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Linear position detection with a hall effect sensor — Parallax Forums

Linear position detection with a hall effect sensor

SteveDSteveD Posts: 64
edited 2007-09-26 19:11 in General Discussion
I have a circuit board that contains a small DC motor.· This motor drives a threaded rod which causes a magnet to travel approximately ½” back and forth parallel with the circuit board.· This magnet, for the purpose of linear proximity positioning, passes over a 3-pin SIP hall effect sensor that is about ⅛” thick by ¼” square.· I cannot find out what the exact part number for these sensors are however the markings on two different ones are 550W13 and 550W14.· I am in the process of selecting something of the same physical size that will work if I am unable to find an exact replacement.· I am completely ignorant about these kind of sensors and am wondering if someone would provide some guidance in selecting the correct one that is if they do not all funtion the same.· If·all of them funtion the same then I already have some picked out.· Also I was wondering what information is being output from the sensor in relation to the changing distance of the magnet is it a varying voltage?
Thank you in advance.
Steve

Comments

  • David BDavid B Posts: 592
    edited 2007-09-26 16:49
    Well, there are a number of different sorts of sensors. Some sensors put out a voltage, and others internally have a threshold that switches the output on or off digitally. Some sensors are intended to be used with a bias magnet fixed behind them. Any Hall effect sensor will have to be installed with the right orientation to work as designed.

    Are you replacing a Hall sensor of unknown characteristics? How much do you know about what happens to the signal that the sensor produces?

    If you want a general introduction to them, why not browse around here -

    http://www.allegromicro.com/en/Products/Design/Tech_Pubs.asp#B

    I've used a few Allegro Hall effect sensors; they're nice - inexpensive, easy to use, and they seem to work well.

    David
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2007-09-26 19:11
    There are two fundamental kinds of Hall sensors - latching and non-latching.

    Generally the latching are NOT what you want to use. They flip into one state and wait for the opposite pole of the magnet to pass by in order to revert to their other state.

    The others just spike when one particular pole passes by.

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