Considerations for outdoor displays

by Matthew | 7 November 2012 8:30 am

By Peter Kaszycki
Digital displays deployed indoors enjoy a comfortable, controlled environment. There is no rain or wind, vandalism is rare, the air is clean and the ambient light levels, humidity and temperature remain consistent. For outdoor installations, on the other hand, digital signage needs to be designed with the assumption none of these factors can be controlled.

With outdoor environments, everything is constantly changing. As a result, almost anything can happen to an installed digital display, with harsh effects.

Dealing with change
Outdoor displays must be built to withstand high humidity, rain, snow, wind, dust, dirt, particulates and occasionally even vandalism, particularly when installed on transit platforms or along sidewalks, in transit shelters and other ‘street furniture.’ They will need to operate in both heat and cold, including extreme temperatures ranging anywhere from -30 to 50 C (-22 to 122 F).

Compared to indoor displays, they are also more likely to operate between 16 and 24 hours a day, rather than a simple workday duty cycle of only eight to 12 hours. And to be effective at communicating their messages, outdoor displays need to be visible even as ambient light levels change throughout the day.

Ambient light sensors can be installed to automatically and gradually adjust a screen’s brightness at different times, based on the surrounding conditions. This function is also helpful at night, when signs that are too bright can annoy the public and digital out-of-home (DOOH) advertisers alike.

Cold-cathode fluorescent lamps (CCFLs) are not recommended for LCD backlighting outdoors. Only light-emitting diode (LED) backlighting systems should be used. They can ensure better uniformity of illumination and create less additional heat to deal with, but can also be adjusted in blocks as needed.

Finally, a glass cover laminated with an anti-reflective coating is recommended to help ensure the screen is as visible as possible when hit by direct or reflected light, whether coming from the sun, nearby buildings’ exterior lights or passing vehicles’ headlights.

Sunlight
One of the most significant factors is the impact of the sun. In a sunny environment, high-brightness displays will be needed for optimal viewing, achieving luminance of between 1,500 and 2,500 candelas per square metre (cd/m²). The displays’ brightness should be measured through their cover glass and/or film, of course, not just at the surface of the liquid crystal display (LCD) itself.

When positioning outdoor digital displays, east and west orientations are the worst, as they will receive the most direct sunlight. North and south orientations are best.

Also, given digital displays face perpendicular to the ground, sunrise and sunset are the worst times of day, whereas high noon will not affect the screen much at all. Sunlight is also harsher in winter, when skies are clearer and haze lower.

LCDs are not all created equal. Some will lose 10 to 12 per cent of their brightness each year. A display that is designed for the direct sun load and can maintain its brightness over time is substantially preferable.

Another concern is ‘solar clearing.’ Under the heat of direct sunlight, the fluid within an LCD can go through a phase change, causing black blotches to appear on the screen or even blot it out entirely. Once the LCD cools down again, its appearance may return to normal. Beyond the temporary visual disruptions, however, solar clearing is a real threat that will reduce the display’s operating life.

Beyond the screen itself, the paint finish should provide protection for the framing unit against harmful ultraviolet (UV) rays over the long term.

Heat and humidity
Some LCDs are specifically rated to operate at temperatures of 20, 27, 43 or 50 C (68, 80, 110 or 122 F). The higher the rating, the better. Embedded electronics, including the media player, data modem and/or router, will need to be rated for the display’s internal temperature.

‘Sealed’ displays are preferable. These will prevent condensation from forming inside the cover glass, as well as keeping out rain, snow, dirt, brake dust, car fumes and other airborne contaminants. They also can be washed down safely when needed.

As mentioned, some LCDs lose brightness over time. Certain models will lose 10 to 15 per cent of their brightness simply due to ambient temperature conditions. So, temperature fluctuations can affect content visibility.

One of the best ways to address the outdoor environment is to attempt to control the display’s temperature as much as possible. There will need to be a plan to heat the display if it will operate in freezing conditions and, similarly, a plan to cool it during extreme heat. Conventional air-conditioning (a/c) systems, unfortunately, will drip condensate water (which could cause condensation to form inside the cover glass), require maintenance for coolants and filters and consume significant power. Fans and alternative methods should be considered instead.

An outdoor digital signage network may also require special startup procedures for hot or cold environments, as powering up at low temperatures is different than at high temperatures.

Considerations relating to sunlight, temperature and humidity may seem overwhelming, but once they have been factored into the procurement and deployment of digital displays and precautions have been taken, the investment will be well-protected.

Wind
The digital display and its mounting structure must be designed to withstand local wind loads, which might include gale winds and hurricane forces. A wind load can certainly reach 225 km/h (140 mph).

Vandalism
To contend with vandalism, the digital display will need breakage-resistant, replaceable cover safety glass. (Some types are ballistic-resistant.) That way, the glass can be replaced without needing to replace the LCD. Displays that are optically bonded to their cover glass should be avoided.

Proximity sensors can be added, so as to sound an alarm when a vandal strikes. Sensors can also be added to the ‘doors’ of the display’s casing, so an alarm goes off specifically when someone tries to open it.

Sealing a unit properly will also protect it from insects and rodents.

Public space
Another difference between indoor and outdoor digital signage deployments is that of private and public space. An outdoor installation may require a municipal, regional or provincial permit—and will probably need to be certified by a professional engineer. Unions and safety personnel might also be required for both installation and subsequent service.

Servicing and maintenance should be made as easy as possible, since repairs may need to be conducted in cold, rainy and/or windy conditions. Modular replacement components will help accelerate such work.

Bylaws can also mean restrictions on full-motion video content for digital displays, particularly when screens face traffic, as well as on audio content. It is important to check local codes before determining what the nature of a new display’s content will be.

Many outdoor digital signs will transition between static images, for example, rather than display video. There may be restrictions that affect the frequency of these transitions (e.g. allowing changes only every 10, 15 or 30 seconds).

Local codes could also determine whether or not an outdoor digital display needs to be automatically dimmed or even shut down at night, generally after 11 p.m.

When choosing a location for an outdoor display installation, it is also important to determine how the power supply and data connectivity will be achieved. Power will need to be run to the unit. Displays with a universal power supply of 85 to 265 V are recommended, keeping in mind that due to their brightness and other aforementioned factors, an outdoor display will consume three to five times more power than an indoor one. Summer could bring brownout conditions if the current draw spikes and trips the circuit breakers.

Connectivity, meanwhile, can be provided with a simple modem and antenna for cellular-based data service. It is important to check area coverage first.

In addition to bringing updated content to and allowing remote control of the screen, connectivity is necessary in terms of sending information back to the network operation centre (NOC), including verifications that content has indeed been displayed, operational data and alerts, such that the screen can ‘phone home’ if it experiences a failure. Under these circumstances, the NOC needs the ability to reboot the modem, switch or embedded media player.

A different world
For all of these reasons, true outdoor digital displays are not simply repackaged indoor displays. With common failure points like overheating, solar clearing, fading brightness and insufficient power, they face a significantly harsher reality, with the sun being ‘enemy number one.’

While there are many considerations, questions and extra costs that come with properly deploying outdoor digital signage, however, the benefits of reaching an out-of-home (OOH) audience are also significant and well worth the time and effort.

Peter Kaszycki is vice-president (VP) of business development for Manufacturing Resources International (MRI), a provider of indoor and outdoor digital displays. For more information, contact him via e-mail at pkaszycki@mri-inc.net[8].

Source URL: https://www.signmedia.ca/considerations-for-outdoor-displays/

---