Charlieplexing Anyone?

The Research & Development (R&D) team at ResTech, our joint venture with the University of Newcastle, was tasked with improving our customers' offerings in relation to a lighting solution made for hazardous areas. The team reviewed the customers' workflow, the overhaul demands required every four to six years, and the high power usage of the current lighting solutions. These unique problems needed to be solved, and the design choices had many unexpected and novel aspects.

The project moved through ResTech’s defined product development process, from ideas to commercial reality through “Design Thinking”. This user-centric approach is constantly aiming at the balance of the feasibility, viability and desirability of the new solution, the Innovation Trifecta (originated from IDEO in the early 2000s)

The development of the IS LEDm project used the stage gate process, D4P – Discover, Prove, Prototype, Pilot and Product, which is underpinned by the Technology Readiness Level scale created by NASA in the 1970s. This process enables the control of the development of new solutions while promoting creativity.

In true engineering protocol, learnings from previous projects supported the commencement of the development process, where experiences from the Enerveter project proved extremely useful for the IS LEDm project.

One of the team leads late night musings resulted in a sketch that was excitedly handed to the designers the next morning “I’ve got an idea!! Can you make it work? …. Okay bye!!”  There were some initial groans but there was real merit in what was detailed in those chicken scratching. It was in this moment that the first  “a-ha!” moment of the project occurred, and ‘Charlieplexing’ caused the project to light up!

Charlieplexing is a technique used in electronics to control many LEDs, switches, or other input/output devices with fewer control pins than traditional methods. It relies on the tristate capabilities of those control pins, allowing them to act as either output (high or low) or as an input (high impedance).

In essence, Charlieplexing cleverly exploits the tri-state capabilities of the hardware’s design to control many LEDs with fewer control pins, or in the case of IS LEDm, fewer terminals, making it a valuable technique for projects involving a large number of LEDs or other I/O entities.

With this knowledge, the team focused on how to make this work with the first pass resulting in a prototype. The next step was to reduce the amount of power used, with LED strings to be controlled with switch mode power supply techniques, which became the adopted circuitry and another pass for the product development process.

There was another memorable “a-ha!” moment that lit up the team. What if the terminal board, made as a printed circuit board itself became a piece of functional artwork—integrating clear, industrial-style design elements directly onto the board? By collaborating with our industrial designer, we created a remarkable, functional electronic component that not only works beautifully but also visually guides the user—no need for extra stickers. The design is both instructional and aesthetic.

The IS LEDm was officially launched in 2023. It is a high-spec integrated lighting package that provides an innovative solution for a multitude of applications.  The components are designed for hazardous areas, underground mining vehicles lighting, mining machine lighting and tunnelling applications.

Overall, this is a testament to our team’s ability to successfully deliver a solution within the available resources and constraints. And now we all the wiser about charlieplexing!

For more information on the IS LEDm click here