What’s a touch switch?

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Tactile switches are manually controlled electrical contacts used for power control in homes and industrial applications. They can be capacitive or resistance-based and are used for safety and convenience in applications such as doorknobs and elevator floor selectors. Electronic switches have a longer life than ordinary switches, which can vaporize due to the arc. Tactile switch kits have an integrated circuit that senses touch and actuates a power switch or semiconductor relay.

A tactile switch is a momentary or latching electrical contact that is manually controlled by touching it. It is used in many home power control applications for convenience. In industrial applications, tact switches are usually used with special considerations for safety.
Switches have been around for as long as electricity has existed. The principle involved is to make or break the electrical circuit. In high current applications, a tact switch is used along with relays which further activate the higher capacity contacts. The touch sensitive tactile sensor is very useful for safety switches and there is fixed cutting equipment designed to stop almost instantaneously when human touch is detected.

While electronic switches are popular due to their longer life, frequently used ordinary switches have a shorter life due to the arc, which gradually vaporizes the switch contacts. Electronic switches can use semiconductor circuits that require very little transient power through the switch. An open switch and a closed switch have no power dissipated in them. The transient power in a normal circuit breaker can be significant depending on the load. For example, capacitive loads and cold resistive loads can cause large transient currents.

Capacitance tact switches utilize the additional capacitance of the switch user’s body. When a person touches this type of touch sensor, the increased capacity is detected and the corresponding result is obtained. Elevator floor selectors are a common use for capacitive touch switches. With the lightest touch, a passenger is able to set the desired floor.

A resistance tactile switch uses two electrodes to sense the resistance of a human finger to an open circuit. Its construction is similar to a raindrop detector. A decrease in resistance can produce a change in voltage level relative to a reference. The result is a durable switch that does not wear out due to the very low current required to sense a human finger.

Tactile switches are used for safety and security applications. Doorknobs can be wired to sense if they have been touched. Light switches and dimmers can use tactile switches for added convenience. A tactile switch kit usually has an integrated circuit with analog circuitry that senses touch and then actuates a power switch or semiconductor relay. The sensing circuit, if not likely designed, may operate erratically when current surges and interference from electrical loads are present.




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