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advice on appropriate (mechanical) switches ...?

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  • Pat Tressel
    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 --
    Message 1 of 24 , Dec 5, 2012
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      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



    • Max Cato
      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
      Message 2 of 24 , Dec 5, 2012
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        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





      • KM6VV
        Run the whisker through a ring contact. Maybe use a foam ring around the whisker to give a little more resistance if wanted. Alan KM6VV
        Message 3 of 24 , Dec 5, 2012
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          Run the "whisker" through a ring contact. Maybe use a foam ring around
          the whisker to give a little more resistance if wanted.

          Alan KM6VV

          On 12/5/2012 4:37 PM, Pat Tressel wrote:
          >
          >
          > 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
          >
          >
          >
          >
          >
          >
        • twcarroll@aol.com
          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
          Message 4 of 24 , Dec 5, 2012
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            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





          • Pat Tressel
            Hi, Max! ... I was thinking nylon or similar plastic. ... Right -- that sort of setup is feeling more and more like the right way to go. I like the mounting
            Message 5 of 24 , Dec 5, 2012
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              Hi, Max!

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

              I was thinking nylon or similar plastic.
               
              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.

              Right -- that sort of setup is feeling more and more like the right way to go.  I like the mounting suggestion! 

              And with switches surrounding the shaft, the shaft wouldn't have to be mounted on the switch -- that join would be a point of failure.  And then the switches would just be bumper switches or similar.
               
              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!

              I might not be using the right search term -- I used variants on "return to center swtich", "joystick switch", and I'd bet there's another term for the switch itself.  ;-)

              -- Pat
            • Pat Tressel
              Hi, Alan! ... Ooo, interesting! You mean something like an inside-out commutator ring? Are there actual parts like that or is this something one would make?
              Message 6 of 24 , Dec 5, 2012
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                Hi, Alan!

                Run the "whisker" through a ring contact. Maybe use a foam ring around the whisker to give a little more resistance if wanted.

                Ooo, interesting!  You mean something like an inside-out commutator ring?  Are there actual parts like that or is this something one would make?

                -- Pat
              • kevinr
                If you mount the proximal end of the whisker through a thin piece of sheet metal and surround it by strain gauges you could determine direction and intensity
                Message 7 of 24 , Dec 5, 2012
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                  If you mount the proximal end of the whisker through a thin piece of sheet metal and surround it by strain gauges you could determine direction and intensity of the push from fingers, &tc. 

                  Kevin.



                  On 12/5/2012 5:10 PM, Pat Tressel wrote:
                   

                  Hi, Max!

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

                  I was thinking nylon or similar plastic.
                   
                  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.

                  Right -- that sort of setup is feeling more and more like the right way to go.  I like the mounting suggestion! 

                  And with switches surrounding the shaft, the shaft wouldn't have to be mounted on the switch -- that join would be a point of failure.  And then the switches would just be bumper switches or similar.
                   
                  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!

                  I might not be using the right search term -- I used variants on "return to center swtich", "joystick switch", and I'd bet there's another term for the switch itself.  ;-)

                  -- Pat

                • KM6VV
                  Probably easy enough to make. Ground the whisker, insulate the ring. Electrical appliance stores sell 1/8 pipe fittings that are threaded 3/8 or so, and
                  Message 8 of 24 , Dec 5, 2012
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                    Probably easy enough to make. Ground the whisker, insulate the ring.
                    Electrical appliance stores sell 1/8" "pipe" fittings that are threaded
                    3/8" or so, and the trim rings or flat nuts thread right onto them.

                    Are you suggesting a split (commutator) ring? That could give you
                    direction of the contact as well!

                    Alan KM6VV

                    On 12/5/2012 5:22 PM, Pat Tressel wrote:
                    >
                    >
                    > Hi, Alan!
                    >
                    > Run the "whisker" through a ring contact. Maybe use a foam ring
                    > around the whisker to give a little more resistance if wanted.
                    >
                    > Ooo, interesting! You mean something like an inside-out commutator
                    > ring? Are there actual parts like that or is this something one would make?
                    >
                    > -- Pat
                    >
                    >
                  • Ryan Lum
                    Ground the whisker, insult the ring Love it! Sent from my HTC One™ S on Solavei. Powered by Relationships. ... From: KM6VV To:
                    Message 9 of 24 , Dec 5, 2012
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                      Greythorn "Ground the whisker, insult the ring" Love it!

                      Sent from my HTC One™ S on Solavei. Powered by Relationships.

                      ----- Reply message -----
                      From: "KM6VV" <KM6VV@...>
                      To: "SeattleRobotics@yahoogroups.com" <SeattleRobotics@yahoogroups.com>
                      Subject: [SeattleRobotics] advice on appropriate (mechanical) switches ...?
                      Date: Wed, Dec 5, 2012 5:44 PM



                       

                      Probably easy enough to make. Ground the whisker, insulate the ring.
                      Electrical appliance stores sell 1/8" "pipe" fittings that are threaded
                      3/8" or so, and the trim rings or flat nuts thread right onto them.

                      Are you suggesting a split (commutator) ring? That could give you
                      direction of the contact as well!

                      Alan KM6VV

                      On 12/5/2012 5:22 PM, Pat Tressel wrote:
                      >
                      >
                      > Hi, Alan!
                      >
                      > Run the "whisker" through a ring contact. Maybe use a foam ring
                      > around the whisker to give a little more resistance if wanted.
                      >
                      > Ooo, interesting! You mean something like an inside-out commutator
                      > ring? Are there actual parts like that or is this something one would make?
                      >
                      > -- Pat
                      >
                      >



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                    • kevinr
                      If you make the inner surface of the broken commutator not circular but some other shape you could change the behavior of the whisker depending on the sector
                      Message 10 of 24 , Dec 5, 2012
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                        If you make the inner surface of the broken commutator not circular but some other shape you could change the 'behavior' of the whisker depending on the sector to which it is pushed.



                        On 12/5/2012 5:42 PM, KM6VV wrote:
                         

                        Probably easy enough to make. Ground the whisker, insulate the ring.
                        Electrical appliance stores sell 1/8" "pipe" fittings that are threaded
                        3/8" or so, and the trim rings or flat nuts thread right onto them.

                        Are you suggesting a split (commutator) ring? That could give you
                        direction of the contact as well!

                        Alan KM6VV

                        On 12/5/2012 5:22 PM, Pat Tressel wrote:
                        >
                        >
                        > Hi, Alan!
                        >
                        > Run the "whisker" through a ring contact. Maybe use a foam ring
                        > around the whisker to give a little more resistance if wanted.
                        >
                        > Ooo, interesting! You mean something like an inside-out commutator
                        > ring? Are there actual parts like that or is this something one would make?
                        >
                        > -- Pat
                        >
                        >


                      • KM6VV
                        One ring to rule them all (no insult). Alan KM6VV
                        Message 11 of 24 , Dec 5, 2012
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                          "One ring to rule them all" (no insult).

                          Alan KM6VV

                          On 12/5/2012 6:29 PM, Ryan Lum wrote:
                          >
                          >
                          > "Ground the whisker, insult the ring" Love it!
                          >
                          > Sent from my HTC One™ S on Solavei. Powered by Relationships.
                          >
                          > ----- Reply message -----
                          > From: "KM6VV" <KM6VV@...>
                          > To: "SeattleRobotics@yahoogroups.com" <SeattleRobotics@yahoogroups.com>
                          > Subject: [SeattleRobotics] advice on appropriate (mechanical) switches ...?
                          > Date: Wed, Dec 5, 2012 5:44 PM
                          >
                          >
                          >
                          > Probably easy enough to make. Ground the whisker, insulate the ring.
                          > Electrical appliance stores sell 1/8" "pipe" fittings that are threaded
                          > 3/8" or so, and the trim rings or flat nuts thread right onto them.
                          >
                          > Are you suggesting a split (commutator) ring? That could give you
                          > direction of the contact as well!
                          >
                          > Alan KM6VV
                          >
                          > On 12/5/2012 5:22 PM, Pat Tressel wrote:
                          > >
                          > >
                          > > Hi, Alan!
                          > >
                          > > Run the "whisker" through a ring contact. Maybe use a foam ring
                          > > around the whisker to give a little more resistance if wanted.
                          > >
                          > > Ooo, interesting! You mean something like an inside-out commutator
                          > > ring? Are there actual parts like that or is this something one would
                          > make?
                          > >
                          > > -- Pat
                          > >
                          > >
                          >
                          >
                          >
                          > Click here <https://www.mailcontrol.com/sr/MZbqvYs5QwJvpeaetUwhCQ==> to
                          > report this email as spam.
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                          >
                          > *Ryan Lum | Principal Recruiter - Technology Practice
                          >
                          > direct tel: +1 425 460 4291
                          > office tel: +1 425 635 0300
                          > mobile tel: +1 253 223 5530
                          > email: Ryan.Lum@...
                          >
                          > 40 Lake Bellevue Dr. Suite 100, Bellevue, 98005
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                        • Pat Tressel
                          Alan said: Are you suggesting a split (commutator) ring? That could give you direction ... Kevin said: If you mount the proximal end of the whisker through a
                          Message 12 of 24 , Dec 5, 2012
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                            Alan said:

                            Are you suggesting a split (commutator) ring? That could give you direction of the contact as well!

                            Kevin said:

                            If you mount the proximal end of the whisker through a thin piece of sheet metal and surround it by strain gauges you could determine direction and intensity of the push from fingers, &tc. 

                            If you make the inner surface of the broken commutator not circular but some other shape you could change the 'behavior' of the whisker depending on the sector to which it is pushed.

                            Right!  I definitely want the direction.  I'm thinking the critter should fold its whiskers back in the same direction they're stroked (as a real cat will if one brushes its whiskers from the front) while leaning toward the stroke.

                            To start with, maybe four bumper switches with little arcs of circles attached to the business end.  Would need to be careful about preventing the whisker from getting shoved past the switches, so maybe foam around the whisker and / or the extensions on the switches should either overlap, or be staggered.

                            If we had the intensity, we could have it react negatively to a hard push...hmm...  I'm seeing "force sensor" as the name for a widget that might measure, er, force.  Pricey things, though...yow.  Are strain gauges cheaper, we wonders, yes preciousss...

                            Anyone know where I might get bumper switches locally?  See, there's this Arduino meetup tomorrow...

                            -- Pat
                          • kevinr
                            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
                            Message 13 of 24 , Dec 5, 2012
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                              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.



                              On 12/5/2012 7:42 PM, Pat Tressel wrote:
                               

                              Alan said:

                              Are you suggesting a split (commutator) ring? That could give you direction of the contact as well!

                              Kevin said:

                              If you mount the proximal end of the whisker through a thin piece of sheet metal and surround it by strain gauges you could determine direction and intensity of the push from fingers, &tc. 

                              If you make the inner surface of the broken commutator not circular but some other shape you could change the 'behavior' of the whisker depending on the sector to which it is pushed.

                              Right!  I definitely want the direction.  I'm thinking the critter should fold its whiskers back in the same direction they're stroked (as a real cat will if one brushes its whiskers from the front) while leaning toward the stroke.

                              To start with, maybe four bumper switches with little arcs of circles attached to the business end.  Would need to be careful about preventing the whisker from getting shoved past the switches, so maybe foam around the whisker and / or the extensions on the switches should either overlap, or be staggered.

                              If we had the intensity, we could have it react negatively to a hard push...hmm...  I'm seeing "force sensor" as the name for a widget that might measure, er, force.  Pricey things, though...yow.  Are strain gauges cheaper, we wonders, yes preciousss...

                              Anyone know where I might get bumper switches locally?  See, there's this Arduino meetup tomorrow...

                              -- Pat

                            • kevinr
                              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.
                              Message 14 of 24 , Dec 5, 2012
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                                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.




                                On 12/5/2012 7:42 PM, Pat Tressel wrote:
                                 

                                Alan said:

                                Are you suggesting a split (commutator) ring? That could give you direction of the contact as well!

                                Kevin said:

                                If you mount the proximal end of the whisker through a thin piece of sheet metal and surround it by strain gauges you could determine direction and intensity of the push from fingers, &tc. 

                                If you make the inner surface of the broken commutator not circular but some other shape you could change the 'behavior' of the whisker depending on the sector to which it is pushed.

                                Right!  I definitely want the direction.  I'm thinking the critter should fold its whiskers back in the same direction they're stroked (as a real cat will if one brushes its whiskers from the front) while leaning toward the stroke.

                                To start with, maybe four bumper switches with little arcs of circles attached to the business end.  Would need to be careful about preventing the whisker from getting shoved past the switches, so maybe foam around the whisker and / or the extensions on the switches should either overlap, or be staggered.

                                If we had the intensity, we could have it react negatively to a hard push...hmm...  I'm seeing "force sensor" as the name for a widget that might measure, er, force.  Pricey things, though...yow.  Are strain gauges cheaper, we wonders, yes preciousss...

                                Anyone know where I might get bumper switches locally?  See, there's this Arduino meetup tomorrow...

                                -- Pat

                              • Pat Tressel
                                Hi, Tom! For simplicity s sake, you could mount each whisker or a group of ... Interesting! I wonder...if we used netting (or macrame with little loops around
                                Message 15 of 24 , Dec 5, 2012
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                                  Hi, Tom!

                                       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.

                                  Interesting!  I wonder...if we used netting (or macrame with little loops around each whisker) and the netting was attached to something that could detect being pulled on, maybe we could detect direction by which attachment points were being yanked.  You're right -- that might be simpler than switches around each.  One issue with that is that it would be harder to allow the whiskers to move independently.  I was thinking of having them ripple, or scull like a fin with one edge leading.  But we could still have strings tied around each whisker, going out to a row of sensors.

                                  -- Pat
                                • 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 16 of 24 , Dec 5, 2012
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                                    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 17 of 24 , Dec 6, 2012
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                                      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 18 of 24 , Dec 6, 2012
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                                        > 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 19 of 24 , Dec 6, 2012
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                                          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 20 of 24 , Dec 6, 2012
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                                            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 21 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 22 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 23 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 24 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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