Real Pushbutton Switches Coming Back Strong

What you’ll learn:

Why designers are rethinking their extreme reliance on touchscreens for the user interface.
The features that are especially desired in tactile switches, in addition to basic contact closure/opening.
New switch families provide needed tactile-switch attributes.

Touchscreens are everywhere, although the term “touchscreen” is a somewhat misleading misnomer as they are actually “look first, then touch” screens. Designers prefer them as they offer flexibility, dynamic reconfiguration, adjustability to different use scenarios, low BOM cost, convenient processor interface, and low assembly cost when compared to discrete switches and indicators, among other factors.

However, user-interface issues are associated with their use as well. First, as noted, you have to look at them first, which isn’t always practical or desirable. In addition, they can offer a mixed user experience (UE) as screens change, buttons move and change location, and perhaps worst of all, accessing basic functions may require going through several layers of response.

For example, in some car models from a high-end European manufacturer, the simple task of changing a radio station involved multiple pull-down menus, leading to considerable driver distraction. This annoyance to users and outright safety hazard was soon re-programmed and downloaded as a “update.”

The Return of Tactile Controls

There’s an increasing recognition that touchscreens have their place, but that place isn’t necessarily everywhere. Momentary-contact tactile pushbuttons are still widely used and, in fact, there’s reconsideration of tactile controls (switches, knobs, sliders) and a trend to increase their use.

This is driven by applications where dedicated buttons are more convenient, make more sense, or are mandated by safety considerations and even regulations. In fact, automakers—among the most aggressive market segment that went to touchscreens for user interfaces—are shifting back to tactile switches for key functions (see References).

Due to their long history, it's easy to assume that there’s little need for new tactile switches, but that’s not the case. Supporting this “less touchscreen, more tactile-switch” trend are two new surface-mount switch families from Littelfuse/C&K Switches that offer momentary-contact functionality but with additional attributes. These are the TLSM Series Tactile Switches and the KSC XA Series Soft Sound Tactile Switches.

TLSM Series of Tactile Switches

The TLSM Series of momentary-contact switches are single-pole, double-throw, normally closed (SPDT-NC) units measuring 6.0 × 6.1 mm with a compact 3.45-mm height, and short travel of only 0.3 mm (Fig. 1).

1. The TLSM Series SPDT-NC momentary-contact switches have a 6.0- × 6.1-mm footprint with a compact 3.45-mm height, and short travel of only 0.3 mm.

They’re rated for up to 2 million cycles, significantly outlasting traditional tactile switches. Thus, they help ensure product durability and reduced maintenance. Applications include industrial control panels, elevator buttons, consumer electronics, smart-home devices, medical devices, and even surgical instruments.

Their soft actuator delivers precise tactile feedback for an improved user experience, especially in quiet, noise-sensitive environments. As they’re IP54-rated for dust and water resistance, the switch provides reliable performance even in harsh industrial or outdoor conditions.

The switches support a wide voltage range (1 to 16 V DC) and current range (10 µA to 50 mA); maximum contact resistance is 100 mΩ.

KSC XA Series of Soft Sound Tactile Switches

The KSC XA Series of single-pole single-throw normally open (SPST-NO) switches, measuring 6.2 × 6.2 × 4.9 mm, have a soft actuation sound for a quieter user experience, particularly important in noise-sensitive environments (Fig. 2). The IP67-rated sealing ensures durability against moisture, dust, and debris, while the extended cage provides potting compatibility for increased protection against harsh conditions.

2. The KSC XA Series SPST-NO momentary-contact switches maintain a soft actuation sound despite the relatively high actuation force.

The relatively high actuation force of up to 9.6 newtons minimizes unintentional button presses and accidental activations, even as the switches are designed for 1 million cycles. Contact resistance is under 100 mΩ, while the contacts can handle up to 42 mA. These characteristics make the KSC XA switches a good fit for industries where noise reduction, durability, and reliability are critical.

Next time you’re planning a user interface using a touchscreen or even a switch-laden control panel, these rugged tactile pushbutton switches might offer you some new options to consider.