Articles

Controllers

Controllers are the essential part of any touch-sensitive screen. They ensure support of detection function and determine coordinates of a control point on a touch-sensitive monitor.

So what is a controller? The controller is a small card that connects a touch-sensitive monitor with a personal computer. Controllers ensure the fastest known response to touch and also possess a very high reliability index.

The controller is usually installed inside the monitor for integrated monitors or is housed in a plastic case for external touch add-on. Such controllers can connect either to a Serial/COM port (PC) or to a USB port. There are also specialized controllers that work with DVD players and other devices.

Controllers can be of different types but the principle of their operation is the same. Controllers differ depending on the type of a touch-screen they are compatible with. All sensor monitors differ depending on the operation technique. Nowadays there are many various systems differing from each other, but if you have a closer look at them you will notice that their diversity traditionally comes to several widely spread types of touch-sensitive screens. There are four of these main technologies: Resistive, Infrared, Capacitive and Surface Acoustic Wave (SAW).

In short, the essence of working of any controller consists in the following. The controller receives a signal of the touch-sensitive screen, converts received signal into digital coordinates of the touch point and then sends obtained information to your computer.

Let us in more detail consider the operating principle of the whole sensory system by the example of capacitive touch-sensitive screen and its components.

The sensing element of a capacitive touch-sensitive screen represents glass, the surface of which is covered with thin layer of transparent conductive coating. Electrodes are placed in every corner of the screen. They evenly distribute direct current low voltage along the screen surface, thus creating an even electric field. A touch to the screen causes disturbance of field homogeneity and occurrence of small currents through all electrodes as well as a finger and body of a person. Transparent coating possesses a certain resistance so the current that goes through each of the electrodes, is proportional to this resistance, i.e. connected with the touch point. The controller can measure either these points or alterations in generators oscillation frequency, if capacitive parameters for each of the screen angles set the oscillation frequency for the corresponding generator. After obtaining the necessary data, the controller makes measurements and then sends the results to the control program for its further processing.

The following controllers are the most well-known and acknowledged in the world: General Touch 4001S controller, General Touch 4001S-5041 controller and General Touch 4001U controller.

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