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A Really Bright 10W LED Floodlight

Light level rivals halogens - at MUCH less power!

By Branko Justic & Ross Tester

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A close-up view of the LED array, already mounted in the lamp case. You can quite clearly see the 3x3 pattern of LEDs in the centre.

When the Australian government announced its ban on incandescent lamps in 2007, one of our first thoughts was “what are we going to do for floodlights?”.

Mainly powered by halogen lamps of 150 and 500W ratings, these floodlights have become incredibly popular in domestic, industrial and public lighting installations.

Until quite recently, there simply wasn’t a viable alternative to the halogen lamp, often called a QI lamp, which stands for Quartz Iodine (the construction and gas inside), not Quite Interesting (the TV show).

But with the recent spectacular developments in LEDs, there is now a very effective replacement for  power-hungry halogen lamps.

To get this into perspective, halogen floodlights comparable in size to this LED floodlight generally use 150W lamps; 15 times the power! Their light output varies depending on type but a typical figure is about 2300 Lumens, or about 15 Lumens per watt (2300/150). And that really only happens with a new lamp as light output drops with age.

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The photo doesn't really do it justice: it's so bright, it's dazzling!

 The light output from this LED floodlight output is not as high, at 720 Lumens and therefore, 72 Lumens per watt. 

OK, so that’s about one third the light output of the Halogen but almost five times as efficient.

But as we show in our measurements, even those figures can be quite deceiving! (See the panel “How Bright?”).

LED array

The majority of high-power LEDs these days are made from a number of individual LEDs forming an “array”. In this case, it’s a 3x3 matrix of pure white LEDs, each one rated at 1.2W. The net result is a single LED light source rated at roughly 10W (there are some losses).

The array itself measures about 1cm square but with mounting, the whole assembly measures about 2cm square – still pretty small compared to a halogen lamp. Attached to each side are tabs for soldering power leads.

The good news is that in this kit, the LED array is already fitted to the lamp housing (which acts as a heatsink) and a reflector drops into place around the LED array. So the hardware side is easy!

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In this and the photo at right, we've disassembled the lamp housing to show how it all goes together. The reflector "drops into" the space above the LED array - but be careful that it doesn't short the two solder connections (on each side of the array). If there is any doubt, we'd be inclined to put a washer or two under the reflector where the screws hold it in place.
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This photo shows the disassembled lamp housing from the rear. Note that in this shot, neither the holes for the PCB mounting screw nor the cable gland have been drilled (the cable gland hole can be seen in the pic at left). The blue item second from front is the reflector, again seen in the photo at left. Don't be tempted to leave out the gaskets - they keep the whole thing waterproof when used outside.

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