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Re: Didn't Motorola already invent this?

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  • ti_wrex
    Hi Steve, I first started this project using the MC33974 back in mid November. I overnighted the eval kit in from DigiKey thinking I would be all set...
    Message 1 of 5 , Apr 30, 2004
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      Hi Steve,

      I first started this project using the MC33974 back in mid November.
      I overnighted the eval kit in from DigiKey thinking I would be all
      set...

      Unfortunately, the MC33974 is very insensitive. It can detect a car
      seat (it's real use) but it cannot detect to the fine levels needed
      for robot work. With a 10 bit AtoD (it has analog output), the chip
      can go to 0.1pF if you are "really" lucky. Most of the details I
      stuck here:

      http://hot-streamer.com/temp/MC33974EvalKitCD/

      Although neat for many uses, it was instantly obvious that the chip
      was not going to work for the range of 0.0001pF which such a system
      really needs. I gave the kit to a guy at the robot club for his
      object grabber where it might be more useful (I think I also have a
      bunch of bare chips in my junk box...). I then started looking into
      the theremin's circuits. There was a version-I which used all analog
      circuits that is still described at:

      http://thereminvision.com/

      However, the new all digital version is vastly better and really made
      this whole system fly:

      http://thereminvision.com/version-2/TV-II-index.html

      ThereminVision can detect capacitance levels about to 1/10000th what
      the Motorola chip can. The Motorola chip does have nine channels and
      can do shield referenced antennas which is cool, but the sensitivity
      is just not there.

      http://hot-streamer.com/temp/MC33974EvalKitCD/CD33794DWBEVM%
      20Documentation/MC33794.pdf

      The key difference is that the Motorola chip just sets up a 120kHz
      capacitance controlled oscillator and measures the frequency delta
      directly. A nice solid thing for critical car safety systems, but
      too insensitive in our case. However, ThereminVision "heterodynes"
      the oscillator signal with a reference signal just like the theremin
      instrument to run the sensitivity way up while still remaining
      stable. That is the key difference. This is all explained in the
      manual under "Theory of Operation" on page 5.

      http://thereminvision.com/version-2/ThereminVision-II-manual.pdf

      What is really sad is that apparently the Motorola chip was
      originally going to heterodyne the signal against a reference and be
      very sensitive just like the theremin. I might guess that the analog
      designers were just not able to get it going or the car application
      changed there plans with million piece sales prospects.
      ThereminVision could actually be adjusted to be just as insensitive
      as the MC33974 if anyone really wanted too. If they had just gone
      all digital and allowed for the full range of sensitivity adjustment,
      the Motorola chip might have been perfect for everyone!! But they
      didn't... Maybe someday they will... The Motorola package is also
      pretty messy for home soldering and such. They added a bunch of
      automotive things too like the incandescent dash board light driver
      circuits (it does have an error signal if it burns out :-p).

      If I have not already told you far more than you wanted to know ;-))
      Here are two posts that go over this too:

      http://groups.yahoo.com/group/FrontRangeRobotics/message/1678

      http://groups.yahoo.com/group/FrontRangeRobotics/message/1711

      There has been a long running saga about this at:

      http://groups.yahoo.com/group/FrontRangeRobotics/messages/1697

      All the relevant posts are "MC33947" or "ThereminVision" reports.

      Cheers,

      Terry


      --- In thereminvision@yahoogroups.com, "bestbobleonard"
      <bestbobleonard@y...> wrote:
      > On Fri, 2004-04-30 at 16:16, Bob Leonard wrote:
      > > The principle of the sensor is based upon the fact
      > > that there is a very weak electromagnetic field which
      > > surrounds an antenna.
      >
      > Didn't Motorola already invent this? Sounds just like Motorola's
      > e-field
      > imaging sensor. It allows you to detect the distance and shape of
      > objects that pass through its electromagnetic field. They're used in
      > cars for things like turning off side impact airbags when your body
      > is
      > blocking the inflation area. Here's a robots.net post from last year
      > with links to the Motorola specs on the e-field sensor and a
      Circuilt
      > Cellar article about them.
      >
      > http://robots.net/article/832.html
      >
      > From a quick glance at the specs it looks like the main difference
      is
      > that you need two electrodes to measure size and shape so the
      > Theramin
      > sensor may be measuring only proximity.
      >
      > -Steve
    • John Edwards
      I received the Motorola MC33974 kit a while back through the Circuit Cellar magazine contest. I had plans on designing a robot sensor around it but quickly
      Message 2 of 5 , May 1, 2004
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        I received the Motorola MC33974 kit a while back through the Circuit Cellar magazine contest. I had plans on designing a robot sensor around it but quickly discover what you just stated about it not having enough sensitivity.
         
        Lat night I received an E-mail through the Seattle Robotics group list telling about the ThereminVision II. This peaked my interest so much that I ordered one immediately.
         
        One question I have is how fast does this sensor react to changes in it's environment? My robots run on a RTOS that refreshes every 16ms and I am hoping that the ThereminVision II can keep it supplied with fresh info every run through the loop.
         
        I am looking forward to experimenting with this new sensor system.
         
         
        ----- Original Message -----
        From: ti_wrex
        Sent: Friday, April 30, 2004 9:07 PM
        Subject: [thereminvision] Re: Didn't Motorola already invent this?

        Hi Steve,

        I first started this project using the MC33974 back in mid November. 
        I overnighted the eval kit in from DigiKey thinking I would be all
        set...

        Unfortunately, the MC33974 is very insensitive.  It can detect a car
        seat (it's real use) but it cannot detect to the fine levels needed
        for robot work.  With a 10 bit AtoD (it has analog output), the chip
        can go to 0.1pF if you are "really" lucky.  Most of the details I
        stuck here:

        http://hot-streamer.com/temp/MC33974EvalKitCD/

        Although neat for many uses, it was instantly obvious that the chip
        was not going to work for the range of 0.0001pF which such a system
        really needs.  I gave the kit to a guy at the robot club for his
        object grabber where it might be more useful (I think I also have a
        bunch of bare chips in my junk box...).  I then started looking into
        the theremin's circuits.  There was a version-I which used all analog
        circuits that is still described at:

        http://thereminvision.com/

        However, the new all digital version is vastly better and really made
        this whole system fly:

        http://thereminvision.com/version-2/TV-II-index.html

        ThereminVision can detect capacitance levels about to 1/10000th what
        the Motorola chip can.  The Motorola chip does have nine channels and
        can do shield referenced antennas which is cool, but the sensitivity
        is just not there.

        http://hot-streamer.com/temp/MC33974EvalKitCD/CD33794DWBEVM%
        20Documentation/MC33794.pdf

        The key difference is that the Motorola chip just sets up a 120kHz
        capacitance controlled oscillator and measures the frequency delta
        directly.  A nice solid thing for critical car safety systems, but
        too insensitive in our case.  However, ThereminVision "heterodynes"
        the oscillator signal with a reference signal just like the theremin
        instrument to run the sensitivity way up while still remaining
        stable.  That is the key difference.  This is all explained in the
        manual under "Theory of Operation" on page 5.

        http://thereminvision.com/version-2/ThereminVision-II-manual.pdf

        What is really sad is that apparently the Motorola chip was
        originally going to heterodyne the signal against a reference and be
        very sensitive just like the theremin.  I might guess that the analog
        designers were just not able to get it going or the car application
        changed there plans with million piece sales prospects. 
        ThereminVision could actually be adjusted to be just as insensitive
        as the MC33974 if anyone really wanted too.  If they had just gone
        all digital and allowed for the full range of sensitivity adjustment,
        the Motorola chip might have been perfect for everyone!!  But they
        didn't...  Maybe someday they will...  The Motorola package is also
        pretty messy for home soldering and such.  They added a bunch of
        automotive things too like the incandescent dash board light driver
        circuits (it does have an error signal if it burns out :-p).

        If I have not already told you far more than you wanted to know ;-)) 
        Here are two posts that go over this too:

        http://groups.yahoo.com/group/FrontRangeRobotics/message/1678

        http://groups.yahoo.com/group/FrontRangeRobotics/message/1711

        There has been a long running saga about this at:

        http://groups.yahoo.com/group/FrontRangeRobotics/messages/1697

        All the relevant posts are "MC33947" or "ThereminVision" reports.

        Cheers,

              Terry
      • ti_wrex
        Hi John, It will work fine. If the difference frequency (between the sensor and reference) is say 100kHz, then one could theoretically run at 0.01mS. But the
        Message 3 of 5 , May 1, 2004
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          Hi John,

          It will work fine.

          If the difference frequency (between the sensor and reference) is say
          100kHz, then one could theoretically run at 0.01mS. But the
          microcontroller probably can't handle that so there is a binary
          counter that divides that frequency by say 1024 for a 10mS pulse
          width. You can adjust the difference frequency as you wish with the
          little pots on the sensors. You can also pick any divide ratio on
          the 74HC4040 chip. So you can set it all to anything you want.

          My robot is running at about 60 loops per second (17mS) and that time
          is mostly governed by the microcontroller doing all the robot's
          control stuff. The pulse widths are set to about 3mS in my case to
          give about 4000 counts on the BasicStamp2. However, that can all be
          set as you wish.

          So the ThereminVision probably can send pulses to the microcontroller
          a few orders of magnitude faster than it could handle. 16mS is no
          problem at all. I made it so you can set up such timing anyway you
          wish.

          Page 15 of the manual talks about this. Be sure to see the Theory of
          Operation section and maybe refer to the 74HC4040 data sheet. I
          wonder if I should have gone over this more in the manual? Let me
          know if you think I should say more in the next manual revision. Of
          course, you can always ask here if you run into any questions.

          Cheers,

          Terry


          --- In thereminvision@yahoogroups.com, "John Edwards"
          <botbuilder@c...> wrote:
          > I received the Motorola MC33974 kit a while back through the
          Circuit Cellar magazine contest. I had plans on designing a robot
          sensor around it but quickly discover what you just stated about it
          not having enough sensitivity.
          >
          > Lat night I received an E-mail through the Seattle Robotics group
          list telling about the ThereminVision II. This peaked my interest so
          much that I ordered one immediately.
          >
          > One question I have is how fast does this sensor react to changes
          in it's environment? My robots run on a RTOS that refreshes every
          16ms and I am hoping that the ThereminVision II can keep it supplied
          with fresh info every run through the loop.
          >
          > I am looking forward to experimenting with this new sensor system.
          >
          > John Edwards
          > botbuilder@c...
          > http://webpages.charter.net/grizzlyrobotics/
          >
          > ----- Original Message -----
          > From: ti_wrex
          > To: thereminvision@yahoogroups.com
          > Sent: Friday, April 30, 2004 9:07 PM
          > Subject: [thereminvision] Re: Didn't Motorola already invent this?
          >
          >
          > Hi Steve,
          >
          > I first started this project using the MC33974 back in mid
          November.
          > I overnighted the eval kit in from DigiKey thinking I would be
          all
          > set...
          >
          > Unfortunately, the MC33974 is very insensitive. It can detect a
          car
          > seat (it's real use) but it cannot detect to the fine levels
          needed
          > for robot work. With a 10 bit AtoD (it has analog output), the
          chip
          > can go to 0.1pF if you are "really" lucky. Most of the details I
          > stuck here:
          >
          > http://hot-streamer.com/temp/MC33974EvalKitCD/
          >
          > Although neat for many uses, it was instantly obvious that the
          chip
          > was not going to work for the range of 0.0001pF which such a
          system
          > really needs. I gave the kit to a guy at the robot club for his
          > object grabber where it might be more useful (I think I also have
          a
          > bunch of bare chips in my junk box...). I then started looking
          into
          > the theremin's circuits. There was a version-I which used all
          analog
          > circuits that is still described at:
          >
          > http://thereminvision.com/
          >
          > However, the new all digital version is vastly better and really
          made
          > this whole system fly:
          >
          > http://thereminvision.com/version-2/TV-II-index.html
          >
          > ThereminVision can detect capacitance levels about to 1/10000th
          what
          > the Motorola chip can. The Motorola chip does have nine channels
          and
          > can do shield referenced antennas which is cool, but the
          sensitivity
          > is just not there.
          >
          > http://hot-streamer.com/temp/MC33974EvalKitCD/CD33794DWBEVM%
          > 20Documentation/MC33794.pdf
          >
          > The key difference is that the Motorola chip just sets up a
          120kHz
          > capacitance controlled oscillator and measures the frequency
          delta
          > directly. A nice solid thing for critical car safety systems,
          but
          > too insensitive in our case. However,
          ThereminVision "heterodynes"
          > the oscillator signal with a reference signal just like the
          theremin
          > instrument to run the sensitivity way up while still remaining
          > stable. That is the key difference. This is all explained in
          the
          > manual under "Theory of Operation" on page 5.
          >
          > http://thereminvision.com/version-2/ThereminVision-II-manual.pdf
          >
          > What is really sad is that apparently the Motorola chip was
          > originally going to heterodyne the signal against a reference and
          be
          > very sensitive just like the theremin. I might guess that the
          analog
          > designers were just not able to get it going or the car
          application
          > changed there plans with million piece sales prospects.
          > ThereminVision could actually be adjusted to be just as
          insensitive
          > as the MC33974 if anyone really wanted too. If they had just
          gone
          > all digital and allowed for the full range of sensitivity
          adjustment,
          > the Motorola chip might have been perfect for everyone!! But
          they
          > didn't... Maybe someday they will... The Motorola package is
          also
          > pretty messy for home soldering and such. They added a bunch of
          > automotive things too like the incandescent dash board light
          driver
          > circuits (it does have an error signal if it burns out :-p).
          >
          > If I have not already told you far more than you wanted to know ;-
          ))
          > Here are two posts that go over this too:
          >
          > http://groups.yahoo.com/group/FrontRangeRobotics/message/1678
          >
          > http://groups.yahoo.com/group/FrontRangeRobotics/message/1711
          >
          > There has been a long running saga about this at:
          >
          > http://groups.yahoo.com/group/FrontRangeRobotics/messages/1697
          >
          > All the relevant posts are "MC33947" or "ThereminVision" reports.
          >
          > Cheers,
          >
          > Terry
        • John Edwards
          Terry, That sounds great. My software actually loops 61 times per second and the Sharp GP2D12 IR ranging sensors I was using took about 40ms (eternity) to
          Message 4 of 5 , May 1, 2004
          • 0 Attachment
            Terry,
             
            That sounds great.
             
            My software actually loops 61 times per second and the Sharp GP2D12 IR ranging sensors I was using took about 40ms (eternity) to update info.
             
            Thank you,
             
            ----- Original Message -----
            From: ti_wrex
            Sent: Saturday, May 01, 2004 2:53 PM
            Subject: [thereminvision] Re: Didn't Motorola already invent this?

            Hi John,

            It will work fine.

            If the difference frequency (between the sensor and reference) is say
            100kHz, then one could theoretically run at 0.01mS.  But the
            microcontroller probably can't handle that so there is a binary
            counter that divides that frequency by say 1024 for a 10mS pulse
            width.  You can adjust the difference frequency as you wish with the
            little pots on the sensors.  You can also pick any divide ratio on
            the 74HC4040 chip.  So you can set it all to anything you want.

            My robot is running at about 60 loops per second (17mS) and that time
            is mostly governed by the microcontroller doing all the robot's
            control stuff.  The pulse widths are set to about 3mS in my case to
            give about 4000 counts on the BasicStamp2.  However, that can all be
            set as you wish.

            So the ThereminVision probably can send pulses to the microcontroller
            a few orders of magnitude faster than it could handle.  16mS is no
            problem at all.  I made it so you can set up such timing anyway you
            wish.

            Page 15 of the manual talks about this.  Be sure to see the Theory of
            Operation section and maybe refer to the 74HC4040 data sheet.  I
            wonder if I should have gone over this more in the manual?  Let me
            know if you think I should say more in the next manual revision.  Of
            course, you can always ask here if you run into any questions.

            Cheers,

                  Terry


            --- In thereminvision@yahoogroups.com, "John Edwards"
            <botbuilder@c...> wrote:
            > I received the Motorola MC33974 kit a while back through the
            Circuit Cellar magazine contest. I had plans on designing a robot
            sensor around it but quickly discover what you just stated about it
            not having enough sensitivity.
            >
            > Lat night I received an E-mail through the Seattle Robotics group
            list telling about the ThereminVision II. This peaked my interest so
            much that I ordered one immediately.
            >
            > One question I have is how fast does this sensor react to changes
            in it's environment? My robots run on a RTOS that refreshes every
            16ms and I am hoping that the ThereminVision II can keep it supplied
            with fresh info every run through the loop.
            >
            > I am looking forward to experimenting with this new sensor system.
            >
            > John Edwards
            > botbuilder@c...
            > http://webpages.charter.net/grizzlyrobotics/
            >
            >   ----- Original Message -----
            >   From: ti_wrex
            >   To: thereminvision@yahoogroups.com
            >   Sent: Friday, April 30, 2004 9:07 PM
            >   Subject: [thereminvision] Re: Didn't Motorola already invent this?
            >
            >
            >   Hi Steve,
            >
            >   I first started this project using the MC33974 back in mid
            November. 
            >   I overnighted the eval kit in from DigiKey thinking I would be
            all
            >   set...
            >
            >   Unfortunately, the MC33974 is very insensitive.  It can detect a
            car
            >   seat (it's real use) but it cannot detect to the fine levels
            needed
            >   for robot work.  With a 10 bit AtoD (it has analog output), the
            chip
            >   can go to 0.1pF if you are "really" lucky.  Most of the details I
            >   stuck here:
            >
            >   http://hot-streamer.com/temp/MC33974EvalKitCD/
            >
            >   Although neat for many uses, it was instantly obvious that the
            chip
            >   was not going to work for the range of 0.0001pF which such a
            system
            >   really needs.  I gave the kit to a guy at the robot club for his
            >   object grabber where it might be more useful (I think I also have
            a
            >   bunch of bare chips in my junk box...).  I then started looking
            into
            >   the theremin's circuits.  There was a version-I which used all
            analog
            >   circuits that is still described at:
            >
            >   http://thereminvision.com/
            >
            >   However, the new all digital version is vastly better and really
            made
            >   this whole system fly:
            >
            >   http://thereminvision.com/version-2/TV-II-index.html
            >
            >   ThereminVision can detect capacitance levels about to 1/10000th
            what
            >   the Motorola chip can.  The Motorola chip does have nine channels
            and
            >   can do shield referenced antennas which is cool, but the
            sensitivity
            >   is just not there.
            >
            >   http://hot-streamer.com/temp/MC33974EvalKitCD/CD33794DWBEVM%
            >   20Documentation/MC33794.pdf
            >
            >   The key difference is that the Motorola chip just sets up a
            120kHz
            >   capacitance controlled oscillator and measures the frequency
            delta
            >   directly.  A nice solid thing for critical car safety systems,
            but
            >   too insensitive in our case.  However,
            ThereminVision "heterodynes"
            >   the oscillator signal with a reference signal just like the
            theremin
            >   instrument to run the sensitivity way up while still remaining
            >   stable.  That is the key difference.  This is all explained in
            the
            >   manual under "Theory of Operation" on page 5.
            >
            >   http://thereminvision.com/version-2/ThereminVision-II-manual.pdf
            >
            >   What is really sad is that apparently the Motorola chip was
            >   originally going to heterodyne the signal against a reference and
            be
            >   very sensitive just like the theremin.  I might guess that the
            analog
            >   designers were just not able to get it going or the car
            application
            >   changed there plans with million piece sales prospects. 
            >   ThereminVision could actually be adjusted to be just as
            insensitive
            >   as the MC33974 if anyone really wanted too.  If they had just
            gone
            >   all digital and allowed for the full range of sensitivity
            adjustment,
            >   the Motorola chip might have been perfect for everyone!!  But
            they
            >   didn't...  Maybe someday they will...  The Motorola package is
            also
            >   pretty messy for home soldering and such.  They added a bunch of
            >   automotive things too like the incandescent dash board light
            driver
            >   circuits (it does have an error signal if it burns out :-p).
            >
            >   If I have not already told you far more than you wanted to know ;-
            )) 
            >   Here are two posts that go over this too:
            >
            >   http://groups.yahoo.com/group/FrontRangeRobotics/message/1678
            >
            >   http://groups.yahoo.com/group/FrontRangeRobotics/message/1711
            >
            >   There has been a long running saga about this at:
            >
            >   http://groups.yahoo.com/group/FrontRangeRobotics/messages/1697
            >
            >   All the relevant posts are "MC33947" or "ThereminVision" reports.
            >
            >   Cheers,
            >
            >         Terry


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