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Re: [beam] Re: I need help with my micro core sensors.........

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  • Wilf Rigter
    Hi Alex, Series light sensors, eh? Well let me think... Ok here is the uCore Photo Bridge: a brand new way to influence a microcore walker with light sensors.
    Message 1 of 14 , Jun 14, 2003
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      Hi Alex,

      Series light sensors, eh?

      Well let me think...

      Ok here is the uCore Photo Bridge: a brand new way to influence a microcore
      walker with light sensors.

      I modified Fred's drawing, using cut and paste in my paint program, to
      incorporate the new circuit and also to point out a slight correction to the
      Miller Solar Engine. Note the small size of the attached schematic file
      after reducing the colors to 16 and converting to gif format.

      The uCore Photo Bridge:

      The two Light Dependent Resistors in series form a ratiometric photobridge
      connected between Nv 1 and Nv3 outputs which also control the rotation of
      the rear motor of a two motor walker.

      Depending on which Nv is active, the polarity across the bridge is reversed.
      When the two LDR sensors are the same resistance, the bridge is balanced and
      the midpoint voltage of the bridge is nominally Vcc/2. If the two LDRs are
      not balanced, the midpoint will be offset from Vcc/2.

      That midpoint voltage is the return point for the two new parallel timing
      resistors isolated with diodes and connected to the inputs of Nv1 and Nv3.

      Each parallel resistor and diode will affect the time constant of the
      corresponding active Nv depending on the voltage of the photo bridge
      midpoint.

      When the midpoint of the LDR bridge is lower than Vcc/2, the active Nv will
      time out faster. If the midpoint is higher, the active Nv will time out
      slower.

      With an unbalanced photobridge, the midpoint voltage will be higher for one
      active and for the other the midpoint will be lower as the voltage across
      the bridge is reversed.
      The parallel resistors remain active until the voltage of the timing
      capacitors on each Nv input drops below the photobridge midpoint voltage and
      the isolation diode becomes reverse biased. After that the original 9M
      resistor ensures that the Nv times out.

      As a result the discharge voltage waveform of the active Nv will have a
      double slope, first steep with two resistors in parallel to discharge the
      cap and then slower with the single resistor to finish the capacitor
      discharge.

      So why is this photobridge better than the "traditional" LDR in parallel
      with the microcore timing resistors arrangement?

      Most importantly it is relatively insensitive to the absolute light level,
      which in the tranditional circuit would cause very short steps in bright
      light and long steps in dim light.

      That problem of sensitivity to absolute light level also occurs in light
      seeking master slave bicore walkers.

      The uCore Photo Bridge only reacts to the ratio of the LDR resistance values
      and insensitive to the absolute light level.

      This makes the period of leg rotation relatively constant over a wide range
      of light levels.

      This circuit comes piping hot from the mind of yours truly, so it is as yet
      untested but I think it will work spectacularly well. This may be an
      opportunity to test out this circuit and help develop into a tried and
      proven design.

      enjoy

      wilf

      ----- Original Message -----
      From: "submachinegunn" <rockbitea@...>
      To: <beam@yahoogroups.com>
      Sent: Saturday, June 14, 2003 8:23 PM
      Subject: [beam] Re: I need help with my micro core sensors.........


      > Cool. Thanks for your help but I still have some questions about
      > somethings you said.
      >
      > > Light sensors like Cadmium Sulfide cells can be placed in parallel
      > with the
      > > Nv timing resistors to decrease the Nv duration and the rotation
      > of the
      > > motor so that one leg on the ground has a shorter stride than the
      > other leg
      > > on the ground.
      >
      > Are you saying that I need to hook up all of these timing resistors
      > to the photo cells or are 2 photo cells (made into a voltage
      > divider, right?) for one timing resistor is enough? Sorry if I am
      > not understanding this.
      >
      > Sincerly:
      > Alex
      >



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    • Bruce Robinson
      ... Hey, Alex. Here s a few circuits that can be used to change the timing of bicores and microcores. As Wilf says, use springs to keep the legs from turning
      Message 2 of 14 , Jun 14, 2003
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        submachinegunn wrote:
        >
        > This machine will use 2 motors for walking (you guessed right ^_^ ).
        > The light detectors are for making the machine go in the direction
        > of the light (light seeking). The proximity detectors will be used
        > for obstacle avoidance. Pretty much I just want to build a walker
        > that is attracted to light and avoids obstales.

        Hey, Alex.

        Here's a few circuits that can be used to change the timing of bicores
        and microcores. As Wilf says, use springs to keep the legs from turning
        too far.

        http://bftgu.solarbotics.net/starting_nvnet_influe.html

        Bruce
      • submachinegunn
        It works!!!! But there is one thing U should know about in the schematic you gave me. The resistors that are attached to the photo cells should be a value
        Message 3 of 14 , Jun 15, 2003
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          It works!!!! But there is one thing U should know about in the
          schematic you gave me. The resistors that are attached to the photo
          cells should be a value that is less than the timing resistors or
          else the machine won't go anywhere. Well.....Thanks Wilf and
          Bruce!!!! You guys have been a great help to making me understand
          this stuff better. ^_^

          Sincerly:
          Alex

          --- In beam@yahoogroups.com, "Wilf Rigter" <wrigter@d...> wrote:
          > Hi Alex,
          >
          > Series light sensors, eh?
          >
          > Well let me think...
          >
          > Ok here is the uCore Photo Bridge: a brand new way to influence a
          microcore
          > walker with light sensors.
          >
          > I modified Fred's drawing, using cut and paste in my paint
          program, to
          > incorporate the new circuit and also to point out a slight
          correction to the
          > Miller Solar Engine. Note the small size of the attached
          schematic file
          > after reducing the colors to 16 and converting to gif format.
          >
          > The uCore Photo Bridge:
          >
          > The two Light Dependent Resistors in series form a ratiometric
          photobridge
          > connected between Nv 1 and Nv3 outputs which also control the
          rotation of
          > the rear motor of a two motor walker.
          >
          > Depending on which Nv is active, the polarity across the bridge is
          reversed.
          > When the two LDR sensors are the same resistance, the bridge is
          balanced and
          > the midpoint voltage of the bridge is nominally Vcc/2. If the two
          LDRs are
          > not balanced, the midpoint will be offset from Vcc/2.
          >
          > That midpoint voltage is the return point for the two new parallel
          timing
          > resistors isolated with diodes and connected to the inputs of Nv1
          and Nv3.
          >
          > Each parallel resistor and diode will affect the time constant of
          the
          > corresponding active Nv depending on the voltage of the photo
          bridge
          > midpoint.
          >
          > When the midpoint of the LDR bridge is lower than Vcc/2, the
          active Nv will
          > time out faster. If the midpoint is higher, the active Nv will
          time out
          > slower.
          >
          > With an unbalanced photobridge, the midpoint voltage will be
          higher for one
          > active and for the other the midpoint will be lower as the voltage
          across
          > the bridge is reversed.
          > The parallel resistors remain active until the voltage of the
          timing
          > capacitors on each Nv input drops below the photobridge midpoint
          voltage and
          > the isolation diode becomes reverse biased. After that the
          original 9M
          > resistor ensures that the Nv times out.
          >
          > As a result the discharge voltage waveform of the active Nv will
          have a
          > double slope, first steep with two resistors in parallel to
          discharge the
          > cap and then slower with the single resistor to finish the
          capacitor
          > discharge.
          >
          > So why is this photobridge better than the "traditional" LDR in
          parallel
          > with the microcore timing resistors arrangement?
          >
          > Most importantly it is relatively insensitive to the absolute
          light level,
          > which in the tranditional circuit would cause very short steps in
          bright
          > light and long steps in dim light.
          >
          > That problem of sensitivity to absolute light level also occurs in
          light
          > seeking master slave bicore walkers.
          >
          > The uCore Photo Bridge only reacts to the ratio of the LDR
          resistance values
          > and insensitive to the absolute light level.
          >
          > This makes the period of leg rotation relatively constant over a
          wide range
          > of light levels.
          >
          > This circuit comes piping hot from the mind of yours truly, so it
          is as yet
          > untested but I think it will work spectacularly well. This may be
          an
          > opportunity to test out this circuit and help develop into a tried
          and
          > proven design.
          >
          > enjoy
          >
          > wilf
          >
          > ----- Original Message -----
          > From: "submachinegunn" <rockbitea@h...>
          > To: <beam@yahoogroups.com>
          > Sent: Saturday, June 14, 2003 8:23 PM
          > Subject: [beam] Re: I need help with my micro core sensors.........
          >
          >
          > > Cool. Thanks for your help but I still have some questions about
          > > somethings you said.
          > >
          > > > Light sensors like Cadmium Sulfide cells can be placed in
          parallel
          > > with the
          > > > Nv timing resistors to decrease the Nv duration and the
          rotation
          > > of the
          > > > motor so that one leg on the ground has a shorter stride than
          the
          > > other leg
          > > > on the ground.
          > >
          > > Are you saying that I need to hook up all of these timing
          resistors
          > > to the photo cells or are 2 photo cells (made into a voltage
          > > divider, right?) for one timing resistor is enough? Sorry if I
          am
          > > not understanding this.
          > >
          > > Sincerly:
          > > Alex
          > >
          >
          >
          >
          > ---
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          > Checked by AVG anti-virus system (http://www.grisoft.com).
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        • Wilf Rigter
          Well done Alex! can you tell us what values of parallel resistors worked for you?How well does it respond to light? Have you build the complete walker? Can you
          Message 4 of 14 , Jun 15, 2003
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            Well done Alex!

            can you tell us what values of parallel resistors worked for you?How well
            does it respond to light? Have you build the complete walker? Can you
            describe the other components and motors you used? What do you mean by "the
            machine won't go anywhere"?

            Thanks for the feedback,

            wilf

            ----- Original Message -----
            From: "submachinegunn" <rockbitea@...>
            To: <beam@yahoogroups.com>
            Sent: Sunday, June 15, 2003 10:56 AM
            Subject: [beam] Re: I need help with my micro core sensors.........


            > It works!!!! But there is one thing U should know about in the
            > schematic you gave me. The resistors that are attached to the photo
            > cells should be a value that is less than the timing resistors or
            > else the machine won't go anywhere. Well.....Thanks Wilf and
            > Bruce!!!! You guys have been a great help to making me understand
            > this stuff better. ^_^
            >
            > Sincerly:
            > Alex
            >
            > --- In beam@yahoogroups.com, "Wilf Rigter" <wrigter@d...> wrote:
            > > Hi Alex,
            > >
            > > Series light sensors, eh?
            > >
            > > Well let me think...
            > >
            > > Ok here is the uCore Photo Bridge




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          • submachinegunn
            Hey Wilf, The values that I first tried for the parallel resistors were 100K ohms. I m sure they could be of larger value but still less than the value of the
            Message 5 of 14 , Jun 15, 2003
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              Hey Wilf,

              The values that I first tried for the parallel resistors were 100K
              ohms. I'm sure they could be of larger value but still less than
              the value of the timing resistors. It responds very well to light.
              If one of the photo cells is recieving less light than the other,
              then the output of it's corresponding Nv will be faster. Since I
              have not wired it up to some motors yet, I have been using LEDs the
              whole time (I'm still working on giving the machine proximity
              detectors). So....when I cover up one photo cell, it's
              corresponding Nv will make it's LED flash faster than the other
              LEDs. The components I have used so far are as follows:

              1 - 74HC14
              4 - 0.1 uF capacitors (electrolytic)
              4 - 3.0M ohms resistors (for the timing resistors)
              4 - red LEDs
              4 - 2.2K ohms resistors (for the LEDs)
              2 - photo cells (resistors)
              4 - 1N4148 switching diodes
              2 - 100K ohms resistors

              What I ment by "the machine won't go anywhere" was that the output
              from the corresponding Nv will be very low and therefore the machine
              will not turn (in the direction of the where the higher light level
              is coming from) quickly. Well....I'm off to make some proximity
              detectors. Later!

              Sincerly:
              Alex

              --- In beam@yahoogroups.com, "Wilf Rigter" <wrigter@d...> wrote:
              > Well done Alex!
              >
              > can you tell us what values of parallel resistors worked for you?
              How well
              > does it respond to light? Have you build the complete walker? Can
              you
              > describe the other components and motors you used? What do you
              mean by "the
              > machine won't go anywhere"?
              >
              > Thanks for the feedback,
              >
              > wilf
              >
              > ----- Original Message -----
              > From: "submachinegunn" <rockbitea@h...>
              > To: <beam@yahoogroups.com>
              > Sent: Sunday, June 15, 2003 10:56 AM
              > Subject: [beam] Re: I need help with my micro core sensors.........
              >
              >
              > > It works!!!! But there is one thing U should know about in the
              > > schematic you gave me. The resistors that are attached to the
              photo
              > > cells should be a value that is less than the timing resistors or
              > > else the machine won't go anywhere. Well.....Thanks Wilf and
              > > Bruce!!!! You guys have been a great help to making me
              understand
              > > this stuff better. ^_^
              > >
              > > Sincerly:
              > > Alex
              > >
              > > --- In beam@yahoogroups.com, "Wilf Rigter" <wrigter@d...> wrote:
              > > > Hi Alex,
              > > >
              > > > Series light sensors, eh?
              > > >
              > > > Well let me think...
              > > >
              > > > Ok here is the uCore Photo Bridge
              >
              >
              >
              >
              > ---
              > Outgoing mail is certified Virus Free.
              > Checked by AVG anti-virus system (http://www.grisoft.com).
              > Version: 6.0.488 / Virus Database: 287 - Release Date: 6/5/2003
            • Ori
              ... microcore ... There s a slight mistake in the schem... should it be the NV1 or NV3 output that is rear motor +? Ori
              Message 6 of 14 , Jun 15, 2003
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                > Ok here is the uCore Photo Bridge: a brand new way to influence a
                microcore
                > walker with light sensors.

                There's a slight mistake in the schem... should it be the NV1 or NV3 output
                that is rear motor +?

                Ori
              • Wilf Rigter
                Depends on motor placement and rotation. Best to experiment. wilf ... From: Ori To: Sent: Sunday, June 15, 2003
                Message 7 of 14 , Jun 15, 2003
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                  Depends on motor placement and rotation. Best to experiment.

                  wilf

                  ----- Original Message -----
                  From: "Ori" <sbarbut@...>
                  To: <beam@yahoogroups.com>
                  Sent: Sunday, June 15, 2003 5:05 PM
                  Subject: Re: [beam] Re: I need help with my micro core sensors.........


                  > > Ok here is the uCore Photo Bridge: a brand new way to influence a
                  > microcore
                  > > walker with light sensors.
                  >
                  > There's a slight mistake in the schem... should it be the NV1 or NV3
                  output
                  > that is rear motor +?
                  >
                  > Ori
                  >
                  >
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                • submachinegunn
                  Hello Wilf, I have another question for you. You know that schematic U made about the light seeking quad-core (with the photo cells that are in series), do U
                  Message 8 of 14 , Jun 18, 2003
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                    Hello Wilf,

                    I have another question for you. You know that schematic U made
                    about the light seeking quad-core (with the photo cells that are in
                    series), do U know how to add a reverse (obsitcle avoidence) circuit
                    to it? I've tried numerous times and I'm out of ideas. I would
                    deeply appreciate your help.

                    Sincerly:
                    Alex

                    --- In beam@yahoogroups.com, "Wilf Rigter" <wrigter@d...> wrote:
                    > Well done Alex!
                    >
                    > can you tell us what values of parallel resistors worked for you?
                    How well
                    > does it respond to light? Have you build the complete walker? Can
                    you
                    > describe the other components and motors you used? What do you
                    mean by "the
                    > machine won't go anywhere"?
                    >
                    > Thanks for the feedback,
                    >
                    > wilf
                    >
                    > ----- Original Message -----
                    > From: "submachinegunn" <rockbitea@h...>
                    > To: <beam@yahoogroups.com>
                    > Sent: Sunday, June 15, 2003 10:56 AM
                    > Subject: [beam] Re: I need help with my micro core sensors.........
                    >
                    >
                    > > It works!!!! But there is one thing U should know about in the
                    > > schematic you gave me. The resistors that are attached to the
                    photo
                    > > cells should be a value that is less than the timing resistors or
                    > > else the machine won't go anywhere. Well.....Thanks Wilf and
                    > > Bruce!!!! You guys have been a great help to making me
                    understand
                    > > this stuff better. ^_^
                    > >
                    > > Sincerly:
                    > > Alex
                    > >
                    > > --- In beam@yahoogroups.com, "Wilf Rigter" <wrigter@d...> wrote:
                    > > > Hi Alex,
                    > > >
                    > > > Series light sensors, eh?
                    > > >
                    > > > Well let me think...
                    > > >
                    > > > Ok here is the uCore Photo Bridge
                    >
                    >
                    >
                    >
                    > ---
                    > Outgoing mail is certified Virus Free.
                    > Checked by AVG anti-virus system (http://www.grisoft.com).
                    > Version: 6.0.488 / Virus Database: 287 - Release Date: 6/5/2003
                  • Wilf Rigter
                    Reversing the walker requires that the control signals to the either the front or the rear motor terminals are swapped. Do you have a 4016 or 4066 or 74HC4066
                    Message 9 of 14 , Jun 19, 2003
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                      Reversing the walker requires that the control signals to the either the
                      front or the rear motor terminals are swapped.

                      Do you have a 4016 or 4066 or 74HC4066 or 74HC240, or 74HC157 handy? Anyone
                      of those chips can be used as a multiplexer inserted between Nv1 and Nv3
                      outputs and the corresponding motor driver inputs to swap the connections.

                      let me know

                      wilf

                      ----- Original Message -----
                      From: "submachinegunn" <rockbitea@...>
                      To: <beam@yahoogroups.com>
                      Sent: Wednesday, June 18, 2003 4:16 PM
                      Subject: [beam] I need help with my micro core
                      sensors...again..................


                      > Hello Wilf,
                      >
                      > I have another question for you. You know that schematic U made
                      > about the light seeking quad-core (with the photo cells that are in
                      > series), do U know how to add a reverse (obsitcle avoidence) circuit
                      > to it? I've tried numerous times and I'm out of ideas. I would
                      > deeply appreciate your help.
                      >
                      > Sincerly:
                      > Alex
                      >
                      > --- In beam@yahoogroups.com, "Wilf Rigter" <wrigter@d...> wrote:
                      > > Well done Alex!
                      > >
                      > > can you tell us what values of parallel resistors worked for you?
                      > How well
                      > > does it respond to light? Have you build the complete walker? Can
                      > you
                      > > describe the other components and motors you used? What do you
                      > mean by "the
                      > > machine won't go anywhere"?
                      > >
                      > > Thanks for the feedback,
                      > >
                      > > wilf
                      > >
                      > > ----- Original Message -----
                      > > From: "submachinegunn" <rockbitea@h...>
                      > > To: <beam@yahoogroups.com>
                      > > Sent: Sunday, June 15, 2003 10:56 AM
                      > > Subject: [beam] Re: I need help with my micro core sensors.........
                      > >
                      > >
                      > > > It works!!!! But there is one thing U should know about in the
                      > > > schematic you gave me. The resistors that are attached to the
                      > photo
                      > > > cells should be a value that is less than the timing resistors or
                      > > > else the machine won't go anywhere. Well.....Thanks Wilf and
                      > > > Bruce!!!! You guys have been a great help to making me
                      > understand
                      > > > this stuff better. ^_^
                      > > >
                      > > > Sincerly:
                      > > > Alex
                      > > >
                      > > > --- In beam@yahoogroups.com, "Wilf Rigter" <wrigter@d...> wrote:
                      > > > > Hi Alex,
                      > > > >
                      > > > > Series light sensors, eh?
                      > > > >
                      > > > > Well let me think...
                      > > > >
                      > > > > Ok here is the uCore Photo Bridge
                      > >
                      > >
                      > >
                      > >
                      > > ---
                      > > Outgoing mail is certified Virus Free.
                      > > Checked by AVG anti-virus system (http://www.grisoft.com).
                      > > Version: 6.0.488 / Virus Database: 287 - Release Date: 6/5/2003
                      >
                      >
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