Oxley Group is setting the standard for intelligent lighting on the latest generation of armoured support vehicles, both for UK forces and across the globe, as vehicle manufacturers increasingly choose LED solutions for enhanced performance and increased reliability.
Maximising LED performance for military vehicles
The reasons for choosing LED lighting over existing technologies are clear but the new challenge is maximising the performance of LEDs in the military vehicle sector. When buying LEDs for military use, it is most likely to be unseen factors that make the big difference in terms of performance and reliability. Those who design and operate military vehicles must be aware of the capabilities and the limitations of LED technology, and should challenge extravagant claims about the performance of LEDs, which are often driven by data collected in carefully controlled laboratory conditions instead of operational scenarios. In turn, suppliers of specialist equipment should be more open about the actual performance of their products. They must encourage their customers to ask the difficult questions and be willing to give detailed answers in return. Otherwise there is a risk that the huge potential for LED technology could fail to live up to expectations.
Aerospace technology for land vehicles
The military vehicle sector has in recent years benefited hugely from the pioneering work undertaken by specialist suppliers to the aerospace industry. Oxley has consistently worked at the frontier of aerospace lighting technology with night vision retrofits for helicopters and fixed wing aircraft to enhance night-flying capabilities. Oxley has also utilised this knowledge on land applications and has developed a specialisation in infra-red driving lights for vehicles. The team’s LED engineering sets the standard in comprehensive testing, and micro-processor control of temperature and power delivery to optimise performance for maximum service life. Many of the NATO forces now use Oxley LED IR lighting systems in their vehicle programmes as do other forces such as those of Australia and Canada.
In the UK, Foxhound is equipped with intelligent internal DC Combi lights. In physical terms the LED technology means they are very low profile – giving more headroom for the soldiers travelling in the vehicle. As the back door opens the light switches from white to a night vision colour – NVIS friendly capability in a single compact unit. Each of the three lights on board a Foxhound incorporates a microprocessor and a three colour LED which means it can colour change simply through software reprogramming to meet different requirements, offering an efficient and flexible solution with no requirement for hardware changes. The Oxley DC Combi also meets high blast test requirements which are a must in a harsh battlefield environment when the reliability of lighting is paramount.
The Ajax programme in the UK is also fitted with the Oxley DC Combi light and the Oxley Gooseneck task light, this is a flexible and dimmable light produced from high quality components to provide a high vibration, low EMC emitting and shock proof construction for reliability in the field.
Electro Magnetic Compatibility (EMC) is a very important factor for lighting in military vehicles; this is governed by DEF-Stan 59-411, a very demanding qualification which sets the industry standard. LEDs are driven by the use of switch mode power supplies which in turn generate Electro Magnetic Interference (EMI), Oxley product design ensures that the generated EMI does not adversely affect sensitive electrical and communications equipment, particularly in the close confines of an armoured vehicle. Both the DC Combi (Series 3) and the Gooseneck (Series 2) not only meet Def-Stan 59-411 Land Class B, but also Land Class A, the highest level within DEF-Stan 59-411, and are the only LED lights available in the market to do so. Both of these lights also meet the very stringent power input requirements of DEF-STAN 61-5 Part 6, Issue 6.
Reliability and Performance
Every Oxley LED product incorporates technology that is designed to make it perform better and last longer. The LEDs themselves are manufactured by specialist companies and Oxley buys the best on the market. What makes the Oxley equipment different is the integration of those LEDs into the systems designed for military vehicles. That means industry leading heat sink technology, meeting the most stringent EMC standards and providing IP sealing suitable for use in a challenging military environment.
Thermal management for longer life
Unlike filament lamps, LEDs radiate very little heat during operation, which means the heat that is generated needs to be “pulled” from the LED with effective heatsinking. Heatsinking is the key to optimising LED life and optical performance. Most power LEDs have a maximum junction temperature of 150 degrees C, and if it is exceeded the LED life would certainly be reduced.
The properties of the LED also change with temperature but in the opposite way to the one you might expect; the hotter an LED gets the dimmer it becomes, but the colder it gets the brighter it becomes. Without effective electrical and thermal management, LED Lighting applications within military or harsh environments become ineffective, and the units can become as un-reliable as the technology they are replacing, therefore a vital element built into a good quality LED product must be effective thermal management. Conventional circuit boards are made of fibreglass which traps heat and makes it difficult to manage LED junction temperature. Aluminium circuit boards can transmit and remove heat – ideally via an aluminium heat sink. Oxley has led the use of aluminium circuit boards, now regarded as an industry standard, and designs its own highly effective and uniquely integrated heat sinks for industry-leading thermal performance. To effectively manage the LED performance the system must also know how hot the LED junction is getting, Oxley developed the use of a thermistor to measure on-board temperature using its own proprietary firmware and software to maximise performance. A microprocessor within the unit monitors temperature; if the board approaches maximum junction temperature the microprocessor will turn the current down but maintain luminosity performance within specification. It never exceeds the maximum junction temperature for the diode, which in turn ensures the life of the LED is not compromised. This embedded technology makes a huge difference to the actual performance of the LED and the working life of the unit.
When assessing performance data for LEDs it is important for purchasers and end users to question the results. Some companies use laboratory test figures when they are citing performance criteria, not operational conditions. So for example they may claim that an LED delivers X brightness at 25 degrees C – but do not reveal that the unit was tested only in a laboratory for 2 seconds and then switched off. An LED unit is normally more expensive than conventional halogen light bulbs – but manufactured correctly it is ultra-reliable and can often last in excess of 25,000 hours, providing high levels of functionality and reducing overall costs through the extended working life
What’s next for LED lighting in the vehicle market?
Extending the use of LED technology, the Oxley team will be launching two new vehicle searchlights at DVD in September. The first is a high intensity LED unit fitted with handles and a clamping system to allow 360 degree rotation. The light can be mounted on a vehicle, alternatively a tripod with feet allows for deployment off the vehicle. This is a bright light offering a peak Intensity of 325,000cd and an MTBF in excess of 50,000 hours. The second light is a compact solution which is also specifically created for vehicle mounted requirements. The light provides an adjustable tilt angle and is available with a range of light distribution and beam intensity options and offers an MTBF of 30,000 hours. Both lights have high build standards which provide excellent resistance to shock and vibration and deliver a high reliability option for military users who require assurance of performance.
About Oxley Group
Oxley Group is an expert in the field of NVG compatible lighting and advanced LED lighting systems. Product ranges cover area lighting for military shelters and field hospitals; IR vehicle lighting and internal and external lighting for military vehicles as well as aircraft & naval lighting and high specification components. Oxley LED lights are suitable for all types of military vehicles including APCs and logistics vehicles, both in the new build and retrofit market. Oxley lighting systems are proven in service on defence platforms across the world including on the Foxhound, Ajax, the BvS10, the Husky and the Eagle.
DVD runs on the 7th & 8th September at Millbrook and the Oxley team will be on Stand C2-53.