Photo credit: Miller Dial
Still trying to wrap your head around the concept of membrane switches and their method of operation? This otherwise simple electronic switch plays a key role in the application of numerous modern-day devices. From the TV remotes and watches to air conditioners and microwave ovens, membrane switches are used in a wide variety of devices. But how exactly do they work? This is a question that we’re going to tackle head-first in today’s blog post.
Membrane Switches: The Basics
A membrane switch is essentially an electrical switch that’s used for turning on and off a circuit. Subsequently, this allows the operator to communicate with the device, issuing commands and/or performing other operations. Membrane switches are closely related to keypads, toggle switches and keyboards in the sense that they are all interface utilities. The operator presses the membrane switch when he or she wants to control the device.
Membrane Switch vs Mechanical Switch: What’s The Difference?
Some people assume that membrane switches are the same as mechanical switches. While they share some similarities in terms of how they function and they are designed for, there’s a key difference between them that shouldn’t go unnoticed. Mechanical switches are normally made of a combination of copper and plastic parts, with the copper being conductive and the plastic being resistive. Membrane switches, on the other hand, are typically printed on either Polyethylene terephthalate (PET) or Indium tin oxide (ITO). When used for screen printing purposes, the ink within a membrane switch usually contains either copper, silver or graphite, all of which are conductive and therefore able to pass electrical currents.
How Membrane Switches are Constructed
Construction of membrane switches varies depending on the manufacturer’s specifications and the exact type of switch being constructed. In most cases, however, it consists of at least four layers, with the top-most layer serving as the graphic interface/display. Underneath this interface is a printed circuit, which is often made of copper and polymide. All of the layers are constructed using pressure-sensing adhesives and held together with a keyboard housing or other mechanical components.
Membrane Switch Back Lighting
We’ve talked about this before on the Nelson Miller blog, but it’s worth mentioning again that membrane switches have three different back lighting methods: light-emitting diodes (LEDs), optical fiber, or electroluminescent (EL) lamps. The purpose of these lights is to illuminate the interface so the operator can see what or she is doing.
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