KY-025 Reed Pipe Magnetron Magnetic switch Module


The Reed Switch Module provides a logic output when a magnetic field comes near or is removed.

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The Reed Switch Module provides a logic output when a magnetic field comes near or is removed.


  • Outputs logic HIGH or LOW depending on if magnetic field is near
  • 3.3 and 5V compatible

This is a SPST Reed Switch module.  Reed switches are mechanical switches which are a activated by a magnet when the magnetic field pulls the switch contacts together.  Real world uses include applications such as home security where a reed switch is placed in proximity to a magnet when a window is closed.  If the window is opened, the magnet moves away from the switch that causes it to change states which can then be detected by an MCU.

The module has a SPST reed switch with NO (Normally Open) contacts until a magnet comes into close proximity to the glass envelope and then the switch contacts are closed.

The D0 output is normally LOW and will transition to HIGH when a magnet comes near.  The A0 output is normally HIGH and will transition to LOW when a magnet comes near.

There are 2 LEDs on-board.  A red LED lights when power is applied.  A second red or green LED lights when the reed switch is activated.

Module Connections

There is a 4-pin header on the assembly for making connections.  The ‘A0’ pin is a misnomer in this application as it is a digital output that is the inverse of the ‘D0’ pin.

1 x 4 Header 

  • A0 = Digital output active LOW. connects to digital input on MCU
  • GND / G  = Ground
  • ‘+’ = 5V
  • D0 = Digital output active HIGH. Connects to digital input on MCU


These modules are useful for evaluating basic reed switch functionality.

Since the sensor is a mechanical switch that inherently has 2 states ON/OFF, so what is normally an analog output (A0) on these types of modules is still just a digital output. For the same reason, the potentiometer has little effect on the output.  That output does provide the complementary output of the D0  output which may be useful in some applications such as if the module is being used to directly drive a relay or something similar.

If it is desired to measure the strength of a magnetic field rather than detect its presence, the Analog Hall Effect sensor is a better option to consider.

The glass envelop enclosing the reed switch sensor can be broken if twisted, so use care if adjusting the position of the sensor.


  • Inspected
  • Basic output verified
  • Packaged in a resealable ESD bag for protection and easy storage.


  1. None


Operating Ratings
 Vcc 3.3 – 5V
Dimensions L x W (PCB) 36 x 15mm (1.4 x 0.60″)
L x W (PCB w/ sensor) 42 x 20mm (1.7 x 0.8″)


Package Include:

1x KY-025 Reed Pipe Magnetron Magnetic switch Module


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