What Is a Hall Effect Sensor?
A Hall Effect Sensor is a small electronic component that detects magnets. When a magnet comes close, it sends a signal to other devices, like an Arduino or an LED light. Think of it as a tiny switch that turns on whenever a magnet is nearby.
How Does It Work?
A Hall Effect Sensor has a tiny strip of conductive material inside. When current flows through it and a magnetic field is applied, a small voltage (the “Hall voltage”) appears and the chip turns that into a useful signal.
No magnet near the sensor → output stays at its normal level (for many digital sensors this is HIGH).
Magnet near the sensor → output changes (digital sensors usually go LOW; analog sensors shift up or down). Which pole (north/south) triggers it depends on the sensor’s orientation and type.
Applications of Hall Effect Sensors
Automotive: Crankshaft/camshaft position, wheel speed (ABS), ignition timing.
Proximity: Detecting open/close in doors or lids.
Speed: Counting rotations in fans, motors, or wheels.
Current sensing: Measuring current without direct contact.
Position: Joysticks, gear shifters, and robotics.
Tips & Troubleshooting
No output change? Check wiring (VCC, GND, OUT), flip the magnet, and adjust distance/strength.
Digital output stuck HIGH? Many Hall sensors have an open-collector/open-drain output and need a pull-up resistor.
Using an analog Hall sensor? Read it with an ADC and consider smoothing (averaging) if the signal is noisy.
This Tutorial is used in the following courses and lessons
Discover the fun of DIY electronics with your child in this self-paced, beginner-friendly online course, where parents and kids work together to build a rotating LED strip display!
Designed for those with no prior experience, this project-based course walks you through the entire process of assembling a spinning LED display that uses persistence of vision to create a glowing clock.
The goal of this lesson is to attach the sensor that measures the speed of the LED display. This is the last lesson where you’ll need to do any soldering!