? on Mr Hall Effect

[Albert Grippo]

  The Hall sensor I am using has 3 pins: VDD(+5 or +9 V), OUT,
  and GND. I connected a 5K pullup resistor between VDD and OUT,
  and a .1 uF decoupling cap beteween VDD and GND. To use it
  I glued a ceramic button magnet to a distributor, mounted
  the Hall sensor over the magnet, and put a slotted steel wheel
  in between the two.  When the solid part of the wheel is
  over the magnet, it shields the field from the sensor and
  you read VDD volts on the OUT pin.  When the wheel is
  turned so the slot exposes the magnet, you read 0 volts. It
  is not sensitive to motion, just to whether the magnetic field
  is exposed or shielded. I am using it to determine the no. 1 
  cylinder. One last thing, the magnet south pole goes toward 
  the sensor.

		  -Al Grippo