Specifying reliable display systems for outdoor use.
The advantages of using industrial electronics in harsh environments is well known, however IP ratings and environmental challenges when using displays outdoors is a somewhat of a quagmire of information.
We see a lot of tenders for public projects, which have been written by consultants and mandate huge specifications for display systems for outdoor use, that could well be unachievable within the project budget. For example, extremely high minimum brightness and unachievable contrast ratios.
It is important to consider the real-world application for the display, and the ultimate requirements of the display, to successfully complete its function.
Today we will look at some of the aspects to consider when using a display in high brightness areas and public outdoor environments.
Brightness / Contrast
Firstly, brightness is an important factor when looking for a display system that will be used outdoors.
However, not every display requires retina piercing brightness to achieve its objective.
For example, a display system used in a parking terminal does not require the same brightness of those used for digital signage.
More important is the contrast ratio, from the position of the user of the display. Achieving high contrast with a reduced brightness, can create better real world viewing experience.
For our experience here at CDS, we have adopted optical bonding as our preferred method of creating a reliable system for use in this environment. The process of optical bonding is described in our capability document.
Outdoor displays need a cover lens to protect the TFT from damage, therefore the benefits of optical bonding for outdoor displays are even more pronounced.
By filling the space between the emissive TFT layer and the cover lens, you can benefit from the following improvements.
- Higher contrast ratio, due to removal of light refraction within the stack
- No possibility for dust ingression behind
- Ruggedised display, as the bonding strengthens the stack and supports the cover lens
- Reduced greenhouse effect and solar gain (with suitable cover lens)
- Removal of the air gap completely removes condensation that can form behind cover glass during rapid temperature changes (such as a sunny winter’s morning)
- Environmentally friendly, as you can reduce the panel brightness.
Below are some application examples of TFTs with and without bonding showing the fogging that can occur in the airgap of the display and cover lens.
Another important consideration when using high brightness displays in public outdoor environments is to ensure you have automatic light adjustment, where required, so the display actively adjust to the ambient conditions. This is not only important to ensure your display looks its best on a mid-summer’s day, but also to ensure it is not blinding its neighbours in the early hours!
Placement of the light sensor is critical to achieve a real life reading of the work around the display.
In the example above the light sensor was moved to the bottom bezel which avoids the shadow cast by the sun visor.
Check out our Fully Outdoor IP66 Digital Signage Solutions in action on YouTube
1,500 nits Optically Bonded 21.5″ Panel with 3mm AR Glass Verses Direct Sunlight!
Weatherproofing your display systems
IP (ingress projection) rating for outdoor displays in an interesting area to consider, and a lot of this comes down to the capabilities of the client and the surround electronics required, along with the usage case.
IP rating also influences the infield serviceability of the item.
The usage case should be considered from Several aspects
- Installation location- fully outdoor (direct / semi outdoors)
- Local climate (California vs Coventry)
- Interconnections between peripherals (connectors and locations)
- High risk location (such as unmanned / remote areas areas)
- In field service requirements.
Cover lens choice is important in outdoor displays, you should consider the surface finish to reduce glare and reflection, as well as protect from the harmful rays of sunlight if required.
For digital signage applications, we would always recommend our IP66K range as an out of the box solution, with all the electronics (Display, PC, player etc) in a completely encloses system. These IP66 solutions are solid state and have no filters, and therefore require no ongoing maintenance other than a good clean down every now and again. They are particularly well suited to areas of high dust concentration, such as railway stations, some examples below. They use the latest high TNI panels and can withstand surface temperatures up to 110C.
In the case where infield service is required, you could adopt an IP65 design which enables the system to be opened for service whilst in situ. These systems include pneumatic rams to aid single person maintenance and are designed to maintain a constant and comfortable temperature and as such are suitable for street level use with touch screens. They can also include water management such as drain locations and run off channels when opening the device for service.
For semi-outdoor, or integrated solutions, such as those built into street furniture including kiosk you can also adopt an IP65 front face display, which embed into the side of your cabinet. These displays can include rubber sealing gasket to maintain the IP rating of the complete enclosure.
This balances the cost and function of the system, offering a neat and simple way to ingrate a display head into your design. The examples below show a 10” Panel PC with IP65 front, custom aluminium bezel (with light sensor) and PCAP touch tuned for rain exposure.
Aspect and Orientation
It is important to consider installation location. In the northern hemisphere, South facing displays are exposed to the longevity of the sun’s rays through the day and need to be designed to cope with that. Operating temperatures need to be considered dependant on the market and climate of the country of installation to find the best product to fit the requirement. CDS can help and offer a customer-led consultation to find the best solutions.
Many customers are now using displays in portrait orientation to differentiate from traditional systems and as such our IP66K models are designed to work in either format.
Also, through our customisation service, we can adapt designs for specific form factors, for example in the case of limited headroom. Below is an example of an IP65 Stretched Panel PC, with incorporated 4G module and REACT antenna. This was designed as a replacement for a discontinued product and enables the customer to seamlessly support the end user service contract.
Anti-Vandal Resistance & Monitoring
All outdoor displays need to be rugged, however some more than others. We can build systems dependant on your needs, and our IP66K range is designed to meet IK10 standard.
For those remote locations where vandalism can be a problem, we also offer monitoring solutions to identify any problems with the system, including shock sensor, temperature sensor, backlight sensor, voltage monitoring and flood alert.
We can offer many off the shelf display systems but can also design systems to meet almost all requirements presented to us.
We can even install customs proprietary electronics into our systems if needed, which has made their software integration much simpler. These can include 4G Router, fibre converter, monitoring board, react module etc.
Testing and Approvals
CDS take pride in only using tested and approved products from our list of partners having worked in the industry for many years. The experience we have gained has been invaluable to help our customers achieve the best total cost of ownership for projects.
In house sample soak testing is achieved through independent environmental testing using our state-of-the-art climate chamber to emulate outdoor conditions. This can test down to -40C and up to 180C!
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