Upgrade options
The two most common methods for upgrading an LCD for outdoor use by controlling solar loading on the front face, improving visibility and prolonging its useful life are (a) optical bonding and (b) an air curtain.
With optical bonding, the display is modified by using an optical-grade adhesive to bond a sheet of glass to the top surface of an LCD panel. The air gap between the cover glass and the panel is then completely filled with a silicon-based gel or adhesive.
Optical bonding reduces unwanted reflection, glare and mirror images that can make a display difficult to read. In addition to better optical performance, the bonded sheet makes the structure more durable. Parts and service, however, will be more expensive and difficult, since the LCD has been modified and is no longer standard.
An air curtain, on the other hand, is added by creating a gap in front of a screen that allows a constant flow of air. This helps prevent heat from building up due to sunlight or high temperatures. It is also the more cost-effective upgrade, since a standard LCD can be used without any direct modifications. This will make a big difference in reducing total life-cycle costs and in the availability of parts.
Rain and snow will corrode the display’s housing if it has not been properly treated and waterproofed.
Variations in temperature
If an LCD and its enclosure are not rated for extreme temperature fluctuations, they may suffer from screen blackouts, damaged electronics and reduced efficiency. When a display rated for up to 30 C (86 F), for example, is installed in a region where summer temperatures regularly reach 40 C (100 F), its useful life will be severely diminished.
In Canada, especially, where temperatures vary drastically throughout the year, a display needs to be designed to function in all four seasons. It should be configured to start up properly under both freezing and hot conditions, operating in temperatures ranging from -40 C (-40 F) to 50 C (122 F). Some newer LCDs are even rated to withstand temperatures up to 110 C (230 F) on the front face.
Typically, enhanced LCDs are directly backlit by either light-emitting diodes (LEDs) or cold-cathode fluorescent lamps (CCFLs), which add to power demands and the spread of heat dissipation. LEDs are the preferred option, as they help prevent problems related to solar loading by reducing the internal temperature of the display compared to CCFLs and they remove harmful UV emissions from the illumination system. LEDs also last longer and exhibit minimal brightness reduction over the life of the display.
There are several ways to keep an outdoor digital display’s internal systems cool and thus extend its useful life, including—from lowest to highest efficiency—air conditioners, heat exchangers and direct air cooling systems (DACSs).
Air conditioners use a cooled refrigerant as a medium for thermal exchange, lowering the unit’s internal temperature relative to the external ambient temperature. Compared to the other options, they are noisy, use a lot of power, have many serviceable parts and will not last as long.
A heat exchanger uses aluminum, copper or polyvinyl chloride (PVC) as the cooling surface in a thermal exchange medium.
Finally, a DACS uses ambient air as a cooling medium. It is the most efficient of the three options, consuming minimal power and operating very reliably.
Inclement weather
When installing a digital display outdoors, it is essential to first consider the effects of weather on the unit. Rain, snow, ice, wind and even humidity can have highly detrimental effects on the housing, the screen and the internal electronics.
Rain and snow will corrode the display’s housing if it has not been properly treated and waterproofed. Strong or gale force winds have the potential to damage or even knock over a display. A rugged enclosure for outdoor digital signage should be strong enough to withstand winds up to 241 km/h (150 mph).
It is crucial to investigate local weather patterns before the displays are installed, ensuring products are selected that can withstand harsh regional conditions.
