KY-025 Reed Switch Sensor Module with Adjustable Digital and Analog Output – Magnetic Detection Module for Arduino

The KY-025 Reed Switch Module is a compact magnetic detection sensor designed for Arduino, microcontrollers and electronic automation projects. It uses a glass-encapsulated reed switch to detect the presence of a nearby magnet without requiring physical contact.

When a magnet approaches the reed switch, the internal metal contacts react to the magnetic field and change the module’s output state. This makes the sensor suitable for door-position detection, security alarms, magnetic counters, limit detection, speed measurement and other contactless switching applications.

The module includes an LM393 comparator circuit and an adjustable onboard potentiometer. The potentiometer allows the user to set the digital-output switching threshold. Two onboard indicator LEDs commonly show power status and digital-output activity.

The KY-025 provides both analog and digital outputs:

• Analog output (A0): Supplies the raw reed-switch signal for monitoring through an analog input.
• Digital output (D0): Supplies a HIGH or LOW switching signal according to the comparator setting.

Its four-pin interface allows easy connection to Arduino UNO, Nano, Mega, ESP32, ESP8266, Raspberry Pi GPIO circuits and other compatible development boards. The module is commonly operated from approximately 3.3V to 5V, although exact specifications can vary between manufacturers.

The sensor is useful for detecting a magnet’s presence, but it does not measure an exact magnetic-field strength or distance. Detection range depends on the size and strength of the magnet, its orientation and the surrounding installation conditions.

Common Applications

• Door-open and door-closed detection
• Window security alarms
• Magnetic proximity detection
• Contactless limit switches
• Bicycle wheel speed measurement
• Rotation and RPM counting
• Position detection
• Magnetic counters
• Smart-home projects
• Robot position sensing
• Arduino security projects
• Electronic lock monitoring
• Industrial model projects
• DIY automation systems
• Student science projects

Package Contents: 1 × KY-025 Reed Switch Sensor Module

Important Usage Notes

• Handle the glass reed switch carefully because it can break if bent or struck.
• Use only the pin labels printed on the module when wiring it.
• Do not exceed the recommended operating voltage.
• Detection distance is not fixed and depends on magnet strength and orientation.
• Adjust the potentiometer slowly while testing the digital output.
• Keep the sensor away from high-current wires and strong unwanted magnetic fields.
• The module detects magnetic presence; it is not a precision magnetic-field measuring instrument.
• Board layout, component markings and PCB colour may vary depending on available stock.