Jeremys LED Lighting Page.pdf
Jeremy's LED Lights Page
What's in this document?
This document contains detailed electronic information and will hopefully be of use to both novices
and more experienced hobbyists and electronic DIYers. It assumes you are familiar with basic
electronic concepts such as Ohm's Law, and the operation of bipolar transistors, MOSFETS and of
course LEDs. If you are not, I suggest looking them up on wikipedia.
I have tried to gather together and interpret many threads of information that it has taken a long time
for me to comprehend, there being many pieces of information scattered about in the world with not
much help on how to use the principals described. I have included a level of detail on the use of
inductance for buck regulating circuits later on in this document that I have not found anywhere but
have had to work out for myself over the last few years.
What do I Need?
Construction of these ideas requires the use of soldering iron and other tools, such as pillar-drill for
accurate drilling of metal. Although I have put all information that I think is necessary I do not
guarantee you will be successful since only YOU can determine that.
Introduction to Power LED's
I have made LED lighting for various spaces to run from solar power. It is the highest efficiency
small scale lighting solution available at this time, thanks to the Z-LED P4, an LED illuminant
which boasts 100 lumens (A measure of total light output) for 1 watt of power. To give some some
scale to this, compare to a good 8W fluorescent strip at 460 lumens (57.5 lumen/watt) or a similarly
good 13W strip giving 1000 lumens (77 lumen/watt). Compact fluorescents are about
60lumen/watt. These LEDs are not cheap at €8 each, but lifetimes are in excess of 50,000 hours, so
replacement is not necessary on any usual time scale. Using them, at this stage, means a little bit of
work since I have not seen any commercial product with them in yet – they don't quite fit easily into
any of the standard fittings for halogen bulbs etc. because of their cooling requirements, though I
have seen some attempts, at nearly twice the price each, and probably using an inferior LED
judging by their ratings.
At full power their efficiency reduces but they still produce 240 lumen at 3.5W input power – 68
lumen/watt, the same as a normal (not special high-output) 13W strip, but the light is considerably
better than a strip, being dimmable, turnable, colourful, UV-free and with appropriate optics
focusable too. My impression is that they are very close in colour to sunlight, confirmed by playing
with my cameras white-balance settings, so do not be scared by the 'cool-white' label; and whereas a
single candle will suddenly “illuminate” a room full of strip lights, when lit by LED's the space is
already lit so the candle doesn't have the same effect. I tend to use them at about 70% since they are
still high efficiency and producing lots of light at that level. Turning them up further doesn't seem to
do very much either. At that level, 3LED's were drawing 0.51A from my caravans 12V lead-acid
battery and the entire caravan was lit well enough to read comfortably in the bed area or chop
vegetables in the kitchen, a task that four 8W strip lights drawing 2.7A had been unable to achieve.
We were using head torches to read and cook (the tubes are all fully functional though older 400
lumen rated, and the somewhat yellowed plastic diffusers removed) though this was partly due to
poor placement of the strip lights