Hall effect switch

Discussion in 'General Electronics Chat' started by NZDave, Aug 29, 2006.

  1. NZDave

    Thread Starter New Member

    Aug 29, 2006
    3
    0
    Hi guys, I've got a data logger and timer. The timer is activated by push button, I want to change this for a hall effect switch to be triggered by a magnit. (40-50mm range). Has anyone got a simple circuit to do this??

    Thanks
     
  2. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    I'm not so familiar with Hall effect sensors or their sensitivity at that distance, but I'm guessing some signal amplification may be involved.
     
  3. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    567
    12
    You will probably need to place the sensor at the input of a comparator, the comparator will then provide the TTL level or other output level required.

    Actual circuit design requires determining the exact sensor to be used, the given magnet, and the distance between the two; along with the comparator details.

    You may want to search on comparator application circuits.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    Put a reed relay in place of the switch. The magnet will close the contacts as long as it is near the reed.
     
  5. NZDave

    Thread Starter New Member

    Aug 29, 2006
    3
    0
    Thanks guys, a reed switch is not senitive enough. Asfor circuit design, I dont know which sensor/comparator to use. Hence my visit to this forum!!
     
  6. Chris Wright

    Well-Known Member

    Jul 26, 2006
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    0
    Have you found a sensor that will work at that range? Here is a site FAQ that indicates 4 to 6mm with the most powerful magnet is more likely.

    http://www.allegromicro.com/faq/hedfaq1.htm

    I'd start googling for sensor specifications first to see if you can find one that will work at that range.

    What is the physical setup that is going to swing the magnet in front of the sensor?
     
  7. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    4
    I've worked with hall effect sensors several times, and I think it is difficult to get one to work at the range that you indicated. The range that Chris mentioned above is more likely.

    If the distance can not be made nearer, then you probably could look at other type of sensors, like proximity or something else.
     
  8. NZDave

    Thread Starter New Member

    Aug 29, 2006
    3
    0
    Thanks guys, the magnet can't be moved..... It's inbeded in the surface of the track that we race (Karts) on. The pickup is mounted on the kart, when the magnit is crossed it triggers the laptimer on the kart. Ok then if a hall effect is no good........... any other sugestions?

    Dave
     
  9. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    Kia Ora.
    Doing a quick google shows the most common method is to use Transponders buried in the track.
    http://www.chronelec.com/
    Good luck.
     
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