Vehicle Location with Hall Effect Switches

Moving on from the use of reed switches to identify the location of moving road vehicles I have been experimenting with Hall Effect switches. These are, in effect, a solid-state reed switch.

Hall Effect switches can be difficult to come by for the hobbyist, although Farnell can supply (search for Hall Effect Sensor) at a pound or so each. Fortunately members of MERG (the Model Electronics Railway Group) can buy them from the society at about 50p each.

The black thing with the silver legs is a Hall Effect Switch shown full size.

The sensor detects a magnetic field - one side will detect a North pole, the other a South and provides an output that can drive an LED or logic circuit.

Lighting a LED using a Hall Effect Switch.

For a standard Faller guidance magnet the sensor needs to be immediately underneath the guide wire and, ideally, have a largish iron screw or nail behind it to concentrate the magnetic field.

The advantages of Hall Effect sensors over reed switches are:

1. Doesn't need a break in the wire (so can be used on curves)
2. Smaller hole in the baseboard
3. Not as fragile - the reeds are easy to break when bending the leads
4. Cost (for MERG members), about 50p instead of 99p.