LCD operation in subzero environments

The problem

As the name suggests, a Liquid-crystal display (LCD) is filled with a liquid crystal between two polarizing filters. In low temperature environments this liquid crystal will suffer from a loss of brightness and much slower response times. In sub-zero environments the liquid-crystal may freeze, causing the screen to cease functioning without the use of supplemental heating.
Traditional methods warming LCD displays in sub zero environments have three main drawbacks.  

1.      They are terribly inefficient, increasing cost of ownership.

2.      They create hot spots in the LCD matrix which risks damaging the display. This is because heat does not travel well laterally or vertically across the panel.

3.      There is a high risk of condensation forming on the LCD. Condensation can shorten the life of electronics and accelerate corrosion in mechanical components.  

The solution

Metromatics has developed a series of rugged high bright LCD displays capable of operating from -40 to +50 degrees Celsius which address the 3 drawbacks listed above.

1.      Efficiency and cost of ownership

Air is a fantastic insulator. When you put on a coat in winter, it’s not the wool or synthetic fibres that keep you warm, it’s the tiny pockets of air the coat traps around your body that help insulate you from the cold. By leveraging this principle and creating a pocket of still air around the screen, we have been able to reduce thermal losses and keep the heat where it needs to be, inside the panel.

2.      Hot spots

Our embedded heating solution ensures heat is evenly distributed across the entire panel, reducing the risk of hot spots forming.

3.      Condensation

Condensation risk is reduced since our embedded heater raises the temperature of the display quicker than the temperature of the surrounding insulating air.

How we tested

To verify the design, Metromatics hired an industrial freezer and tested a display for months on end, cycling the temperature to test different heating configurations and evaluate reliability.


The results can be distilled down into the following graph.

The key points to take away from the above graph are

·         The display was warmed to above 0^oC in under 18 minutes in a -20 ^oC ambient environment.

·         The LCD is evenly heated across the whole surface (left, middle and right).

·         The internal insulating air pocket temperature remains below the LCD screen temperature, reducing the risk of condensation forming.

Immediate operation

If 18 minutes is too long for the display to reach the optimum operating temperature, our ruggedized displays support immediate operation in below zero environments. There is a trade-off is a reduced response time of each pixel while the screen warms above 0^oC, but for largely static images like those used on passenger information displays (PID’s) this is not an issue. As you can see from the videos below, there is some motion blur for fast movements, but slow movements or transitions are still highly legible.

<Insert video of screen operating below zero degrees>

https://www.youtube.com/watch?v=c3lTCwNO7oM

https://www.youtube.com/watch?v=-JjoyAEGE3I

Remote management

Using our networked monitoring and control solution (the MPMS) screen heating can be remotely managed to optimise power consumption and monitor temperatures.

The Metromatics PID Monitoring System (MPMS) is Australian designed technology providing remote monitoring and control of Passenger Information Displays (PID) and digital signage. Its compatibility with SNMP allows ease of interface with existing IT infrastructure and management tools. The integrated Ethernet switch allows for network traffic to be forwarded to other devices without additional hardware, creating a simple, cost effective design.

The configurable inputs and outputs means the MPMS can interface with 3^rd party hardware including temperature, power, door and shock sensors, as well as fans, modems, video cards, heating pads, humidity controllers and power relays. This combination makes MPMS a powerful SNMP tool for a broad range of remote hardware monitoring applications, not just digital signage. The MPMS can be purchased either as a feature of a Metromatics digital sign, or as a standalone circuit board ready to be integrated into your own solution. 

For further information, please contact Metromatics on +61 7 3868 4255 or sales@metrospec.com.au

Infrared Lockout Remote Control Solution

Description

The MetroSpec Infrared (IR) lockout provides a solution to the TV-B-Gone nuisance that plagues transport authorities. It work as a gate keeper, preventing these and other unauthorised remote controls from turning off public information displays (PID’s). 

It works by blocking all remote control signals until a 4 digit security pin code is entered. Once the correct 4 digit code is entered the user is free to use the remote control for up to 10 minutes before the IR lockout is re-established.

Features

·         Locks out unauthorised remotes such as TV-B-Gone.

·         User programmable lockout code.

·         Automatically re-locks after 10 minutes.

·         Low power.

·         Small footprint.

·         Compatible with the NEC IR transmission protocol.

·         Can be retrofitted to existing systems.

Functional Block Diagram

 Warranty

1 Year Warranty

For more information:

Contact sales@metrospec.com.au

High Bright LCD Displays

For an LCD to be viewable outdoors in a bright environment, it needs to be extra bright. The LCD TV in your house is only designed for indoor viewing. If you move it outside it will look washed out and images will be difficult to distinguish. Not what you want for digital signage displaying advertising or other public content.

Brightness is measured in the unit cd/m² (candelas per meter squared), also known as “nits”. Your TV at home will be somewhere between 300 and 400 nits. For a LCD to be clearly viewable in an outdoor environment, it needs to be between 1500 and 2000 nits depending on the size and positioning of the display. In the picture below you can clearly see the difference between a standard brightness and high bright LCD. On the left is a standard TV display (350nits), on the right is a Metrospec X47i display (2000nits).

Picture: (left) 350nit CHEMI LCD (right) 2000nit Metrospec X47i High Bright LCD outside in full sunlight.

The CHEMI LCD on the left (350nits) looks to have terrible contrast because the sunlight defines the minimum black level, while conversely the high lumen output of Metrospec X47i on the right (2500nits) pushes the brightness of the highlights well above the minimum black level set by the sunlight reflecting off the display.

The backlight is a modern LCD display is made up of an array of LED’s. LED’s are much more efficient than the ancient incandescent bulbs or compact fluorescent lamps (CFL’s) they replaced, but they are still not terribly efficient. Only about 3% of the electrical energy is turned into light. The rest is given off as heat. 

Picture: The backlight inside a Metrospec X47i high bright LCD display.

High bright displays are specially engineered to handle the higher power needed to project more light. There is almost a linear relationship between the brightness and power consumption. A 1500nit display might be 4 times brighter than your TV at home, but it will also use about 4 times as much electricity, much of which is given off as heat.

To give you some feel for the magnitude of the numbers we are talking about here, the Metrospec X47i utilizes a 214watt backlight to achieve a brightness of 2000nits. If we assume an LED efficiency of 3% (that is, 3% of the energy used is turned into photons of light) then approximately 207 watts of heat energy will be produced by the backlight set at full brightness.

If you are concerned about your power bill, don’t worry. All Metrospec displays can be equipped with an optional light sensor that will automatically dim the display based on ambient light conditions, reducing energy consumption and running costs.

Hopefully you now have a better understanding of one of the key differences between a Metrospec display and what you might find in your local electronics outlet.

If you have any questions about our products or services, please drop us a line. Our sales team would be happy to help sales@metrospec.com.au or +61 7 3868 4255

Passenger Information Display Maintenance Philosophy

Overview

Metromatics offers two distinctly different rugged high bright LCD designs typically used for Passenger Information Displays (PID’s) at bus, tram and train stations. Both are highly reliable and backed by almost a decade of Engineering expertise, but by changing the physical design we have been able to slash manufacturing costs by 40%. The X-series, equipped with a door, makes on site servicing possible. H-series does not have a door, making it cheaper and reducing your capital expenditure.

In this discussion paper we will compare the two distinct designs to help you decide which design is right for you and your organisation. Ultimately, you want to answer this question.

“What do you want your maintenance philosophy to be?”

Do you want to employ the technical expertise to manage servicing yourself, or use a pool of rotatable spares which get swapped out by low skilled workers and send the broken unit to a 3^rd party for repair?

Servicing

So why would anyone even care about a door on the front of the X-series display? In a word, serviceability.   A door allows the display to be serviced on site and for period inspections to be performed.       A door can be replaced in the event of vandalism.

·      Faults can often be diagnosed and rectified on site by a single technician with no special equipment other than a ladder, screw driver and multimeter.

But that is not to say the H-series is not serviceable. It most certainly is, it just requires a different service and maintenance philosophy. By having a rotatable pool of spares, displays can be quickly swapped out and sent to a service technician for repair. This means

·         

     Maintenance staff do not need a high degree of technical knowledge. They simply swap out the faulty display with one from the rotatable pool of spares and send the broken display away for repair. The H-series is up to half the weight of an X-series, making this a viable option.

·         For serious faults, like an LCD failure or smashed glass, a rotatable pool of spares means display up-time can be kept high. This is of particular importance at critical transport hubs servicing tens of thousands of people every day.

Mean Time To Repair (MTTR)

As already mentioned, both the X and H-series are highly reliable. Both use components with mean times between failure (MTBF) in excess of 50,000 hours. That’s 24/7 operation for more than 5 years. But what about mean time to repair (MTTR)? MTTR is a basic measure of the maintainability of repairable items and represents the average time required to repair a failed component or device.

Serious damage caused by vandalism can take weeks to repair, blowing the MTTR way out and impacting customer service. By leveraging the lower price of the H-series to create a pool of spares, the MTTR can be pulled in, improving your operational availability.

Cost – Capital vs Maintenance

So if having a door is so great, why create a door-less model in the first place? Well, it’s cheaper. If you do a like for like feature cost comparison of X-series and H-series, the H-series will cost 40% less.

With purchasing departments are under more pressure than ever to keep capital expenditure low, the savings offered by cheap imported products can be tempting. But with poor reliability these cheap imports mean sacrificing the long term maintenance budget and increased down time.

The H-series lets you have your cake and eat it too. Thanks to some smart design choices of our Engineering team, the H-series is a rugged extremely reliable high bright display at a rock bottom price. Typically, three H-series displays will cost less than two X-series displays. This means for large installations you can hold a 10% pool of spares and still reduce your capital cost by as much as 34%.

The X-series does have a higher capital cost, but long term maintenance can be lower. It really depends on the expertise within your organization, Occupational Health and Safety (OHS) rules and the size of the display in question. The X-series might be for you if

·         You already employ technicians on staff capable of servicing on-site.

·         Your OHS rules don’t require a team of people to change a light bulb.

·         You don’t have the tools (i.e. scissor lift) to safely remote larger displays mounted high off the ground.

Why such a big price difference?

A door adds a lot of material and labour to the build cost. Metal needs to be folded and welded. Locks, hinges, door stays and rubber seals need to be fitted. The bezel around the screen needs to be larger to accommodate the door seal, leading to more materials being used in the construction of the enclosure.

 Handy comparison

The table below is a handy comparison of the X-series and H-series, highlighting their relative pro’s and con’s when going head to head with each other.

X-Series		H-Series
Pro	Con	Pro			Con
Same reliability as H-series.	More expensive.	Same reliability as X-series.			Pool of spares need to be kept.
Same IP rating as H-series (IP65)	Heavy. It is up to twice the weight of an H-series display.	Same IP rating as X-series (IP65)			Whole display must be replaced in the event of glass vandalisation.
Can be serviced on site.	Damage to door seals may reduce the IP rating.	40% lower cost.			Lifting devices or work platforms required to remove large units for repair.
Except for major faults (i.e. LCD failure), system can be repaired within 30 minutes or less where spares are taken to site.	Requires qualified technicians to service.	Thinner and lighter*.			Whole display must be swapped out in the event of any component failure.
			X-series	H-series
		32”	34kg	12kg
		38”	40kg	21kg
		42”	45kg	25kg
		47”	60kg	38kg
Enclosure is large enough to house extra client equipment and the door provides easy access.		While the H-series is typically smaller, its depth can be increased to house client equipment at an additional cost.
Door can be replaced in the event of vandalism.		Maintenance staff do not require technical training. Repair work can be outsourced.
		Smaller bezel allows larger displays to be fitted in small spaces.
		Pool of spares leads to lower down time in cases of LCD failure or smashed glass.

*Final weight will vary depending on internal equipment and glass options.

If you are still not sure which design is right for you and your organization, give us a call on +61 7 3868 4255 or send an email to sales@metrospec.com.au We would be happy to help you make the right choice.

Rugged Large Format LCD Displays - get "Class A" testing recognition

The MetroSpec Model MS42LFD is a 42 Inch High Definition Rugged Large Format Display designed and manufactured by Metromatics. It is designed for Naval Applications that require high definition video information.

 The MS42LFD is available in single or triple model formats with Anti-glare strengthened glass, LED Backlighting, MIL-SPEC connectors and Elastomeric Shock isolators. This particular model utilises low level display control from 7 to 500 nits but an optional High brightness Display for sunlight readable applications is also available.

The MetroSpec MS42LFD was built, designed and tested to MIL-STD-810F, MIL-STD-167-1, MIL-STD-461 and received a Worlds First – “Class A” Category for Rugged Displays meet­ing shock requirements.

Should you require any further information on the MS42LFD, please contact Metromatics on +61 73868 4255 or sales@metrospec.com.au