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Encoder

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  • kevinrock@earthlink.net
    Has the Encoder been phased out of existence? Kevin.
    Message 1 of 12 , Jul 7 9:59 AM
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      Has the Encoder been phased out of existence?
      Kevin.
    • Doug Kelley
      No, I m trying to contact Kevin to see what he needs to get the next issue out. Doug
      Message 2 of 12 , Jul 8 7:25 AM
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        No, I'm trying to contact Kevin to see what he needs to get the next issue out.

        Doug

        kevinrock@... writes:
        >Has the Encoder been phased out of existence?
        > Kevin.
        >
        >
        >
        >Visit the SRS Website at http://www.seattlerobotics.org
        >
        >To unsubscribe from this group, send an email to:
        >SeattleRobotics-unsubscribe@yahoogroups.com
        >
        >
        >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
        >
        >
      • Kevin Ross
        Its here! Its here! http://www.seattlerobotics.org/encoder/200205/index.html This is a great issue that you should really check out. My sincere apologies for
        Message 3 of 12 , Jul 8 5:07 PM
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          Its here!

          Its here!

          http://www.seattlerobotics.org/encoder/200205/index.html

          This is a great issue that you should really check out. My sincere apologies
          for making everyone wait. I should be back on schedule for monthly releases
          again. Do check this issue out, it is worth your time.

          Kevin
        • twcarroll@aol.com
          Kevin, Having been a past editor for The Robot Builder for the Robotics Society of Southern California for several years, I know what it takes to put out a
          Message 4 of 12 , Jul 8 6:01 PM
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            Kevin,
            Having been a past editor for "The Robot Builder" for the Robotics
            Society of Southern California for several years, I know what it takes to
            put out a technical newsletter. Quite frankly, my efforts did not come
            close to the quality that you put into the "Encoder," and we all appreciate
            your hard work. It is people like you who make the SRS the number one
            experimental robotics group in the country.
            We all understand that other things sometimes interrupt our best laid
            plans, and building a new home certainly ranks high in the "must do"
            category. This Spring 2002 issue is great. Keep up the good work.
            Tom Carroll


            [Non-text portions of this message have been removed]
          • Doug Kelley
            Great issue! Well worth the wait. Thanks! Doug
            Message 5 of 12 , Jul 9 8:03 AM
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              Great issue! Well worth the wait. Thanks!

              Doug

              kevinro@... writes:
              >Its here!
              >
              >Its here!
              >
              >http://www.seattlerobotics.org/encoder/200205/index.html
              >
              >This is a great issue that you should really check out. My sincere apologies
              >for making everyone wait. I should be back on schedule for monthly releases
              >again. Do check this issue out, it is worth your time.
              >
              >Kevin
            • Doug Kelley
              We didn t publish an Encoder this quarter because we only have two articles. We d like to have at least two more. Why not take this opportunity to write about
              Message 6 of 12 , Jan 7, 2003
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                We didn't publish an Encoder this quarter because we only have two articles.
                We'd like to have at least two more. Why not take this opportunity to write
                about the contraption (I mean robot) you're currently building? Or, write a
                piece about a circuit or algorithm you use. As long as it's robot-related and
                a good, quality piece, we'll publish it.

                Our next Encoder will be published March 1st. Please give Kevin your
                submissions by mid-February.

                Thanks!

                Doug
              • barip100
                Can some one tell me how to get in touch with the editor of the Encoder news leter. kevinro@nwlink.com bounced back to me Thanks
                Message 7 of 12 , Nov 16, 2003
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                  Can some one tell me how to get in touch with the editor of the
                  Encoder news leter. kevinro@... bounced back to me

                  Thanks
                • Kevin Ross
                  I have replied.
                  Message 8 of 12 , Nov 16, 2003
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                    I have replied.

                    >-----Original Message-----
                    >From: barip100 [mailto:barip100@...]
                    >Sent: Sunday, November 16, 2003 1:38 PM
                    >To: SeattleRobotics@yahoogroups.com
                    >Subject: [SeattleRobotics] Encoder
                    >
                    >
                    >Can some one tell me how to get in touch with the editor of the
                    >Encoder news leter. kevinro@... bounced back to me
                    >
                    >Thanks
                    >
                    >
                    >Visit the SRS Website at http://www.seattlerobotics.org
                    >
                    >To unsubscribe from this group, send an email to:
                    >SeattleRobotics-unsubscribe@yahoogroups.com
                    >
                    >
                    >Your use of Yahoo! Groups is subject to
                    >http://docs.yahoo.com/info/terms/
                    >
                    >
                    >
                    >
                  • harishpkl
                    hi all does anyone know how to use a small dc motor as speed transducer. any working schematic of the same if someone can supply. thanx in advance. regds hm
                    Message 9 of 12 , Dec 28, 2003
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                      hi all
                      does anyone know how to use a small dc motor as speed
                      transducer.
                      any working schematic of the same if someone can supply.

                      thanx in advance.

                      regds

                      hm
                    • Chuck Harrison
                      Hi, Almost any ordinary DC motor (i.e. permanent magnet field) will work as a tachometer. The voltage between the two brush leads is proportional to speed, and
                      Message 10 of 12 , Dec 29, 2003
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                        Hi,

                        Almost any ordinary DC motor (i.e. permanent magnet field) will
                        work as a tachometer. The voltage between the two brush leads
                        is proportional to speed, and will go negative if you reverse
                        the direction of shaft rotation.

                        This is *not* an encoder -- you can't reliably tell that you
                        have gone 10 rotations, for example, or that you have gone
                        forward and back to the same spot. It just gives you speed
                        information.

                        The main problem with DC motors as tachometers is that they
                        have a lot of ripple. Even when the shaft is turning smoothly,
                        the voltage will increase and decrease as the commutator bars
                        pass under the brushes. It will look as if the shaft is going
                        fast-slow-fast-slow. It helps to "gear up" the tach (gears,
                        belts, etc) so it runs at higher rpms. This makes the ripple
                        frequency higher so you can often filter it out. It also
                        makes the voltage output higher, which sometimes helps with
                        circuit design. You can also filter out the ripple component
                        in software with some simple calculations.

                        The motor brushes sometimes make a little bit of very high-
                        frequency "hash" noise during rotation. Putting a small
                        capacitor (e.g. 0.1 uf) directly across the motor leads
                        can help.

                        The ripple filter may need a long time constant, which would
                        suggest using electrolytic capacitors, either aluminum or
                        tantalum. Remember that electrolytics are polarized, and
                        the tachometer voltage will reverse when the shaft rotation
                        does. It's easy to make a non-polarized capacitor by putting
                        two identical electrolytics back-to-back. If each capacitor
                        is 100 uf, for example, the combination will be 50 uf.

                        ASCII art:
                        R
                        +--------+--... ...---/\/\/\/----+------
                        | motor | basic | filtered
                        ( ) --- tachometer simple --- tachometer
                        | --- signal lowpass --- signal
                        | 0.1uf | filter | C
                        +--------+--... ...--------------+------

                        time constant = R*C


                        | |
                        --- value = C |
                        --- + |
                        | ===> --- value = C/2
                        | ---
                        --- + | non-polarized
                        --- value = C |
                        | |


                        Cheers,
                        Chuck

                        harishpkl wrote:
                        >
                        > hi all
                        > does anyone know how to use a small dc motor as speed
                        > transducer.
                        > any working schematic of the same if someone can supply.
                        >
                        > thanx in advance.
                        >
                        > regds
                        >
                        > hm
                        >
                      • harish
                        hi harrison thanx for ur prompt reply.Shd i go for digital method of speed measurement.like mouting sensor athe edge of gear teeth. and using timers for
                        Message 11 of 12 , Dec 30, 2003
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                          hi harrison
                          thanx for ur prompt reply.Shd i go for digital method of speed measurement.like mouting sensor athe edge of gear teeth.
                          and using timers for calculating the pulse width.


                          regds

                          hm


                          ---- Original Message -----
                          From: "Chuck Harrison" <cfharr@...>
                          To: <SeattleRobotics@yahoogroups.com>
                          Sent: Monday, December 29, 2003 11:23 PM
                          Subject: Re: [SeattleRobotics] Encoder


                          > Hi,
                          >
                          > Almost any ordinary DC motor (i.e. permanent magnet field) will
                          > work as a tachometer. The voltage between the two brush leads
                          > is proportional to speed, and will go negative if you reverse
                          > the direction of shaft rotation.
                          >
                          > This is *not* an encoder -- you can't reliably tell that you
                          > have gone 10 rotations, for example, or that you have gone
                          > forward and back to the same spot. It just gives you speed
                          > information.
                          >
                          > The main problem with DC motors as tachometers is that they
                          > have a lot of ripple. Even when the shaft is turning smoothly,
                          > the voltage will increase and decrease as the commutator bars
                          > pass under the brushes. It will look as if the shaft is going
                          > fast-slow-fast-slow. It helps to "gear up" the tach (gears,
                          > belts, etc) so it runs at higher rpms. This makes the ripple
                          > frequency higher so you can often filter it out. It also
                          > makes the voltage output higher, which sometimes helps with
                          > circuit design. You can also filter out the ripple component
                          > in software with some simple calculations.
                          >
                          > The motor brushes sometimes make a little bit of very high-
                          > frequency "hash" noise during rotation. Putting a small
                          > capacitor (e.g. 0.1 uf) directly across the motor leads
                          > can help.
                          >
                          > The ripple filter may need a long time constant, which would
                          > suggest using electrolytic capacitors, either aluminum or
                          > tantalum. Remember that electrolytics are polarized, and
                          > the tachometer voltage will reverse when the shaft rotation
                          > does. It's easy to make a non-polarized capacitor by putting
                          > two identical electrolytics back-to-back. If each capacitor
                          > is 100 uf, for example, the combination will be 50 uf.
                          >
                          > ASCII art:
                          > R
                          > +--------+--... ...---/\/\/\/----+------
                          > | motor | basic | filtered
                          > ( ) --- tachometer simple --- tachometer
                          > | --- signal lowpass --- signal
                          > | 0.1uf | filter | C
                          > +--------+--... ...--------------+------
                          >
                          > time constant = R*C
                          >
                          >
                          > | |
                          > --- value = C |
                          > --- + |
                          > | ===> --- value = C/2
                          > | ---
                          > --- + | non-polarized
                          > --- value = C |
                          > | |
                          >
                          >
                          > Cheers,
                          > Chuck
                          >
                          > harishpkl wrote:
                          > >
                          > > hi all
                          > > does anyone know how to use a small dc motor as speed
                          > > transducer.
                          > > any working schematic of the same if someone can supply.
                          > >
                          > > thanx in advance.
                          > >
                          > > regds
                          > >
                          > > hm
                          > >
                          >
                          > Visit the SRS Website at http://www.seattlerobotics.org
                          >
                          > Yahoo! Groups Links
                          >
                          > To visit your group on the web, go to:
                          > http://groups.yahoo.com/group/SeattleRobotics/
                          >
                          > To unsubscribe from this group, send an email to:
                          > SeattleRobotics-unsubscribe@yahoogroups.com
                          >
                          > Your use of Yahoo! Groups is subject to:
                          > http://docs.yahoo.com/info/terms/
                          >
                          >
                          >

                          [Non-text portions of this message have been removed]
                        • harish
                          hi harrison if i place a bridge rectifier across the motor outputs and then using RC filter will that help.. regds hm ... From: Chuck Harrison
                          Message 12 of 12 , Jan 1, 2004
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                            hi harrison
                            if i place a bridge rectifier across the motor outputs
                            and then using RC filter will that help..

                            regds

                            hm

                            ----- Original Message -----
                            From: "Chuck Harrison" <cfharr@...>
                            To: <SeattleRobotics@yahoogroups.com>
                            Sent: Monday, December 29, 2003 11:23 PM
                            Subject: Re: [SeattleRobotics] Encoder


                            > Hi,
                            >
                            > Almost any ordinary DC motor (i.e. permanent magnet field) will
                            > work as a tachometer. The voltage between the two brush leads
                            > is proportional to speed, and will go negative if you reverse
                            > the direction of shaft rotation.
                            >
                            > This is *not* an encoder -- you can't reliably tell that you
                            > have gone 10 rotations, for example, or that you have gone
                            > forward and back to the same spot. It just gives you speed
                            > information.
                            >
                            > The main problem with DC motors as tachometers is that they
                            > have a lot of ripple. Even when the shaft is turning smoothly,
                            > the voltage will increase and decrease as the commutator bars
                            > pass under the brushes. It will look as if the shaft is going
                            > fast-slow-fast-slow. It helps to "gear up" the tach (gears,
                            > belts, etc) so it runs at higher rpms. This makes the ripple
                            > frequency higher so you can often filter it out. It also
                            > makes the voltage output higher, which sometimes helps with
                            > circuit design. You can also filter out the ripple component
                            > in software with some simple calculations.
                            >
                            > The motor brushes sometimes make a little bit of very high-
                            > frequency "hash" noise during rotation. Putting a small
                            > capacitor (e.g. 0.1 uf) directly across the motor leads
                            > can help.
                            >
                            > The ripple filter may need a long time constant, which would
                            > suggest using electrolytic capacitors, either aluminum or
                            > tantalum. Remember that electrolytics are polarized, and
                            > the tachometer voltage will reverse when the shaft rotation
                            > does. It's easy to make a non-polarized capacitor by putting
                            > two identical electrolytics back-to-back. If each capacitor
                            > is 100 uf, for example, the combination will be 50 uf.
                            >
                            > ASCII art:
                            > R
                            > +--------+--... ...---/\/\/\/----+------
                            > | motor | basic | filtered
                            > ( ) --- tachometer simple --- tachometer
                            > | --- signal lowpass --- signal
                            > | 0.1uf | filter | C
                            > +--------+--... ...--------------+------
                            >
                            > time constant = R*C
                            >
                            >
                            > | |
                            > --- value = C |
                            > --- + |
                            > | ===> --- value = C/2
                            > | ---
                            > --- + | non-polarized
                            > --- value = C |
                            > | |
                            >
                            >
                            > Cheers,
                            > Chuck
                            >
                            > harishpkl wrote:
                            > >
                            > > hi all
                            > > does anyone know how to use a small dc motor as speed
                            > > transducer.
                            > > any working schematic of the same if someone can supply.
                            > >
                            > > thanx in advance.
                            > >
                            > > regds
                            > >
                            > > hm
                            > >
                            >
                            > Visit the SRS Website at http://www.seattlerobotics.org
                            >
                            > Yahoo! Groups Links
                            >
                            > To visit your group on the web, go to:
                            > http://groups.yahoo.com/group/SeattleRobotics/
                            >
                            > To unsubscribe from this group, send an email to:
                            > SeattleRobotics-unsubscribe@yahoogroups.com
                            >
                            > Your use of Yahoo! Groups is subject to:
                            > http://docs.yahoo.com/info/terms/
                            >
                            >
                            >
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