If you want to REALLY save battery energy, use the most efficient LEDs available and try and use a radiation patter directly out of the LED that puts the light where you want it. if you can manage to not use LED covers you also get extra output BUT you don't really want to have to be cleaning the actual LED surface AND some modern LEDs have a soft silicone dome which should not be handled. Top luminance bin LEDs are usually available from most major makers. The gains can be substantial. Price differences will pay for themselves in extended run times for a given battery charge. A Good modern 1A to 1.5A LED will five 130+ lumen?Watt at 350 mA. Running them derated like this helps efficiency. Cree, Nichia, Lumileds, Osram and a few more make superb product. Most others make rubbish, or use die from the ones who know how. "Cree inside" is common. (This is one area where reputation and "appeal to authority" actually works). Making LEDs which work and last approches a black art. The number of manufacturer's who CAN'T get it right is stunning. Keep temperature down - helps lifetime substantially and also output. Passing light through almost any transparent cover will lose about 10% minimum. Around 92% transmission for typical thickness low iron tempered glass, slightly better for good polycarbonate. Reflectors and lenses lose light. 72 W of incandescent should be able to be reduced to about 10 Watt of LED with the same radiation pattern and with properly directed LEDs you probably need About 6 Watts. Try a few high efficiency LEDs first to see what you can achieve. If truly keen you can get 160 lumen/Watt from Nichia "Raijins" at 30 mA and under 100 mW each. (Vf is about 2.9 V). Hard to get at present. Not cheap in volume compared to using eg far fewer Cree XP-E at much higher current. In a top efficeincy modern LED, approaching half the energy input leaves as light! Russell McMahon On 21 February 2010 01:47, David V. Fansler wrote: > I saw an article yesterday > ( > http://www.elektor.com/news/white-power-led-achieves-200-lumen-per-watt.126 > 3836.lynkx?utm_source=UK&utm_medium=email&utm_campaign=news) > where a company > has reached 200 Lumen per watt - they should be interesting. > > Owning a sailboat, I have been looking for ways to reduce power consumption > (since we run off batteries when away from shore). The four 12vdc bulbs in > the galley consume 6A total. I am in the process of replacing them with > strips of 80 Lumen LEDs. The design uses a TI TPS61161 driving a string of > 10 LEDs. The current consumption of a single string is 300mA. We are > hoping that 6 strings will be enough (waiting of the LEDs to arrive) - this > would cut the current by almost 1/3. I am using my CNC machine to route > out > the circuit board, which around the TPS61161 is really small. The TPS61161 > is a 2x2mm chip with 6 pads (3 on opposite sides) - a real bugger to > solder. > David > > David V. Fansler > s/v Annabelle > dfansler@dv-fansler.com > www.dv-fansler.com > > > -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf > Of > Apptech > Sent: Sunday, February 21, 2010 1:50 AM > To: Microcontroller discussion list - Public. > Subject: Re: [OT]LED Light Bulb, how many lumen is enough? > > > Try to replace the 60W and 100W regular light bulb with "LED light bulb", > > I am curious how many lumen of the "LED light bulb" shall I use? > > It very very very much depends on what you are trying to illuminate and how > much area you want to illuminate. > As a rough guide, multiply the area to be illuminated in sqare metres by > the > > followin figures, or by 1/10th as much for quare feet. > > 0.5 See dimly night light > 10 Usefully bright, colour discernible, not vreally enough for > reading. > 20 Good for color reading and detail discernment. Dimmer than some > would be happy with > 50 Very adequate for most things > 300 Stupidly high recomended level for detai work. > > eg for "Very adequate for most things" over a 2 square metre table you need > 2 x 50 = 100 lumen. > That's about 20 square foot table so using table value/10 gives 20 x 5 = > 100 > > lumen (of course) > > 100 lumen can be had from a top / very efficient modern 1 Watt LED with > minimal diffuser or reflector losses. > Say a top bin Cree XP-E etc. Or an equivalent xxx Dragon, Rebel etc. > So to be safe about 1.5 Watts. > > You can do a lot of good in a "personal illuminator" with 15 lumens! :-) > > To light a 3m x 3m = 1 ' x 1-' room to "Good for clour reading" needs (3 x > 3) x 20 = 180. > Say about 3 Watts. Note that this is if you can get all the light evenly > distributed and with minimal losses and with a highly efficint LED giving > 100+ lumen/Watt OUTPUT. > > Real Worls modern LED bulbs are unlikely to give much more than about 70 > l/W - about the same as a good modern CFL. > > Note that these levels are below what people are generallyt used to, even > though the brain will handle them very well with time. > > Using the 300 lumen/m^2 western guideline on the 3x3 metre room gives 3x3 x > 300 = 2700 lumen of about 30 Watt. > You would be very very very well illuminated with 30 W of good quality LED > lighting in a 3m x 3m room :-). > > YMMV but that's a good start. Try buying a few top quality LEDs high angle > white LEDs rated at say 1500 mA, heat sink them well, tun them at 1000 mA > or > > so and try them out in various locations. That will open your eyes (pun > only > > vaguely intended) to how much you can do with 3 Watts of energy - and what > the real limitations are. If you want to light a very large area as with > say > > a security spot then you need some real power. For most applications you > don't. > > > Russell > > > > ----- Original Message ----- > From: "Funny NYPD" > To: > Sent: Thursday, February 04, 2010 7:40 PM > Subject: [OT]LED Light Bulb, how many lumen is enough? > > > > Try to replace the 60W and 100W regular light bulb with "LED light bulb", > > I am curious how many lumen of the "LED light bulb" shall I use? > > > > Funny N. > > Au Group Electronics, http://www.AuElectronics.com > > http://www.AuElectronics.com/products > > http://augroups.blogspot.com/ > > > > > > > > > > -- > > http://www.piclist.com PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist