Loading ...
Sorry, an error occurred while loading the content.

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

Expand Messages
  • Pat Tressel
    Kevin -- If the contact surface of the split commutator was elliptical (as an ... Might also handle the sensitivity in the code, so long as we get separate
    Message 1 of 24 , Dec 5, 2012
    • 0 Attachment
      Kevin --

      If the contact surface of the split commutator was elliptical (as an example) one could make the whisker more sensitive to vertical or horizontal motion while making it less sensitive along the other axis of the ellipse.  If it was octagonal you could separate the eight sectors.  But if each 'leg' of the octagon was placed at a different radial distance one could change the sensitivity in numerous ways.

      Might also handle the sensitivity in the code, so long as we get separate signals for the directions.

      Octagonal -- sounds like joysticks again.  ;-)  Hmm...wonder if I could turn up some surplus joysticks to take apart.  I really really miss Lafayette Electronics in Pasadena, CA -- they got in all sorts of curious components.  (Lafayette story:  Once upon a time, I and a bunch of fellow frosh taking an intro to digital electronics lab were in Lafayette, and came across a box of very accurate 1 MHz crystal oscillators with ovens for about $5 each.  We each bought one, and proudly marched back to the campus electronics stockroom, where we held them out for the manager to admire.  He took one look, chased us all out, locked the door, and rushed off to Lafayette, where he scooped up the entire box.)

      If you remember the pendulum switch on the older pinball tables you know they were more sensitive along one axis when you 'hudged' the table.

      Heh.  I was too "proper" to do that ("but that's not right!").

      -- Pat
    • Peter Balch
      How many whiskers? How closely spaced are they at their base? My experience with metal-ring-and-central-wire feelers for robots is that they re not very
      Message 2 of 24 , Dec 6, 2012
      • 0 Attachment
        How many whiskers? How closely spaced are they at their base?

        My experience with metal-ring-and-central-wire feelers for robots is that
        they're not very sensitive. They need a good whack to make contact. No
        matter what wire you choose, if gets a surface coating - maybe oxide - and a
        light momentary touch no longer works. I think you'll be disappointed.

        I've also tried small momentary contact "tactile" switches like these
        http://uk.rs-online.com/web/p/tactile-switches/4791435/

        If you choose one with a large plunger, you can fit a piece of plastic tube
        over the plunger (e.g. a ballpoint inner) then fit a rod of some sort into
        the tube (in your case, glue a dozen "whiskers"). Altought these buttons are
        meant to be pushed down, they also work well if pushed to the side so they
        work as obstacle detectors for small robots.

        Unfortunately, for robot work, I found they're not robust enough but I was
        using quite stiff antennae - if you use flexible whiskers they might survive
        much better.

        But to me, none of those solutions is ideal for you. What I would do is use
        a microphone insert.
        http://www.rapidonline.com/Audio-Visual/Electret-microphone-30212
        and glue the whiskers onto the surface.

        I bet that would produce huge crackle when anyone touched it. You could also
        glue microphones under the fur fabric of the body.

        You could also experiment with piezo transducers glued onto the inside of
        the fur fabric. They have a bigger area but would probably be less
        sensitive.

        Peter
      • Peter Balch
        ... If you re determined to go with switches then look at these http://www.rapidonline.com/Electronic-Components/Switches/Tactile-Switches/Multi-Direction You
        Message 3 of 24 , Dec 6, 2012
        • 0 Attachment
          > Octagonal -- sounds like joysticks again. ;-) Hmm...wonder if I could
          > turn up some surplus joysticks to take apart.

          If you're determined to go with switches then look at these
          http://www.rapidonline.com/Electronic-Components/Switches/Tactile-Switches/Multi-Direction

          You could also think about the "nipple nouse" devices used in some laptops:
          http://en.wikipedia.org/wiki/Pointing_stick
          that would give you direction and force. But I've no idea where to buy them,

          Peter
        • Xandon Frogget
          I think Peter is right on with the microphone and piezo transducers. If glueing directly to the fabric doesn t give enough crackle you could also glue the hook
          Message 4 of 24 , Dec 6, 2012
          • 0 Attachment
            I think Peter is right on with the microphone and piezo transducers. 

            If glueing directly to the fabric doesn't give enough crackle you could also glue the hook side of some velcro to the back of a fur patch to provide a nice rough crisp crackle. Attach the piezo to something that will transform the vibration really well like the plastic from a milk carton. The interaction between the velcro and the plastic sheet should give a nice scratchy sound as you pet the fur. If that is too much then a sheet of crackly material like they use on potato chip bags offers good pops when distorted.

            For the whiskers, my thought was to modify an electric bass guitar. Use the big bass strings as the whiskers and place the pickups close to the attachment point, something to allow you to measure the change in the magnetic field really well.

            -Xandon


            On Dec 6, 2012, at 2:15 AM, Peter Balch wrote:

            But to me, none of those solutions is ideal for you. What I would do is use 
            a microphone insert.
            http://www.rapidonline.com/Audio-Visual/Electret-microphone-30212
            and glue the whiskers onto the surface.

          • Dick Curtiss
            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
            Message 5 of 24 , Dec 6, 2012
            • 0 Attachment

              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


               

            • 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 6 of 24 , Dec 6, 2012
              • 0 Attachment
                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 7 of 24 , Dec 7, 2012
                • 0 Attachment
                  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 8 of 24 , Dec 8, 2012
                  • 0 Attachment

                    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 9 of 24 , Dec 8, 2012
                    • 0 Attachment
                      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
                    Your message has been successfully submitted and would be delivered to recipients shortly.