Magnetic contact switch (door sensor)

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. But these also have a sticky-foam-tape back so you can also place them in locations you can't attach with screws.

Revision History: As of June 2, 2021, Adafruit sells these with premium wire ends for easy breadboarding.

• 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 15.2mm x 9mm
• Cable Length: ~29cm / ~11.4"