Very rapidly we seem to be approaching an age of artificial light no longer being the result running current through filaments of wire. While fluorescent lighting is pretty old, we are finding it being condensed into the compact fluorescent form which is able to replace the regular incandescents. What hasn’t really taken off yet though is a much more efficient lighting method – Light Emitting Diodes. While LEDs are also quite old (we just watched an early 70’s Columbo episode where the murderer ran an electronics company and he was proudly showing off his red LED digital watch he had designed), only in probably the last 3 or 4 years have the ultra-bright white LEDs been around. These have found much favour with the outdoor types for use in long lasting torches and the like. We even have now almost ubiquitous solar-powered garden light. I bought my wife a LED equipped book light recently as well which is pretty good use of this technology.
I have been keeping an eye out for LEDs for general architectural use for a little while now. One problem is that the colour temperature has tended to be very blue and narrow – this meant that illuminated objects didn’t seem to be in full colour. Also you really did need a lot LEDs to get good brightness. Finally they have been pretty costly. Anyway, I visited my local electronics store the other day and spied some 12V MR16 halogen replacements. Unfortunately at $40 each (and the sales guy not all that convinced a permanent store display was worthwhile), I decided to scour Ebay instead . Sure enough, an enterprising Chinese company was able to sell me 3 LED spotlights posted to me for just over $40. We got these last week and installed them in one of our living room fittings. They look pretty cool (warm actually – the colour temperature is definitely redder than the halogen and maybe even a tunsten filament incandescent). They replaced 20W halogens – I would say their brightness is about the same. They certainly are cool to touch, I should measure their current use to find how efficient they are. Unfortunately though they don’t respond to dimmers well. Rather than getting less bright, when I turn down the dimmer they start to falter, flash and then just go out. I guess being a first generation of this type of thing, I am presuming that are using a fairly simple regulator. The dimmer would be a duty cycle chopper but I am not sure whether the 12V halogen supply is a simple transformer or a switch-mode supply. Either way, these can dim and control a halogen bulb properly. I would have thought that a circuit to sense the input supply (whether chopped or simply lower voltage) and could drive the LEDs appropriately shouldn’t be all that hard (though it needs to remain efficient of course).
The other interesting thing is that all the LED lamps I have seen to date (including the ones I bought) use regular discrete LEDs in large arrays. I am surprised that no one has developed some sort of array substrate that contains lots of LEDs. This way a direct area light could be created that could be molded in all sorts of shapes. Even one that resembled a regular light bulb – but with lots of light spots around it. I expect that there will be heaps of innovation along this front in the next few years – particular with a drive to reduce our energy footprint. (And of course the other things is that LEDs themselves should have a 100 000 hour life – which means these new LED bulbs I bought might simply become quaint and old-fashioned before they actually burnout!)