1 Introduction

In joystick applications such as game controllers, remote controllers or gimbal camera, a sensor component or device is required to detect the movement of the joystick. The sensor converts the original mechanical displacement signals into electrical signals and communicates with the host MCU to update the sensing electrical signal. Using the information from the sensor, the MCU then provides the user control of the larger system.

Both the 5D switch or carbon film resistor joystick have been used as direct mechanical contact detection methods in joystick applications.

A 5D switch sets 5 mechanical triggers around the joystick. When the mechanical structure is pressed or triggered by the movement of the joystick, a continuous high-level signal is output from the switch to indicate the direction of movement. This method can only output high or low signal, cannot detect the tilt angle or movement speed to provide more precise detection.

Carbon film resistor joysticks change resistance for each axis relative to the movement of joystick. The carbon film has a good linear response, but this requires a larger mechanical package and regular use can result in resistance changes that cause joystick drift problems that limit the product life.

Figure 1-1 Carbon Film Resistor Joystick and 5D Switch Joystick

Recently, there has been increased interest in moving away from mechanical contact based designs to Hall-effect based designs which offer contact free position sensing and help resolve drift concerns that arise over the lifetime of the product. Depending on the joystick design, both standard 1D (single axis sensitivity) and 3D (x,y,z sensitivity) can be used for this purpose.

A 3D Hall-effect sensor integrates three Hall elements into one chip with a single plastic packaging, provides an ultra-small size and low cost while maintaining a good performance design. The size of TI newest generation 3D linear hall sensor TMAG3001 can achieve a packaging size of 0.83mm x 1.32mm.

Configuration of joysticks using Hall-effect sensors is explored in more detail in Joystick and Lever Design With Hall-Effect Sensors, application note.

Figure 1-2 TI TMAG3001 EVM

A single 3D linear Hall-effect sensors can be used in joystick application to replace carbon film or 5D mechanical switch. The Hall-effect elements are arranged orthogonally to each other which allows for detection of the complete magnetic field as explained in Introduction to 3D Hall-effect sensors. Using angle calculations output by the TMAG3001 integrated CORDIC engine, the host MCU can determine the position of the joystick quickly. In addition to the ability to track the XY angle input, the use of a 3D Hall-effect sensor enables button press detection by capturing a step in magnitude of the magnetic field vector.