Switches for industrial and off-highway apps

Switches for industrial and off-highway apps

From greater functionality to the complete solution

BY KYLE PETERSON
C&K Components
Newton, MA
http://www.ck-components.com

Shock, vibration, and environmental contaminants are just a few of the concerns associated with industrial and off-highway applications. When designing switch components for such use, high reliability and sealing requirements must be considered, while also conforming to the demands of increased life cycles, precise outputs, and simplified assembly processes for ease of use and minimal maintenance. Additional issues are increasing demands for increased functionality such as visual status indication.

Switches are evolving to conform to the requirements of harsh environments. While temperatures are still similar to the industry standard (40° to 85°C), sealing to IP67 and IP68 specifications to combat hydraulic fluid, dust, dirt, and water are primary concerns.

Combating environmental elements is often accomplished with switches featuring an internal seal to protect the switching mechanism and an external panel seal designed to keep liquids from entering the panel or enclosure. The materials used in these switches must be robust against agricultural chemicals, hydraulic fluids, hydrocarbons, UV, oils, and other potential contaminants.

High actuation forces, extended life cycles, audible clicks, and feedback discernible through thick work gloves are a few more demands often posed by industrial and off-highway applications. Precision is yet another consideration, particularly when switches are designed into large construction equipment to adjust a particular element on equipment such as front-end loaders, bulldozers, forklifts, and other construction equipment where precision is important.

Hall-effect switch

While standard pushbutton switches have long been deployed in these applications, Hall-effect pushbuttons and rocker switches are increasingly being incorporated into designs due to their extended life cycles (up to 10 million actuations) and precision capabilities (see Fig. 1 ).

Fig. 1. The Hall-effect pushbutton switch, employed in off-highway and industrial equipment, features precision control and life cycles to 10 million actuations.

Hall-effect switches are solid-state electronic devices with no mechanical parts, and therefore they are more reliable than a mechanical switch. Hall-effect switches use a magnet and IC to detect the motion, position, or change in the field strength of the magnet to give a clean, fast, and linear output that is switched without bounce an inherent problem with mechanical contact switches.

The Hall-effect circuit is virtually immune to environmental contaminants and is suitable for use in harsh environments. The circuit is very sensitive and provides reliable, repetitive operation in close tolerance applications. Because the design utilizes a magnet, the electrical life is virtually limitless and the switch will not experience field failures.

While Hall-effect switches are not as popular as traditional pushbutton solutions, they provide manufacturers’ a long-term high-reliability solution along with a controllable linear motion, which isn’t typically available in a regular switch. This linear motion allows for precise output, which can be varied depending upon the exact position or travel of the switch, which is extremely important in off-highway vehicles.

Illumination

Along with increased life cycles and greater demands for precision and control, illumination is becoming more popular in switch designs for industrial and off-highway applications. Many switch designs incorporate illumination in the switch to give the user a visual indication of the status or function in the machines.

The LEDs are often independent of the switching mechanism, allowing the designer to have a solid, slow, or fast blinking LED, and a change in voltage can provide a different color. By adding LED illumination into switches, the BOM is simplified by not having to use external indicators and the cost of materials is greatly reduced, while at the same time increasing the design engineer’s flexibility with the circuit and panel designs.

As such, many switches are being offered in illuminated and nonilluminated versions to meet these demands. For example, snap-on caps in a variety of colors are available, allowing customers to purchase one standard switch with or without LED illumination and incorporate many different colored caps based on their application-specific needs (see Fig. 2 ). This modular solution allows users to have very few part numbers to inventory, thus simplifying materials and assembly processes.

Fig. 2. Epoxy-sealed with illuminated snap-on caps are ideal for joystick applications in bulldozers.

Switches such as C&K Components’ AP Series feature extended life cycles (oftentimes to as many as 1 million cycles) and can be offered with wire leads and epoxy-sealing, furthering their robustness and allowing installers much quicker assembly times as well as quick field replacement.

Turnkey switch

Because many designs now feature illumination, precision control, and greater circuit functionality, to name a few, switch manufacturers are more often developing turnkey switch solutions for customers. For example, a four-way navigation switch designed for off-road vehicles and industrial-handling equipment is available with backlit illumination and painted and laser-etched buttons (see Fig. 3 ). With the additional features of the fully decorated face surface and a wire harness ready to plug into a mating connector, customers are provided with a complete module and thus a one-stop-shop solution to meet a variety of application needs.

Fig. 3. With a fully decorated face surface, backlit illumination, and wire harness with connector, the quad navigation switch assembly provides a complete module

Switch manufacturers aren’t just developing switches anymore they are providing the complete solution. From developing Hall-effect switches with nearly unlimited electrical cycles to complete turnkey solutions that even include the end customer’s logo or custom symbols, customers today are often looking for a one-stop shop to meet their industrial and off-highway application needs. ■