Hall-Effect Joysticks: How do they work and how will they eliminate joystick drift?

You may have experienced this on your controllers before: your character starts moving with no input, your aim creeps upwards or to the side while trying to stay still, your controller seems to be possessed by a ghost that constantly wants to move ever-so-slightly to the left. This phenomenon is referred to as “joystick drift” and is exceedingly common in gaming controllers. It isn’t because you dropped the controller or tossed it across the room after a particularly intense gaming session; rather this is a design flaw inherent to the mechanism behind most controllers on the market: the potentiometer.

A potentiometer is simply a variable resistor that forms a variable voltage divider. This might not mean much if you’re unfamiliar with electrical components and theory. All you need to know is that the voltage divider output changes depending on the stick's position. Your controller reads this voltage and translates it to a coordinate. Say 0.1V means “down” and 0.9V means “up”. Center might be defined as 0.5V. Potentiometers are not super accurate so these calibrations are usually done at the factory, meaning that the controller always expects 0.5V to be the center.

As you move your joystick, it moves a conductive wiper against a resistive contact pad, which varies the resistance, and thus output voltage. You move your joystick up, and the resistance and output voltage increase. You move the joystick down, and the resistance and output voltage decreases. There are two potentiometers on each stick for horizontal and vertical movement, so your controller reads the voltages from both to determine where you want your character to go.

The problem arises when these resistive contact pads get worn down over time due to friction. You can imagine how many repetitions this system gets after just an hour of gaming. Every time you move your joystick back and forth these contact pads lose a minuscule amount of material. Over time, this alters the resistance of the contact pads. Once the resistance value of the neutral position changes—boom, joystick drift. Because your controller is reading a different voltage than expected while stationary, it interprets it as joystick input, resulting in your character slowly walking off that cliff while you get a snack.

Here’s where Hall-Effect sensors come in. Where the potentiometer joystick uses a resistive pad and wiper to vary the voltage, a Hall-Effect joystick uses a contactless alternative: magnets.

In a Hall-Effect joystick, the conductive pin (the wiper) is replaced by a magnet, and the resistive contact strip is replaced by a flat conductor (Hall Element) that is sensitive to magnetic fields.

As electrons flow through this material, the magnetic field effectively “pushes” them to one side of the conductive material or the other depending on the field polarity.

When the joystick is moved, the sensor detects which side electrons were pushed to in the conductive material and interprets this as movement. This all happens without physical contact eliminating any chance of friction wear to the sensor!

Voila! A contactless joystick input method—one that can drastically increase the lifetime of your controller and is far less prone to drift. Whereas a potentiometer joystick is nearly guaranteed to fail eventually, a Hall-Effect joystick could hypothetically last the entire lifetime of the controller.