A Brief Talk on Membrane Switches

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A Brief Talk on Membrane Switches [Copy link]

Membrane switches have the advantages of simple structure, beautiful appearance, good sealing, and long service life (up to more than 1 million times). They are widely used in various types of microcomputer-controlled electronic equipment.

Membrane switches can be divided into two categories according to the base material: soft and hard; according to the key type, they can be divided into two categories: tactile keys and non-tactile keys; according to the panel structure, they can be divided into flat type and concave-convex type.

The structural characteristics of the membrane switch determine that its working voltage is low (< 30V), the DC current it carries is small (< 300mA), and it has no self-locking function. It cannot directly control the load circuit. The membrane switch is a touch-on normally open switch. Under normal circumstances, the two contacts of the switch are disconnected. When an external force is applied to the contacts of the membrane switch, the two normally open contacts are instantly connected. After the external force disappears, the switch contacts return to the normally open state, so it cannot be used for alternating switching or interlocking. The membrane switch cannot be directly connected to a 220V circuit. During use, it needs to cooperate with the auxiliary circuit. The trigger signal (weak current) controlled by the membrane switch controls the auxiliary circuit, and the auxiliary circuit controls the main circuit (strong current) to achieve the function of weak current controlling strong current.

When the membrane switch is used in digital circuits, attention should be paid to overcoming the jitter phenomenon. The general method is to add a delay circuit and a monostable shaping circuit to the circuit to overcome the jitter of the membrane switch due to unstable state at the moment of connection and disconnection; you can also connect a 0.1uF filter capacitor between the switch contact and the ground to eliminate the jitter.