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RE: [beam] HELP!!!!! (Photopopper problem)

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  • Wilf Rigter
    Interesting. I don t think anyone has used photodiodes in the 1381 ground pin (similar to the Miller SE). This can be nicely combined in a photo popper circuit
    Message 1 of 21 , Feb 3, 2002
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      Interesting. I don't think anyone has used photodiodes in the 1381 ground
      pin (similar to the Miller SE). This can be nicely combined in a photo
      popper circuit as shown in the attached. The 1uF timing caps should be
      adjusted to give the right discharge duration. The series 1N4148 diodes may
      not be required. For those not familiar with the photopopper and Miller SE
      operation, it works as follows:

      The main cap charges up until the voltage reaches the trigger of the 1381
      which is equal to the rated trigger level plus the PD photovoltaic voltage
      (~.5V) plus the 1N4148 forward voltage (~100mV@5uA) plus the voltage drop
      (@5uA) across each leg of the 100K pot. The pot can therefore be used to
      match the 1381 trigger levels. The PD photovoltaic voltage is proportional
      to the light level. The SE whose PD has the lower light level will have a
      lower combined trigger level and will fire first.

      One the SE is triggered two things happen:

      1.The ground pin current drops to about 1uA lowering the SE reset voltage
      (increased hysteresis).
      2.The ground pin voltage becomes negative with respect to 0V as the main
      storage cap discharges.

      The voltage across the 1381 is now equal to the timing cap and is
      independent of the main capacitor voltage. While triggered, the 1381 supply
      current is just 1uA and the reset time (when the 1381 turns off) is
      determined by the size of the timing capacitor. With 1uF the reset time is
      about one second. When the 1381 turns off, the 1381 ground pin current jumps
      to 5uA and starts to discharge the timing capacitor more quickly until
      voltage rise on the main capacitor voltage catches up and the cycle repeats.

      Hope this all makes sense and I'll confirm my analysis when I get a chance
      to scope the circuit.

      Have fun.

      wilf

      -----Original Message-----
      From: Bryan Yeung [mailto:ba_alazmon@...]
      Sent: Sunday, February 03, 2002 7:11 AM
      To: beam@yahoogroups.com
      Subject: [beam] HELP!!!!! (Photopopper problem)


      Hello,

      This is my fourth unsuccessful attempt at getting a
      photopopper to work and I'm beginning to think I'm
      cursed. I am just trying to get one that will seek
      light: no touch sensors. The problem is the eyes. If
      I bypass them everything works fine. But I can't
      figure out what is wrong with them, if I measure the
      voltage between the output on them and ground (or pin
      three on the 1381) it seems to say it should trigger.
      I'm really stumped.

      Oh, I'm using two miller solar engines, the
      photodiodes from solarbotics.com, and a 100k trimpot
      (also from solarbotics.com).

      Bryan

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    • Wilf Rigter
      Ah! The photopopper is working but your problem is the main storage capacitor is too small for the motors and there is not enough stored energy to turn over
      Message 2 of 21 , Feb 3, 2002
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        Ah! The photopopper is working but your problem is the main storage
        capacitor is too small for the motors and there is not enough stored energy
        to turn over the motor. So either increase the capacity or get more
        efficient motors.

        wilf

        -----Original Message-----
        From: Bryan Yeung [mailto:ba_alazmon@...]
        Sent: Sunday, February 03, 2002 8:34 AM
        To: beam@yahoogroups.com
        Subject: Re: [beam] HELP!!!!! (Photopopper problem)


        Okay, so that analysis wasn't quite right. The motors
        are firing but they aren't turning over. If I hold
        the shaft I can feel it twitching a little bit but it
        never makes a revolution. The odd thing is, if I
        connect pin 2 on the 1381 to Vcc the motor buzzes
        quite nicely. Grrrrrr.

        Bryan

        --- Bryan Yeung <ba_alazmon@...> wrote:
        > Hello,
        >
        > This is my fourth unsuccessful attempt at getting a
        > photopopper to work and I'm beginning to think I'm
        > cursed. I am just trying to get one that will seek
        > light: no touch sensors. The problem is the eyes.
        > If
        > I bypass them everything works fine. But I can't
        > figure out what is wrong with them, if I measure the
        > voltage between the output on them and ground (or
        > pin
        > three on the 1381) it seems to say it should
        > trigger.
        > I'm really stumped.
        >
        > Oh, I'm using two miller solar engines, the
        > photodiodes from solarbotics.com, and a 100k trimpot
        > (also from solarbotics.com).
        >
        > Bryan
        >
        > __________________________________________________
        > Do You Yahoo!?
        > Great stuff seeking new owners in Yahoo! Auctions!
        > http://auctions.yahoo.com
        >


        __________________________________________________
        Do You Yahoo!?
        Great stuff seeking new owners in Yahoo! Auctions!
        http://auctions.yahoo.com


        To unsubscribe from this group, send an email to:
        beam-unsubscribe@egroups.com



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      • Bryan Yeung
        There isn t any noise, just the pulsing of the motor. It tries to turn, stops, trys again, etc. I am using two 2.5v .33F caps in series. The motors are pager
        Message 3 of 21 , Feb 3, 2002
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          There isn't any noise, just the pulsing of the motor.
          It tries to turn, stops, trys again, etc. I am using
          two 2.5v .33F caps in series. The motors are pager
          motors from BG Micro.

          Bryan

          --- Ori <sbarbut@...> wrote:
          > Is there any noise when the motors pop? A
          > high-pitched whine? What's your
          > cap? Motors?
          >
          > Ori
          >
          > ----- Original Message -----
          > From: "Bryan Yeung" <ba_alazmon@...>
          > To: <beam@yahoogroups.com>
          > Sent: Sunday, February 03, 2002 8:34 AM
          > Subject: Re: [beam] HELP!!!!! (Photopopper problem)
          >
          >
          > > Okay, so that analysis wasn't quite right. The
          > motors
          > > are firing but they aren't turning over. If I
          > hold
          > > the shaft I can feel it twitching a little bit but
          > it
          > > never makes a revolution. The odd thing is, if I
          > > connect pin 2 on the 1381 to Vcc the motor buzzes
          > > quite nicely. Grrrrrr.
          > >
          > > Bryan
          > >
          > > --- Bryan Yeung <ba_alazmon@...> wrote:
          > > > Hello,
          > > >
          > > > This is my fourth unsuccessful attempt at
          > getting a
          > > > photopopper to work and I'm beginning to think
          > I'm
          > > > cursed. I am just trying to get one that will
          > seek
          > > > light: no touch sensors. The problem is the
          > eyes.
          > > > If
          > > > I bypass them everything works fine. But I
          > can't
          > > > figure out what is wrong with them, if I measure
          > the
          > > > voltage between the output on them and ground
          > (or
          > > > pin
          > > > three on the 1381) it seems to say it should
          > > > trigger.
          > > > I'm really stumped.
          > > >
          > > > Oh, I'm using two miller solar engines, the
          > > > photodiodes from solarbotics.com, and a 100k
          > trimpot
          > > > (also from solarbotics.com).
          > > >
          > > > Bryan
          > > >
          > > >
          > __________________________________________________
          > > > Do You Yahoo!?
          > > > Great stuff seeking new owners in Yahoo!
          > Auctions!
          > > > http://auctions.yahoo.com
          > > >
          > >
          > >
          > > __________________________________________________
          > > Do You Yahoo!?
          > > Great stuff seeking new owners in Yahoo! Auctions!
          > > http://auctions.yahoo.com
          > >
          > >
          > > To unsubscribe from this group, send an email to:
          > > beam-unsubscribe@egroups.com
          > >
          > >
          > >
          > > Your use of Yahoo! Groups is subject to
          > http://docs.yahoo.com/info/terms/
          > >
          > >
          > >
          >
          >


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        • Bryan Yeung
          I m using two 2.5v .33F caps in series and they seem to power the motor just fine without the trimpot and photodiodes. Bryan ...
          Message 4 of 21 , Feb 3, 2002
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            I'm using two 2.5v .33F caps in series and they seem
            to power the motor just fine without the trimpot and
            photodiodes.

            Bryan

            --- Wilf Rigter <wilf.rigter@...> wrote:
            >
            > Ah! The photopopper is working but your problem is
            > the main storage
            > capacitor is too small for the motors and there is
            > not enough stored energy
            > to turn over the motor. So either increase the
            > capacity or get more
            > efficient motors.
            >
            > wilf
            >
            > -----Original Message-----
            > From: Bryan Yeung [mailto:ba_alazmon@...]
            > Sent: Sunday, February 03, 2002 8:34 AM
            > To: beam@yahoogroups.com
            > Subject: Re: [beam] HELP!!!!! (Photopopper problem)
            >
            >
            > Okay, so that analysis wasn't quite right. The
            > motors
            > are firing but they aren't turning over. If I hold
            > the shaft I can feel it twitching a little bit but
            > it
            > never makes a revolution. The odd thing is, if I
            > connect pin 2 on the 1381 to Vcc the motor buzzes
            > quite nicely. Grrrrrr.
            >
            > Bryan
            >
            > --- Bryan Yeung <ba_alazmon@...> wrote:
            > > Hello,
            > >
            > > This is my fourth unsuccessful attempt at getting
            > a
            > > photopopper to work and I'm beginning to think I'm
            > > cursed. I am just trying to get one that will
            > seek
            > > light: no touch sensors. The problem is the eyes.
            >
            > > If
            > > I bypass them everything works fine. But I can't
            > > figure out what is wrong with them, if I measure
            > the
            > > voltage between the output on them and ground (or
            > > pin
            > > three on the 1381) it seems to say it should
            > > trigger.
            > > I'm really stumped.
            > >
            > > Oh, I'm using two miller solar engines, the
            > > photodiodes from solarbotics.com, and a 100k
            > trimpot
            > > (also from solarbotics.com).
            > >
            > > Bryan
            > >
            > > __________________________________________________
            > > Do You Yahoo!?
            > > Great stuff seeking new owners in Yahoo! Auctions!
            >
            > > http://auctions.yahoo.com
            > >
            >
            >
            > __________________________________________________
            > Do You Yahoo!?
            > Great stuff seeking new owners in Yahoo! Auctions!
            > http://auctions.yahoo.com
            >
            >
            > To unsubscribe from this group, send an email to:
            > beam-unsubscribe@egroups.com
            >
            >
            >
            > Your use of Yahoo! Groups is subject to
            > http://docs.yahoo.com/info/terms/
            >
            >


            __________________________________________________
            Do You Yahoo!?
            Great stuff seeking new owners in Yahoo! Auctions!
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          • Bryan Yeung
            Hi, Thank you for all of that information. It will give me lots to play with tonight. Why can t I just substitute the Miller SE for the 1381 solar engines
            Message 5 of 21 , Feb 3, 2002
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              Hi,

              Thank you for all of that information. It will give
              me lots to play with tonight.

              Why can't I just substitute the Miller SE for the 1381
              solar engines (two transistor) that I have in my
              schematic (the schematic from the photopopper kit at
              solarbotics.com)?

              Bryan

              --- Wilf Rigter <wilf.rigter@...> wrote:
              > Interesting. I don't think anyone has used
              > photodiodes in the 1381 ground
              > pin (similar to the Miller SE). This can be nicely
              > combined in a photo
              > popper circuit as shown in the attached. The 1uF
              > timing caps should be
              > adjusted to give the right discharge duration. The
              > series 1N4148 diodes may
              > not be required. For those not familiar with the
              > photopopper and Miller SE
              > operation, it works as follows: [...]

              __________________________________________________
              Do You Yahoo!?
              Great stuff seeking new owners in Yahoo! Auctions!
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            • Wilf Rigter
              Ah! more information. Are these gold caps? Try increasing the size of the timing capacitor. wilf ... From: Bryan Yeung [mailto:ba_alazmon@yahoo.com] Sent:
              Message 6 of 21 , Feb 3, 2002
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                Ah! more information. Are these gold caps? Try increasing the size of the
                timing capacitor.

                wilf


                -----Original Message-----
                From: Bryan Yeung [mailto:ba_alazmon@...]
                Sent: Sunday, February 03, 2002 2:00 PM
                To: beam@yahoogroups.com
                Subject: Re: [beam] HELP!!!!! (Photopopper problem)


                There isn't any noise, just the pulsing of the motor.
                It tries to turn, stops, trys again, etc. I am using
                two 2.5v .33F caps in series. The motors are pager
                motors from BG Micro.

                Bryan

                --- Ori <sbarbut@...> wrote:
                > Is there any noise when the motors pop? A
                > high-pitched whine? What's your
                > cap? Motors?
                >
                > Ori
                >
                > ----- Original Message -----
                > From: "Bryan Yeung" <ba_alazmon@...>
                > To: <beam@yahoogroups.com>
                > Sent: Sunday, February 03, 2002 8:34 AM
                > Subject: Re: [beam] HELP!!!!! (Photopopper problem)
                >
                >
                > > Okay, so that analysis wasn't quite right. The
                > motors
                > > are firing but they aren't turning over. If I
                > hold
                > > the shaft I can feel it twitching a little bit but
                > it
                > > never makes a revolution. The odd thing is, if I
                > > connect pin 2 on the 1381 to Vcc the motor buzzes
                > > quite nicely. Grrrrrr.
                > >
                > > Bryan
                > >
                > > --- Bryan Yeung <ba_alazmon@...> wrote:
                > > > Hello,
                > > >
                > > > This is my fourth unsuccessful attempt at
                > getting a
                > > > photopopper to work and I'm beginning to think
                > I'm
                > > > cursed. I am just trying to get one that will
                > seek
                > > > light: no touch sensors. The problem is the
                > eyes.
                > > > If
                > > > I bypass them everything works fine. But I
                > can't
                > > > figure out what is wrong with them, if I measure
                > the
                > > > voltage between the output on them and ground
                > (or
                > > > pin
                > > > three on the 1381) it seems to say it should
                > > > trigger.
                > > > I'm really stumped.
                > > >
                > > > Oh, I'm using two miller solar engines, the
                > > > photodiodes from solarbotics.com, and a 100k
                > trimpot
                > > > (also from solarbotics.com).
                > > >
                > > > Bryan
                > > >
                > > >
                > __________________________________________________
                > > > Do You Yahoo!?
                > > > Great stuff seeking new owners in Yahoo!
                > Auctions!
                > > > http://auctions.yahoo.com
                > > >
                > >
                > >
                > > __________________________________________________
                > > Do You Yahoo!?
                > > Great stuff seeking new owners in Yahoo! Auctions!
                > > http://auctions.yahoo.com
                > >
                > >
                > > To unsubscribe from this group, send an email to:
                > > beam-unsubscribe@egroups.com
                > >
                > >
                > >
                > > Your use of Yahoo! Groups is subject to
                > http://docs.yahoo.com/info/terms/
                > >
                > >
                > >
                >
                >


                __________________________________________________
                Do You Yahoo!?
                Great stuff seeking new owners in Yahoo! Auctions!
                http://auctions.yahoo.com


                To unsubscribe from this group, send an email to:
                beam-unsubscribe@egroups.com



                Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
              • Bryan Yeung
                Yes they are. Right now I m using a 1uF timing capacitor which gives me a nice little burst if I bypass the eyes. That is what I really don t understand: why
                Message 7 of 21 , Feb 3, 2002
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                  Yes they are. Right now I'm using a 1uF timing
                  capacitor which gives me a nice little burst if I
                  bypass the eyes. That is what I really don't
                  understand: why would the eyes require me to use a
                  larger timing capacitor?

                  Thank you all, especially Wilf, for your speedy and
                  informative assistance. It's very helpful and
                  encouraging when I get all frustarted and feel like
                  flinging the poor helpless bot (that refuses to run
                  away :) across the room.

                  Bryan

                  --- Wilf Rigter <wilf.rigter@...> wrote:
                  > Ah! more information. Are these gold caps? Try
                  > increasing the size of the
                  > timing capacitor.
                  >
                  > wilf


                  __________________________________________________
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                  Great stuff seeking new owners in Yahoo! Auctions!
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                • Wilf Rigter
                  Hi Bryan, I guess I should have back tracked to your original posts to see what you were up to. In the orginal popper design, the 1381 just provides a short
                  Message 8 of 21 , Feb 3, 2002
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                    Hi Bryan,

                    I guess I should have back tracked to your original posts to see what you
                    were up to.

                    In the orginal popper design, the 1381 just provides a short
                    (microsecond)pulse to the NPN base After that the NPN provides base current
                    to the PNP which in turns supplies the NPN base current in a regenerative
                    SCR type way.

                    Contrary to first impressions, the Miller SE timing cap does not supply the
                    NPN base current. It just supplies current to the 1381. The 1381 can be
                    thought of as a series switch which supplies current directly from the main
                    supply cap to the base resistor. Since the 1381 "senses" the volatge between
                    the input and the ground pin, the series diode isolates the ground pin and
                    becomes reverse biased as the ground pin side of the timing cap drops below
                    0V maintaining the full voltage of the timing cap between input and the
                    ground pin while the main cap is discharging.

                    If you use the photodiodes and the pot on the positive then it is easy to
                    see that the NPN base current will be limited by the voltage drop across the
                    pot and PD and can't generate enough collector (motor) current. A Darlington
                    or FET transistor should work much better.

                    The effect of the instantaneous voltage drop (because of NPN base of FET
                    gate capacitance current) across the PD and pot at the input of the 1381
                    will also interfer with the normal Miller SE operation. For example you
                    might expact that the trigger level of the Miller SE can be increased by
                    adding a LED or diode in series with the 1381 input but that mod does not
                    work because of the above mention reason.

                    Similar to the original diode, by placing the PDs etc in the ground lead for
                    the Miller SE you will raise the trigger voltage without interfering with
                    the notmal operation of the SE.

                    Hope that helps

                    wilf


                    -----Original Message-----
                    From: Bryan Yeung [mailto:ba_alazmon@...]
                    Sent: Sunday, February 03, 2002 2:05 PM
                    To: beam@yahoogroups.com
                    Subject: RE: [beam] HELP!!!!! (Photopopper problem)


                    Hi,

                    Thank you for all of that information. It will give
                    me lots to play with tonight.

                    Why can't I just substitute the Miller SE for the 1381
                    solar engines (two transistor) that I have in my
                    schematic (the schematic from the photopopper kit at
                    solarbotics.com)?

                    Bryan

                    --- Wilf Rigter <wilf.rigter@...> wrote:
                    > Interesting. I don't think anyone has used
                    > photodiodes in the 1381 ground
                    > pin (similar to the Miller SE). This can be nicely
                    > combined in a photo
                    > popper circuit as shown in the attached. The 1uF
                    > timing caps should be
                    > adjusted to give the right discharge duration. The
                    > series 1N4148 diodes may
                    > not be required. For those not familiar with the
                    > photopopper and Miller SE
                    > operation, it works as follows: [...]

                    __________________________________________________
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                    Great stuff seeking new owners in Yahoo! Auctions!
                    http://auctions.yahoo.com


                    To unsubscribe from this group, send an email to:
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                  • Bryan Yeung
                    Okay, I was right with you until .... ... Here. I have always wondered what the diode is supposed to do and apparanetly this answers it but I don t quite
                    Message 9 of 21 , Feb 3, 2002
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                      Okay, I was right with you until ....

                      > Contrary to first impressions, the Miller SE timing
                      > cap does not supply the
                      > NPN base current. It just supplies current to the
                      > 1381. The 1381 can be
                      > thought of as a series switch which supplies current
                      > directly from the main
                      > supply cap to the base resistor. Since the 1381
                      > "senses" the volatge between
                      > the input and the ground pin,

                      Here. I have always wondered what the diode is
                      supposed to do and apparanetly this answers it but I
                      don't quite understand.

                      First of all what does reverse biased mean?

                      Secondly, to paraphrase, does this mean that the diode
                      somehow keeps the trigger on, no matter what the
                      voltage of the storage capacitor drops to, by making
                      the trigger look at the voltage across the timing
                      capacitor instead?

                      This brings me to another question: all larger
                      capacitors have values for voltage, but none of the
                      smaller ones do. How come and what voltage can small
                      capacitors hold?

                      > the series diode
                      > isolates the ground pin and
                      > becomes reverse biased as the ground pin side of the
                      > timing cap drops below
                      > 0V maintaining the full voltage of the timing cap
                      > between input and the
                      > ground pin while the main cap is discharging.


                      > If you use the photodiodes and the pot on the
                      > positive then it is easy to
                      > see that the NPN base current will be limited by the
                      > voltage drop across the
                      > pot and PD and can't generate enough collector
                      > (motor) current. A Darlington
                      > or FET transistor should work much better.

                      Not so easy actually. I thought the current for the
                      motor came from the storage capacitor, not the
                      transistor. Doesn't the transistor just turn on/off
                      the ground to the motor so that current can flow
                      through from the storage capacitor?

                      > Hope that helps

                      You are an absolute wealth of information and this is
                      being tremendously helpful. Thank you.

                      Bryan

                      __________________________________________________
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                      Great stuff seeking new owners in Yahoo! Auctions!
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                    • Ori
                      Try it with a 4700 uF, 6.3 V cap... just for the heck of it... :) Or, it ll be more suitable for your timing caps. Ori ... From: Bryan Yeung
                      Message 10 of 21 , Feb 3, 2002
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                        Try it with a 4700 uF, 6.3 V cap... just for the heck of it... :) Or, it'll
                        be more suitable for your timing caps.

                        Ori

                        ----- Original Message -----
                        From: "Bryan Yeung" <ba_alazmon@...>
                        To: <beam@yahoogroups.com>
                        Sent: Sunday, February 03, 2002 2:00 PM
                        Subject: Re: [beam] HELP!!!!! (Photopopper problem)


                        > There isn't any noise, just the pulsing of the motor.
                        > It tries to turn, stops, trys again, etc. I am using
                        > two 2.5v .33F caps in series. The motors are pager
                        > motors from BG Micro.
                        >
                        > Bryan
                        >
                        > --- Ori <sbarbut@...> wrote:
                        > > Is there any noise when the motors pop? A
                        > > high-pitched whine? What's your
                        > > cap? Motors?
                        > >
                        > > Ori
                        > >
                        > > ----- Original Message -----
                        > > From: "Bryan Yeung" <ba_alazmon@...>
                        > > To: <beam@yahoogroups.com>
                        > > Sent: Sunday, February 03, 2002 8:34 AM
                        > > Subject: Re: [beam] HELP!!!!! (Photopopper problem)
                        > >
                        > >
                        > > > Okay, so that analysis wasn't quite right. The
                        > > motors
                        > > > are firing but they aren't turning over. If I
                        > > hold
                        > > > the shaft I can feel it twitching a little bit but
                        > > it
                        > > > never makes a revolution. The odd thing is, if I
                        > > > connect pin 2 on the 1381 to Vcc the motor buzzes
                        > > > quite nicely. Grrrrrr.
                        > > >
                        > > > Bryan
                        > > >
                        > > > --- Bryan Yeung <ba_alazmon@...> wrote:
                        > > > > Hello,
                        > > > >
                        > > > > This is my fourth unsuccessful attempt at
                        > > getting a
                        > > > > photopopper to work and I'm beginning to think
                        > > I'm
                        > > > > cursed. I am just trying to get one that will
                        > > seek
                        > > > > light: no touch sensors. The problem is the
                        > > eyes.
                        > > > > If
                        > > > > I bypass them everything works fine. But I
                        > > can't
                        > > > > figure out what is wrong with them, if I measure
                        > > the
                        > > > > voltage between the output on them and ground
                        > > (or
                        > > > > pin
                        > > > > three on the 1381) it seems to say it should
                        > > > > trigger.
                        > > > > I'm really stumped.
                        > > > >
                        > > > > Oh, I'm using two miller solar engines, the
                        > > > > photodiodes from solarbotics.com, and a 100k
                        > > trimpot
                        > > > > (also from solarbotics.com).
                        > > > >
                        > > > > Bryan
                        > > > >
                        > > > >
                        > > __________________________________________________
                        > > > > Do You Yahoo!?
                        > > > > Great stuff seeking new owners in Yahoo!
                        > > Auctions!
                        > > > > http://auctions.yahoo.com
                        > > > >
                        > > >
                        > > >
                        > > > __________________________________________________
                        > > > Do You Yahoo!?
                        > > > Great stuff seeking new owners in Yahoo! Auctions!
                        > > > http://auctions.yahoo.com
                        > > >
                        > > >
                        > > > To unsubscribe from this group, send an email to:
                        > > > beam-unsubscribe@egroups.com
                        > > >
                        > > >
                        > > >
                        > > > Your use of Yahoo! Groups is subject to
                        > > http://docs.yahoo.com/info/terms/
                        > > >
                        > > >
                        > > >
                        > >
                        > >
                        >
                        >
                        > __________________________________________________
                        > Do You Yahoo!?
                        > Great stuff seeking new owners in Yahoo! Auctions!
                        > http://auctions.yahoo.com
                        >
                        >
                        > To unsubscribe from this group, send an email to:
                        > beam-unsubscribe@egroups.com
                        >
                        >
                        >
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                        >
                        >
                      • Wilf Rigter
                        Hi Bryan, ... A diode conducts current in only one direction with a small forward voltage drop when the voltage across the diode is forward biased . When a
                        Message 11 of 21 , Feb 3, 2002
                        • 0 Attachment
                          Hi Bryan,

                          >First of all what does reverse biased mean?

                          A diode conducts current in only one direction with a small "forward"
                          voltage drop when the voltage across the diode is "forward biased". When a
                          diode has a "reverse" voltage applied between the terminals, it is said to
                          be "reverse biased" and does not conduct.

                          >Secondly, to paraphrase, does this mean that the diode
                          >somehow keeps the trigger on, no matter what the
                          >voltage of the storage capacitor drops to, by making
                          >the trigger look at the voltage across the timing
                          >capacitor instead?

                          Exactly!

                          >>it is easy to see that the NPN base current ....


                          >Not so easy actually. I thought the current for the
                          >motor came from the storage capacitor, not the
                          >transistor. Doesn't the transistor just turn on/off
                          >the ground to the motor so that current can flow
                          >through from the storage capacitor?

                          Right again! The base current (Ib) in the so called "common emitter" circuit
                          controls the maximum collector current (Ic) that the transistor can "sink".
                          The base current in this circuit is always wasted since it does not flow
                          through the load and performs no work. In a conservative motor driver design
                          the gain of a 2N2222 is assumed to be about 10 at 100mA.

                          With a 1K resistor in the base of output transistor and say a 5V supply, the
                          Miller 1381 supplies about 4.4mA of control current Ib to turn on the
                          transistor which can then efficiently sink up to 44mA Ic.

                          The Ic can rise higher than 44mA, but the rising collector to emitter
                          voltage (Vce-sat) drop will reduce the voltage across the motor leading to
                          the second source of wasted power. When this voltage drop (Vce-sat) is low
                          (>200mV) the transistor is said to be saturated.

                          If the 1K resistor is replaced with a jumper, the base current is limited by
                          the 1381 to about 15mA. This would be enough Ib to control about 150mA of
                          maximum Ic in a 2N2222 or 100mA in a 2N3904 before the onset of voltage
                          losses.

                          There is always some trade off between the Ib losses and the Vce-sat losses
                          across the output transistor when conducting.

                          For maximum power to the motor, the output transistor Ib is set at 0.1-0.2
                          times the maximum collector current (for Ic >100mA) with a Vce-sat across
                          the transistor emitter collector of less than 200mV.

                          In the Bio Bugs for example, the total wasted base current in the two
                          h-bridge motor drivers is a whopping 200mA which flows continuously whether
                          the motors are connected or not.

                          wilf

                          -----Original Message-----
                          From: Bryan Yeung
                          To: beam@yahoogroups.com
                          Sent: 2/3/02 3:04 PM
                          Subject: RE: [beam] HELP!!!!! (Photopopper problem)
                        • Bryan Yeung
                          Thanks for the suggestion but I think that Wilf has found the problem. I glued together the pieces for a free form of my new little friend today and I will
                          Message 12 of 21 , Feb 4, 2002
                          • 0 Attachment
                            Thanks for the suggestion but I think that Wilf has
                            found the problem. I glued together the pieces for a
                            free form of my new little friend today and I will get
                            back to you all once I get it all soldered up.

                            Bryan

                            --- Ori <sbarbut@...> wrote:
                            > Try it with a 4700 uF, 6.3 V cap... just for the
                            > heck of it... :) Or, it'll
                            > be more suitable for your timing caps.
                            >
                            > Ori
                            >
                            > ----- Original Message -----
                            > From: "Bryan Yeung" <ba_alazmon@...>
                            > To: <beam@yahoogroups.com>
                            > Sent: Sunday, February 03, 2002 2:00 PM
                            > Subject: Re: [beam] HELP!!!!! (Photopopper problem)
                            >
                            >
                            > > There isn't any noise, just the pulsing of the
                            > motor.
                            > > It tries to turn, stops, trys again, etc. I am
                            > using
                            > > two 2.5v .33F caps in series. The motors are
                            > pager
                            > > motors from BG Micro.
                            > >
                            > > Bryan
                            > >
                            > > --- Ori <sbarbut@...> wrote:
                            > > > Is there any noise when the motors pop? A
                            > > > high-pitched whine? What's your
                            > > > cap? Motors?
                            > > >
                            > > > Ori
                            > > >
                            > > > ----- Original Message -----
                            > > > From: "Bryan Yeung" <ba_alazmon@...>
                            > > > To: <beam@yahoogroups.com>
                            > > > Sent: Sunday, February 03, 2002 8:34 AM
                            > > > Subject: Re: [beam] HELP!!!!! (Photopopper
                            > problem)
                            > > >
                            > > >
                            > > > > Okay, so that analysis wasn't quite right.
                            > The
                            > > > motors
                            > > > > are firing but they aren't turning over. If I
                            > > > hold
                            > > > > the shaft I can feel it twitching a little bit
                            > but
                            > > > it
                            > > > > never makes a revolution. The odd thing is,
                            > if I
                            > > > > connect pin 2 on the 1381 to Vcc the motor
                            > buzzes
                            > > > > quite nicely. Grrrrrr.
                            > > > >
                            > > > > Bryan
                            > > > >
                            > > > > --- Bryan Yeung <ba_alazmon@...> wrote:
                            > > > > > Hello,
                            > > > > >
                            > > > > > This is my fourth unsuccessful attempt at
                            > > > getting a
                            > > > > > photopopper to work and I'm beginning to
                            > think
                            > > > I'm
                            > > > > > cursed. I am just trying to get one that
                            > will
                            > > > seek
                            > > > > > light: no touch sensors. The problem is the
                            > > > eyes.
                            > > > > > If
                            > > > > > I bypass them everything works fine. But I
                            > > > can't
                            > > > > > figure out what is wrong with them, if I
                            > measure
                            > > > the
                            > > > > > voltage between the output on them and
                            > ground
                            > > > (or
                            > > > > > pin
                            > > > > > three on the 1381) it seems to say it should
                            > > > > > trigger.
                            > > > > > I'm really stumped.
                            > > > > >
                            > > > > > Oh, I'm using two miller solar engines, the
                            > > > > > photodiodes from solarbotics.com, and a 100k
                            > > > trimpot
                            > > > > > (also from solarbotics.com).
                            > > > > >
                            > > > > > Bryan
                            > > > > >
                            > > > > >
                            > > >
                            > __________________________________________________
                            > > > > > Do You Yahoo!?
                            > > > > > Great stuff seeking new owners in Yahoo!
                            > > > Auctions!
                            > > > > > http://auctions.yahoo.com
                            > > > > >
                            > > > >
                            > > > >
                            > > > >
                            > __________________________________________________
                            > > > > Do You Yahoo!?
                            > > > > Great stuff seeking new owners in Yahoo!
                            > Auctions!
                            > > > > http://auctions.yahoo.com
                            > > > >
                            > > > >
                            > > > > To unsubscribe from this group, send an email
                            > to:
                            > > > > beam-unsubscribe@egroups.com
                            > > > >
                            > > > >
                            > > > >
                            > > > > Your use of Yahoo! Groups is subject to
                            > > > http://docs.yahoo.com/info/terms/
                            > > > >
                            > > > >
                            > > > >
                            > > >
                            > > >
                            > >
                            > >
                            > > __________________________________________________
                            > > Do You Yahoo!?
                            > > Great stuff seeking new owners in Yahoo! Auctions!
                            > > http://auctions.yahoo.com
                            > >
                            > >
                            > > To unsubscribe from this group, send an email to:
                            > > beam-unsubscribe@egroups.com
                            > >
                            > >
                            > >
                            > > Your use of Yahoo! Groups is subject to
                            > http://docs.yahoo.com/info/terms/
                            > >
                            > >
                            >
                            >


                            __________________________________________________
                            Do You Yahoo!?
                            Great stuff seeking new owners in Yahoo! Auctions!
                            http://auctions.yahoo.com
                          • Bryan Yeung
                            ... Okay, sorry if I m belaboring the subject but I m trying to get my head wrapped around this. I think I understand why the diode does this provided I
                            Message 13 of 21 , Feb 4, 2002
                            • 0 Attachment
                              > >Secondly, to paraphrase, does this mean that the
                              > diode
                              > >somehow keeps the trigger on, no matter what the
                              > >voltage of the storage capacitor drops to, by
                              > making
                              > >the trigger look at the voltage across the timing
                              > >capacitor instead?
                              >
                              > Exactly!

                              Okay, sorry if I'm belaboring the subject but I'm
                              trying to get my head wrapped around this. I think I
                              understand why the diode does this provided I
                              understand why the ground pin goes negative with
                              respect to 0v when the 1381 triggers. Think you could
                              explain?

                              > Right again! The base current (Ib) in the so called
                              > "common emitter" circuit
                              > controls the maximum collector current (Ic) that the
                              > transistor can "sink".

                              Thank you so much for this explanation. Transistors
                              make so much more sense now.

                              From a previous email:

                              > The main cap charges up until the voltage reaches
                              > the trigger of the 1381
                              > which is equal to the rated trigger level plus the
                              > PD photovoltaic voltage
                              > (~.5V) plus the 1N4148 forward voltage (~100mV@5uA)
                              > plus the voltage drop
                              > (@5uA) across each leg of the 100K pot. The pot can
                              > therefore be used to
                              > match the 1381 trigger levels.

                              Why do we have to add all of these things up to get
                              the trigger voltage? If the 1381 measures the voltage
                              between pin 2 and pin 3 why does it matter what is
                              attached to these pins?

                              Since we have to add all of the voltage drops after
                              the 1381, does that mean I could connect a switch (ie.
                              touch sensor) along with a resistor to add obstacle
                              avoidance. If the switch was closed, there would be a
                              voltage drop across the resistor that would raise the
                              trigger voltage of the 1381 on that side, helping the
                              motor on the other side to trigger first. Right?

                              Bryan

                              __________________________________________________
                              Do You Yahoo!?
                              Great stuff seeking new owners in Yahoo! Auctions!
                              http://auctions.yahoo.com
                            • Wilf Rigter
                              ... It is easier to describe in simple circuit of the Miller SE. A diode is reverse biased and turns off when the voltage on the anode is more negative than
                              Message 14 of 21 , Feb 4, 2002
                              • 0 Attachment
                                >I think I understand why the diode does this provided I
                                >understand why the ground pin goes negative with
                                >respect to 0v when the 1381 triggers. Think you could
                                >explain?

                                It is easier to describe in simple circuit of the Miller SE.

                                A diode is reverse biased and turns off when the voltage on the anode is
                                more negative than the voltage on the cathode (stripe) .

                                When the 1381 triggers the voltage on the main cap drops as it is
                                discharged through the transistor and motor. The timing cap does not
                                discharge because it is isolated from the 0V line by the (reverse biased)
                                diode. Therefore the voltage across the main cap becomes less than the
                                voltage on the timing cap.

                                Since one side of timing cap and the main cap are both connected to the +V
                                line and the voltage across the timing cap is greater than the voltage
                                across the main cap then the 1381 ground pin side of the timing cap (and the
                                anode of the diode) must be more negative than the 0V line (the cathode of
                                the diode).

                                >Why do we have to add all of these things up to get
                                >the trigger voltage? If the 1381 measures the voltage
                                >between pin 2 and pin 3 why does it matter what is
                                >attached to these pins

                                The 1381 will trigger when the voltage between the input pin 2 and the
                                ground pin 3 is equal to the rated trigger voltage. In the Miller SE, the
                                1381 ground pin is not connected directly to 0V but through a series diode.
                                That adds a small (100mV) voltage drop between the 1381 ground pin and the
                                0V line. Therefore the voltage across the 1381 is equal to the main
                                capacitor voltage less the voltage drop across the diode. So the 1381
                                triggers when the main cap voltage rises to the rated 1381 trigger voltage
                                plus the diode drop.

                                In the Miller Popper there are several more voltage drops (the PD and 1/2 of
                                the potentiometer) between the 1381 ground pin and the 0V line. Therefore
                                the voltage across the 1381 is equal to the main capacitor voltage less the
                                voltage drops across the diode, the PD and the 1/2 potentiometer. So the
                                1381 triggers when the main capacitor voltage rises to the rated 1381
                                trigger voltage plus the diode, PD and potentiometer drops.

                                >Since we have to add all of the voltage drops after
                                >the 1381, does that mean I could connect a switch (ie.
                                >touch sensor) along with a resistor to add obstacle
                                >avoidance. If the switch was closed, there would be a
                                >voltage drop across the resistor that would raise the
                                >trigger voltage of the 1381 on that side, helping the
                                >motor on the other side to trigger first. Right?

                                Right! Just connect the left and right touch sensor switches across the each
                                half of the potentiometer. When one sensor switch closes, the voltage drop
                                across that half of the pot is zero and that SE will fire first.

                                Hope this helps.


                                -----Original Message-----
                                From: Bryan Yeung
                                To: beam@yahoogroups.com
                                Sent: 2/4/02 4:40 PM
                                Subject: RE: [beam] HELP!!!!! (Photopopper problem)
                              • xycon_3
                                Just a couple things that I wanted to point out on this. The 1K resistors should not be included in this schematic, because you only need a resistor if you are
                                Message 15 of 21 , May 23, 2002
                                • 0 Attachment
                                  Just a couple things that I wanted to point out on this. The 1K
                                  resistors should not be included in this schematic, because you only
                                  need a resistor if you are driving a non-inductive load, and since
                                  this is a popper schematic (driving motors), it shouldn't be there.
                                  And, shouldn't the left 1381 be flipped? The cap is going from pin 1
                                  to pin 2, instead of from pin 2 to pin 3. Just wanted to contribute!

                                  -xycon

                                  --- In beam@y..., Wilf Rigter <wilf.rigter@p...> wrote:
                                  > Interesting. I don't think anyone has used photodiodes in the 1381
                                  ground
                                  > pin (similar to the Miller SE). This can be nicely combined in a
                                  photo
                                  > popper circuit as shown in the attached. The 1uF timing caps should
                                  be
                                  > adjusted to give the right discharge duration. The series 1N4148
                                  diodes may
                                  > not be required. For those not familiar with the photopopper and
                                  Miller SE
                                  > operation, it works as follows:
                                  >
                                  > The main cap charges up until the voltage reaches the trigger of
                                  the 1381
                                  > which is equal to the rated trigger level plus the PD photovoltaic
                                  voltage
                                  > (~.5V) plus the 1N4148 forward voltage (~100mV@5uA) plus the
                                  voltage drop
                                  > (@5uA) across each leg of the 100K pot. The pot can therefore be
                                  used to
                                  > match the 1381 trigger levels. The PD photovoltaic voltage is
                                  proportional
                                  > to the light level. The SE whose PD has the lower light level will
                                  have a
                                  > lower combined trigger level and will fire first.
                                  >
                                  > One the SE is triggered two things happen:
                                  >
                                  > 1.The ground pin current drops to about 1uA lowering the SE reset
                                  voltage
                                  > (increased hysteresis).
                                  > 2.The ground pin voltage becomes negative with respect to 0V as the
                                  main
                                  > storage cap discharges.
                                  >
                                  > The voltage across the 1381 is now equal to the timing cap and is
                                  > independent of the main capacitor voltage. While triggered, the
                                  1381 supply
                                  > current is just 1uA and the reset time (when the 1381 turns off) is
                                  > determined by the size of the timing capacitor. With 1uF the reset
                                  time is
                                  > about one second. When the 1381 turns off, the 1381 ground pin
                                  current jumps
                                  > to 5uA and starts to discharge the timing capacitor more quickly
                                  until
                                  > voltage rise on the main capacitor voltage catches up and the cycle
                                  repeats.
                                  >
                                  > Hope this all makes sense and I'll confirm my analysis when I get a
                                  chance
                                  > to scope the circuit.
                                  >
                                  > Have fun.
                                  >
                                  > wilf
                                  >
                                  > -----Original Message-----
                                  > From: Bryan Yeung [mailto:ba_alazmon@y...]
                                  > Sent: Sunday, February 03, 2002 7:11 AM
                                  > To: beam@y...
                                  > Subject: [beam] HELP!!!!! (Photopopper problem)
                                  >
                                  >
                                  > Hello,
                                  >
                                  > This is my fourth unsuccessful attempt at getting a
                                  > photopopper to work and I'm beginning to think I'm
                                  > cursed. I am just trying to get one that will seek
                                  > light: no touch sensors. The problem is the eyes. If
                                  > I bypass them everything works fine. But I can't
                                  > figure out what is wrong with them, if I measure the
                                  > voltage between the output on them and ground (or pin
                                  > three on the 1381) it seems to say it should trigger.
                                  > I'm really stumped.
                                  >
                                  > Oh, I'm using two miller solar engines, the
                                  > photodiodes from solarbotics.com, and a 100k trimpot
                                  > (also from solarbotics.com).
                                  >
                                  > Bryan
                                  >
                                  > __________________________________________________
                                  > Do You Yahoo!?
                                  > Great stuff seeking new owners in Yahoo! Auctions!
                                  > http://auctions.yahoo.com
                                  >
                                  >
                                  > To unsubscribe from this group, send an email to:
                                  > beam-unsubscribe@e...
                                  >
                                  >
                                  >
                                  > Your use of Yahoo! Groups is subject to
                                  http://docs.yahoo.com/info/terms/
                                • xycon_3
                                  The schematic and original description is shown here: http://groups.yahoo.com/group/beam/message/22358 -xycon ... only ... 1 ... 1381 ... should ...
                                  Message 16 of 21 , May 23, 2002
                                  • 0 Attachment
                                    The schematic and original description is shown here:
                                    http://groups.yahoo.com/group/beam/message/22358

                                    -xycon

                                    --- In beam@y..., "xycon_3" <xycon_3@l...> wrote:
                                    > Just a couple things that I wanted to point out on this. The 1K
                                    > resistors should not be included in this schematic, because you
                                    only
                                    > need a resistor if you are driving a non-inductive load, and since
                                    > this is a popper schematic (driving motors), it shouldn't be there.
                                    > And, shouldn't the left 1381 be flipped? The cap is going from pin
                                    1
                                    > to pin 2, instead of from pin 2 to pin 3. Just wanted to contribute!
                                    >
                                    > -xycon
                                    >
                                    > --- In beam@y..., Wilf Rigter <wilf.rigter@p...> wrote:
                                    > > Interesting. I don't think anyone has used photodiodes in the
                                    1381
                                    > ground
                                    > > pin (similar to the Miller SE). This can be nicely combined in a
                                    > photo
                                    > > popper circuit as shown in the attached. The 1uF timing caps
                                    should
                                    > be
                                    > > adjusted to give the right discharge duration. The series 1N4148
                                    > diodes may
                                    > > not be required. For those not familiar with the photopopper and
                                    > Miller SE
                                    > > operation, it works as follows:
                                    > >
                                    > > The main cap charges up until the voltage reaches the trigger of
                                    > the 1381
                                    > > which is equal to the rated trigger level plus the PD
                                    photovoltaic
                                    > voltage
                                    > > (~.5V) plus the 1N4148 forward voltage (~100mV@5uA) plus the
                                    > voltage drop
                                    > > (@5uA) across each leg of the 100K pot. The pot can therefore be
                                    > used to
                                    > > match the 1381 trigger levels. The PD photovoltaic voltage is
                                    > proportional
                                    > > to the light level. The SE whose PD has the lower light level
                                    will
                                    > have a
                                    > > lower combined trigger level and will fire first.
                                    > >
                                    > > One the SE is triggered two things happen:
                                    > >
                                    > > 1.The ground pin current drops to about 1uA lowering the SE reset
                                    > voltage
                                    > > (increased hysteresis).
                                    > > 2.The ground pin voltage becomes negative with respect to 0V as
                                    the
                                    > main
                                    > > storage cap discharges.
                                    > >
                                    > > The voltage across the 1381 is now equal to the timing cap and is
                                    > > independent of the main capacitor voltage. While triggered, the
                                    > 1381 supply
                                    > > current is just 1uA and the reset time (when the 1381 turns off)
                                    is
                                    > > determined by the size of the timing capacitor. With 1uF the
                                    reset
                                    > time is
                                    > > about one second. When the 1381 turns off, the 1381 ground pin
                                    > current jumps
                                    > > to 5uA and starts to discharge the timing capacitor more quickly
                                    > until
                                    > > voltage rise on the main capacitor voltage catches up and the
                                    cycle
                                    > repeats.
                                    > >
                                    > > Hope this all makes sense and I'll confirm my analysis when I get
                                    a
                                    > chance
                                    > > to scope the circuit.
                                    > >
                                    > > Have fun.
                                    > >
                                    > > wilf
                                    > >
                                    > > -----Original Message-----
                                    > > From: Bryan Yeung [mailto:ba_alazmon@y...]
                                    > > Sent: Sunday, February 03, 2002 7:11 AM
                                    > > To: beam@y...
                                    > > Subject: [beam] HELP!!!!! (Photopopper problem)
                                    > >
                                    > >
                                    > > Hello,
                                    > >
                                    > > This is my fourth unsuccessful attempt at getting a
                                    > > photopopper to work and I'm beginning to think I'm
                                    > > cursed. I am just trying to get one that will seek
                                    > > light: no touch sensors. The problem is the eyes. If
                                    > > I bypass them everything works fine. But I can't
                                    > > figure out what is wrong with them, if I measure the
                                    > > voltage between the output on them and ground (or pin
                                    > > three on the 1381) it seems to say it should trigger.
                                    > > I'm really stumped.
                                    > >
                                    > > Oh, I'm using two miller solar engines, the
                                    > > photodiodes from solarbotics.com, and a 100k trimpot
                                    > > (also from solarbotics.com).
                                    > >
                                    > > Bryan
                                    > >
                                    > > __________________________________________________
                                    > > Do You Yahoo!?
                                    > > Great stuff seeking new owners in Yahoo! Auctions!
                                    > > http://auctions.yahoo.com
                                    > >
                                    > >
                                    > > To unsubscribe from this group, send an email to:
                                    > > beam-unsubscribe@e...
                                    > >
                                    > >
                                    > >
                                    > > Your use of Yahoo! Groups is subject to
                                    > http://docs.yahoo.com/info/terms/
                                  • xycon_3
                                    Hey, Wilf! Please take a look at my comments and see if I am right. I don t want to make any mistakes. Thanks! -xycon ... since ... there. ... pin ...
                                    Message 17 of 21 , May 23, 2002
                                    • 0 Attachment
                                      Hey, Wilf! Please take a look at my comments and see if I am right. I
                                      don't want to make any mistakes. Thanks!

                                      -xycon

                                      --- In beam@y..., "xycon_3" <xycon_3@l...> wrote:
                                      > The schematic and original description is shown here:
                                      > http://groups.yahoo.com/group/beam/message/22358
                                      >
                                      > -xycon
                                      >
                                      > --- In beam@y..., "xycon_3" <xycon_3@l...> wrote:
                                      > > Just a couple things that I wanted to point out on this. The 1K
                                      > > resistors should not be included in this schematic, because you
                                      > only
                                      > > need a resistor if you are driving a non-inductive load, and
                                      since
                                      > > this is a popper schematic (driving motors), it shouldn't be
                                      there.
                                      > > And, shouldn't the left 1381 be flipped? The cap is going from
                                      pin
                                      > 1
                                      > > to pin 2, instead of from pin 2 to pin 3. Just wanted to
                                      contribute!
                                      > >
                                      > > -xycon
                                      > >
                                      > > --- In beam@y..., Wilf Rigter <wilf.rigter@p...> wrote:
                                      > > > Interesting. I don't think anyone has used photodiodes in the
                                      > 1381
                                      > > ground
                                      > > > pin (similar to the Miller SE). This can be nicely combined in
                                      a
                                      > > photo
                                      > > > popper circuit as shown in the attached. The 1uF timing caps
                                      > should
                                      > > be
                                      > > > adjusted to give the right discharge duration. The series
                                      1N4148
                                      > > diodes may
                                      > > > not be required. For those not familiar with the photopopper
                                      and
                                      > > Miller SE
                                      > > > operation, it works as follows:
                                      > > >
                                      > > > The main cap charges up until the voltage reaches the trigger
                                      of
                                      > > the 1381
                                      > > > which is equal to the rated trigger level plus the PD
                                      > photovoltaic
                                      > > voltage
                                      > > > (~.5V) plus the 1N4148 forward voltage (~100mV@5uA) plus the
                                      > > voltage drop
                                      > > > (@5uA) across each leg of the 100K pot. The pot can therefore
                                      be
                                      > > used to
                                      > > > match the 1381 trigger levels. The PD photovoltaic voltage is
                                      > > proportional
                                      > > > to the light level. The SE whose PD has the lower light level
                                      > will
                                      > > have a
                                      > > > lower combined trigger level and will fire first.
                                      > > >
                                      > > > One the SE is triggered two things happen:
                                      > > >
                                      > > > 1.The ground pin current drops to about 1uA lowering the SE
                                      reset
                                      > > voltage
                                      > > > (increased hysteresis).
                                      > > > 2.The ground pin voltage becomes negative with respect to 0V as
                                      > the
                                      > > main
                                      > > > storage cap discharges.
                                      > > >
                                      > > > The voltage across the 1381 is now equal to the timing cap and
                                      is
                                      > > > independent of the main capacitor voltage. While triggered, the
                                      > > 1381 supply
                                      > > > current is just 1uA and the reset time (when the 1381 turns
                                      off)
                                      > is
                                      > > > determined by the size of the timing capacitor. With 1uF the
                                      > reset
                                      > > time is
                                      > > > about one second. When the 1381 turns off, the 1381 ground pin
                                      > > current jumps
                                      > > > to 5uA and starts to discharge the timing capacitor more
                                      quickly
                                      > > until
                                      > > > voltage rise on the main capacitor voltage catches up and the
                                      > cycle
                                      > > repeats.
                                      > > >
                                      > > > Hope this all makes sense and I'll confirm my analysis when I
                                      get
                                      > a
                                      > > chance
                                      > > > to scope the circuit.
                                      > > >
                                      > > > Have fun.
                                      > > >
                                      > > > wilf
                                      > > >
                                      > > > -----Original Message-----
                                      > > > From: Bryan Yeung [mailto:ba_alazmon@y...]
                                      > > > Sent: Sunday, February 03, 2002 7:11 AM
                                      > > > To: beam@y...
                                      > > > Subject: [beam] HELP!!!!! (Photopopper problem)
                                      > > >
                                      > > >
                                      > > > Hello,
                                      > > >
                                      > > > This is my fourth unsuccessful attempt at getting a
                                      > > > photopopper to work and I'm beginning to think I'm
                                      > > > cursed. I am just trying to get one that will seek
                                      > > > light: no touch sensors. The problem is the eyes. If
                                      > > > I bypass them everything works fine. But I can't
                                      > > > figure out what is wrong with them, if I measure the
                                      > > > voltage between the output on them and ground (or pin
                                      > > > three on the 1381) it seems to say it should trigger.
                                      > > > I'm really stumped.
                                      > > >
                                      > > > Oh, I'm using two miller solar engines, the
                                      > > > photodiodes from solarbotics.com, and a 100k trimpot
                                      > > > (also from solarbotics.com).
                                      > > >
                                      > > > Bryan
                                      > > >
                                      > > > __________________________________________________
                                      > > > Do You Yahoo!?
                                      > > > Great stuff seeking new owners in Yahoo! Auctions!
                                      > > > http://auctions.yahoo.com
                                      > > >
                                      > > >
                                      > > > To unsubscribe from this group, send an email to:
                                      > > > beam-unsubscribe@e...
                                      > > >
                                      > > >
                                      > > >
                                      > > > Your use of Yahoo! Groups is subject to
                                      > > http://docs.yahoo.com/info/terms/
                                    • wilf_nv
                                      The 1K resistor in series with the transistor base limits the base current to about 3 mA and sets the maximum collector (motor) current to about 40mA or good
                                      Message 18 of 21 , May 25, 2002
                                      • 0 Attachment
                                        The 1K resistor in series with the transistor base limits the base
                                        current
                                        to about 3 mA and sets the maximum collector (motor) current to about
                                        40mA or good for a small lens motor. Without the resistor the base
                                        current will be 20mA and max motor current will be 200mA and OK for
                                        a pager motor. The on time is set by the 1uF cap and should be
                                        adjusted so that the main cap drops to no less than about 1.5V or 2V.
                                        You're right about the 1381 orientation: At least one should be
                                        opposite to the other. Check the data sheet (Solarbotics.com download
                                        section) for the right pin out. I'll breadboard the circuit later to
                                        confirm efficiency, etc.

                                        hope that helps

                                        wilf



                                        --- In beam@y..., "xycon_3" <xycon_3@l...> wrote:
                                        > Hey, Wilf! Please take a look at my comments and see if I am right.
                                        I
                                        > don't want to make any mistakes. Thanks!
                                        >
                                        > -xycon
                                        >
                                        > --- In beam@y..., "xycon_3" <xycon_3@l...> wrote:
                                        > > The schematic and original description is shown here:
                                        > > http://groups.yahoo.com/group/beam/message/22358
                                        > >
                                        > > -xycon
                                        > >
                                        > > --- In beam@y..., "xycon_3" <xycon_3@l...> wrote:
                                        > > > Just a couple things that I wanted to point out on this. The 1K
                                        > > > resistors should not be included in this schematic, because you
                                        > > only
                                        > > > need a resistor if you are driving a non-inductive load, and
                                        > since
                                        > > > this is a popper schematic (driving motors), it shouldn't be
                                        > there.
                                        > > > And, shouldn't the left 1381 be flipped? The cap is going from
                                        > pin
                                        > > 1
                                        > > > to pin 2, instead of from pin 2 to pin 3. Just wanted to
                                        > contribute!
                                        > > >
                                        > > > -xycon
                                        > > >
                                        > > > --- In beam@y..., Wilf Rigter <wilf.rigter@p...> wrote:
                                        > > > > Interesting. I don't think anyone has used photodiodes in the
                                        > > 1381
                                        > > > ground
                                        > > > > pin (similar to the Miller SE). This can be nicely combined
                                        in
                                        > a
                                        > > > photo
                                        > > > > popper circuit as shown in the attached. The 1uF timing caps
                                        > > should
                                        > > > be
                                        > > > > adjusted to give the right discharge duration. The series
                                        > 1N4148
                                        > > > diodes may
                                        > > > > not be required. For those not familiar with the photopopper
                                        > and
                                        > > > Miller SE
                                        > > > > operation, it works as follows:
                                        > > > >
                                        > > > > The main cap charges up until the voltage reaches the trigger
                                        > of
                                        > > > the 1381
                                        > > > > which is equal to the rated trigger level plus the PD
                                        > > photovoltaic
                                        > > > voltage
                                        > > > > (~.5V) plus the 1N4148 forward voltage (~100mV@5uA) plus the
                                        > > > voltage drop
                                        > > > > (@5uA) across each leg of the 100K pot. The pot can therefore
                                        > be
                                        > > > used to
                                        > > > > match the 1381 trigger levels. The PD photovoltaic voltage is
                                        > > > proportional
                                        > > > > to the light level. The SE whose PD has the lower light level
                                        > > will
                                        > > > have a
                                        > > > > lower combined trigger level and will fire first.
                                        > > > >
                                        > > > > One the SE is triggered two things happen:
                                        > > > >
                                        > > > > 1.The ground pin current drops to about 1uA lowering the SE
                                        > reset
                                        > > > voltage
                                        > > > > (increased hysteresis).
                                        > > > > 2.The ground pin voltage becomes negative with respect to 0V
                                        as
                                        > > the
                                        > > > main
                                        > > > > storage cap discharges.
                                        > > > >
                                        > > > > The voltage across the 1381 is now equal to the timing cap
                                        and
                                        > is
                                        > > > > independent of the main capacitor voltage. While triggered,
                                        the
                                        > > > 1381 supply
                                        > > > > current is just 1uA and the reset time (when the 1381 turns
                                        > off)
                                        > > is
                                        > > > > determined by the size of the timing capacitor. With 1uF the
                                        > > reset
                                        > > > time is
                                        > > > > about one second. When the 1381 turns off, the 1381 ground
                                        pin
                                        > > > current jumps
                                        > > > > to 5uA and starts to discharge the timing capacitor more
                                        > quickly
                                        > > > until
                                        > > > > voltage rise on the main capacitor voltage catches up and the
                                        > > cycle
                                        > > > repeats.
                                        > > > >
                                        > > > > Hope this all makes sense and I'll confirm my analysis when I
                                        > get
                                        > > a
                                        > > > chance
                                        > > > > to scope the circuit.
                                        > > > >
                                        > > > > Have fun.
                                        > > > >
                                        > > > > wilf
                                        > > > >
                                        > > > > -----Original Message-----
                                        > > > > From: Bryan Yeung [mailto:ba_alazmon@y...]
                                        > > > > Sent: Sunday, February 03, 2002 7:11 AM
                                        > > > > To: beam@y...
                                        > > > > Subject: [beam] HELP!!!!! (Photopopper problem)
                                        > > > >
                                        > > > >
                                        > > > > Hello,
                                        > > > >
                                        > > > > This is my fourth unsuccessful attempt at getting a
                                        > > > > photopopper to work and I'm beginning to think I'm
                                        > > > > cursed. I am just trying to get one that will seek
                                        > > > > light: no touch sensors. The problem is the eyes. If
                                        > > > > I bypass them everything works fine. But I can't
                                        > > > > figure out what is wrong with them, if I measure the
                                        > > > > voltage between the output on them and ground (or pin
                                        > > > > three on the 1381) it seems to say it should trigger.
                                        > > > > I'm really stumped.
                                        > > > >
                                        > > > > Oh, I'm using two miller solar engines, the
                                        > > > > photodiodes from solarbotics.com, and a 100k trimpot
                                        > > > > (also from solarbotics.com).
                                        > > > >
                                        > > > > Bryan
                                        > > > >
                                        > > > > __________________________________________________
                                        > > > > Do You Yahoo!?
                                        > > > > Great stuff seeking new owners in Yahoo! Auctions!
                                        > > > > http://auctions.yahoo.com
                                        > > > >
                                        > > > >
                                        > > > > To unsubscribe from this group, send an email to:
                                        > > > > beam-unsubscribe@e...
                                        > > > >
                                        > > > >
                                        > > > >
                                        > > > > Your use of Yahoo! Groups is subject to
                                        > > > http://docs.yahoo.com/info/terms/
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