Not all switches rely on moving parts to open and close a circuit. All switches do, in fact, control a circuit. While some of them contain moving parts, though, others use do not. Capacitive switches fall under the latter category. Rather than using moving parts to control a circuit, they use capacitance. Capacitive switches measure capacitance to determine when the circuit should be opened or closed.
#1) Based on Touchscreen Technology
Capacitive switches work in a similar way as capacitive touchscreens. They both generate a uniform electrostatic field, which they measure for changes in capacitance. Touching a capacitive switch with a bare finger — or any conductive object — will change the capacitance. The capacitive switch will then respond by opening or closing the circuit.
#2) Supports FPCs and PCBs
When ordering a capacitive switch, you can choose from either a Flexible Printed Circuit (FPC) or a Printed Circuit Board (PCB). FPCs are PCBs are both circuits. And like all circuits, they contain conductive pathways that can be opened or closed. FPCs are simply flexible, whereas PCBs are rigid.
#3) Requires Little or No Pressure
Unlike mechanical switches, capacitive switches require little or no pressure. In other words, you don’t have to forcefully press them. Just placing your finger on the surface of a capacitive switch is often enough to activate it. Capacitive switches work by measuring capacitance. As long as your finger is touching a capacitive switch, it will change the capacitance.
#4) Available With Backlighting
Capacitive switches are available with backlighting. You can find them with electroluminescent (EL) backlighting as well as light-emitting diode (LED) backlighting. Capacitive switches even support light guides. Also known as light guide film, light guides are designed to distribute the light of the backlighting. The backlighting system will produce light that travels through the light guides before being distributed out the top of the capacitive switch.
#5) Features 3 Sections
Most capacitive switches feature three sections. The top section is the graphic overlay. All of the capacitive switch’s buttons and legends are printed on the graphic layer. Below the graphic overlay is the circuit layer. The circuit layer, of course, consists of either an FPC or PCB, the former of which is flexible. Finally, there’s the backer layer. The backer layer holds the capacitive switch together. On some capacitive switches, the backer layer may contain adhesive. On others, it does not. Regardless, most capacitive switches feature a graphic layer, circuit layer and backer layer.