Magnetic contact switch (door sensor)


Please note:  Adafruit has an updated version of this switch.  We currently have a limited number of the original version.  If you are concerned about which version you may receive, please contact us!

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.

Technical Details

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


  • Box size (each side): 29mm x 15.2mm x 9mm
  • Cable Length: ~29cm / ~11.4"
    RoHS 2 2011 65 EU CompliantRoHS 2 2015 863 EU Compliant