Magnetic contact switch (door sensor)

Description

This sensor is essentially a reed switch, encased in an ABS plastic shell. Normally the reed is ‘open’ (no connection between the two wires). The other half is a magnet. When the magnet is less than 13mm (0.5″) away, the reed switch closes. They’re often used to detect when a door or drawer is open, which is why they have mounting tabs and screws. You can also pick up some double-sided foam tape from a hardware store to mount these, that works well without needing screws.

Normally open reed switch
ABS enclosure
Rated current: 100 mA max
Rated voltage: 200 VDC max
Distance: 15mm max

Dimensions:

Box size (each side): 29mm x 14mm x 9mm / 1.1″ x 0.6″ x 0.4″
Cable Length: 305mm ± 12mm / 12″ ± 0.5″
Weight (per side): 5.4g

Netduino driver and Netduino sample. This sample shows how to use an interrupt handler to respond to a button press or a magnetic contact switch closing.