How to Use Hall Effect Sensors

Developed in the 1950s and 1960s, modern Hall Effect sensors are a convenient, economical way to detect position in mechanical systems. The effect, first discovered by Edwin Hall in 1879, produces a voltage in a material proportional to the strength of a nearby magnetic field. Using it, you can determine the position of a magnet by the voltage you get from the Hall Effect device. Combining them with microcontrollers has led to uses in many areas, from toys, to cars, to industrial machines.

Difficulty:

Moderately Challenging

Instructions

Things You'll Need

• Hall Effect sensor Power source for sensor Sensor interface Microcontroller Small permanent magnet Multimeter

1. Mark a location on an object you want to sense. The magnet will be mounted here.
   Example: To sense a door closing, make a mark near the door's edge.

2. Attach the Hall Effect sensor to a stationary object so that the magnet will pass within a few millimeters of the sensor.
   Example: Attach the sensor to the door frame near the mark you made in step 1.

3. Align and mount the magnet where you marked in step 1. Point the magnet so one of its poles is toward the sensor.

4. Wire the power source to the sensor. It should have (+) and common input terminals clearly marked. A typical sensor runs on between 4.5 and 8 volts at 5 milliamps DC.

5. Test the sensor by measuring its output with the voltmeter. Disconnect the voltmeter when the test is done.
   Example: Connect the voltmeter's positive lead to the Hall Sensor output terminal, and the negative lead to the Hall Sensor supply common. When the door is closed, the sensor's output voltage should be close to the supply voltage. When it's open, it should drop to a smaller value, either zero or a nominal voltage, depending on the sensor.

6. Connect the Hall Effect sensor's output and common leads to the sensor interface.

7. Connect the sensor interface to external equipment, such as a microcontroller.
   Example: Connect and program the microcontroller to increment and display a counter when the door is opened.

Tips & Warnings

• Refer to the sensor's data sheet for alignment tips. Take care to avoid placing other strong magnets near the Hall Effect sensor; it might give false readings.

References

• Hall Sensor Product Data
• Hall Effect Sensors -- Automotive Applications

Resources

• Hall Effect Explained
• Hall-Effect Gaussmeter Project