Designing COTS LCD Displays For Rugged Applications
- Thursday, 01 March 2012
Since by definition, mission critical, high availability displays may have to operate 24 X 7 for up to several years, consideration should be given to ways of extending useful life. The primary method is selection of power and backlighting components which operate comfortably within the environmental conditions expected. Further advantage is gained by 100% brightness if possible, as well as automatically shutting off backlights when not in use. The very nature of a mission critical or life safety display usually precludes the use of PC power saving options. However, techniques such as the proximity sensing of a viewer to turn on a display, or reduced brightness during dark conditions may extend the life of the backlight and power system. In addition, sensing light output and using it to dynamically adjust display brightness over the life of the display can extend the life of the display.
Parts within a large screen display are considered to have a large Mean Time Between Failures (MTBF) usually measured in tens of thousands of hours or higher. The first reaction is to divide this number by 8760 hours per year and feel assured your 24X7 display will last that many years before it fails. However the MTBF is just a probability of failure and is calculated during the “useful life” of a part, typically at room temperature. As a part starts to wear out, or gets used at high temperature, its reliability can decrease rapidly. Solid-state components such as ICs are thought of as lasting virtually forever, but within an LCD there are several components that, when routinely maintained or changed out, will keep the reliability at its maximum. The use of intelligent health monitoring such as temperature, brightness, fan speed or air flow to trigger maintenance events will increase overall reliability and availability.
Leveraging the performance and value of large format commercial off the shelf (COTS) displays requires careful attention and understanding of the environment and operation by the end user. Using this information to develop specific design requirements, engineering a design that meet these requirements, and finally developing test steps that validate the product meets these requirements will ensure a successful large format COTS display implementation.