Hall effect sensor help

Discussion in 'General Electronics Chat' started by Garurumon, Aug 29, 2013.

  1. Garurumon

    Thread Starter Member

    Mar 17, 2013
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    Trying to build a levitron, decided to use hall switch for sensing the distance of the lifted object. TLE4945L was the only one I was able to obtain.

    I wasn't able to find much about hall effect sensors online, and there is one thing that bothers me.

    It works fine when I bring the south pole of the magnet to it, the led lights on, but when I move it away, it won't turn off. It only turns off I bring the north pole close to it.

    http://www.youtube.com/watch?v=GO2j785Xhqg&feature=youtu.be

    Why is it so? Cause if it's gonna work like that, I won't be able to sense when it starts falling down.

    Also, if I attach it to the bottom of my electromagnet, with it's "back" near it, will the electromagnet also effect it somehow?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    There are three types, Unipolar, bi-polar and Latch, the latch type switches with one pole and unlatches with the other.
    Honeywell make a small series of all three.
    Max.
     
  3. Garurumon

    Thread Starter Member

    Mar 17, 2013
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    So, I cannot make my levitron with this type?

    Damn :(
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If you only use one magnet face, then no.
    You need either uni or bi polar.
    Max.
     
  5. Garurumon

    Thread Starter Member

    Mar 17, 2013
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    Thanks for your help again Max :)
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    There are also linear hall sensors, like the KMZ10 made by philips.
    I have attached the datasheet and an application note.

    Bertus
     
  7. Garurumon

    Thread Starter Member

    Mar 17, 2013
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    And how about the ones used in the floppy disk? I could find old floppy drives easily, are the ones from there good?
     
  8. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    It could be that you can use one of them.
    There are also hall sensors inside DC fans.
    If you have a broken one, just look inside.

    Bertus
     
  9. Garurumon

    Thread Starter Member

    Mar 17, 2013
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    yeah, i have those! not broken, but about to be :) Thanks, I'll look for those now :)!
     
  10. Garurumon

    Thread Starter Member

    Mar 17, 2013
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    Ummmm, just destroyed one fan, and there is only a bunch of SMD components in there. There is one component that is protruding through the pcb, could that be a hall switch?
     
  11. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    I have taken a picture of some fan PCBs that I have laying around.
    I have circled the hall sensors on the picture.

    [​IMG]

    Bertus
     
  12. Garurumon

    Thread Starter Member

    Mar 17, 2013
    99
    1
    Thank you, and sorry if you destroyed something because of me :(

    I have found that but it's SMD, so I can as well forget it, heh :) I bought a floppy drive on internet, hopefully it'll have a better one.

    Thanks for your help Bertus!
     
  13. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    I have not destroyed anything.
    The PCBs are from broken fans at work.
    I take them out for the parts.
    The ones with 4 pins might be the most interesting.
    Those are likely to be linear ones.

    Bertus
     
  14. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    His device definitely seems to be a bipolar one.

    I'm not convinced even if he changes to a unipolar type that it will work, they usually have digital switching (hard ON or OFF) and some hysteresis. Those two things would make it very hard to use in a levitator.

    "Linear hall effect sensor" should be very easy to google and source some cheap sensors.

    Free linear sensors can be pulled from some types of pancake motors in VCRs and disk drives but they are often "bridge" type with 4 pins and low gain.

    Better linear hall sensors are now available that give better linearity and better gain (more voltage change for the same change in magnetic flux).
     
  15. MaxHeadRoom

    Expert

    Jul 18, 2013
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    He in fact describes is as a latching type in his OP.
    Max.
     
  16. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I thought the "bipolar" was in fact the latching type?

    They turn on with a S pole, and only turn off again with a N pole. I've used them before in projects and just ordered "bipolar" if I remember right.
     
  17. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Usually Bi-Polar means they momentary switch on either N or S pole, Uni-Polar switch on one pole only.
    Latch stay on until the other pole is presented.
    Max.
     
  18. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Thanks Max, I was wrong there. :)

    The Honeywell page lists unipolar/bipolar/bipolar latching types, so the sensors I used must have been "bipolar latching" type.
     
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