Question: Lifetime and reliabilityI have been told that LED’s work for 100,000 hours but I hear that some only last 10,000 hours. What is the truth?

Answer: The short answer is ‘both’, it’s all down to how you define lifetime of an LED and reliability. One key difference between current lighting and LED’s is in the definition of a failure. Led’s, if driven correctly, are inherently reliable and do not stop working. Their failure mode is decreasing light output, so it is the norm to specify the point in time when the light output drops to 50% of its initial output and even after this time, the LED is still working but it is not as bright.

LumiLed has taken a leaf out of the lighting industry and raised the bar to 75% of initial light output, which matches the Lighting industries requirements for Lumen Maintenance targets.

So the claim for Luxeon LED’s is 50,000 hours before the light output drops to 75%. However the LED is only one piece of the solution, so we design all our drivers and Colour engines to match the lifetime of the Luxeon LED at 50,000 hours or more.

For more details visit www.luxeon.com and click on search tab and type in the following: - AB07 Lumen Maintainance.pdf. Click on the found file for ‘AB07’ which should take you to the Documents store, where you find this article (and many more).

Question: How do I wire three HaloLED's together to work with the MicroDriver 9?

Answer: The connection is straight forward and please use the following application note to assist you “Application Brief - HaloLED and MicroDriver 9 wiring.pdf” on the Lumidrives website under Applications.

Question: How do I set the DMX address on your ColourDriver?

Answer: The address is set using the DIP switches on the side of the ColourDriver. Please note that any numbers found on the DIP switch itself do not have any relevance to the addressing of the unit. The Datasheet shows the DMX address and how to set the switches.

Please note that the driver needs to be powered off, for any address changes to take effect and that the termination is only set on the last driver in the chain.

Question: How many ColourDrivers can be connected together using DMX?

Answer: 32. The Colour Driver has two DMX ports allowing loop in and loop out wiring. Remember only the last driver in the chain needs to have the terminal switch on!

Question: All your LED boards are wired in series, why?

Answer: For ease of wiring and flexibility. LED technology requires a constant current to power the LED and in the past, the control circuit to achieve this was very simple (resistor). With the Luxeon LED, an electronic power control driver that ensures the LED’s are powered at the correct current under all circumstances.

By using a constant current controller and wiring the LED’s in series, we can ensure that any manufacturing variations in the LED (Vf) and volt drops in the cabling is overcome. This allows the driver to be remotely located and allow long cable between the driver and LED boards (30m) without loss of performance.

One offshoot from this approach is the ability to mix different colours of LED ’s together in a spring.

Question: I am writing regarding information about LED lighting. I am trying to find out about LED light output. What is a lumen and how does it compare to the way we measure conventional light bulbs?

Also, could you advise me on a suitable LED product that could help a first timer get started and understand the general principles of LEDs?

Answer: Thank you for your email regarding LED's. Your quest to compare current light sources against LED sources will be a tough one and you hear the phrase "it depends..." an awful lot! I have attached an article written by Gordon, which covers LED lighting. IEE Review Routledge 21-25.pdf

Beware the claims of no heat, LED's do generate heat BUT in a very small space, so the key to successful designs is the heatsinking of the LED, which is why LED's are blended in with the fixture and not stand alone, like a capsule or gls lamp.

Second key point is LED's require a driver and please make sure that the driver is the correct one for the LED's you wish to use! Also beware of electricians who think LED's are low voltage Halogens, and can save money by using a cheap LV ballast. (The LED works really bright for 0.5 milliseconds as one-shot flash bulb!!)

Finally, White LED are made from a mixture of Blue and Yellow which fools the eye into seeing a high colour temperature white ~6000 degK (Blue LED with a Yellow Phosphor coating).

The LED is not a pure white source of light; it is a monochromatic light source, red, yellow, blue and green. It strength is the saturation of colour, it's control, reliability (50K hours) and low energy usage. Its weakness is lumens output per emitter and cost.

So if you need colour and especially changing colour, LED is the only way forward and by using Red, Green and Blue LED's you can generate all the colours needed just like a TV screen.

If you need low maintenance, stylised, controllable, low heat, rugged and reliable lighting then LED's will have a play. If you need cheap white light then you will need to wait a few years.

Question: How long can the cable be between the ColourDriver and the LED fixture/board?

Answer: The cable can be 20 to 30 metres long however longer runs can be achieved using a higher grade cable.

The reason for this, is that we use constant current techniques to drive the LED’s which compensates for the voltage drop losses in the cable.