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Re: Question about wilf Rirter's phototropic 2-motor walker schematic

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  • rameses32
    http://www.solarbotics.net/library/circuits/bot_walker_phototrope.html Have a look at the 74HC125 at the photo-bridge, the enable pin goes to VCC, making the
    Message 1 of 7 , Jul 1, 2008
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      http://www.solarbotics.net/library/circuits/bot_walker_phototrope.html

      Have a look at the 74HC125 at the photo-bridge, the enable pin goes
      to VCC, making the output high Z.

      Charley




      --- In beam@yahoogroups.com, "wilf_nv" <wrigter@...> wrote:
      >
      > Hi Charley,
      >
      > can you post a link to the schematic,
      >
      > thanks
      >
      > wilf
      >
      >
      > --- In beam@yahoogroups.com, "rameses32" <rameses32@> wrote:
      > >
      > > I built this circuit But I have a question about the photo bridge
      > > buffer, the enable pin in the schematic is tied to high, and this
      > makes
      > > the output high-Z, and the walker is not phototropic, but when I
      > run
      > > the enable pin to ground the robot becomes phototropic, my
      question
      > is
      > > should it go straight to ground? or through a resistor or connect
      > > somewhere else?
      > > Charley
      > >
      >
    • S
      It also seems the diodes in the Motor Drivers are backwards. At least according to this anyway:
      Message 2 of 7 , Jul 1, 2008
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        It also seems the diodes in the Motor Drivers are backwards. At least according to this anyway:


        rameses32 <rameses32@...> wrote:
        http://www.solarbot ics.net/library/ circuits/ bot_walker_ phototrope. html

        Have a look at the 74HC125 at the photo-bridge, the enable pin goes
        to VCC, making the output high Z.

        Charley

        --- In beam@yahoogroups. com, "wilf_nv" <wrigter@... > wrote:
        >
        > Hi Charley,
        >
        > can you post a link to the schematic,
        >
        > thanks
        >
        > wilf
        >
        >
        > --- In beam@yahoogroups. com, "rameses32" <rameses32@> wrote:
        > >
        > > I built this circuit But I have a question about the photo bridge
        > > buffer, the enable pin in the schematic is tied to high, and this
        > makes
        > > the output high-Z, and the walker is not phototropic, but when I
        > run
        > > the enable pin to ground the robot becomes phototropic, my
        question
        > is
        > > should it go straight to ground? or through a resistor or connect
        > > somewhere else?
        > > Charley
        > >
        >


      • Joseph Charles
        The circuit you reference uses NPN input transistors. The two-motor walker H-bridges use PNP input transistors. ...
        Message 3 of 7 , Jul 1, 2008
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          The circuit you reference uses NPN input transistors.

          The two-motor walker H-bridges use PNP input transistors.


          --- In beam@yahoogroups.com, S <garvinguy@...> wrote:
          >
          > It also seems the diodes in the Motor Drivers are backwards. At
          least according to this anyway:
          >
          http://f1.grp.yahoofs.com/v1/QBxqSAwD1LX4pBNME-YZNAgNbRIlbN-0yIvy7GSLugrKOcoKEDXuXTglfPTSJDEmqLXpNvdN7QFKLU1FJzFViXWi1dFthg/smoke%20proof%20Hbridge.gif
          >
        • S
          Ahh you re right. Thought I checked that. Joseph Charles wrote: The circuit you reference uses NPN input transistors. The
          Message 4 of 7 , Jul 1, 2008
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            Ahh you're right.  Thought I checked that.

            Joseph Charles <jodicalhon@...> wrote:
            The circuit you reference uses NPN input transistors.

            The two-motor walker H-bridges use PNP input transistors.

            --- In beam@yahoogroups. com, S <garvinguy@. ..> wrote:
            >
            > It also seems the diodes in the Motor Drivers are backwards. At
            least according to this anyway:
            >
            http://f1.grp. yahoofs.com/ v1/QBxqSAwD1LX4p BNME-YZNAgNbRIlb N-0yIvy7GSLugrKO coKEDXuXTglfPTSJ DEmqLXpNvdN7QFKL U1FJzFViXWi1dFth g/smoke%20proof% 20Hbridge. gif
            >


          • wilf_nv
            You are absolutely right Charley, the photobridge PWM oscillator 74HC125 buffer enable pin should be connected to ground (not to Vcc as shown). Alternately
            Message 5 of 7 , Jul 1, 2008
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              You are absolutely right Charley,

              the photobridge PWM oscillator 74HC125 buffer enable pin should be
              connected to ground (not to Vcc as shown).

              Alternately connect that enable pin to same point as the microcore
              74HC125 enable signal. By making the latter connection, it makes the
              circuit operation a bit more complex and possibly more difficult to
              troubleshoot. That is only justified if stopping the optical bridge
              controlled PWM oscillator will reduce the standby current when bright
              light is detected and the walker is "basking" in a bright light pool.

              Just to remind you, the purpose of the PWM oscillator is to change
              the timing of the microcore to turn the walker towards the light
              source. When the microcore is disabled, the PWM oscillator has no
              effect anyway and just wastes power. How much power? You will need
              to measure it to find out if it is significant compared to the
              charging current of the solar cells.

              The 2 diodes in each h-bridge are included to avoid "smoke" that can
              occur if both inputs of the h-bridge go low at the same time.

              Can you say oops?

              Thanks for your feedback and keep us updated on your progress!

              wilf


              --- In beam@yahoogroups.com, "rameses32" <rameses32@...> wrote:
              >
              >
              http://www.solarbotics.net/library/circuits/bot_walker_phototrope.html
              >
              > Have a look at the 74HC125 at the photo-bridge, the enable pin goes
              > to VCC, making the output high Z.
              >
              > Charley
              >
              >
              >
              >
              > --- In beam@yahoogroups.com, "wilf_nv" <wrigter@> wrote:
              > >
              > > Hi Charley,
              > >
              > > can you post a link to the schematic,
              > >
              > > thanks
              > >
              > > wilf
              > >
              > >
              > > --- In beam@yahoogroups.com, "rameses32" <rameses32@> wrote:
              > > >
              > > > I built this circuit But I have a question about the photo
              bridge
              > > > buffer, the enable pin in the schematic is tied to high, and
              this
              > > makes
              > > > the output high-Z, and the walker is not phototropic, but when
              I
              > > run
              > > > the enable pin to ground the robot becomes phototropic, my
              > question
              > > is
              > > > should it go straight to ground? or through a resistor or
              connect
              > > > somewhere else?
              > > > Charley
              > > >
              > >
              >
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