Research shows that the most important criteria for people, who choose public transportation, are the quality of the provided service, the comfort of travel, as well as the timeliness, and legibility of information about it. To ensure the passengers’ satisfaction LCD modules, which are used in transport information systems, should be adapted to long-lasting, continuous operation and displaying dynamic content. Modern transport systems are able to meet these expectations.
Dedicated aspect ratio and features
To get the most of even untypically sized surfaces, display manufacturers have developed the TFT glass cutting technology, which allows you to get shapes from square to a longitudinal rectangle with non-standard proportions.
LCD modules used in transport systems have been designed to meet the requirements of a diverse range of difficult environments. In the case of Litemax products, the average time between failures (MTBF) is about 100,000 hours, which makes them ideal for applications requiring a round-the-clock operation, and thanks to an optimized backlight system characterized by the reduced level of electromagnetic disturbances and lower energy consumption.
The most important features for LCD monitors used outdoors is the readability of the information also in direct sunlight. High brightness (from 1000 to 2500 cd), wide viewing angles and high contrast are essential. Below table presents selected models which can be used in transport applications.
Selected BAR TFT displays (stretched)
|Size||Vendor||PN||Resolution||Active Area [mm]||Brightness||Contrast||OT [st.C]|
Selected displays for outdoor applications
|Size||Vendor||PN||Resolution||Active Area [mm]||Brightness||Contrast||OT [st.C]||Hi-Tni|
The operating temperature range for this type of products is on average 0 – 50°C, however, TFT glass resistance can be as high as -40 to 110°C (Hi-Tni), which makes it possible to use it in places with high insolation without the risk of black stains on the matrix.
Manufacturers also provide resistance to other harsh environmental conditions. In monitor solutions, the standard sealing between the glass protecting the display and the housing allows obtaining resistance at IP65 level (dust and water jets). There are also products with increased resistance – up to IP68, which is completely resistant to dust and adapted to stay underwater (for a limited time, depending on the model, about 30-60 minutes).
Even better readability
To further enhance the reception of the displayed information manufacturers use technologies that improve color reproduction and area brightness adjustment. This feature is responsible for local dimming of the image, which maximizes the contrast between the dark and light areas of the screen significantly improving the depth of black.
In addition, manufacturers offer optical bonding services. This technology allows you to combine the display with special coatings, i.e. AG (anti-glare), AR (anti-reflex) or polarizing filters. Due to the high popularity of polarized glasses, outdoor display manufacturers are increasingly opting to use a special polarizer design, so that the displayed content will be readable also for people using this type of lenses.
E-paper – an alternative for LCD displays
In the case of applications displaying static information, an interesting alternative may be the use of e-paper displays. Their unquestionable advantage is exceptional readability in direct sunlight, almost full viewing angles and very low power consumption. Comparing LCD and e-paper displays of similar sizes (LCD: 32“ Hyundai IBT, H325SSI-outdoor, EPD: 31.2“ E Ink, ED312TT2) assuming working time 16h per day, you can see that LCD display consumes more than 111 times more energy than EPD (assuming image update every 1h and its duration – 1s) – you can find the results in below table.
|Power consumption||Total energy consumption for the 1 day cycle||Total energy consumption for the 1 year cycle|
|LCD||145W||2,3 kWh||846,8 kWh|
|EPD||23,7W (for the content update)|
1,3W (image maintenance)
|0,02 kWh||7,6 kWh|
A problem with EPD displays may be their low thickness and susceptibility to damage, which makes installation in end devices difficult. The solution to this problem was the open frame modules created by Unisystem. They provide not only mechanical safety and protection against degradation of e-paper (thanks to a laminated UV filter) but also thanks to the use of front glass, a modern and elegant look. Open frames offer also dedicated controllers enabling communication using one of four interfaces (SPI, USB, Wi-Fi, GSM).
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