Characteristic of Membrane Switches

Simple structure, attractive appearance, air-tight and durable (≥1 million closures) etc are the characteristic of Membrane Switches. They are widely used in electronic equipments of various types. From different substrate, membrane switches can be soft or hard. The hard type consists of non-tactile feel and tactile feel depending on the structure of the keys whether they are flat or embossed. The structure of the membrane switches contributes to their low operational voltage (<30v), carrying light direct current (<300mA) and no self-locking function. They cannot directly control the main circuit. Membrane switches are open circuit touch switches. Under normal circumstances, the key contact and the circuit are at a distant. When external force is applied onto the key, the circuit is connected instantly. When the external force is released, the key restores to its original open position. Therefore, they cannot be used on alternate or interlock function. They cannot connect directly to 220V circuit and require an adaptor to do so. The trigger signal (weak) from the membrane switch controls the adaptor which in turn controls the main circuit (strong) performing the function. When membrane switch is used for digital circuit, attention should be paid to overcome the jittery phenomenon. Generally, adding a delay circuit and a single steady circuit in between to overcome the jitter caused by the on and off activity. It can also be resolved by connecting a 0.1uF capacitor filter.