Joysticks

Joysticks translate the physical movement of people’s hands into information that computers can read -- codes of zeroes and ones. It is found in a lot of machines like computers, fighting jets and wheelchairs, but is most commonly used in game consoles.

Put simply, a joystick works like an electrical switch. The basic joystick design has a stick that is attached to a plastic base. Inside the base is a circuit board that rests directly under the stick and is composed of printed wires that connect to several contact terminals. These contact points are linked by ordinary wires to the computer. Printed wires are circuits made up of smaller broken circuits that upon the movement of the stick, carry electrical information from one to another. A tiny metal button covers each broken circuit so that when the stick is moved in any direction, it presses a particular button against the circuit board and closes the circuit, thus, completing the link between two wire sections. A closed circuit communicates signals from the joystick to the computer. This simple joystick design can only translate four directions of movement (up, down, left, right).

A more complicated joystick design allows for a full range of motion. It consists of the same basic features but instead of housing a circuit board, inside the base are two rotatable, slotted metal shafts placed perpendicular to each other. One represents the X-axis and the other, the Y-axis. Moving the stick from left to right pivots the X-axis, and up to down the Y-axis. Tilting the stick diagonally rotates both shafts. Just like basic geometry, it is on these axes that coordinates are pinpointed to tell the exact position of the stick. Each analog joystick has two potentiometers (variable resistors) with each connected to a respective shaft. These monitor the movement and determine the location of the stick.

Each potentiometer consists of a resistor, in the form of a curved track and a movable contact arm. Since a potentiometer is attached to each of the rotatable shafts, moving the shaft also moves the contact arm. For example, if the stick is moved towards the user, it will turn the contact arm to one end of the track and onto the other end if tilted away from the user. Moving the contact arm along the track increases or decreases the resistance acting on the current flowing through the circuit. Current will experience maximum resistance if contact arm is away from the input terminal and vice versa.

All images and flash are from http://electronics.howstuffworks.com/joystick.htm. (accessed August 6, 2009).

Reference: http://electronics.howstuffworks.com/joystick.htm (accessed August 6, 2009)