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LCD displays for demanding applications

What are challenging applications? – Generalizing, we can say that it is any equipment that is exposed to undesirable factors, such as, for example, electromagnetic interference, dusty and humid environment or changing weather conditions. Any of them can affect the functioning of the electronics resulting even in damage to the module. What steps should be taken to avoid such situations?

Anyone who has used a smartphone in “extreme” weather conditions, ie. on particularly hot or frosty days, he could see how these factors affected its performance – slower operation of the device, faster discharge of batteries, resistant control; at the same time, vulnerability to mechanical damage is also increasing. Such problems affect all kinds of electronics, not indifferent to components such as LCD displays. In this article, using selected industrial and digital signage applications as examples, we show what can be done to ensure the most efficient operation of LCD modules in extreme environments.

LCD displays for industry

Portable measuring devices. To this group we can qualify various types of meters, recorders or detectors, which are commonly used in industry, such as mineral extraction or shipbuilding. Such equipment usually requires solutions with higher brightness (at least 1000 cd/m2) and the widest possible operating temperature range (at least -20~70°C). It is also advisable to maintain full viewing angles to facilitate access to the presented content, regardless of the viewing plane.

Such applications may include. 5-inch WF50DSYA3MNN0# from Winstar (1100 cd/m2, -20~70°C, 80°/80°/80°/80°). It’s a model with a MIPI interface, which – although primarily associated with phones, tablets or laptops – is also widely used in other portable devices, such as those used for measurements. Its most important advantages are providing high performance with low power consumption, as well as resistance to electromagnetic interference.

HMI Control Panels. Today, touchscreen solutions with diagonal sizes of 5 to 10 inches are the standard for HMI devices. They are ideal for streamlining process supervision, such as in production halls. To ensure the best quality of presented content, it is worth choosing models with a brightness of at least 750 cd/m2and an operating temperature of -20 to 70°C. Users are also sure to appreciate the full viewing angles.

For this type of application, Unisystem’s customers are keen on, for example, the 7-inch WF70A8SYAHLNN0# fromWinstar (1100 cd/m², -20~70°C, 85°/85°/85°/85°, interface – LVDS). However, there may currently be problems with the supply of such products – we have already been experiencing shortages of certain components in the electronics market for several months, due to the pandemic demand for consumer equipment, such as tablets (of which 7 inches is one of the most popular sizes). According to analysts, this situation may continue until the end of 2021. To avoid delays, we encourage customers to place framework orders – especially for projects where lead time is crucial(contact us to learn more about framework orders).

In the case of industrial touch solutions, it is also worth considering other special considerations that may be crucial for user convenience, such as the ability to operate with work gloves achieved by proper calibration of the module.

An interesting solution for industry is the Smart Display series from Winstar, which is represented by, among others. Model WL0F00050000FGAAASA00(400 cd/m², -20~70°C, 80°/80°/80°/80°, interface – CAN). These are “out of the box” modules that allow you to design the appearance of device interfaces using a database of standard objects such as, for example, indicators, counters and meters, sliders, charts, process progress icons. However – with brightness set at just 400 cd/m² – this solution may not work well in intensely lit spaces (learn more about the Smart Display series).

LCD displays for digital signage

LCD displays used in digital signage systems are usually designed for continuous operation – 24/7. In this type of application, it is worth paying attention to a parameter referred to as “LED life time,” or LED lifetime. This is the average service life of the LEDs that make up the backlights in LCD displays. It is expressed as the number of hours after which LEDs gradually degrade (learn more about LED life). In solutions for digital signage systems, this parameter should reach the highest possible values – usually approx. 70,000 hours.

Advertising in the city space. This category includes a wide range of media placed in urban areas. These include. Billboards, panels at stations and stops, interactive kiosks and totems, etc. For LCDs installed in our temperate climate zone, one of the key issues will be the module’s uninterrupted operation in both low and high temperatures. It can be assumed that the operating temperature range for this type of solution should be at least between -20 and 60°C. (The use of LCDs with a narrower temperature range, e.g., 0~50°C, involves additional heating in winter and cooling in summer.) In order for the presented content to be sufficiently legible, it is necessary to ensure adequate brightness – a minimum of 1000 cd/m2*, as well as viewing angles – 89°/89°/89°/89°. In addition, if the device will be located in a sunny location, it is worth using a model with hiTNI technology, which prevents the occurrence of the so-called “sunlight”. “black spots” appearing on LCD displays as a result of liquid crystals temporarily losing their original properties when exposed to intense solar radiation (learn more about liquid crystals).

The right parameters include. The 31.5-inch P320HVN07.0 fromAUO (2500 cd/m2, 89°/89°/89°/89°, -20~60°C, interface – LVDS, LED lifetime – 70,000 hours) or the 43-inch DLH4309-B from Litemax (1800 cd/m², 89°/89°/89°/89°, -20~60°C, interface – DVI, HDMI or DP, LED life – 100,000 hrs). hiTNI technology has been implemented in both models.

*Provided these are not sunny locations, in which case we recommend using LCD displays with a brightness of at least 2500 cd/m2 (available from Litemax, among others).

Passenger information media in vehicles. These are various types of solutions that we can encounter in public transport – they display, for example, timetables, routes with the expected time of arrival at the next station/stop, as well as additional information, such as the current weather condition. They can also be used to present advertisements. In this type of applications, the operating temperature range will not be crucial (certainly, the range of 0-50°C will suffice), but it is worth noting the parameters that affect the readability of the presented content, i.e. Brightness (optimally approx. 1000 cd/m2) or viewing angles (89°/89°/89°/89°). However, it is important to remember that these are devices that must also meet a number of other requirements in order to be approved for use in transportation. In the case of, for example, rail vehicles, they are regulated by EN 50155, indicating, among other things. The required resistance of the equipment to shock, vibration or interference.

Unisystem’s offerings include. The 28-inch SSH2845-E from Litemax (1000 cd/m², 89°/89°/89°/89°, 0~50˚C, interface – VGA or DVI, LED lifetime – 70,000 hours), for which the manufacturer declares compliance with the PN-EN 50155 standard. Its panoramic shape will fit perfectly into the limited space of, for example, compartments in trains.

Additional forms of protection for LCD displays

The above-described “fine-tuning” of LCD parameters provides protection only against such factors as low and high temperatures. In addition to these, a number of other harmful factors remain, including. dust and water. The best form of protection against dust and flooding will be to place the module in a suitably sealed enclosure, the degree of protection of which is determined using the IP codes defined in PN-EN 60529 (learn more about IP codes).

It is also worth considering the use of optical bonding technology for devices where displays are combined with touch sensors and protective glass. It involves bonding individual layers together with transparent adhesives or films, which are cured, for example, with UV light. As a result, the air that exists between the components is removed, reducing the possibility of fogging that occurs due to dirt penetrating the module’s gaps (learn more about optical bonding technology).

There are also a number of coatings on the market that are applied to modules, which, depending on the application, can benefit device users. Quite common are AG (anti-glare) and AR (anti-reflective) coatings, which reduce glare. In the case of devices located in public spaces, such as touch-operated kiosks or totems, it may be advisable to apply an AS coating, or anti-shatter, which prevents the spread of glass shards when the screen surface is damaged, such as when it is broken, or an AM coating, or anti-microbial, which reduces the amount of microorganisms applied to the surface of screens by users.

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In the article, we pointed out selected parameters and treatments on which the smooth functioning of a device designed for operation in extreme conditions may depend. We always say that each concept requires an individual approach; the same with this type of module – we should carefully analyze all the factors that may affect it, which will help in choosing the right LCD for the demanding application being designed.

2021-03-03

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