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RE: [beam] New Pvore

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  • Wilf Rigter
    The monocore capacitor is for positive feedback for fast switching between the two motors and to slow down and avoid high frequency oscillations. With average
    Message 1 of 12 , Feb 16 4:26 PM
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      The monocore capacitor is for positive feedback for fast switching between
      the two motors and to slow down and avoid high frequency oscillations. With
      average light and 100pf, the frequency is 1KHz so there is a kind of
      vibration as each motor rapidly turns on and off. The overall effect is
      continuous rotation of both motors while moving straight towards the
      balanced light condition. Larger values will slow the oscillations so that
      each motor stays on longer (1 second on/1 second off)and the motion is a
      "waddle" or even a twirling motion. With so much "overshoot" the motion will
      be somewhat random but the average direction should be towards balanced
      light. Try 1000pf or 0.01 uF for more purposeful motion.

      If you connected the PDs in the direction shown in your first schematic they
      are probably blown. That is because they act like two diodes in series
      across the powere supply and the with a 3V battery they would last less than
      a second before overheating and self-destructing.

      The input of a CMOS gate has a small "stray" capacitance to ground and Vcc.
      If the input is left floating the cap will be charged and discharged by
      tapping the input pin to + and Gnd. Since there is almost no input current,
      the input capacitance will maintain it's charge state and therefore the
      inverter will keep its logic state, for quite a long time. It is a form of
      short term memory.

      wilf


      -----Original Message-----
      From: David [mailto:dsg123456789@...]
      Sent: Friday, February 15, 2002 3:16 PM
      To: beam@yahoogroups.com
      Subject: RE: [beam] New Pvore


      Wilf-
      What are the capacitors for? And how exactly does a
      capacitor work? Can they conduct between there two
      terminals? B/c I only understood the R/C time
      constants. And also, is there any other value then
      100pf for the caps? Like, .22uf or .47uf?

      Thanks,
      David

      P.S. I couldn't get my circuit to respond to light, so
      i cut off the pd's and then left the first inverter
      floating, it went to ground and then when i tapped
      positive to the first inverter the other motor would
      spin for a short time even though the input was
      floating then it would switch back. Is this like a
      volitile memory device?
    • David
      Thanks David ... __________________________________________________ Do You Yahoo!? Yahoo! Sports - Coverage of the 2002 Olympic Games http://sports.yahoo.com
      Message 2 of 12 , Feb 16 10:47 PM
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        Thanks

        David
        --- Wilf Rigter <wilf.rigter@...> wrote:
        >
        > The monocore capacitor is for positive feedback for
        > fast switching between
        > the two motors and to slow down and avoid high
        > frequency oscillations. With
        > average light and 100pf, the frequency is 1KHz so
        > there is a kind of
        > vibration as each motor rapidly turns on and off.
        > The overall effect is
        > continuous rotation of both motors while moving
        > straight towards the
        > balanced light condition. Larger values will slow
        > the oscillations so that
        > each motor stays on longer (1 second on/1 second
        > off)and the motion is a
        > "waddle" or even a twirling motion. With so much
        > "overshoot" the motion will
        > be somewhat random but the average direction should
        > be towards balanced
        > light. Try 1000pf or 0.01 uF for more purposeful
        > motion.
        >
        > If you connected the PDs in the direction shown in
        > your first schematic they
        > are probably blown. That is because they act like
        > two diodes in series
        > across the powere supply and the with a 3V battery
        > they would last less than
        > a second before overheating and self-destructing.
        >
        > The input of a CMOS gate has a small "stray"
        > capacitance to ground and Vcc.
        > If the input is left floating the cap will be
        > charged and discharged by
        > tapping the input pin to + and Gnd. Since there is
        > almost no input current,
        > the input capacitance will maintain it's charge
        > state and therefore the
        > inverter will keep its logic state, for quite a long
        > time. It is a form of
        > short term memory.
        >
        > wilf
        >
        >
        > -----Original Message-----
        > From: David [mailto:dsg123456789@...]
        > Sent: Friday, February 15, 2002 3:16 PM
        > To: beam@yahoogroups.com
        > Subject: RE: [beam] New Pvore
        >
        >
        > Wilf-
        > What are the capacitors for? And how exactly does a
        > capacitor work? Can they conduct between there two
        > terminals? B/c I only understood the R/C time
        > constants. And also, is there any other value then
        > 100pf for the caps? Like, .22uf or .47uf?
        >
        > Thanks,
        > David
        >
        > P.S. I couldn't get my circuit to respond to light,
        > so
        > i cut off the pd's and then left the first inverter
        > floating, it went to ground and then when i tapped
        > positive to the first inverter the other motor would
        > spin for a short time even though the input was
        > floating then it would switch back. Is this like a
        > volitile memory device?
        >


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