Membrane switches or membrane touch switches are printed electronic circuits acting as momentary electrical on/off switches for activating or deactivating circuits. When arranged in an array, they are collectively also known as a membrane keyboard. These switches are normally of the open type, requiring a push to close them, and immediately open when the pressure is released. That means the switch requires to be pressed, either with a finger or with an actuator, to make its two poles make contact and close the low-voltage, low-current switch. As soon as the pressure is released, the spring action of the membrane makes the poles separate immediately, and the switch returns to its original open state.
The membrane switch is most often screen printed onto a heat-stabilized polyester film base or substrate using conductive inks, typically of silver, carbon, and/or graphite. An overlay acting as the graphic interface is applied to the outer surface of the switch. The word membrane comes from the use of thin, pliable materials for the substrates. Sometimes, the substrates are also known as graphic overlay films.
Most membrane switches form an interactive part of devices and act as user interface, operator interface, or man-machine interface. They supplement other user interfaces such as slide, rocker, toggle, push-button switches, and display based touch screens. As with other switches and interfaces, the ultimate purpose of using a membrane switch is to facilitate an interface between the operator and the machine, enabling the operator to control or communicate with an equipment, machinery, or instrument.
A variety of industries use membrane touch switches. These include consumer appliances, aerospace and medical applications, industrial control systems, computer keyboards, touch-sensitive toys, cellphones, and many more. Used mostly with microprocessor-based control systems, and with the advantage of being more durable compared to other types of switches, membrane switches are being increasingly used in manufacturing and engineering industries. Additionally, membrane switches enhance the aesthetics of the human-machine interface.
As the membrane switch technology offers a sealed switch, it has become a reliable front panel solution for equipment requiring frequent cleaning or facing environmental concerns. Several industries prefer the use of membrane switches because of their reliability, and the ability to offer tremendous flexibility in aesthetics.
As a broad classification, there are two types of membrane switches—tactile and non-tactile types—based on the type of feedback the switches offer to their operators. While tactile membrane switches operate with a snap action that lets the operator notice immediately the switch has operated, the non-tactile membrane switch has a softer action, and offers no indication of the action of the switch. In most cases, placing an LED near the non-tactile membrane switch and linking it to glow along with the switch operation provides the necessary feedback.
Although this requires additional components, circuitry, and expense, non-tactile membrane switches find more favor in the industry because they require less force to operate, are sturdier, and more reliable than their tactile brethren are. In place of optical feedback, audible feedback may also be considered, commensurate with the electronic design of the equipment. It is also possible to use a mix of tactile and non-tactile membrane switches in the same panel.
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