Magnetic Reed Switch Mini Module KY-021

The Magnetic Reed Switch Mini Module KY-021 is a small sensor board with a glass reed switch that closes when a magnet comes near it. It gives a simple digital signal to an Arduino, ESP32 or Raspberry Pi, which makes it an easy way to detect whether a door or window is open, count rotations, or sense the position of a moving part without any physical contact.

Magnetic Reed Switch Mini Module Specifications

• Sensor: miniature glass reed switch, normally open
• Trigger: contacts close in the presence of a magnetic field
• Output: digital, switch contact with a 10 kΩ resistor on the board
• Operating voltage: 3.3–5 V
• Pins: 3 (signal, +V and GND; check the labels on the board)
• Series: KY-021, part of the KY-0xx sensor module family

Magnetic Reed Switch Mini Module Applications

• Door and window open/closed sensors
• Home alarm and security projects
• Bicycle speedometers and rotation counters
• End-of-travel and position detection in machines
• Float switches using a magnet on the float

What's in the Box

• 1 × KY-021 mini magnetic reed switch module

Tip: Hold the magnet within a few centimetres of the reed switch, parallel to the glass tube, for the most reliable switching. The glass is fragile, so do not bend the switch leads close to its body.

Orders placed before 14:00 are ready for pickup the same day. Delivery across Lebanon usually takes 1–3 working days.