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Mechanical Buttons and Switches Address Critical Design Requirements

Touchscreens and membrane switches are useful for visual and low-profile control panels. However, some applications require designers to emphasize safety, ease of access, the switching of high voltages or current, a known configuration at power up, or robustness. For such situations, mechanical switches and buttons are often ideal, but designers need to choose carefully.

There are numerous types of mechanical switches with variances in shape, style, size, function, power capabilities, and mechanical behavior. This article will help designers sort through the selection parameters and how to best apply some of the latest devices.

Which switch or button?

To decide which switch is appropriate, first determine the requirements for the system. To find a mechanical switch for an application, first find the switch form factor that fits the ergonomic and physical needs, then choose a switch with the appropriate electrical and environmental specifications that fits the form factor.

Emergency stop

An obvious example of safety is the emergency stop button. Many industrial systems absolutely must have a big red or orange button with the words “Emergency Stop” in large, reader friendly letters. This button must be in an obvious and easily reachable position, must be easy to depress, and there must be clear tactile feedback to indicate the switching function has been completed. Failure to meet this criteria can be hazardous in some industrial environments.

An excellent solution for this application is the Lumotast 16 Emergency Stop pushbutton from RAFI USA. This NO (normally open) button has the familiar big, conical mushroom shaped button (Figure 1). When an operator slams their hand down on this button, the two silver contacts connect, latch, and remain in contact even when the operator’s hand is removed. To reset the button to the open position, the mushroom head is rotated in either direction.