Big Ass Touchscreen

Five massive 95inch Samsung displays tiled end-to end across one wall creating a huge interactive surface certainly qualifies as one bigass touchscreen. In fact this interactive wall at the entrance of the Museum of History in El Paso, Texas is the largest in the US and it is only the second in the world of its kind.

Digital History WallGigantic Interactive Wall

This is not five individual touch screens, it is one touch screen that covers the entire five displays and provides tracking of unlimited touch points over a diagonal span of approximately 425”. The sensor system is able to track virtually an unlimited number of users providing an immersive, interactive experience like no other.

The wall’s developer Gibson Group of Wellington New Zealand, who specializes in interactive museum projects, was looking for an alternative to the home grown touch screen used in the first version of their DigiWall in Copenhagen, Denmark. To simplify construction and reduce maintenance, they began searching for an off-the-shelf product. “We wanted a system that didn’t need individual frames for each screen, to get that seamless bigger than Texas look, and we wanted accuracy and reliability in up to 5000 lux of daylight”, said Gibson’s Director of Exhibition Projects, Allan Smith. “Frankly, almost all touch systems we evaluated were nowhere near meeting our requirements.”

History Wall, El Paso TexasWhat was chosen is a technology based on an infrared (IR) detection system with LED IR emitters on the bottom and right side and IR detectors on the top and left side. It is different than the touchscreen used in most portable devices which is primarily projected capacitive (ProCap) which works by tracking the changes in capacitance caused by your body’s own electrical field. In an IR system, however, a touchpoint is determined when a light path is interrupted.

The reason IR is used instead of ProCap is not only because it would have been cost prohibitive but ProCap is simply not yet ready for ultra large multi-touch surfaces.   Moreover, ProCap requires a conductive coating which would impact the screens brightness and clarity. An IR system, on the other hand scales easily with size and is far less costly and much easier to integrate and since it is an edge-based detection system, the display quality is preserved.

Museum of HistoryThis IR touchscreen system is comprised of a frame (40mm wide x 14mm high) which is positioned around the perimeter of the displays and using a patented processing algorithm, is able to scan the touch surface more than 250 frames per second and track an unlimited number of touch points. The result is a high performance touchscreen which provides a smooth experience and rapid response even fully loaded with guests.

Since opening in February this year, Gibson Group reports the system has clocked up 8.5 million touches “without missing a beat. It’s a robust and impressive touchscreen system”, said Smith.

Redundancy and Reliability

Redundancy and reliability is also built in. For instance if an LED goes out the system is self-healing and is still able to operate. In fact, according to the manufacturer, over 75% of the sensors can be turned off and the system would still detect touch — though with a very limited number of touch points. The reason it can do this is the way in which it detects the touch. Rather than a one-to-one relation between emitter and detector, the receivers scan multiple emitters many, many times per second and can compensate for damaged LEDs.

El Paso Museum of HistoryAs this is an outdoor display and the sensor uses an optical detection system it has to be able to compensate for ambient light conditions. First and foremost, the design of the structure incorporates shades and filters to minimize direct sunlight and to reduce direct IR heat loading directly on the display. In addition, the touchscreen frame uses a frequency similar to your IR remote, however, sunlight is still comprised of the full IR spectrum. To compensate for potential oversaturation of the system, the touchscreen uses a process similar to what was used in WWI when radar was first developed. By cycling the LED’s on and off and measuring the light when the LED emitters are off, the system can take a reading of the ambient light levels and therefor remove the ambient light readings from the processing leaving only the very bright light of the LEDs of the IR frame for touch detection.

Integration and Installation

Digital Wall Construction

Digital Wall Construction

For the developers Gibson Group, not only was the touchscreen installation easier and simpler to maintain than the original, homegrown version, but the new touchscreen solution offers an SDK to allow developers to easily integrate interactivity into their applications by providing helpful hooks to the touchscreen’s data to make programing easy.

Global integrator, U-Touch, Ltd. of London England was called upon for its extensive expertise in very large interactive displays. The most important aspect of the installation being flatness of the surface. The touchscreen system has some tolerance for an uneven surface but since the surface could not be covered with one continuous piece of glass, the mechanical structure had to be developed to minimize expansion and contraction in the structure from fluctuations in the outside temperature which could be as high as 120F in the summertime.

Digital Wall Construction

Digital Wall Construction

It was a massive undertaking to design a structure that would not only hold the 95” panels but also the glass and supporting assembly. It was a collaborative effort between the design team and integrators in which the mounting structure was fine-tuned before the custom structure could be deemed ready for installation. After which, the system was fully tested at U-Touch’s US facility in PA before being shipped to El Paso for onsite assembly and implementation.

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