How Joysticks Work

Joystick manufacturers have addressed these problems in a couple of different ways. One solution is to add a sensitiveanalog-to-digital converter chipin a specialized game adapter card or in the joystick itself. In this system, the converter spits out digital information directly to the computer, which improves the accuracy of the stick and reduces the work load on the host processor. These new joystick models can usually connect toUSB ports, which also improves speed and reliability (seeUSB接口的工作原理for details).

Another solution is to skip the analog potentiometer technology all together. Many newer controllers useoptical sensorsto read stick movement digitally.

In this system, the two shafts are connected to twoslotted wheels. Each wheel is positioned between twolight-emitting diodes(LEDs) and twophotocells(the graphic only shows one photocell, LED pair for simplicity's sake). Whenlightfrom each LED shines through one of the slots, it causes the photocell on the other side of the wheel to generate a small amount of current. When the wheel rotates slightly, it blocks the light and the photocell doesn't generate current (or it generates less, anyway).

When the shaft pivots, it spins the wheel, and the moving slots repeatedly break the light beam shining on the photocell. This causes the photocell to generate rapidpulses of current. Based on the number of pulses that the photocells have generated, the processor knows how far the stick has moved. By comparing the patterns coming from both photocells monitoring one wheel, the processor can figure out which way the stick is moving. This is the same basic system used in manycomputer mice. (Check out电子Circuits Reference Archivefor more information.)

One of the biggest additions to the world of joysticks isforce feedbacktechnology. In the next section, we'll find out how these joysticks let you experience the game on a new level.