Looking hall effect circuit as dc motor indicator

Discussion in 'The Projects Forum' started by mrel, Nov 11, 2011.

  1. mrel

    Thread Starter Active Member

    Jan 20, 2009
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    Hello
    Have DC motor i like to know where the shaft is point at been that the motor is outdoor .
    Looking for hall effect circuit that will show where shaft is point at as the motor turn.
    Thank for the help mrel
     
  2. wayneh

    Expert

    Sep 9, 2010
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    How much angular resolution do you need?
     
  3. mrel

    Thread Starter Active Member

    Jan 20, 2009
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    360 deg
    mrel
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    What speed is the motor running at?

    An optical encoder wheel will give you close to angular resolution you need, depending on conditions and output.

    A Hall effect sensor will let you know when 1 complete turn of the shaft has happened, if you attach a magnet to the output shaft.

    If you need finer control of angular position and speed, you may want to look into stepper motors.

    Without knowing the application/desired outcome, it is difficult to give a "best answer", only an incomplete menu.
     
  5. wayneh

    Expert

    Sep 9, 2010
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    Huh? Position ± 360° means you just need to know whether the shaft exists or not. That would tell you nothing about its position. ±90° would tell you roughly which quadrant the pointer is in. ±10° would locate the pointer rotation into one of 36 little segments. And so on.

    So again, how much resolution do you need?
     
  6. BillB3857

    Senior Member

    Feb 28, 2009
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    Two properly positioned hall devices with a single N/S bar magnet mounted to the motor shaft CAN give positioning within 360 degrees but requires a lot of support circuitry to work out the Sin/Cos analog info. This is similar to a technique used in extended range absolute encoders in some BLDC motors. They have a clockwork arrangement driving 3 or 4 such devices within one encoder.
     
  7. mrel

    Thread Starter Active Member

    Jan 20, 2009
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    Actual went I wrote asking for a hall effect circuit I should said looking for hall effect circuit that show where motor shaft is point in the circle like north , south ,east , west.
    Hope this is more clear what I am trying to say.
    mrel
     
  8. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Do you mean what direction an antenna that is rotated by a motor is pointed?
     
  9. mrel

    Thread Starter Active Member

    Jan 20, 2009
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    Do you mean what direction an antenna that is rotated by a motor is pointed?
    __________________
    Thatoneguy : Right.
     
  10. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Building an electronic compass is a rather complex starting project, especially when there is metal around it. A microcontroller is required, though the actual compass ICs are available somewhat low cost, calibration of them is in code and not so easy.

    Electronic compasses use 3 Hall Effect sensors on 3 axis, the output is measured while the compass turns a full circle a few times, so which combination of axis produce the best result for the environment it is in.

    If you are looking for a simpler solution, such as an 8 point feedback LED, you could use a three ring encoder disc on the antenna shaft, read by 3 LED Reflection based transducer units. Search for "Grey Code" for the counting method. This solution would get you 45 degree accuracy and an idea of which way the antenna is pointing.

    I don't think you need +- 1 degree in 360 measurment/display accuracy for a TV antenna, you only need to get to the right direction, and the picture will tell you when it is correct.

    It comes down to: How fast does the antenna shaft rotate, and how much time and money do you want to spend on it?
     
  11. mrel

    Thread Starter Active Member

    Jan 20, 2009
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    So is there more simple circuit to show where the antenna is pointing?
    All these formula is getting to hard to understand and build.
     
  12. BillB3857

    Senior Member

    Feb 28, 2009
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