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A Seriously Bright 20W LED Floodlight

Last February, we published a DIY 10W LED Floodlight, which has been enormously popular. We said that one was almost blinding - but to paraphrase Croc Dundee, that's not bright. THIS one is BRIGHT!

Design by Branko Justic* Words and music by Ross Tester

SILICON CHIP has just returned from two days at the Sydney Electronex exhibition, where we met a large number of existing readers and also (hopefully!) new readers.  On our stand, we displayed several recent – and even a couple of future – projects.

Believe it or not, one project which attracted perhaps the most attention was the 10W LED Floodlight, featured in our February 2012 issue.

This floodlight compared more than favourably with PAR38 incandescent and quartz-halogen floods we all know so well. In fact, few could believe just how bright this was and quite a number wanted the Oatley Electronics phone number so they could order their own kits.

What’s this? A 20W?

Click for larger image
The heart of the project is this 20W LED array. It contains 20 individual LEDs. Like all LEDs, it requires a constant current supply, as described in this article. The light has hit this module “just right” to highlight the “–” and “+” symbols moulded into the plastic – these tell you the polarity of the two metal tabs (as it happens, the top tab, under the finger, is the positive).

As luck would have it, waiting for us back in the office was another kit from Oatley Electronics – this time a 20W version of the LED Floodlight.

We quickly assembled this kit and, despite a few wrinkles (which we’ll get to shortly) were very impressed with the light output.

To the naked eye (no mean feat because it was far too bright to look at!) it looked much brighter than the 10W LED version, indeed, much brighter than a 150W QI portable floodlight.

We ran some tests using a Jaycar Lux meter on the original 10W LED floodlight, this 20W LED floodlight, the 150W QI floodlight we originally compared the 10W LED to and finally a 500W QI floodlight.

The results appear on the photograph opposite but you’d have to agree that they are pretty impressive for the LEDs.

Of course, the 500W QI does look a lot brighter in the photos – and it is. But remember, we are comparing this to the 20W LED alongside. That’s 500 compared to 20 – 25 times the power. It sure ain’t 25 times the brightness – both are far too bright to stare into for more than a brief instant.

Just a note of caution, though: we don’t know what wavelength that meter is calibrated to. So there could be a “skew” in the figures if it is more sensitive to the bottom (red) end of the spectrum than the top (blue).

The QIs look very yellow indeed compared to the LEDs – and we all know that QIs have a very much “whiter” light than do standard incandescents.

But as a relative A:B:C:D test, the results are quite telling. And of course, the LED lamps run MUCH cooler than the QIs.

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