A Weather Proofed Outdoor LED Light - How It Is Made

This outdoor led light is an early generation led light using 28 small ultrabright LEDs. Power consumption is about 1.5W to 2W. AC input is 230VAC. This is one of the 2830 odd  that lights up the designer domes of the Esplanade Theatres and Esplanade Concert Hall and are currently in the process of replaced by the Esplanade Theatres with new generations more energy efficient and programmable colored LED lightings.

It has been designed for high reliability with the LEDs driven at about 8mA of current, well below the nominal of about 20mA for such LEDs. Measurement shows that the LEDs used norminally have a forward voltage drop of 2.8V.The LEDs are all connected in parallel each with its own 470 ohm current limiting resistor. This configuration allows the LED light to still work even if a few LEDs burns out. The power supply is a proven and simple step down transformer giving 6VAC and  2 rectifier diodes and a smoothing capacitor giving 6.5V DC when all the LEDs are lighted. The LEDs could potentially be driven with 12VDC increasing the operating current to about 20mA, but the increased in brightness seems marginal and the 470 ohm resistor get very warm to the touch. However 8mA seems like a good choice since the LEDs lights are just to illuminate the domes at night.

A Inside Look At A Disassembled Outdoor LED Light.

The LED Lamps are connected in parallel ( daisy-chained ) so for each lamp
there are two AC power cables connected via joins inside the housing.
Making these joints outside the housing will simplify installation and maintenance
but may increase initial costs because weather-proof  electrical T-joints will be needed.

This particular light seems to be better weather sealed.



There seems to be a bit of corrosion inside due to the seepage of moisture or water.

The aluminium clamp ring. Note the use of two different types of screws.
Two screws are fastened directly to the threaded hole in the aluminium case.
Two screws needs a nut each, these are difficult to fastern as an additional tool
needs to be use to hold the nut stationary while turning the screw. This can be
difficult if the LED light is mounted in difficult to acess locations.
This may have contributed to the less than perfect weather proofing in the LED lamp.

Simple robust proven AC DC power supply using a
step down transformer and 2 diodes and a filter capacitor.

A corroded electrical terminal. Because many lights are use they need to be chained up
electrically. This requires the use of T-joints to distribute the electrical power.
Putting the T-joints inside the loght casing in this case makes maintenace difficult.
A better way is to use weather proof T-joints outside the lamp, with only one cable going into the case.

Cable gland for the AC power cable. Two needed for each LED lamp.

At about 10mA for each LED, it is still pretty bright.
The LEDs are operating just before they reach forward voltage saturation,
which makes them quite efficient in terms of lumens/watt.