The reed switch is an electrical switch which is operated by an applied with a magnetic field. When the magnet close the Reed Switch it will activate as HIGH, The Reed Switch was invented at Bell Telephone Laboratories in 1936. It consists of a pair of contact on ferrous metal reeds in a hermetically sealed glass tube.

Working with Magnets and Reed Switch

Magnet and Reed switch must be brought within a specific proximity of each other. The distance will vary in accordance with the sensitivity of the reed switch and the strength of the magnet. When the magnet is close enough the reed switch, normally open contacts will close or operate. When the magnet is taken away, the contacts will open or release. Below are the proximity motion switching as our example.

Perpendicular Motion > It give only one closure with maximum magnet travel.


Parallel Motion > Give as many as three closure with maximum magnet travel its allows one closure with minimum magnet travel.

Reed Switch Pararel

Reed Swith Application Pararel

Front to Back Motion > This is similar to parallel motion, excepts the magnet motion is at the right angles to switch and provides only one closure with maximum magnet travel.


Front to Back Reed Switch

Pivoted Motion > This a Large angular magnet to travel and achieve on switch closure.

pivoted reed switch magnet

Rotation > Rotating magnet or rotation reed switch, this is normal to their axes, reverses magnetic polarity resulting in two closures per revolution. When these axes are paralleled. When the axes are perpendicular, the switch opens. Although the poles reverse, they still induce the opposite poles that close the reed switch.

rotation reed switch magnet

Biasing > A biasing effect is produced by placing a stationary magnet near the reed switch, to keep it normally closed. When n another magnet witch reversed polarity cancels the magnetic lines of force, and the reed switch opens.

Biasing Reed Switch Magnets

Shielding > This type of actuation the magnet and the reed switch are permanently fixed in such a position that the reed switch contacts are closed. A piece of ferromagnetic material is passed between the magnet and the reed switch, cause the drop out. The magnetic field is shunted, eliminating the attraction between the reeds, and when the shield is remove the reed switch will close.

Shielding Reed Switch with Magnets

Wiring the Reed Switch Module


Arduino Sketch Code


Working with Reed Switch and Magnetic Field
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