 6:37 PM
        Subject: [SeattleRobotics] advice on appropriate (mechanical) switches ...?



        Hi, all!

        I'm looking for advice on what sort of switch or other sensor might be appropriate:  I'm going to be helping build a robot that reacts to touch -- think of a cat being petted or whose whiskers are touched.  Won't be a literal cat -- more a fantasy creature, but we want to have it respond when its whiskers / quills / ruff / fronds are stroked.  Kids are involved, so it'll have to be fairly sturdy.  It'll be on the order of 4-6 feet long, and the "whiskers" might be 1 - 1.5 feet long, so not really tiny switches, but not something that needs a solid shove, as the whiskers will be flexible (for safety).

        I was thinking of something like the switch in a return to center joystick, but I'm only finding actual human-hand-sized joysticks, not bare switches.  Could probably do with some sort of return to center bidirectional switch, or maybe mount the "whisker" shaft between some bumper switches.  For bumper switches, I suppose one could surround the shaft with four bumper switches.

        Any ideas or suggestions?  Got favorite places for buying this sort of thing?  Any local retailers where I might be able to get some for trying out?  (Does Vetco carry bumper switches or joystick-like switches?)

        Thanks!!!

        -- Pat

        P.S.  Hmm, found this list on the UW Dxarts site:
        http://wiki.dxarts.washington.edu/groups/general/wiki/1d4c7/Where_to_Shop_for_Fabrication_Supplies.html







      • Chuck Harrison
        Going an entirely different direction, how about something optical? Imagine a plastic optical fiber attached to the whisker base and arranged so that as the
        Message 3 of 24 , Dec 8, 2012
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          Going an entirely different direction, how about something optical?

          Imagine a plastic optical fiber attached to the whisker base and arranged so that as the whisker bends the fiber end gets closer to one or another of a triad of LEDs (rgb). Run the fibers out to an xy array you can look at with a webcam. Each fiber spot in the video image will change color and brightness as the corresponding whisker moves. You should be able to watch the deflection of several hundred whiskers this way.

          The video processing would be a bit much for arduino but I bet it would fit a raspberry pi just fine.

          On Dec 7, 2012 10:56 AM, "robotMaker" <robotmeiker@...> wrote:
           

          Maybe this might help a little bit.

          http://www.youtube.com/watch?feature=player_embedded&v=rO2TR_8jXPc



          From: Pat Tressel <ptressel@...>
          To: SeattleRobotics@yahoogroups.com
          Sent: Wednesday, December 5, 2012 6:37 PM
          Subject: [SeattleRobotics] advice on appropriate (mechanical) switches ...?



          Hi, all!

          I'm looking for advice on what sort of switch or other sensor might be appropriate:  I'm going to be helping build a robot that reacts to touch -- think of a cat being petted or whose whiskers are touched.  Won't be a literal cat -- more a fantasy creature, but we want to have it respond when its whiskers / quills / ruff / fronds are stroked.  Kids are involved, so it'll have to be fairly sturdy.  It'll be on the order of 4-6 feet long, and the "whiskers" might be 1 - 1.5 feet long, so not really tiny switches, but not something that needs a solid shove, as the whiskers will be flexible (for safety).

          I was thinking of something like the switch in a return to center joystick, but I'm only finding actual human-hand-sized joysticks, not bare switches.  Could probably do with some sort of return to center bidirectional switch, or maybe mount the "whisker" shaft between some bumper switches.  For bumper switches, I suppose one could surround the shaft with four bumper switches.

          Any ideas or suggestions?  Got favorite places for buying this sort of thing?  Any local retailers where I might be able to get some for trying out?  (Does Vetco carry bumper switches or joystick-like switches?)

          Thanks!!!

          -- Pat

          P.S.  Hmm, found this list on the UW Dxarts site:
          http://wiki.dxarts.washington.edu/groups/general/wiki/1d4c7/Where_to_Shop_for_Fabrication_Supplies.html







        • Paul J. Ste. Marie
          ... A spring around a central pin works, too. The feelers on the Hexbugs work this way. If the feeler bumps into something, the spring bends and contacts the
          Message 4 of 24 , Dec 8, 2012
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            On 12/5/2012 5:22 PM, Pat Tressel wrote:
            > Ooo, interesting! You mean something like an inside-out commutator ring?
            > Are there actual parts like that or is this something one would make?


            A spring around a central pin works, too. The feelers on the Hexbugs
            work this way. If the feeler bumps into something, the spring bends and
            contacts the pin in the center.

            -- Paul
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