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DC motor using hall sensors — Parallax Forums

DC motor using hall sensors

fang-weifang-wei Posts: 7
edited 2007-04-25 15:15 in Robotics
Hi everyone!

I want to use a DC motor (EMG30) which instead of optical encoders is using hall sensors to determine the position. I couldn't find anywhere which kind of outputs are these of hall sensors , square maybe?

Could anyone help me??

Thanks!

Comments

  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2007-04-25 10:06
    I wonder what kind of DC motor. Most that have Hall sensor are 3 phase motors [noparse][[/noparse]the kind used in CD players] and really only good at a constant speed.

    If it is a 3-phase motor; it isn't really DC and requires a converter to make it operate.

    There are basically two types of Hall Sensors - one's that latch and one's that do not.
    I believe that you are looking at the ones that do not.

    Used alone, they may not give a true square wave. But, the microprocessor can respond to them as if they are a square wave. In other words, when the voltage goes below a threshold, the microprocessor reads low. When it goes abot a threshold, it reads high. It doesn't concern itself with the actual shape of the wave so much as the speed and duration.

    As long as the Hall Sensor's output voltage is not above 5.5volts; I suspect you can use it directly with a BasicStamp.
    What you really need to do is to look at the output on an oscilloscope.

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    "If you want more fiber, eat the package.· Not enough?· Eat the manual."········
    ···················· Tropical regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
  • fang-weifang-wei Posts: 7
    edited 2007-04-25 10:47
    Thanks Kramer!

    The motor is a DC motor which uses 2 Hall sensor to detect the rotor position.
    I think you are right, the best thing is to see how the signals look like with the oscilloscope... the thing is that I still don't have the motor [noparse]:)[/noparse] so I wanted to check if somebody had used something like that before.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2007-04-25 12:42
    Hi, I located the web site that is selling the motor and they don't seem to provide the kind of detail that Parallax is so good about.· But it is a really nice robotics motor.

    The motor is 12 volt, but the 'absolute maximum' and 'normal operating' voltages of the Hall sensor are not discussed.· Ask them why?

    You really have to ask them everything as they are the vendor.· The latching sensors don't change until the magnet pole changes.· They could be used, but it seems to me that you would need to know how many magnets there are to determine what is the relationship to position and speed.·

    And I would ask them how the two Hall Effect sensors are configured?· 90 degrees apart?· Or maybe some other method for better resolution

    Even if you can't get the answers, I suspect you can adjust the parameters in software.

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    "If you want more fiber, eat the package.· Not enough?· Eat the manual."········
    ···················· Tropical regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
  • fang-weifang-wei Posts: 7
    edited 2007-04-25 15:15
    Hi! Finally I got the answers from the vendor! Just in case anyone wants to use this motor, here there are some more specs.


    Sensor halls outputs are quadrature, open collector, 3 pulses each per motor shaft
    revolution.
    Power the sensor from 12v and pull-up the signals to 5v.

    U were right Kramer [noparse]:)[/noparse] that was the easiest way!
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