Tactile Function and Smooth Operation Are Key to Reliable Industrial Knobs & Switches

Sometimes, the simplest-looking part in complex equipment can be the most critical. Knobs and switches for example, tend to be an afterthought…turn, push…what more could they do? A lot actually. In fact, these small, often overlooked parts can provide big control functions and incorporate more capabilities than you might think.

Millions of rotary switches and knobs are sold globally every year for heavy-duty commercial and industrial applications, where reliable operation, precise positional setting and the ability to withstand harsh environments are absolutely critical parameters for rugged use.

Reliable operation and dependability out in the field are just two of the core requirements needed for rotary switches and knobs. What good is the knob or switch on a “control panel” if the components fail to “control”? Elma Electronic has spent over six decades focusing on constant improvements to the feel (haptics) and robustness of its switches as well as on the aesthetics, including the finish and the precision fit of its knobs.

Construction is Important to Reliability

Another important consideration is panel and shaft sealing up to IP68 to prevent dust and water ingress into the equipment’s chassis. The option for panel sealing is a standard offering for all of Elma’s rotary switches and encoders. Shaft material should also be of primary concern because the shaft itself is overwhelmingly the point of damaging contact in equipment drops or radial or axial impacts of any kind. Brass as standard material, or stainless steel for added durability in harsh conditions, should always be considered.

In addition to the added robustness provided by brass and stainless, these two premium materials add to the reliability of panel sealing, due to the resultant machine finish on the exterior surface of the shaft, providing a much smoother surface for O-rings to seat against versus machined or tooled aluminum. Lastly, to ensure years of trouble-free electrical performance, all internal contacts are plated with hard gold over a nickel sealing layer.

Functionality Plays a Role

Rugged design elements for switches and knobs are only half the story; switches are available in many competing technologies and knobs are available in many different materials and fixing schemes…all with their advantages and disadvantages. Selecting the correct switch functionality or technology can be confusing, due to some of the common industry vernacular, and knob materials can range from basic plastic to high temperature plastic to different kinds of metals. These elements need to be considered, depending on the application.

Many factors influence the right switch technology, so be sure to ask questions, like the following, before selecting a knob or switch:

• What rotational or switching cycle life is needed for the application?
• What is the turning force (turning torque) required for the application?
• Is the actuator stepped (click/click) or continuous (smooth turning)?
• What is the expected indexing angle (space between position) desired for the application?
• What are the cost consideration in comparison to your budget?

The following examples highlight some of the non-traditional uses where knobs and switches are helping to provide greater control and functionality in a growing number of rugged applications:

 

Multi-Mode Selection in Agricultural Applications

An increasingly diverse group of industries are turning to a more sophisticated user interface as digital technologies force the transition from inexpensive components to more sophisticated switches and knobs, and these components are finding their way into traditionally manual, heavy-duty applications.

In the agricultural world, switches and knobs play a critical role in all equipment from planting, harvesting and storage of crops. Because much of the machinery used in commercial agriculture spends its life outdoors, components need to stand up to challenging environmental conditions. Protection against moisture, dust and fine particles is critical to maintaining reliable operation.

In one case, Elma Electronic’s MR50 multi-rotary coded switch is used as the mode selector switch on a grain spreader that needed a switch capable of up to 16 positions with only 1/2” of round space horizontally and 10mm depth behind the panel.

The switch’s front panel meets IP68 panel sealing for ingress protection and operates in temperatures from -45°C to +85°C, ensuring reliable operation across the seasons, wet or dry, hot or cold.

The positive tactile feedback from the MR50 is excellent, even while using heavy-duty gloves; and the standard, low-profile, stainless steel shaft provides resistance to lateral impacts of all kinds that can occur on a routine basis.

Highest Precision for Performance Aircraft

Air races…fast paced, high flying fun…and at the annual Red Bull Air Race, an official World Championship accredited by the FAI – The World Air Sports Federation, Elma was there, helping pilots cruise through the course!

At the event, pilots navigated their extremely light and maneuverable racing aircraft at a speed of up to 370 km/h (300 mph). This demanding, and extremely safety-critical, environment requires all on-board equipment to include the most reliable and haptic-rich switches available, as pilots do not always look at their controls, but rather turn and count the clicks to know where they are setting the switch, a practice commonly used in public safety radios, as well.

Elma’s robust, mechanical encoder type E33, as well as our space-saving, dual concentric encoder type E37, are staples in the innovative, high-performance aircraft navigation systems developed by LXNAV, and used in a competition aircraft.

Both encoders offer the switching torque, tactile feedback and rotational life needed to ensure safe control of the aircraft during flight.