I've recently been playing with a 30 watt RGB LED. It's a similar size
at around 25 x 25 mm, and each 'channel' comprises 10 individual LED
chips in a vertical line. I'm using a collimating reflector and lens
made to go with it, and the heatsink supplied with it as part of the
package. It is a heavily finned 'cube' about 50 x 50 x 60 mm and the
makers state that it requires force cooling - and it does - so that adds
another 15 mm in fan depth, and as you say, then there is the power supply.
The reflector does a good job of collecting all of the output from the
die, and the lens does a similarly good job of producing a basic beam.
However, because the R, G and B LEDs are arranged in parallel lines, the
colour mixing, as you have discovered, is poor, and the individual
colours are patchy. I found that this could be completely overcome with
only a very tiny reduction in perceived output, by placing a sheet of
translucent polythene under the face of the lens that is the LED side.
I'm talking the stuff that's like builder's polythene here. Opaque
enough that you can't see detail through it, but still very neutrally
light transmissive.
In my experience, LEDs are funny old things when it comes to light
output. As a 'for instance'. LED torches (flashlights) are so bright
that you can't look at them. And yet they are poor at producing a light
to see by, and do little to produce any overall lighting in comparison
to a standard incandescent torch bulb. Basically, go into a dark room
with a conventional torch and a LED torch, and you will see better with
the conventional torch. I have a 10 watt white LED that I've also been
playing with, and for some weeks, it has been sitting on the bench just
running. On several occasions when I have dropped screws etc that have
rolled under the bench, I have picked it up with its power supply, and
taken it down to the floor. It lights the area under the bench like
daylight, and yet fallen parts are still more difficult to spot than
they are with a conventional torch. It might be something to do with
either the colour of the light, or the very stark shadows that it
creates ...
Arfa
