How Do Capacitive Switches Work?

Jun 15, 2022

Ever wonder how capacitive switches work? Even if you’ve used them, you may not be familiar with their underlying mechanics. Like all switches, capacitive switches are designed to control a circuit. You can touch them to open or close a circuit, such as the circuit to a light fixture or industrial machinery. Capacitive switches, though, don’t feature any moving parts. They are non-mechanical switches that use a touch-based method of operation.

The 3 Parts of a Capacitive Switch

Capacitive switches feature three main parts: a graphic overlay, circuit and backer. The graphic overlay is the top layer that, as the name suggests, features the switch’s graphics. It’s the part of the capacitive switch that you can see and touch.

Below the graphic overlay is the circuit. Capacitive switches may feature either a Flexible Printed Circuit (FPC) or a Printed Circuit Board (PCB), the former of which can bend and flex. Finally, capacitive switches feature a backer. The backer is the bottommost layer that holes the capacitive switch together.

How Capacitive Switches Control a Circuit

Capacitive switches control a circuit by measuring changes in capacitance. They work by applying a uniform voltage to the graphic overlay while simultaneously measuring this voltage for changes. If you touch the graphic overlay with a finger — or if you touch it with any other electrically conductive object — the voltage will change. Your finger will absorb some of the voltage. The capacitive switch will then register this change in capacitance as an input command, in which case it will open or close the circuit.

There are no moving parts in capacitive switches. Capacitive switches are known as touch switches because they work via touch. You don’t have to physically press them. As long as your finger is touching the graphic overlay, the capacitive switch will open or close the circuit.

Capacitive touchscreens, of course, use a similar method of operation. They apply a uniform voltage to the top layer, which they constantly measure while looking for changes in capacitance. The difference is that capacitive touchscreens feature an integrated display, whereas capacitive switches may or may not feature an integrated display.

In Conclusion

There are different types of switches. Capacitive switches are circuit-controlling devices that work by measuring changes in capacitance. If they detect a change in capacitance, they’ll open or close the circuit. Without any moving parts, capacitive switches typically last longer than mechanical switches, the latter of which have moving parts.

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