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Re: [SeattleRobotics] Re: Magnetic Encoder Problem

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  • Stephen Noel
    Another disadvantage is that magnetic sensors such as this generate a voltage which is proportional to the speed of the motor. At normal operating speeds, the
    Message 1 of 9 , Feb 5, 2006
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      Another disadvantage is that magnetic sensors such as this generate a
      voltage which is proportional to the speed of the motor. At normal
      operating speeds, the output signal is conditioned and clipped as Randy
      indicates, but as you progressively run the motor slower, the signal
      will eventually fade away.

      randycarter2001 wrote:
      > It's not really an encoder. It is a frequency generator. The faster
      > the motor rotates the higher the frequency output. The comparater
      > takes the small sine wave coming off of the sensor coil and turns it
      > into a square wave. It will be TTL compatable when it is powered with 5V.
      >
      > The 393 chip has an open collector output. It requires a pull-up
      > resistor on the output in order to work. A 1k to 4.7k will do the job
      > nicely.
      >
      > This same circuit is used in VCR's to regulate the speed of the
      > motors. The big disadvantage is that it will NOT tell you which way
      > the motor is turning, only how fast. But it is dust and light resistant.
      >
      >
      > --- In SeattleRobotics@yahoogroups.com, Michael Holder <md.holder@...>
      > wrote:
      >
      >>I believe this is called a "resolver." Ferrand make these under the
      >>trade name Inductosyn... wish I knew how they work.
      >>
      >>
      >
      >
      >
      >
      >
      >
      >
      > Visit the SRS Website at http://www.seattlerobotics.org
      > Yahoo! Groups Links
      >
      >
      >
      >
      >
      >
      >
      >
      >

      --
      Stephen Noel
      Pronetiq Consultation
      networks - systems - infrastructure
      http://www.pronetiq.com
      (514) 926-4700
    • Ahmet İrfan Savaşır
      I just put a 2.2k resistor as you told, and counted the pulses from output with MCU. It generates 50 pulses/rev and reaches to 1350 pulses/rev when 12 Volts is
      Message 2 of 9 , Feb 7, 2006
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        I just put a 2.2k resistor as you told, and counted the pulses from output
        with MCU. It generates 50 pulses/rev and reaches to 1350 pulses/rev when 12
        Volts is supplied to motor. I believe that it will provide me great easiness
        in my project. Thank you all for all your helps.
        Nice days.

        On 2/6/06, randycarter2001 <rwcarter.wa@...> wrote:
        >
        > R6 the 470K is not connected as a pull-up resistor (I had to look at
        > it twice). It is connected between the output an the + input of the
        > comparator. This provides some hysterisis to square up and clean the
        > output signal. If it wasn't there the output may ring as it
        > transitions from low to high or vice versa.
        >
        > On your controller board you will need a 2.2K resistor between the
        > output of this circuit and the Vcc of your processor. Other wise
        > there won't be any signal.
        >
        > Most IC outputs are totem pole type. Inside the chip there is a
        > transistor to pull the output high and another one to pull it low.
        > Most comparator outputs are open collector (drain) type where the
        > upper transistor is omitted. Therefor, without a pull-up resistor,
        > there is no way for the output to go high.
        >
        > Comparators are often used to transition from analog electronics to
        > digital electronics. The missing transistor allows the output side
        > (5v for example) to run at a different voltage than the analog system
        > (12v for example). It also allows the outputs to be ORED together to
        > form what is known as a window comparater where the output only goes
        > high if the input is between 2 preset points. To high or to low the
        > output goes low indicating a fault.
        >
        >
        >
        > > --- In SeattleRobotics@yahoogroups.com, Ahmet Ýrfan Savaþýr
        > <aisavasir@...> wrote:
        > >
        > > hi again,
        > > randy carter said a pull-up resistor should be used for TA75393. I am
        > > actually studying mechanical engineering, and not familiar with
        > > electronics. I have searched web for "pull-up resistor". There is a
        > resistor
        > > between VCC and Vout, R6 in the pictures. It is 470k . can it be a
        > pull-up
        > > resistor? If it is not, where should i put the resistor? One terminal to
        > > output, but other?
        > > And I'm not sure about the way of using the Inductosyn ...
        > (Considering it
        > > generates square wave output..) if I count the output signals for a
        > specific
        > > time, this will give me the speed of the motor, for instance 80 pulses /
        > > sec. But can I succeed this via simply using Picbasic "count"
        > command? Any
        > > suggestion?
        >
        >
        >
        >
        >
        > Visit the SRS Website at http://www.seattlerobotics.org
        > Yahoo! Groups Links
        >
        >
        >
        >
        >
        >
        >
        >


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