This section provides overview, applications, and principles of touch switches. Also, please take a look at the list of 4 touch switch manufacturers and their company rankings.
A touch switch is a switch that switches ON/OFF when a person or object comes into contact with its sensing element.
Some are operated by a person's light touch, such as in lighting and home appliances, while others are installed inside machines as sensors for object detection and positioning.
There is a wide range of touch switches, and when selecting one, it is necessary to select the one that best suits the purpose, taking into consideration factors such as convenience, durability, the strength of the force required for actuation, the direction in which the force is applied, and the environment in which it is installed.
Touch switches that we often see in our daily lives are mainly intended for human operation. These include electrical appliances in the home and push buttons on elevators and automatic doors in shopping malls. Recently, capacitive touch switches that are activated by simply touching the screen, such as smartphones and touch panels, have become mainstream.
Touch switches are also widely used inside industrial robots and machine tools. At hazardous sites such as factories, touch switches also serve as safety devices to prevent workers from entering or being pinched and to detect broken tools.
The principle of how touch switches operate can be roughly divided into the following two types.
Capacitance is generated when a finger (conductor) approaches the sensing element (electrode). The capacitive sensor detects this and outputs an ON/OFF signal. Since the capacitive touch switch is activated when a conductor comes close to it, glass or acrylic plates can be attached to the sensing area. Since it does not require direct contact with the machine, it does not deteriorate even after repeated use and has higher durability than the conventional pushbutton type.
This is a touch switch that is activated when a certain amount of pressure is applied to the sensing section. Generally, these switches are designed to respond only to a push-in force parallel to the axis of the switch, but there are also ball-bearing types that can respond to a force tilted against the axis. In the pressure-sensitive type, the operating point at which the switch is activated, the signal switching point, and the maximum stroke is all set in detail. Therefore, the pressure-sensitive type is suitable for applications that require high precision, such as positioning on the micron order.
Capacitive touch switches calculate the touch position by detecting the change in capacitance generated by the proximity of the fingertip and the sensing element through which electricity flows. There are two types of detection methods, surface type and projection type, and they are used according to cost and application.
The surface type capacitance method consists of a conductive film that serves as the sensing element and four electrodes placed at the four corners, and electricity flows from the electrodes at the four corners to the conductive film, generating low pressure and uniform static electricity across the entire conductive film. The touched position increases the capacitance and causes a change in the conductive film. The touch position is detected by calculating the change in capacitance at the touch position using the conductive film and electrodes at the four corners of the panel.
While the simple structure is advantageous in terms of cost, it also makes multi-touch difficult. It tends to be used for inexpensive products and large displays that do not require multi-touch.
The projected capacitive method consists of a layer of multiple electrodes arranged in large quantities and a layer of substrate on which an integrated circuit (IC) that performs arithmetic processing is mounted. The touch position is detected by calculating the changes in capacitance that occur at the touched position using the integrated circuit (IC).
Multiple electrodes and ICs enable accurate multi-touch detection and are widely used in smartphones and other mobile terminals. To enable multi-touch detection on large displays, the number of electrodes must be further increased due to electrical resistance.
Capacitive touch switches, which are often used in smartphones, may not operate properly due to external currents or changes in fingertips.
Static electricity generated by the friction of clothing can cause changes in the electrode or electric membrane, resulting in temporary touch unresponsiveness.
As the moisture content of the fingertips decreases due to dryness in winter, it becomes harder for electricity to pass through. As a result, the change in electrostatic capacitance becomes smaller, resulting in a malfunction that slows down the touch response.
*Including some distributors, etc.
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