Design of Two Circuits for Membrane Switch

1. Membrane switch public bus method

The design of the membrane switch circuit can be roughly divided into two types, one is the common bus method. One end of a certain contact of each membrane switch is directly connected by a bus, and the other end of the membrane switch leads out several independent lines. This method is common in mechanical discrete membrane switches. It has the advantage that each switch directly controls a dedicated function, in which case the resulting signal does not require further decoding in the post circuit. However, membrane switches are generally only suitable for occasions where there are not many function keys. When the number of switches increases, it is not beneficial enough. At the same time, the number of leads will increase a lot, and the total number of outlets is greater than the number of switches.

2. Membrane switch x-y moment arrangement method

It is a matrix composed of "rows" and "columns". In the direction of the same row (that is, the x-direction), no matter how many switches are, one end of the switch is led out by a common line. Similarly, in the direction of the switch (that is, the y-direction), a common line is used to connect and lead out to the other end of the switch, regardless of the number of switches, so that the arrangement of the matrix can form the x-y combination of any switch. It is often necessary to set the decoding in the subsequent circuit before it can control each special function. However, this is not that difficult in the logic circuit.

As a guidance document for the process production, the design of the membrane switch circuit should strive for the matrix in the design, and the membrane switch can be consistent with the actual key position. This can reduce the trouble of rearranging the wiring during production. At the same time, it is also conducive to inspection and avoiding errors. The best way to express it is to directly mark the function content of each key in the matrix when drawing the circuit diagram, and the membrane switch should be consistent with the actual position of the key, and then number the leads in the order from left to right, so that it is clear at a glance. There is no need to list the wiring relationship table.

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