Using hall effect latch

Discussion in 'The Projects Forum' started by U4EAH, Apr 10, 2010.

  1. U4EAH

    Thread Starter New Member

    Jun 10, 2008
    Trying to locate info on choosing the correct H.E. latch.

    Circuit uses a small 3v lithium battery and latch to power up an LED.
    Magnet would be a small neo, robbed out of old hard drive parking arm.

    Distance from latch to magnet surface </= 8mm.
  2. SgtWookie


    Jul 17, 2007
    Well, you'd need to determine the Gauss of your magnet at 8mm distance.

    Some H.E. sensors are latching, some are linear, and there are a wide range of sensitivities.

    If you don't know what the strength of your magnet is, you'll have to make a wild guess.

    Or, you could order a magnet of known field strength, and a HE sensor with matching specs.

    Or, you could order a H.E. sensor and try to adapt it to your magnet by using ferrous metals to concentrate the flux lines in the right amount through your sensor.
  3. U4EAH

    Thread Starter New Member

    Jun 10, 2008
    Ah, I should have written "equal or less than" 8 mm,
    my bad :(

    It's been a long time since I've read about H.E. switches,
    I do believe it's the latch-type I'm seeking. My application-
    the H.E. goes flying past the magnet, latches on, turns on LED.
    H.E. is toggled off by exposing it to opposite magnetic field.

    Pretty straight-forward, except there's no way I could find the
    gauss of the little mags I have now. I'll keep searching here
    for more basic application circuits, maybe I can dig up something
    simple from Jameco or Digikey, thanks SgtWookie.