Loading ...
Sorry, an error occurred while loading the content.

PWM controls motor bicore dutycycle was Re: [beam] phototropic bicore walker question

Expand Messages
  • Wilf Rigter
    Hi Jo, One more comment: It doesn t take much asymmetry in the dutycycle of a phototropic bicore output to cause a walker to turn. Adding some series and
    Message 1 of 6 , Aug 10, 2004
    • 0 Attachment
      Hi Jo,
       
      One more comment: 
       
      It doesn't take much asymmetry in the dutycycle of a phototropic bicore output to cause a walker to turn.
       
      Adding some series and parallel resistors to the photo diodes can help control the min and max frequency deviation of the bicore with changes in absolute light. This does limit the sensitivity range of the circuit 
       
      For operation over a wider range of light,  try the attached variation on the unicore circuit.  Unlike the unicore circuit, the operation of this circuit is designed to be more predictable.  
       
      It uses a phototropic bicore front-end which operates at a high  (100Hz-100kHz) frequency. This generates complementary rectangular output waveforms with dutycycles determined by the ratio of light on the two photodiodes and frequency proportional to the absolute light level.
       
      These two waveforms Pulse Width Modulate, the current in the two 1M timing resistors of the motor control bicore. When the light is ballanced the dutycycle of these PWM signals is 50% which connects the grounded bicore timing resistors to ground 50% of the time. With 50% PWM wavforms, the effective values of the 1M resistors are therefore 2M respectively.
       
      As the PWM dutycycle of the two complementary signals varies, the effective values of the two 1M timing resistors goes up and down respectively, changing the dutycycle of the grounded bicore motor controller but leaving the frequency relatively unchanged.
       
      The increased frequency of the phototropic PWM signals with increasing absolute light levels has no effect on the grounded bicore.
       
      The lowest PWM frequency should be at least 100 times the grounded bicore frequency to interaction with the grounded bicore frequency. 
       
      A 1M resistor in parallel with the photodiodes sets the minimum phototropic bicore frequency to about 100Hz.
       
      regards
       
      wilf
       
        
      ----- Original Message -----
      Sent: Monday, August 09, 2004 6:30 AM
      Subject: [beam] phototropic bicore walker question

      Hi all

      Is there a better way to make a bicore walker phototropic than putting
      back to back photodiodes across the inputs? This method varies the
      frequency of oscillation with the light intensity and makes it
      difficult to configure for a wide range of light conditions.

      Any help appreciated.

      Thanks

      Jo C

    • Mike Scharf
      Hey Wilf, if you get a chance could you please post this circuit schematic in the files section for a short while so I can check it out. I don t seem to be
      Message 2 of 6 , Aug 12, 2004
      • 0 Attachment
        Hey Wilf, if you get a chance could you please post this circuit
        schematic in the files section for a short while so I can check it
        out. I don't seem to be receiving my regular e-mails lately from the
        yahoo group.

        Thanks a Bunch!
        Mike Scharf :)



        --- In beam@yahoogroups.com, "Wilf Rigter" <wrigter@d...> wrote:
        > Hi Jo,
        >
        > One more comment:
        >
        > It doesn't take much asymmetry in the dutycycle of a phototropic
        bicore output to cause a walker to turn.
        >
        > Adding some series and parallel resistors to the photo diodes can
        help control the min and max frequency deviation of the bicore with
        changes in absolute light. This does limit the sensitivity range of
        the circuit
        >
        > For operation over a wider range of light, try the attached
        variation on the unicore circuit. Unlike the unicore circuit, the
        operation of this circuit is designed to be more predictable.
        >
        > It uses a phototropic bicore front-end which operates at a high
        (100Hz-100kHz) frequency. This generates complementary rectangular
        output waveforms with dutycycles determined by the ratio of light on
        the two photodiodes and frequency proportional to the absolute light
        level.
        >
        > These two waveforms Pulse Width Modulate, the current in the two 1M
        timing resistors of the motor control bicore. When the light is
        ballanced the dutycycle of these PWM signals is 50% which connects the
        grounded bicore timing resistors to ground 50% of the time. With 50%
        PWM wavforms, the effective values of the 1M resistors are therefore
        2M respectively.
        >
        > As the PWM dutycycle of the two complementary signals varies, the
        effective values of the two 1M timing resistors goes up and down
        respectively, changing the dutycycle of the grounded bicore motor
        controller but leaving the frequency relatively unchanged.
        >
        > The increased frequency of the phototropic PWM signals with
        increasing absolute light levels has no effect on the grounded bicore.
        >
        > The lowest PWM frequency should be at least 100 times the grounded
        bicore frequency to interaction with the grounded bicore frequency.
        >
        > A 1M resistor in parallel with the photodiodes sets the minimum
        phototropic bicore frequency to about 100Hz.
        >
        > regards
        >
        > wilf
        >
        >
        > ----- Original Message -----
        > From: Joseph Charles
        > To: beam@yahoogroups.com
        > Sent: Monday, August 09, 2004 6:30 AM
        > Subject: [beam] phototropic bicore walker question
        >
        >
        > Hi all
        >
        > Is there a better way to make a bicore walker phototropic than
        putting
        > back to back photodiodes across the inputs? This method varies the
        > frequency of oscillation with the light intensity and makes it
        > difficult to configure for a wide range of light conditions.
        >
        > Any help appreciated.
        >
        > Thanks
        >
        > Jo C
      • David Simmons
        test
        Message 3 of 6 , Aug 12, 2004
        • 0 Attachment
          test
        • Ian Davison
          hi test
          Message 4 of 6 , Aug 12, 2004
          • 0 Attachment
            hi test
            On Aug 12, 2004, at 5:27 PM, David Simmons wrote:

            > test
            >
            >
            >
            > Yahoo! Groups Sponsor
            >
            > ADVERTISEMENT
            > <yhoo0504_testb_300250a052604.gif>
            > <l.gif>
            >
            > Yahoo! Groups Links
            >
            > • To visit your group on the web, go to:
            > http://groups.yahoo.com/group/beam/
            >  
            > • To unsubscribe from this group, send an email to:
            > beam-unsubscribe@yahoogroups.com
            >  
            > • Your use of Yahoo! Groups is subject to the Yahoo! Terms of
            > Service.
            >
            >
          • Wilf Rigter
            Done. ... From: Mike Scharf To: beam@yahoogroups.com Sent: Thursday, August 12, 2004 2:11 PM Subject: PWM controls motor bicore dutycycle was Re: [beam]
            Message 5 of 6 , Aug 12, 2004
            • 0 Attachment
              Done.
              ----- Original Message -----
              Sent: Thursday, August 12, 2004 2:11 PM
              Subject: PWM controls motor bicore dutycycle was Re: [beam] phototropic bicore walker que

              Hey Wilf, if you get a chance could you please post this circuit
              schematic in the files section for a short while so I can check it
              out. I don't seem to be receiving my regular e-mails lately from the
              yahoo group.

              Thanks a Bunch!
              Mike Scharf     :)


            • Joseph Charles
              Hi Wilf Thanks so much for the bicore PWM circuit, and explanation. I ve been trying a few bastardised versions of the BEAMant circuit I found on the Beam
              Message 6 of 6 , Aug 14, 2004
              • 0 Attachment
                Hi Wilf

                Thanks so much for the bicore PWM circuit, and explanation.

                I've been trying a few bastardised versions of the BEAMant circuit I
                found on the Beam reference library site (thanks Eric Searle!) and have
                had great fun watching my bot trying its hardest to turn and doing all
                sorts of odd things as I tried different resistor values, front or rear
                motor leading etc. Consequently I've learned quite a bit I think. (I've
                borrowed my brother's CRO which helps no end!). I still had my bicore
                suspended, with an attached photo-bicore feeding it, unlike your
                grounded version.

                I'll be trying your circuit tonight when all is quiet and will report
                my results when I get the chance.

                Thanks again.

                Jo C

                --- In beam@yahoogroups.com, "Wilf Rigter" <wrigter@d...> wrote:
                > Hi Jo,
                >
                > One more comment:
                >
                > It doesn't take much asymmetry in the dutycycle of a phototropic bicore output to cause a walker to turn.
                >
                > Adding some series and parallel resistors to the photo diodes can help control the min and max frequency deviation of the bicore with changes in absolute light. This does limit the sensitivity range of the circuit
                >
                > For operation over a wider range of light, try the attached variation on the unicore circuit. Unlike the unicore circuit, the operation of this circuit is designed to be more predictable.
                >
                > It uses a phototropic bicore front-end which operates at a high (100Hz-100kHz) frequency. This generates complementary rectangular output waveforms with dutycycles determined by the ratio of light on the two photodiodes and frequency proportional to the absolute light level.
                >
                > These two waveforms Pulse Width Modulate, the current in the two 1M timing resistors of the motor control bicore. When the light is ballanced the dutycycle of these PWM signals is 50% which connects the grounded bicore timing resistors to ground 50% of the time. With 50% PWM wavforms, the effective values of the 1M resistors are therefore 2M respectively.
                >
                > As the PWM dutycycle of the two complementary signals varies, the effective values of the two 1M timing resistors goes up and down respectively, changing the dutycycle of the grounded bicore motor controller but leaving the frequency relatively unchanged.
                >
                > The increased frequency of the phototropic PWM signals with increasing absolute light levels has no effect on the grounded bicore.
                >
                > The lowest PWM frequency should be at least 100 times the grounded bicore frequency to interaction with the grounded bicore frequency.
                >
                > A 1M resistor in parallel with the photodiodes sets the minimum phototropic bicore frequency to about 100Hz.
                >
                > regards
                >
                > wilf
                >
                >
                > ----- Original Message -----
                > From: Joseph Charles
                > To: beam@yahoogroups.com
                > Sent: Monday, August 09, 2004 6:30 AM
                > Subject: [beam] phototropic bicore walker question
                >
                >
                > Hi all
                >
                > Is there a better way to make a bicore walker phototropic than putting
                > back to back photodiodes across the inputs? This method varies the
                > frequency of oscillation with the light intensity and makes it
                > difficult to configure for a wide range of light conditions.
                >
                > Any help appreciated.
                >
                > Thanks
                >
                > Jo C
              Your message has been successfully submitted and would be delivered to recipients shortly.