As digital kiosks and displays make the transition from interior to exterior locations, a new set of unique challenges must be surmounted. For example, a high bright commercial display cannot be allocated for an outdoor setting without first understanding the environment in which such a display will perform well, and what must be done to maintain and maximize the life of the display. It is important to recognize that all commercial displays do not have the same requirements or impediments to operating in an exterior location.
Additionally, not all displays will function well in a housing enclosure such as a kiosk. In some cases the effort to protect a digital display this way has failed. Such a failure is, without question, an instance where the designer did not fully understand the limitations of the display and what needed to be done in order to help that display survive in a harsh environment.
Failures can occur when:
•In extreme heat. It is not anticipated how hot the inside of the kiosk or display housing would get under direct solar load vs. the highest operating temperature of that display. Heat will quickly cause degradation to the LED’s and AD wires which will cause them to fail. Understanding these conditions will allow you to properly calculate the air movement in order to maintain a steady internal temperature.
•Or, in extreme cold. If a digital display will be turned off at night will that display turn back on in the morning? The liquid crystals will freeze and depending on what commercial display you will be using, this display may not turn back on. There are ways to design against this by adding a heating element but that only leads to additional design and product costs as well as a higher operating cost to the end user.
•Or, in high humidity. Do you need to have glass bonded to the front of the display or do you design an air gap in your kiosk between the back of the glass and the front of the display. It is important to know if the display air gaps between the display and the back of the glass or if the glass should be bonded. Many designers prefer to create an air gap between the back of the glass front and the display face allowing airflow to cool the front of the display. This design will work in dryer climates but it won’t work very well in high humidity environments when using heat exhaust fans. Introducing ambient air under high humidity will cause condensation buildup between the back of the glass and the display. In these conditions glass bonding is recommended. This condition can be simulated in a test chamber by adding up to 95% relative humidity to the chamber.
A real example of humidity problems occurred with one of our clients last year on an outdoor kiosk retrofit in New York. The municipality needed (8) outdoor kiosks retrofitted in the field with 42” LCD displays. The existing kiosks had LED displays in them and the clarity of these displays up close were virtually unreadable. The municipality had already chosen a display manufacturer that did not have bonded glass. Understanding the high humidity levels in New York in the summer we tried to convince the municipality to go with a display manufacturer that bonds the glass directly to their displays or at very least, have us edge bond the glass in our facility. Despite our best efforts to change their minds the stayed with their original choice.
We completed the retrofit work on time and within budget and they were happy with the results. There were no problems with the displays for the first month because this work was performed in early June, but along came July and they started to notice something wrong going on. In the mornings condensation started to accumulate on the back of the glass but go away in the afternoon. As the days progressed and July became hotter the condensation did not evaporate in the afternoon, eventually the displays became unreadable. Maintenance needed to clean the inside of the glass every afternoon, which became very costly. In August we were called to replace all the displays with displays that had bonded glass. This was an expensive lesson that they learned.
Accelerated environmental life testing performed by an accredited laboratory helps a designer understand the positives and negatives of a design. Environmental simulation and accelerated aging are methods of determining how a product will perform in a specific environment by accelerating the exposure to that environment. Environmental simulation is often a critical part of product reliability testing.
The designer needs to understand the environment in which the application needs to survive and for how long it should reasonably operate (typically 3 years). Establishing such parameters enables the lab to create a test that will simulate those conditions within a five to seven day test. This laboratory testing can be done for a specific location or for multiple locations. A simple search will help identify these test labs in your area. It is wise to get a test performed to prove out the outdoor kiosk and display designs before implementation – such testing can save a lot of time and money.
Author Chuck Lewis will be a panelist on the Digital Signage Federation’s November “Hangout” discussion entitled, “Accelerated Environmental Life Testing for Digital Kiosks and Displays,” on Wednesday, November 16 at 2pm EST. More information on this and other DSF events can be found on the DSF website. Both DSF members and non-members may join this or any of the DSF’s scheduled Hangout discussions for free – but registration is required and can be accessed on the DSF website at http://digitalsignagefederation.com/hangouts
Charles W. “Chuck” Lewis currently serves as Director of Business Development for Elite Manufacturing Technologies.