Touchpad : The Technology Behind the Square Input Device

Touchpad is a touch-sensitive input device, mostly used as a mouse replacement in laptops but other electronic instruments come with touchpad controls as well. Previously we have posted two interesting guides on Touchpad – one is Tips on using touchpad and the other is How to Enable Multiple finger gesture on any laptop with Synaptic touchpad. In this article, we will go through the technical part of Touchpad.

Principles of how a Touchpad works

Modern touchpad mostly uses the electrical capacitance , the position of the finger on the surface of the pad is determines the location of the cursor ( pointer ) on the screen. This can be done through various methods of construction of a Touchpad. Usually, the surface of a Touchpad consists of an array of vertical and horizontal electrodes, forming a grid. This grid is coated with an insulating protective layer, which ensures that the electrodes are not touched and the finger slides over the surface of the Touchpad. Below this, there is a circuit that continuously measures the capacitance between the electrodes. Coming now to the finger, which – because its water content – is also a kind of electrode in the vicinity of this arrangement, the capacitance between the electrodes is changed. The position on the Touchpad can be determined regardless of the strength of the pressure. After evaluating the information is forwarded, for example as a cursor position to the computer. This also explains why you can only control through a Touchpad with a finger, but not with thick gloves, pins or patches on the fingers, and therefore the strength of the pressure exerted no effect on the cursor movement.

As you drag your finger across the touchpad to move the cursor on the screen, most of the touchpad drivers evaluate a light tap of your finger and simulate a click. We can generate double click by double tap. If you hold after the second tap your finger on the touchpad, so you can select objects (icons) or (drag) to move.

Some manufacturers reserve one or more areas of the touchpad for frequently used functions such as scrolling. Touchpad with modern equipment can have multi-touch touch register supporting multiple finger gestures and transform them into software-application-specific commands.

Advantages and Disadvantages of Touchpad

Due to the compact design, touchpad devices sits directly into the casing of laptops or keyboards. Sweat or moisture on the finger affect the function of the touchpad, the compact location might be not so ergonomic.