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A Bot with Peripheral Vision

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  • Clifford Boerema
    Hello all, I wanted to share a circuit that results in a bot with a form of Peripheral Vision. It s a Master/Slave form of the SC-Head. The photo-diodes should
    Message 1 of 12 , Feb 15, 2002
      Hello all,

      I wanted to share a circuit that results in
      a bot with a form of Peripheral Vision.

      It's a Master/Slave form of the SC-Head.

      The photo-diodes should be positioned across
      the front of the bot with the ones marked
      Far Left and Far Right mounted at a greater
      angle off center than the ones marked left
      and right.

      I'm putting together a write up on the
      circuit and will post it to my site as
      soon as I can.

      Hope you find it interesting.

      So long,
      Droidmakr






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    • R. Martin Keen
      I m not so sure about this one. It seems like a clever way to get around the lockup that SC-head pvores suffer from. Toggling the pdiodes bias voltage might
      Message 2 of 12 , Feb 16, 2002
        I'm not so sure about this one. It seems like a clever way to get around
        the lockup that SC-head pvores suffer from. Toggling the pdiodes bias
        voltage might cause some odd stuff. Interesting stuff with the diodes, I
        can't wait for the write up. I'm guessing with is a variant of the diode
        based SC-head, not the negative feedback SC-head. For those who find the
        original cryptic, I included an easier to read schematic. Sorry about
        the eraser marks. Took me a few tries to get it right.

        -Martin

        THE resource for beginners
        http://beamlinks.botic.com
        "The best of everyone's BEAM"


        On Fri, 15 Feb 2002 15:53:42 -0800 (PST) Clifford Boerema
        <droidmakr@...> writes:
        >
        > Hello all,
        >
        > I wanted to share a circuit that results in
        > a bot with a form of Peripheral Vision.
        >
        > It's a Master/Slave form of the SC-Head.
        >
        > The photo-diodes should be positioned across
        > the front of the bot with the ones marked
        > Far Left and Far Right mounted at a greater
        > angle off center than the ones marked left
        > and right.
        >
        > I'm putting together a write up on the
        > circuit and will post it to my site as
        > soon as I can.
        >
        > Hope you find it interesting.
        >
        > So long,
        > Droidmakr
        >
        >
        >
        >
        >
        >
        > __________________________________________________
        > Do You Yahoo!?
        > Yahoo! Sports - Coverage of the 2002 Olympic Games
        > http://sports.yahoo.com
        >
        > ------------------------ Yahoo! Groups Sponsor
        >
        > To unsubscribe from this group, send an email to:
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        >
        >
      • Bruce Robinson
        ... Hi, Cliff. Very nice design. By my quick analysis ... 1) Normal behaviour is both motors running forward . 2) When the robot is pointing in the general
        Message 3 of 12 , Feb 16, 2002
          Clifford Boerema wrote:
          >
          > I wanted to share a circuit that results in
          > a bot with a form of Peripheral Vision.
          >
          > It's a Master/Slave form of the SC-Head.

          Hi, Cliff. Very nice design.

          By my quick analysis ...

          1) Normal behaviour is both motors running "forward".

          2) When the robot is pointing in the general direction of a light,
          increased light on one of the "normal" photodiodes causes the motor on
          that side of the robot to stop. This causes the robot to pivot about the
          stopped wheel and face toward the light.

          3) When "peripherial" photodiodes detect a difference between one side
          and the other, they over-ride the "normal" PD's. The PD that detects the
          brighter light reverses the motor on that side so the robot pivots
          sharply about its center (one wheel forward, the other reverse) to face
          more toward the light.

          4) When the robot bumps into something on one side, it over-rides all
          the PD circuits and reverses the motor on the OPPOSITE side, causing the
          robot to pivot sharply away from the obstacle.

          5) When both touch sensors contact an object, the robot backs up.

          All done with a single 74HC14 (the '240 being a motor driver).

          How's that for a back-of-the-envelope analysis?

          Bruce
        • droidmakr
          ... Right on the noeny Bruce. A perfect description of what happens.
          Message 4 of 12 , Feb 16, 2002
            > How's that for a back-of-the-envelope analysis?

            Right on the noeny Bruce.
            A perfect description of what happens.
          • dkbovaird@aol.com
            My apologies to both Martin and Clifford, but I had to redraw it...hopefully I didn t mess it up. Lotta diodes. looks like another good app for what started as
            Message 5 of 12 , Feb 16, 2002
              My apologies to both Martin and Clifford, but I had to redraw it...hopefully
              I didn't mess it up. Lotta diodes.

              looks like another good app for what started as a head circuit.

              dave.

              --- In beam@y..., "R. Martin Keen" <keenerd@j...> wrote:
              > I'm not so sure about this one. It seems like a clever way to get around
              > the lockup that SC-head pvores suffer from. Toggling the pdiodes bias
              > voltage might cause some odd stuff. Interesting stuff with the diodes, I
              > can't wait for the write up. I'm guessing with is a variant of the diode
              > based SC-head, not the negative feedback SC-head. For those who find the
              > original cryptic, I included an easier to read schematic. Sorry about
              > the eraser marks. Took me a few tries to get it right.
              >
              > -Martin
              >
              > THE resource for beginners
              > http://beamlinks.botic.com
              > "The best of everyone's BEAM"
              >
              >
              > On Fri, 15 Feb 2002 15:53:42 -0800 (PST) Clifford Boerema
              > <droidmakr@y...> writes:
              > >
              > > Hello all,
              > >
              > > I wanted to share a circuit that results in
              > > a bot with a form of Peripheral Vision.
              > >
              > > It's a Master/Slave form of the SC-Head.
              > >
              > > The photo-diodes should be positioned across
              > > the front of the bot with the ones marked
              > > Far Left and Far Right mounted at a greater
              > > angle off center than the ones marked left
              > > and right.
              > >
              > > I'm putting together a write up on the
              > > circuit and will post it to my site as
              > > soon as I can.
              > >
              > > Hope you find it interesting.
              > >
              > > So long,
              > > Droidmakr
              > >
            • droidmakr
              ... No appology needed. In fact thanks. You did a great job and I do not see any errors. My schematic may make it easier to assemble and wire but yours makes
              Message 6 of 12 , Feb 17, 2002
                dkbovaird@a... wrote:
                > My apologies to both Martin and Clifford,
                > but I had to redraw it...hopefully
                > I didn't mess it up. Lotta diodes.
                >
                > looks like another good app for what started
                > as a head circuit.
                >
                > dave.

                No appology needed. In fact thanks. You did a
                great job and I do not see any errors.

                My schematic may make it easier to assemble and wire
                but yours makes how the circuit works more clear.
                Would you mind if I use it when I post my write-up
                on the circuit?

                Which I think will be ready after one more proof
                reading. That is unless i decide to rewrite a part
                of it again LOL.

                So long,
                Droidmakr
              • Wilf Rigter
                Thanks Martin, Your sketch is easier to understand but the layout drawing is valuable during construction. Huge thanks to Cliff for this wonderfully elegant
                Message 7 of 12 , Feb 17, 2002
                  Thanks Martin,

                  Your sketch is easier to understand but the layout drawing is valuable
                  during construction.

                  Huge thanks to Cliff for this wonderfully elegant circuit creation.

                  Let me take a stab of how it will respond to its environment:

                  The behaviour of this circuit depends on the location of the PDs. From the
                  title it would appear that all 4 Pds face forward but the 2 inner PDs face
                  directly forward and the outer 2 are angled to the left and right. Then the
                  effect is that the robot turns towards a light that is in directly in front
                  by turning off one motor and pivots around the stopped wheel. But if there
                  is a brighter light on the periphery (front left or front right) then the
                  bot reverses one motor and the robot rotates around its center towards the
                  light. So light in front only = small adjustment and brighter light to the
                  side = rapid large adjustment. This effect of a strong peripheral light
                  response mimics natural behavior.

                  The tactiles switches behave even more strongly: if a switch is closed then
                  the bot turns away unconditionally. If both switches are closed the robots
                  reverse straight back regardless of light level.

                  In fact the behavior is even more complex and interesting as the light
                  conditions themselves change with turning, etc. All in all, inmho this
                  circuit is destined to become a classic.

                  Kudos to Cliff the droidmakr!

                  wilf
                • Wilf Rigter
                  Grrr. Scooped again! Right on Bruce. Wilf ... From: Bruce Robinson To: beam@yahoogroups.com Sent: 2/16/02 2:40 PM Subject: Re: [beam] A Bot with Peripheral
                  Message 8 of 12 , Feb 17, 2002
                    Grrr. Scooped again! Right on Bruce.

                    Wilf


                    -----Original Message-----
                    From: Bruce Robinson
                    To: beam@yahoogroups.com
                    Sent: 2/16/02 2:40 PM
                    Subject: Re: [beam] A Bot with Peripheral Vision

                    Clifford Boerema wrote:
                    >
                    > I wanted to share a circuit that results in
                    > a bot with a form of Peripheral Vision.
                    >
                    > It's a Master/Slave form of the SC-Head.

                    Hi, Cliff. Very nice design.

                    By my quick analysis ...

                    1) Normal behaviour is both motors running "forward".

                    2) When the robot is pointing in the general direction of a light,
                    increased light on one of the "normal" photodiodes causes the motor on
                    that side of the robot to stop. This causes the robot to pivot about the
                    stopped wheel and face toward the light.

                    3) When "peripherial" photodiodes detect a difference between one side
                    and the other, they over-ride the "normal" PD's. The PD that detects the
                    brighter light reverses the motor on that side so the robot pivots
                    sharply about its center (one wheel forward, the other reverse) to face
                    more toward the light.

                    4) When the robot bumps into something on one side, it over-rides all
                    the PD circuits and reverses the motor on the OPPOSITE side, causing the
                    robot to pivot sharply away from the obstacle.

                    5) When both touch sensors contact an object, the robot backs up.

                    All done with a single 74HC14 (the '240 being a motor driver).

                    How's that for a back-of-the-envelope analysis?

                    Bruce


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                  • Bruce Robinson
                    ... Now THAT doesn t happen often :) Bruce
                    Message 9 of 12 , Feb 17, 2002
                      Wilf Rigter wrote:
                      >
                      > Grrr. Scooped again! Right on Bruce.

                      Now THAT doesn't happen often :)

                      Bruce
                    • dkbovaird@aol.com
                      I d be flattered if you did use it, no problem. I think that layout drawings such as yours are probably more useful to the group in general and take longer to
                      Message 10 of 12 , Feb 17, 2002
                        I'd be flattered if you did use it, no problem. I think that layout drawings such as yours are probably more useful to the group in general and take longer to create since both the design as well as the hookups need to be thought out before the presentation. The layout drawing together with the schematic may help people who are trying to understand how to read a schematic. And a schematic definitely helps me understand what the circuit is doing.

                        And for those wondering about the semantics of the whole thing, your use of the term "schematic" and my use of "schematic" are both valid descriptors of the drawings, just different conventions.

                        Nice work, you might want to discuss "why all the diodes?" and "what if I don't use so many (or used more) in between the photodiodes?" since neither wilf nor bruce touched on this aspect.

                        dave.

                        In a message dated 02/17/2002 2:00:35 AM Pacific Standard Time, droidmakr@... writes:


                        My schematic may make it easier to assemble and wire
                        but yours makes how the circuit works more clear.
                        Would you mind if I use it when I post my write-up
                        on the circuit?


                      • Wilf Rigter
                        As a matter of fact, Cliff will remember earlier comments when discussing the Schmitt Comparator that apply here as well: the multiple Si diodes provide a
                        Message 11 of 12 , Feb 17, 2002
                          As a matter of fact, Cliff will remember earlier comments when discussing
                          the Schmitt Comparator that apply here as well:

                          the multiple Si diodes provide a "dead band with memory" between one or two
                          Schmitt inverters switching state. They are used as a constant voltage drop
                          and can be replaced with LEDs, each of which has a higher forward voltage
                          drop providing the same function as 2 or 3 series diodes.

                          The nested (hierachical) SC architecture of Cliff's circuit and the use of
                          the PDs as diode logic makes for the compact and highly functional design of
                          the PeriPhoBot.

                          wilf

                          -----Original Message-----
                          From: dkbovaird@...
                          To: beam@yahoogroups.com
                          Sent: 2/17/02 11:30 AM
                          Subject: Re: [beam] Re: A Bot with Peripheral Vision

                          Nice work, you might want to discuss "why all the diodes?" and "what if
                          I don't use so many (or used more) in between the photodiodes?" since
                          neither wilf nor bruce touched on this aspect.
                        • Bruce Robinson
                          ... More useful for building, less so for understanding. I personally like to redraw the circuit myself, whatever form it s in, because I find the act of
                          Message 12 of 12 , Feb 17, 2002
                            dkbovaird@... wrote:

                            > ... I think that layout drawings such as yours are probably
                            > more useful to the group in general ...

                            More useful for building, less so for understanding. I personally like
                            to redraw the circuit myself, whatever form it's in, because I find the
                            act of redrawing it helps me understand it better. But then my brain is
                            a little strange anyway :)

                            > Nice work, you might want to discuss "why all the diodes?"
                            > and "what if I don't use so many (or used more) in between
                            > the photodiodes?" since neither wilf nor bruce touched on
                            > this aspect.

                            Alters the hysteresis (or dead band) between left and right. Each diode
                            has a small voltage drop across it, so the points where the inverter
                            inputs tap off are at slightly different voltages. I haven't played with
                            this at all, but it seems useful to have the "peripheral" PD's with a
                            greater voltage difference between them than the "regular" PD's. They
                            also prevent a direct short through the PD's if they both happen to be
                            forward biased (e.g., both touch sensors tripped at once).

                            Bruce
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