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How to connect a US1881 hall sensor to Arduino


  1. Introduction
  2. Specification
  3. Applications to use hall sensor
  4. PIN Assignment
  5. Example code
  6. Reference


A hall-effect sensor is a device that reacts to a magnetic field. The reaction known by everyone is that the sensor acting as a digital switch "turns on" in the presence of a strong enough magnetic field.

The US1881 is an integrated Hall effect latched sensor. It means that once it is triggered it latches and will not unlatch until a magnetic force of reverse polarity and strength is sensed. So if the north pole of a magnet turned it on, the south pole of a magnet is then needed to turn it off.

Holding a magnet near the sensor will cause the output pin to toggle. This makes for a robust presence sensor. If a magnetic flux density larger than threshold Bop, Digital Output is turned on (low). The output state is held until a magnetic flux density reversal falls below Brp causing Digital Output to be turned off (high).

Playing with magnetic field is one of the most interesting topic in Arduino building.

Interesting facts


  • 3.5V to 24V DC operation voltage
  • Low current consumption
  • Temperature compensation
  • Wide operating voltage range
  • Open-Collector pre-driver
  • 50mA maximum sinking output current
  • Reverse polarity protection
  • Lead Free Package: TO-92

US1881 hall effect sensor

Applications to use hall sensor

  • Automotive, consumer and industrial
  • Solid state switch
  • Brushless DC motor commutation
  • Speed detection
  • Linear position detection
  • Angular position detection
  • Proximity detection

PIN Assignment

  • Connect pin 1 of the switch to the Arduino 5V supply
  • Connect pin 2 to Ground (GND)
  • Connect pin 3 to Arduino Digital pin 2

How to connect hall sensor to Arudino

US1881 hall sensor pin

Example code

int hallPin=2;
int statePin=LOW; 
void setup()

void loop()
if (Serial.available())
if( statePin==HIGH)
else if(statePin==LOW)


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