Low cost light source for flats

[The Admiral]

I'm investigating a cheap LED light source for possible use in making flats. It's basically a mains-powered round light fitting intended for use in ceilings. Here: http://led.me.uk/led-ceiling-lights/round/12w-round-recessed-ultra-slim-ceiling-light-in-cool-white. This one I purchased is a 12w cool white version that has an overall diameter (including fascia) of 170mm, and an open lit aperture of 125mm, so it's ideal for my 102mm frac. It cost under a tenner. The supplied leads are very short, and the "driver" is, I suspect, just a resistor, as the unit is very light. On the other hand, the light unit itself is made of cast alloy, which is good. Here are some photos.

 

 

Looking straight down on the un-lit unit.

 

 

 

And now with it lit. I've underexposed so that you can see any unevenness of light. The periphery looks a little darker than the centre, but much better than I expected.

 

 

Camera

DMC-GH2

Exposure

1/500s

ISO

160

 

 

 

There's clearly a bit more work to do yet, but it shows promise.

Ian

Edit. Sorry, I just can't seem to get rid of the EXIF panel.
 

[The Admiral]

Here's the more-or-less finished item.

 

I've bolted through the periphery of the light, and included a 3mm sheet of opal Perspex in order to diffuse the light still further. Here it is on the 'scope, but I need to acquire some pipe insulation of the proper size to centre it on the tube.

 

 

I also photographed the light to see how uniform the light levels are. It was taken with a 'copy' lens and cropped from the centre of the frame so I don't expect a lot of inherent fall-off other than due to the source.

 

Just to put this light fall off into perspective, here is the same image but with circles representing the inside orifice of the dew shield (orange line) and the objective (blue). Overall, I'm quite happy with this.

 

The resulting light is, though, very bright. I needed something like 1/10,000th second at ISO 200  with everything mounted on the 'scope' in order to get the histogram below half way. Maybe it is possible to provide an alternative feed to the LEDs so that they can be dimmed. This wouldn't be a bad idea anyway as I'm not entirely happy that the so called 'driver' unit provides isolation from the mains. The light colour is a touch green-ish, typical of the cheap 'white' LEDs.

For info, I got the hardware from Kays Fasteners, the plastic spacers from TBW Fasteners (both via EBay), and the opal Perspex, cut to size and drilled, from SimplyPlastics. I got good service from all suppliers. Total cost I reckon is under 30 quid, and I've still got some of the hardware left over.

Anyway, food for thought.

Ian