In this final blog of our five-part series on backlighting, we will be looking at electroluminescent lamps in detail. In the first blog, we discussed how to approach a backlighting project and reviewed the different backlighting solutions in the subsequent blogs, namely discrete LEDs, light guide film, and fiber optic weave.
What is electroluminescent lighting?
Popularized in the 1980s, electroluminescence is a technology that works by sending an electric current through phosphorus, a semiconductor that emits light when charged. Electroluminescent (EL) lamps can be mounted on printed membranes or printed circuit boards.
Advantages of electroluminescent lighting
Governed by the design requirements, EL lamps can be zoned in selective areas to ensure optimum diffusion of light. With minimal light bleed, it doesn’t require blocking layers between different sections that are lit. Like fiber optic technology, EL lamps can also be integrated with discrete LEDs to have indictor lights and light up large areas simultaneously. Some of the advantages of EL backlighting technology include –
- Ability to illuminate large surfaces
- Limited impact on the tactile feel of buttons or domes
- No light bleeds
- Varied color options via overlay printing
Unlike light guide films and fiber optics where the light color can be changed at the source, there are certain limitations with the EL backlighting method. The core colors that phosphorus can produce are white and blue-green. While generating other exotic colors is possible, it can significantly add to the cost of the design. One way to navigate this shortcoming is to have the EL light in one color (preferably white) and then print the graphic overlay in the desired color scheme. If you need different colored lighting for separate areas, the sections can be isolated by adding additional traces.
Disadvantages of electroluminescent lighting
The biggest limitation with EL is the half-life of phosphorus. After 4,00 hours, the phosphorus begins to degrade, thereby dimming the backlit area. EL also requires a DC to AC power conversion which may not be possible to integrate into many designs. This typically means that EL backlighting needs to be designed in from the very beginning of the design cycle and cannot be added as a last-minute drop-in feature. The main challenges with EL include –
- The half-life of 4,000 hours (phosphorus begins to degrade after)
- Requires DC to AC convertor
Considering the limited life span of this backlighting solution and the price point of this mature technology, it is a viable solution in a few unique cases.
To see how electroluminescent lighting works, watch our short video below.
In our backlighting blog series, we have discussed how to approach a backlighting project and reviewed two popular backlighting technologies – discrete LEDs and light guide film. In this blog post, we will be focusing on the third backlighting technology – fiber optic weave.
What is fiber optic backlighting technology?
Fiber optic technology utilizes a bundle of thin optic fibers that transport light from a single LED to a large surface. Made of acrylic, every individual optic strand is thin, pliable, and extremely durable. However, it should be noted that the LED used is always a bullet LED, which requires a printed circuit board or copper flex circuit as a base. Bullet LEDs cannot be mounted directly on printed membranes.
Advantages of fiber optic backlighting technology
Fiber optics are often integrated in tandem with discrete LEDs, where surface-mount LEDs are used for indicator lighting and fiber optics are utilized to light up the larger area, including icons, texts, patterns, or graphics. As this backlighting technology requires only one LED to illuminate the entire assembly, the power consumption is fairly low.
Given the working mechanism of fiber optics, the color of the lit area or assembly is dictated by the color of the bullet LED. RGB bullet LEDs can be employed to achieve a wide array of color options. Lighting up different sections with different colors can be achieved by utilizing separate layers (separate optic bundles) and using desired colored LEDs as the light source. Alternatively, you can also use a white bullet LED and regulate the colors through the printed graphic overlay.
The main benefits of fiber optic include –
- Ability to illuminate large surfaces with a single bullet LED
- Low power consumption
- Minimal impact on tactile feedback over metal domes
- Mid-range price point
Limitations of fiber optic backlighting technology -
While using a single LED is one of the biggest advantages of a fiber optic technology, it may not be bright enough to illuminate a very large area, especially if the device is primarily used in ambient light. It may also be challenging to light different areas with different colors. This issue can be addressed by configuring more than one fiber optic bundle in the design. However, integrating multiple bundles often translates to increased cost.
While we continue to see this backlighting technology in several user interfaces, we anticipate that it may soon give way to thinner backlighting solutions as devices become smaller and lighter.
To see how a fiber optic backlighting technology works, watch our short video below.
If you have read our previous posts in this backlighting series, you should already know what questions to ask before starting a backlighting project as well as when to use discrete LEDs. In this blog, we will be discussing the next backlighting technology – light guide film.
What is a light guide film?
Light guide film, much like it sounds, uses a thin film to guide the light from the LED(s) to the areas that need to be lit. The film has a reflective coating on the top and bottom layers of the film. The top layer is laser etched or abraded in the areas where we need light to escape and light the overlay. With varying depths and customized etching patterns, the distribution of light can be easily controlled, allowing specific areas to be brighter or dimmer.
Since the light feeds directly into the edge of the film, this technique uses side-fire or right-angled LED(s) to facilitate the optimal diffusion of light through the entire length of the film. The precise alignment and orientation of the film and LED(s) are extremely critical to the success of the design.
Advantages of a light guide film
The film’s low profile allows it to limit the impact on tactile feedback of metal snap domes or buttons. As a result, it is usually mounted directly below the graphic overlay and can be seamlessly integrated into thin and tight spaces. With minimal loss of light from the source to the other edge of the film, this technique promises uniform lighting across the entire plane with increased efficiency. It is a great solution for lighting large areas while still maintaining a mid-range price point.
Some of the core benefits of a light guide film include –
- Uniform lighting and brightness
- Limited impact on the tactile feel of buttons or domes
- Energy efficiency Ideal for lighting small, large, and curved surfaces
- Suited for thin, compact, and flexible designs
Limitations of a light guide film
While light guide films are gaining momentum across several industries, few challenges need to be addressed while working with this technology. When the light travels from the LED through the film material, the edges are often illuminated very brightly, resulting in unwanted light leaks. This can be overcome by employing an opaque panel filler along the border of the film. Since LED(s) are butted up against one end of the film, it can create hotspots in areas around the light source. This can be eliminated by adjusting the printing process of the overlay to add a printed opaque layer. Due to the placement of the LEDs, light guide films generally struggle with lighting up the same area with multiple colors.
The main design concerns with light guide films include –
- Light leaks from the edges
- Potential hotspots around the LEDs
- Limitations to backlighting the same area with multiple colors
Regardless of the drawbacks, light guide films are continuing to grow in popularity and the challenges will be mitigated as the technology evolves.
To see a few examples of light guide film projects and learn more about this backlighting technology, watch our short video below.
Last week we kickstarted a five-part blog series on backlighting technologies. Our first blog provides a framework to approach any new backlighting project and overcome design challenges. In this blog, we will be focusing on the first and the most popular backlighting technology – discrete LEDs.
Light-emitting diodes (LEDs), also referred to as discrete LEDs, are point-source lights that can be lit individually or in a group to illuminate a small area. Thanks to their low cost, thin construction, and long operating life, discrete LEDs have enjoyed widespread popularity and adoption across industries as diverse as medical, aerospace, automotive, and more.
Types of LEDs
LEDs come in different packages of varying shapes, sizes, types, and heights. The most commonly utilized types include surface-mount LEDs (top-fire or side-fire) and bullet LEDs. LED-backlit designs can be constructed in a range of colors and brightness levels. For example, a bi-colored LED as an indicator light turns green when the device is in use and the same light turns orange when the device is in standby mode.
In addition to the traditional single and bi-colored LEDs, RGB LEDs have opened doors to a wide gamut of colors and accent lighting options. RGB technology, combining three LEDs in a single package, mixes the three primary colors (red, green, and blue) in varying intensities to generate any color on the RGB spectrum. As a result, a single LED is capable of producing multiple colors.
LEDs are available in different correlated color temperature (CCT) values like the cool blues, warm yellows, and other tints. Whether you need dimmable, flashing, or non-flashing lights, LED designs can be composed in various styles. They can also be configured to light up all at once or selectively, as the design dictates. While surface-mount LEDs can either be mounted on a silver printed membrane, copper-etched flex circuit, or a printed circuit board with a connector that attaches to the mainboard, bullet LEDs can only be mounted on the latter two.
Advantages of LED backlighting
As point-sources of light, LEDs are great for small icons or indicator light applications, communicating the working or the status of the device. Some of the core advantages of discrete LEDs are:
- Thin and robust construction
- Limited impact on the tactile feel of buttons or snap domes
- Long operating life (100,000 - 500,000+ hours)
- Ability to illuminate the same area with different colors
- Varying brightness level and color options
Limitations with LED backlighting
LEDs usually struggle with lighting up large surfaces uniformly. A high count of LEDs in a concentrated area or placement of them close to a graphic overlay can create unwanted hotspots (bright areas) over or near the light source. Fortunately, both of these issues can be overcome by utilizing an elastomer keypad or overlay. Rubber overlays optimize light diffusion from LEDs, thereby mitigating hotspots and ensuring consistent brightness over the surface. A common challenge with elastomer is that it has a very different texture compared to a polycarbonate overlay and adds substantial thickness to the construction stack-up. Light dams or barricades often need to be incorporated in the design to overcome light bleed from one LED to the adjacent window. If you need to backlight a larger area and elastomer is not possible, you may want to consider a light guide film or fiber optic weave, which will be covered in our upcoming blogs.
To see a few examples of LED backlighting projects and learn more about this technology, watch our short video below.
This month we are kicking off a five-part blog series on backlighting. The series will begin with an overview of how to approach a backlighting project and each subsequent blog will review one of the four most popular backlighting technologies: discrete LEDs, light guide film, fiber optic weave, and electroluminescence.
Why should you be thinking about backlighting?
Backlighting has become an industry standard to augment the functionality and aesthetics of a device. From home appliances to aircraft cabins, and car dashboards to industrial controllers, backlit devices and accents are becoming increasingly ubiquitous. Backlighting is a simple way to improve visual appeal, enhance the user experience, and lend a distinctive style to your user interfaces. It can assist and guide users towards the correct operation of a device, especially in dimly lit and dark environments. It also provides vital feedback about user actions and interactions.
How to determine the most optimal backlighting solution?
Designers and product development teams often wonder when the right time is to start thinking about backlighting when developing new products. Ideally, backlighting should be considered at the very beginning of the design phase. This gives you the flexibility to evaluate available technologies and allows engineers to integrate backlighting seamlessly with the other technologies and features of the design.
To establish the best backlighting solution, the first step is to create a list of requirements and assess the proposed design. Start by asking these questions:
- What environment will the device be primarily used in - indoor or outdoor?
- Will the device be primarily used in ambient light, bright sunlight, or dimly lit spaces?
- Do you want to light up a small indicator window or backlight large areas like texts and graphics?
- How many colors do you need?
- Will all the areas be lit at once or do they need to be independently controlled?
- Are there any buttons or snap domes that need to be integrated into the design as well?
- What power type is available – is it a portable unit or a plug-in?
- What are the cost constraints?
Backlighting design concerns and considerations
Based on the responses to these questions, you should be able to evaluate which backlighting solution or combination of backlighting solutions could work with your device. Once you have evaluated and selected the most appropriate technology, you need to address all the design concerns and challenges that the technology presents. A few parameters to address include –
- Will the light source create hotspots? If yes, how can they be mitigated?
- Will the light bleed from one section to the other? Do I need a light-blocking layer?
- Is the construction stack-up too thin or too thick for the design?
- Is the backlighting affecting the tactile feedback of the buttons or switch technology?
- What brightness level does the design demand?
- Should the light source be mounted on a printed circuit board or printed membrane?
- What are the minimum and maximum sizes of the light source that can be used in the design?
- How many light sources do I need?
It is the interplay of several factors that ultimately dictate and influence the design, each of which is important when examining the cost structure of the project. While this is not an exhaustive list of design considerations and concerns, it provides a framework to effectively begin to approach your backlighting project by forecasting design hurdles and addressing them promptly.
To dive deeper into the four most popular backlighting technologies, read our other blogs in this series -
In a recent blog post, we discussed what optical encoders are and how they are used. Simply put, an optical encoder is an electro-mechanical component for measuring position, velocity, and acceleration. GMN’s optical encoders have been used for years in printers, scanners, medical equipment, and much more. Lately, our optical encoders have found an exciting new application as a vital component in LiDAR (light detection and ranging) sensors for autonomous vehicles.
What is a LiDAR sensor?
Originally developed in the 1960s for military use, LiDAR sensors use lasers to survey an area and create a 3D representation. They allow for highly accurate readings of distance and motion around the sensor and are commonly used for robotic and artificial intelligence applications.
A LiDAR sensor works by rapidly emitting pulses of light, which bounce off any surrounding objects and return to the sensor. The sensor then calculates the distance from each object in real-time, providing a three-dimensional representation of the surrounding area.
Recently, LiDAR technology has found its way into autonomous vehicles to aid navigation. Typically, the sensors are adhered to the top and sides of a vehicle, allowing a connected computer to have reliable environmental perception and to navigate terrain safely in real-time.
How do optical encoders make this possible?
GMN’s optical encoder disks are placed within each sensor, allowing them to accurately gauge position and rotation when the sensor emits pulses of light. Having accurate positioning is crucial for autonomous vehicles, as any error in calculating position can result in inefficiencies or accidents. Most notably, this is used for navigation by analyzing the 3D rendering around the vehicle and adjusting movement accordingly to avoid obstacles. They’re also used for modifying speed to keep safe distances from other moving objects, and to alter course to reduce the severity of an accident should it be unavoidable.
LiDAR sensors are a versatile technology where new applications are frequently being found. Currently, they are used to gather data and create models in a wide variety of industries including agriculture, manufacturing, and forensics. GMN is excited to provide a crucial piece of this exciting technology. To find out more about optical encoders and their many uses, take a look at our capabilities page or reach out to our technical experts for a free consultation.
When designing an electronic product, one important consideration is preventing unwanted substances from getting inside of the device. While internal components are typically protected by the main enclosure, any openings related to buttons, switches, and/or screens on the user interface can potentially allow for ingress of dust, liquids, and other substances that can cause possible damage or malfunction.
Fortunately, there are several methods to control, mitigate, and even eliminate liquid and particulate ingress. Below, we’ll be going over a few of the most common sealing methods.
What is sealing?
Liquid, chemicals, and dust can find their way inside of a product at any point where components meet. Sealing is the process of shoring up these connection points or openings to ensure undesired liquids or particles don’t affect function. But what are key considerations when it comes to sealing?
One of the most important factors when deciding on a type of seal is the level of protection required. In many industries, being able to withstand harsh environments or heavy cleaning while staying functional is paramount to the success of a product. For regulated industries, electronic devices often need to meet certain standards for the ability to resist liquids, chemicals, and other particles. Standards such as the National Electrical Manufacture Association (NEMA) 250 rating and Ingress Protection (IP) ratings per IEC EN 60529 are commonly used to define ingress requirements.
Another important consideration when designing sealing for a part is the amount of physical space available, as enough room is needed to achieve the required sealing. The look of a part can also play a large role here, as any visible sealants or adhesives may need to meet aesthetic requirements.
The overall construction of the part can dictate the sealing method as well. Sealing methods involving elastomer are generally only used on parts that are already committed to an elastomer construction, while a perimeter adhesive seal may only be viable for other constructions.
Common types of sealing methods:
- Perimeter adhesive sealing: One of the most common methods of sealing, this involves using an adhesive to adhere a graphic overlay to the front of the component. The adhesive goes completely around the perimeter underneath the overlay, preventing any liquid or chemical ingress. Because it requires a specific amount and type of adhesive for an effective seal, the available space on the bezel and under the overlay is an important consideration. Also, any other functional layers underneath the graphic overlay need to be accounted for in the sealing design.
- Front surface sealing: If there are any gaps or areas in which there can be potential for ingress on the front of a bezel or case, front surface sealing can be an effective option. For this method, a sealing compound is dispensed into a gap around any areas in which particulates or liquids could enter (typically the part perimeter). While this provides an effective seal, the sealant is typically black and cannot be matched to other colors, so it may not work with all aesthetic requirements.
- Rear surface sealing: Similar to front surface sealing, rear surface sealing seals off any openings around tails or cables that come through the rear housing of the device. Because the sealant is added to the back of the case where it generally can’t be seen, this is a good option for any device where there might be stringent visual requirements on the front. Many devices are designed with this in mind to avoid aesthetic issues.
- Front surface compression: Similar to a television remote, the elastomer rises through the bezel or case to seal off openings. The elastomer is molded to be compression sealed to the front of the part and offers a high level of protection from liquids and chemicals. As the seal is fashioned out of molded elastomer, usage of this sealing method is contingent on elastomer being an integral part of the product design.
- Wrap around elastomer: As shown in the image, with this sealing method, the silicone rubber keypad is molded to wrap around the edge of the part, sealing off the front and edges of a device. While this offers a high level of protection for internal components, like with front surface compression sealing, it requires a part where elastomer is already part of the design. Due to the use of compression molded elastomer, this undercut feature can generally be tooled and produced with little to no added expense.
Ultimately, choosing the most optimal sealing method comes down to the specific requirements of the project. To discuss which sealing method is right for your next product, schedule a consultation with our experts.
When developing a user interface, it’s important to consider what the user needs to see during an interaction. For certain applications, calling attention to an indicator or warning light while keeping others hidden can be crucial. For situations where eliminating distractions, keeping a clean aesthetic, and emphasizing certain switches or indicators is imperative, look no further than dead front printing.
What is dead front printing?
Dead front printing is the process of printing alternate colors behind the main color of a bezel or overlay. This allows indicator lights and switches to be effectively invisible unless actively being backlit. Backlighting can then be applied selectively, illuminating specific icons and indicators. Unused icons stay hidden in the background, calling attention solely to the indicator in use.
Printing methods and substrates for dead front overlays
There are two ways to illuminate a dead front overlay, each of which requires a different printing approach. The first method is to use LEDs directly behind each indicator or icon. This approach simplifies the printing process (since LEDs provide the colors, the printing generally employs a single color behind each button). Alternatively, different translucent colors can be printed selectively behind various indicators. With the use of translucent colors, almost any backlighting method can be used since it’s the ink behind the iconography that gives the indicator its hue.
Diffusers are often applied behind the lights to maintain consistency throughout an overlay. Particularly with LEDs, diffusers can help eliminate hotspots, where one part of the letter or icon appears much brighter than other parts. Once a part is ready, a standard is made, so any future overlays or alterations are readily available and can easily be matched to the standard.
While dead front printing is technically possible with almost any colored bezel or overlay, it’s generally seen on overlays and bezels printed with neutral colors. Typically printed on polycarbonate, polyester, or glass, colors such as white, black, or gray tend to hide unused indicators the most effectively.
Developing dead front control panels with GMN
When developing a new dead front overlay, experimentation is often necessary to get the perfect look. Given the breadth of possible lighting options, ink densities, color palates, and substrates, maintaining a consistent look across an overlay often requires several prototypes to be developed. At GMN, we have a state-of-the-art color lab, a light lab, and a full printing team that works in tandem to match and perfect colors. Within our color lab, spectrophotometers and spectroradiometers are frequently utilized to get specific color values necessary for matching. Our light lab will then work with the printing team to narrow down the exact mixture and density of ink necessary for the specific substrate and required look.
Dead front printing is an excellent option for a wide variety of applications such as automotive dashboards, aerospace indicators, and touch user interfaces. Want to learn how dead front printing can help your product be more efficient while ensuring a clean aesthetic? Watch the video below and schedule a consultation with our experts.
In our previous blog, we talked about the different kinds of resistive touchscreens and how they compare. While resistive screens offer a high level of versatility, another one of the most widely used touchscreen varieties is the projected capacitive touchscreen. Below, we’ll be discussing the key features and advantages that make projected capacitive technology such a popular touchscreen option.
What are projected capacitive (PCAP) touchscreens?
In contrast to resistive touchscreens, projected capacitive touchscreens don’t require any physical pressure to activate. Rather, they rely on projecting a capacitive field through the display. This field is then disrupted by electrical impulses from the human body when the cover glass is touched. PCAP touchscreens have grown immensely in popularity over the last several years and are primarily used in smartphones, monitors, and any other device that requires both durability and precision.
Advantages of projected capacitive (PCAP) touchscreens
Originally thought of as expensive and unreliable, the technology for projected capacitive touchscreens has consistently improved. Over the years, the cost of manufacturing has come down significantly enough to rival that of many resistive options. The specificity to which the input sensitivity can be tuned has also become advanced enough to reject dust, oil, grease, gels, and other agents, while still effectively gauging user input. This makes them ideal for industries where high cleanability and input precision is required.
Since the input is simply a disruption to the capacitive field, PCAP screens allow for multi-touch functionality, such as zooming, rotating, and more. However, due to the reliance on electrical impulses for input, there are limits to what can be used to activate it. The sensitivity can be tuned to register styluses and gloves, but the item used has to be able to successfully disrupt the capacitive field. This may be less ideal than resistive touchscreens for certain applications, where it may be necessary to use other objects to input information.
Due to PCAP touchscreens not relying on separate panels making contact, damage to the cover glass or acrylic generally won’t affect user input, making them durable enough to handle nearly infinite activations. Because of their construction, PCAP touchscreens also display an extremely high-clarity image. Since the layers are bonded together with optically clear adhesive (as opposed to with an air gap between layers as with resistive touchscreens), the displayed image has a high level of light transmission and is very clear. Coupled with rarely losing calibration, they are durable and remain precise throughout their lifespan.
Ultimately, the decision to use either a resistive or projected capacitive touchscreen comes down to the application. Regardless of what type of user interface system you’re looking for, GMN’s experts can help you find the perfect touchscreen for your next product. Find out more about our display integration capabilities or set up a consultation with our experts.
In today’s world, touchscreens are omnipresent and expected by users on almost any interface system. Widely used in a variety of industries, there are many different types of touchscreen constructions available. Once you have decided to use a touchscreen, there are important design considerations to take into account. How should the touchscreen function when interacted with? Does it need to be durable enough for heavy usage and millions of actuations? Should it be incredibly precise and not require any calibration? Whether your biggest concern is cost, durability, or functionality, there are many different options.
The most commonly used touchscreens broadly fall into two categories: resistive and capacitive. In this blog, we will be focusing solely on the different types of resistive screens and their core advantages.
What are resistive touchscreens?
Resistive screens are made up of two conductive and transparent layers: a flexible top panel (typically made out of polyester or PET) and a rigid bottom panel. An adhesive spacer lies between the two layers. When pressure is applied to the top panel, it makes contact with the panel below. This contact interrupts a continuous current flowing between the panels, where a grid of horizontal and vertical lines allows a controller chip to know what was touched and gauge input accordingly. Since the input is calculated through physical pressure causing the two layers to make contact, resistive touchscreens work well for any gloved or stylus usage.
Types of resistive touchscreens
4-wire resistive touchscreen
The least expensive of all of the touchscreen options, 4-wire touchscreens are typically found in games, toys, and other inexpensive touchscreen applications. Since the accuracy is based on the top panel interacting with the bottom panel, any damage to the top panel will cause the accuracy to degrade. This generally makes them less reliable after heavy usage or many actuations. 4-wire touchscreens also have to be calibrated frequently as they get used to ensure that they register the correct input.
8-wire resistive touchscreen
Very similar to 4-wire in durability and usage, the only difference with an 8-wire screen is additional wiring. This additional wiring keeps the screen more precisely calibrated and allows it to auto-calibrate, meaning that it requires less maintenance to maintain accuracy than its 4-wire counterpart.
5-wire resistive touchscreen
Despite the similar name, 5-wire touchscreens are significantly different from the 4-wire and 8-wire variations. 5-wire screens measure input from the bottom panel only, not in tandem with the top panel. This means that regardless of any damage to the top layer, the usage of the touchscreen and accuracy of input won’t degrade. This makes them more durable and they generally last through many more actuations than other resistive options.
Resistive multi-touch screen (RMTS)
Resistive multi-touch screens (RMTS) are the only type of resistive screens that allow for multiple-touch functionality, such as pinching, zooming, or rotating. Similar to 5-wire screens, the bottom layer is the only layer that measures input, meaning that they’re more durable and well-suited for a rugged environment. EMI mesh can also be applied to the front surface, protecting internal components from outside electrical activity. This, in combination with the durability, makes them favorable for military and industrial applications.
Resistive touchscreens are a great option for a wide variety of applications and industries. To learn which touchscreen option is right for your next product, take a look at our front panel integration and bonding capabilities or request a free consultation with our technical experts.