KY-025 Reed Switch Module

The KY-025 Reed Switch Module is a small electrical switch operated by an applied magnetic field, commonly used as proximity sensor.

The module has both digital and analog outputs. A trimmer is used to calibrate the sensitivity of the sensor.

Compatible with Arduino, Raspberry Pi, ESP32 and other microcontrollers. For digital output only use the KY-021 mini reed switch.

KY-025 reed switch module fritzing part
Arduino KY-025 Reed switch module

KY-025 Specifications

This module consist of a 2x14mm normally open reed switch, an LM393 dual differential comparator, a 3296W-104 trimmer pontetiometer, 6 resistors, 2 LEDs and 4 male header pins.

Operation Voltage3.3V ~ 5.5V
Board Dimensions1.5cm x 3.6cm [0.6in x 1.4in]

Connection Diagram

Connect the board’s analog output (A0) to pin A0 on the Arduino and the digital output (D0) to pin 3.

Connect the power line (+) and ground (G) to 5V and GND respectively.

A0Pin A0
D0Pin 3
Arduino KY-025 connection diagram

KY-025 Arduino Code

In this Arduino sketch we’ll read values from both digital and analog interfaces on the KY-025, you’ll need a magnet to interact with the module.

The digital interface will send a HIGH signal when a magnetic field is detected, turning on the LED on the Arduino (pin 13).

On the other hand, the analog interface will return a HIGH numeric value when there’s no magnetic field present and it’ll drop to zero when a magnet is near.

int led = 13; // define the LED pin
int digitalPin = 3; // KY-025 digital interface
int analogPin = A0; // KY-025 analog interface
int digitalVal; // digital readings
int analogVal; //analog readings
void setup()
  pinMode(led, OUTPUT);
  pinMode(digitalPin, INPUT);
  //pinMode(analogPin, OUTPUT);
void loop()
  // Read the digital interface
  digitalVal = digitalRead(digitalPin); 
  if(digitalVal == HIGH) // if magnetic field is detected
    digitalWrite(led, HIGH); // turn ON Arduino's LED
    digitalWrite(led, LOW); // turn OFF Arduino's LED
  // Read the analog interface
  analogVal = analogRead(analogPin); 
  Serial.println(analogVal); // print analog value to serial

Use Tools > Serial Plotter on the Arduino IDE to visualize the values on the analog interface, use a magnet to trigger the switch.

KY-025 arduino serial plotter output


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1 thought on “KY-025 Reed Switch Module”

  1. Kann man das Modul auch für elektromagnetische Felder nutzen und welche Reichweite hat das Modul?