It reviews the most recent developments in the technologies for bringing light to the front panel.
The design of the front panel for professional and consumer electronics is a key part of the user experience of the equipment. The first thing a user sees switching the equipment on is one or more status indicators. The reliability, accuracy and helpfulness of the messages these indicators convey will continue to be central to as the operator interacts with the system.
To address this critical need, designers have numerous options. LED neon, incandescent or halogen panel indicators, are available, as are light pipes, which can deliver light reliably to front panels over long distances and can be used where the environment does not permit a panel indicator to be fitted to the front panel directly. This might be due to the presence of corrosive vapour or flammable gas, restrictions on static discharge and EMI restrictions. LED panel indicators
LED panel indicators are becoming increasingly popular. Their advantages include long lifespan, low energy consumption, low heat generation and reliability. LEDs are more durable, shock resistant and have faster turn on/off speed than other light sources. Although specific design consideration may vary, typically, a standard LED panel-mount indicator contains an LED light source, housing and wire leads. The connectors and mounting hardware are often added as an option to enhance the design and for easy installation. There are lots of options available when selecting the optimal LED light source and housing for a panel indicator. In addition to the popular green, red, amber, yellow, orange, blue, or white single colour LEDs, bi-colour indicators are available. Red and green are most commonly used, and by lighting up both LED chips, it creates yellow or orange yellow as a third mixing colour. The chosen lens is central to the visual performance of the LED. LED lenses are typically available in clear, tinted and diffused with sizes of 3, 5, 7 and 25mm. The LEDs viewing angles range from 10 to 130°. A wide viewing angle means that the indication is more likely to be visible wherever the operator is standing, but narrower viewing angles such as 20, 30, 45° give a brighter effect. Different LED housings are designed to match the panel profile or give a better aesthetic appearance. The panel indicator housing materials available include plastic/nylon, metal chrome, polycarbonate, stainless steel, copper, aluminium anodised and IP67-rated for dustproof and water tight environments.
If the front panel is adjacent to the PCB, the panel indicator can be soldered directly to it, but if this is not the case a wire lead will be needed to power the LED. The most common wire leads used are UL-approved wires of gauges (AWG) running from 16, 24 to 26. The mounting methods are either push-through type or to utilise a lock washer and nut. The nut is attached from the rear of panel to secure the panel indicator. These types of panel indicators are typically used for high vibration application. The IP67 type housings are available both in metallic and polycarbonate material. The connector options are available through factory standard or customer specific. With the connectors attached, it allows quick plug in to the PCB power source and to simplify integration. Flexible light pipes
Similar to panel indicators, flexible light pipes deliver light remotely from a PCB onto the user-interface panel. Through the use of optical core, the light transmission can cover 100m with minimum attenuation – much more than ordinary copper wires. Since the optical media is non-conductive, the LEDs are protected and located on the PCB side, this eliminates the potential wire shortening, provides ESD protection to LED and PCB and minimises the potential for EMI due associated with the conductive material. The design provides important safety features for environments that are prone to chemical vapour and flammable gas exposure, providing an excellent alternative to LEDs. Since the LED is located remotely on the PCB, the flexible light pipe assembly typically contains the lens cap, optical core and adaptor which are designed for the core attachment. The adapters are located on the PCB directly over the LED. Adapter styles for mating with SMT or TH LEDs, for right angle or vertical mounting, are available. The PC lens cap can run through the front panel, or push from the rear panel with the other end attached directly to the adapter, which completes the set-up. There are multiple selections on the lens sizes and styles. The IP67-rated housing, made of either polycarbonate or metal, has a more ruggedised design, is more robust, dustproof and water-tight and is for harsh environments.
As to the optical core, the typical sizes are 2mm (1mm core) and 3mm (2mm core). A special 2mm (1.5mm core) and 3mm extra flex (2mm core) material are available from Bivar, for users who need increased brightness over a regular 1mm core and easier bending characteristic than the 3mm. The main advantage of optical light transmission is that it exceeds the distance available from ordinary copper wires. The optical core can be trimmed to any length, easily fit inside any tight corner and offer greater flexibility if multiple bends are necessary; no precise core cutting is needed. Conclusion
There is a solution to the challenge of bringing light to the front panel for every application, and the two companies provide standard, semi-custom and custom designs for panel indicators and flexible light pipes. As manufacturers they offer multiple variants of LED colour, operating voltage, housing, mounting hardware and wire lead. The 8 to 48V AC/DC operation LEDs eliminate the need for AC/DC power conversion and polarity-reverse concerns. They are designed for optimal performance in a variety of challenging environments including green energy, industrial control, communications and commercial industries.
Figure 1 Flexible light indicators can be standard, semi-custom and custom.Figure 2 LEDs offer long lifespan, low energy consumption, low heat generation and reliability.
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