Touchpad

The term touchpad [ ˌ tʌtʃ Paed ] or touch pad called a touch-sensitive surface that can be attached, for example as a mouse and keyboard replacement in laptops mostly below the keyboard.

Even with electronic musical instruments and effects processors come as a touchpad controls are used. In addition to the approximately square design to control in two dimensions there are often one-dimensional working ribbon controller that operate on the same principle.

There are different modes of operation.

Principle of operation

Modern touchpad determined from the electrical capacity, the position of the finger on the pad's surface and thus determine, for example, the location of the cursor ( pointer ) on the screen. This can be done by various methods of construction. Typically, the surface is composed of an array of vertical and horizontal electrodes which form a lattice. This grid is coated with an insulating protective layer, which ensures that it does not affect the electrodes and the finger slides over the well surface. Below this grid is a circuit that continuously measures the capacitance between the electrodes. Coming now to the finger - by its water content - also a kind of electrode is in the vicinity of this arrangement, the capacitance between the electrodes is changed. Thereby, the position can be determined irrespective of the magnitude of the pressure. After evaluation of the information is forwarded, for example, as a cursor position on the computer. This also explains why you can take the mouse with your fingers influence, but not with thick gloves, pins or patches on the finger, and so the strength of the applied pressure does not affect the cursor motion.

When you swipe your finger across the touchpad to move the cursor on the screen. The most touchpad drivers evaluate a light tap of your finger and thereby simulate a click. A double is produced consistently, by double-tapping. If you hold after the second tap your finger on the touchpad, so you can select or move objects (symbols ) ( pull ).

Some manufacturers reserve one or more areas of the touchpad for frequently used functions, such as scrolling. Modern touchpad devices with multi-touch touch can register with multiple fingers and transform a software point of application-specific commands. Thus, a slight tap with two fingers to call a context menu or the " Wipe " with three fingers move to the next image. In this case, the strength of the pressure can be evaluated in order to influence the speed of scrolling.

The technology of the touch pad can be applied with a pen to draw and paint on the computer. Here, the pressure of the pen is crucial, as is so decidedly analogous to conventional techniques over the thickness of the line. What is interesting is that rare pads measure the compressive force rather than the pins themselves Refer graphics tablet.

See also: touch screen, signature pad

Benefits

The use of the touchpad makes it possible to dispense with additional input devices such as a mouse. Due to the compact design touchpad devices can be directly integrated in the housing of laptops or keyboards. Its proximity to the keyboard allows for faster access to the cursor, as for example the handle to the mouse, in which the hand placed for a longer distance only and the cursor must be repositioned. Another important advantage that is about for the usability in public institutions such as libraries and lecture halls of significance is considerably lower compared to the use of a mouse noise during operation, when exhausted the option of finger pressure on the touchpad for easy clicks will. Also, no further requirements such as additional flat surfaces or wiring (mouse, external trackball ), radio links or power sources ( wireless mouse ) must be fulfilled, which reduces the overall weight and makes mobile use of these devices.

Disadvantages

When the touchpad is often found no third button. However, it is necessary in some applications. Sometimes pressing both keys from the driver is interpreted as a middle button. Fix the problem creates a driver update, which brings a recognition of the second or third finger. Otherwise, the only possibility is to use an external mouse.

It is often bothersome when the touchpad located below the keyboard - especially if you are used to typing with one hand. The palm then generated on the touchpad completely voluntary movements and clicks. Some manufacturers position the touch pad, therefore, in a small bowl and smack in the middle of the keyboard ( see picture above), so that one does not touch it in normal two-handed typing. Is reinforced, the disadvantage for models that have a particularly large or poorly positioned touchpad. As a workaround, you can disable the touchpad and connect an external mouse to the notebook instead. Many newer notebooks, there is a predefined key combination or an extra key to easily enable the touch pad to ( de - ). Also, there are now touchpad drivers that are capable because of the very different behavior of the palm and fingers, to distinguish them from each other and thus to ignore a possibly stored on the touchpad hand.

From the property of the touchpad that they can only be operated with the naked finger, but do not use a stylus or gloved there is a serious drawback especially for people with prosthetic hands, as they have no way to activate the panels and thus practically the use of most laptops are excluded. In this sense, capacitive systems form a hurdle in terms of accessibility. Electrically conductive gloves (eg Agloves ) offer remedy, heat insulating even in cold temperatures.

Another disadvantage is that sweat or moisture on the finger impair the function of the touchpad, so that can make typing difficult, for example, at high temperatures. In addition, the touch pad for fast accurate inputs as they are needed, for example in games, ill-suited.

Operating concepts / gestures

Especially by the possibilities of multi- touch pad expands the vocabulary regarding the operation:

Wipe ( wipe)

Horizontal and vertical movement with more than one finger can be interpreted, instead of a mouse movement as an additional function ( for example zurück-/vorblättern ).

Tap and Hold ( tap & hold )

Double-click without lifting the finger after the second click and subsequent movement can be interpreted depending on the touchpad as a single click, followed by drag- n-drop. Without this feature, an operable solely on the touchpad drag- n-drop function would not be possible.

Scrolling ( scroll)

Drag with two fingers simultaneously on the touch pad up or down is interpreted by many manufacturers as scrolling. It can also be simulated by a double-click with two fingers of the pressure of the " mouse wheel button ".

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