LED lighting

[Paul Bailey]

Anyone in the group using/or experimenting with LED lighting in the HOME as yet. ,with positive results. As they say Every kilowatt counts..and I might be able to get a couple here!.:)

[Joe Blake]

Not in a big way, but it's certainly on my "list of things". However, a couple of weeks ago I did purchase a set of LED bicycle lights, front and rear (white and red). The front light has 3 white LEDs and is too bright to be looked at directly, even from a distance of about about 4-5 metres in twilight. It uses three "AAA" batteries, and is reckoned to give 8 hours of continuous light (although the capacity of the batteries was not made clear).

The lamp is probably the size of a smallish banana (although not bent) and weighs very little. It fits into a pocket and has a clip on the end. The lensing arrangement focuses the light in a narrow, bright beam, so it's not really suitable for "overall" lighting. However, I wonder whether it would be possible to construct some sort of "exponential horn" mirror which would disperse the light in an annular fashion, with the light shining vertically (either up or down).

Cost? Well, I bought the two lamps plus a bicycle computer with all the appropriate mounting hardware for $39 Australian. I already had 4xAAA batteries (rechargeable NiMH) and I have a couple of solar powered metered battery chargers, so in some senses, I've got free spotlighting.

Might be able to build some sort of stand to hold the lamp as a reading light.

I'll keep my eyes open for a set which has only got the headlight, because I think they are very useful anyway, as a torch, storm light, and so forth.

As a follow on, or tangential thought, I am almost fully equipped with compact fluorescent light sources through my house, and usually have the smallest ones which draw about 3 watts. However, these ARE obviously very dim, and sometimes I need something brighter, so I've had a thought that perhaps instead of having to get up and unscrew the dim globe and replace it with the brighter ones, perhaps it might be possible to have two sockets in the same fitting, with two different wattage globes, and two switches on the wall, one for each globe, or even a chain operated "swap" switch which would turn one on and the other off. I don't think money wise it would be worthwhile, but it's certainly a way of using less power. (With all the climate change happening "suddenly" (Hah!!) our pollies are starting to talk about people having to pay a more "realistic" (ie higher) price for power and water. So who knows? It MIGHT pay off in the long-run.)

Joe

[Rob Beckers]

This has come up before in http://www.greenpowertalk.org/showthread.php?t=412

To reiterate, the average currently available LED bulb is about as efficient in lumens/Watt as the average CFL bulb. So, your 1 Watt LED will give off about as much light as a 1 Watt CFL, ie. not very much. LEDs are much more directional though, so that 1 Watt LED may well be too bright to look at. Just don't try to light up a room with it though. The other issue with LEDs at this time is their CRI.

This is a fast moving field though. So hopefully a really useful LED bulb will come along sooner rather than later!

-Rob-

[Mark Parsons]

Hi Paul,

I recently replaced 3 - MR16 20W Halogen with these 1.2W LED units in my kitchen.
http://www.e-sonic.com/whatsnew/weekly_VaOpto_MR16.htm

Much improved over a multi-LED version I tried about a year ago. I would say these units put out about 1/2 the 20W halogen lux - to my eye anyway. The CRI is poor - quite blue. Wouldn't want to cook under them but they work great to see what is in the pantry. Saving over 18 watts per light is also great. My track light is a transformer 12VAC type so I just barely see a little flicker from them due to 1/2 wave rectification, I assume. I presume that 12VDC full wave would resolve this.

Mark

[Paul Bailey]

These MR-16 LED units are NOT dimmable ...correct??

[Rob Beckers]

Not sure if one can buy this in the shop, but LEDs are actually very easy to dim: By driving them with a current source instead of a voltage source, and simply regulating the current. Done it many times.

-Rob-

[Ted Sanford]

Hi,
I'm just passing on something that a friend showed me.
If you take two of the 36" long, 3/4" dia flourescent bulbs, wire up ends for them to a 2 lamp, T8 ballast, and put them on opposite sides of a 16'x16' room, they will light it very well. The bulbs, ends and ballast are available at Home Depot for not much.
You get more light, and more even light, for 60 watts this way than compact flourescents. I made a little deflector from some cedar I had laying around to shine lthe light up and down, instead of into your eyes.
Ted

[Paul Bailey]

Anyone in the group have a link or a reasonably accurate converter ??? More so for LED's and the amount of lumens thier producing for various wattages. In other words...I'm getting interested in these Led's again:)

[Rob Beckers]

Paul, lumens/Watt for LEDs is all over the place. From less than CFL, to about twice as much for the more experimental LEDs (most better commercial ones are just about the same as CFL in lumens/Watt these days). The manufacturer's docs give the numbers.

-RoB-

[Joe Blake]

Not quite sure if this converter is of any use.

http://www.mastlight.com/tool.html

If you're into caving, this may be useful.

http://caves.org.uk/led/foot1.pdf

http://caves.org.uk/led/foot3.pdf


Just yesterday I bought a handful of white automotive LED "globes" as used in turn indicators. I'm going to play round and see if I make some sort of "multi-spot" light from PVC pipe, that will run directly off 12 volts. The globes were just under $10 (Aus) each and the appropriate globe holder (pre-wired) were $4+ each. So for under $15 plus scraps of PVC water pipe I may have a viable light.

Will keep you informed.

Joe

[Paul Bailey]

Thanks Joe and Rob for the followup. I also did some more internet digging and I'm presently stalled on this since led's still don't represent good value ( $$ spent vs light output) Especially now that regular compact flouresants are now Cheap and are of good value with lots of bulb sizes available ( I now have about 55 compacts in service for over 15 years and lost only a few) I'm also testing 4 Led bulbs but really there just way too much $$$ money for the available light output ...Paul:)

[Rob Beckers]

Paul, what you write pretty much sums up my take on LEDs at this time.They are currently no more efficient than CFLs, and for most of them their spectral output is horrendous. Both of these things are changing though and LEDs may very well have a bright future (pun intended). It just hasn't arrived yet...

-RoB-

[Joe Blake]

Finally finished my basic light fitting using LED car globes.

http://i82.photobucket.com/albums/j245/saxeharp/lights.jpg

Haven't been able to give it a full try out, but a couple of points of interest. The globe holder base is wrapped in foam rubber and gaffer tape, which gives each individual fitting a small amount of flexibility. Plus of course the T-junctions can also give some directionality. Using these 4 lights can give a "broad spot" ie an area of very bright light with faint shadows where there's no overlap between. And being auto sockets the globes can be changed very quickly to give different colours (if you really want them).

I haven't been able to measure the wattage drawn, but based upon very sketchy research on the net I calculate that it should be drawing about 2-3 watts.

I've already given the cost of the lights etc. The T-junctions and right angled fittings were $1.50 and .90 cents each respectively, and obviously can be re-used for something else.

And of course the whole thing is presently just a "press fit" model, and can be reconfigured into different shapes.

Joe

[Joe Blake]

These piccies show the sharp definition of the lit area comparing the lighting on my hand to that on my face and the shadow pattern generated on being lit from behind. The room is rough 4-5 metres across, and I'm standing about a metre and a half from the light source.

http://i82.photobucket.com/albums/j245/saxeharp/lights02.jpg

http://i82.photobucket.com/albums/j245/saxeharp/lights03.jpg

Joe

[Mike Green]

Anyone in the group have a link or a reasonably accurate converter ??? More so for LED's and the amount of lumens thier producing for various wattages. In other words...I'm getting interested in these Led's again:)

lumens per watt is the very parameter by which we rate the lighting efficiancy of an installation. Joe posted some converters for candela to lumens. (candelas are handy when evaluating a beam, as in using halogens for hi-lighting, lumens are necessary for calculating the amount of light on a surface- Lux)
As such a watt lumen converter would not exist as an empirical converter across the board, rather the opposite is so. the lumens per watt ratio is a value specific to a specific brand and model number of light bulb.

[Larry Hollenberg]

I have one of those multi led lamps in a stairway light because it uses very little power and can be left on for some time if I wished. I tried it in a lamp with very unsatisfactory results, very blue light and not flattering to the surroundings. Worst part was it was the most expensive bulb I ever bought. So I would say till they perfect something better I wouldn't want them other than for the steps.

[Joe Blake]

Since putting together my little system shown above, I managed to make some "diffusers" would you believe by cutting a suitably sized hole in a white ping-pong ball.

http://i82.photobucket.com/albums/j245/saxeharp/P8140044.jpg

If you're wondering about the reddish tint, the LED globe on the left is actually a red 12 v automotive one, and in real life, it looks a bright red ping pong ball.

These globes have 19 LEDs, which is probably the same as the ones you are using.

I've got these light running off my old 12 volt battery pack from my electric trike, and I had them on for something 5 days continously before I realised the batteries weren't connected to the charger. The globes (ping pong balls) stayed at air temperature (15-16 degrees C) after all that time. They're not bright, but I'd certainly say they're a great emergency light.

http://i82.photobucket.com/albums/j245/saxeharp/ping.jpg


In Australia, they cost about $10 each globe.

I'm making up a bracket so I can carry one white and one red LED globe on my trike if I ride at night time.

Joe

[Aawebdev Piter]

The key strength of LED lighting is reduced power consumption. When designed properly, an LED circuit will approach 80% efficiency, which means 80% of the electrical energy is converted to light energy. The remaining 20% is lost as heat energy. Compare that with incandescent bulbs which operate at about 20% efficiency (80% of the electrical energy is lost as heat). In real money terms, if a 100 Watt incandescent bulb is used for 1 year, with an electrical cost of 10 cents/kilowatt hour, $88 will be spent on electricity costs. Of the $88 expense, $70 will have been used to heat the room, not light the room. If an 80% efficient LED system had been used, the electricity cost would be $23 per year - there would be a cost savings of $65 on electricity during the year.

[Rob Beckers]

Aawebdev, welcome to the forum!

Not to rain on the LED parade, and they do have a bright future, but the current reality isn't quite as good as you describe. There are a few LED chip manufacturers that make very efficient ones, reaching around 100 lumen/Watt, maybe even slightly higher. Most notably Cree. Once put into a fixture, their efficiency depends very much on how hard they are driven (they are more efficient at lower currents, but because they are so expensive they are usually run at a higher current and light output), real-world numbers get these from 75 to 90 lumen/Watt. They are very expensive.

Move to the no-name Chinese LED chips found in all the cheap LED bulbs and you're more realistically looking at 50 - 65 lumen/Watt. This is described in detail by the ongoing tests done under the 'Caliper' program of the US Department of Energy (http://www1.eere.energy.gov/buildings/ssl/reports.html). They also report an average CRI of around 80 to 85 (which describes the quality of the light, the lower the number, the more 'artificial' it will look and the more colors will be off).

For comparison, the average CFL bulb at this time will do around 65 lumen/Watt, while a T5 fluorescent reaches 90 - 100 lumen/Watt (and those are mid-life values). CRI for those is a wide range with about 85 average, and bulbs all the way up to 97-or-so available (the latter would be "full spectrum", or "daylight"). For current light bulbs the top spot is the low-pressure sodium bulb (the ugly orange light used for parking lots and roads) with about 150 lumen/Watt and a low, low CRI of just 5. Now you know why they use these bulbs for road lights...

A regular incandescent reaches around 8 to 10 lumen/Watt, while halogen bulbs do slightly better. They have a good CRI though.

The theoretical maximum (I got this from Wikipedia) is 683 lumen/Watt, though it would have a piss-poor CRI since it would consist of only green light. For white light with a decent CRI the maximum is somewhere around 300 lumen/Watt. If we take that number, and the average LED/CFL bulb light output at this time (65 lm/W), it works out to an efficiency of about 22% from electrical power to light. That's still a very far cry from the 80% you mention...

What LED chips have going for them is that they are very directional. For certain applications, such as high-bay and parking lot lights, and spot-lights, that means they reach very good luminous flux per Watt (lux/W), similar to the best of the fluorescent bulbs. For most regular incandescent bulb replacements where the chips are arranged to project light all around that is not the case though.

The short of it is that I believe LED bulbs have a very bright future, but they are still not quite there yet for general purpose lighting. LED fixtures are already there for specific applications such as parking lot lighting and possibly high-bay lights (warehouses and such). For the time being I'm sticking to CFLs for my house.

P.S. The reason I have all this information handy is because I looked into LED bulbs very recently to see if they would make sense for lighting the new warehouse/office we are building for my business. My conclusion was that they do not at this time, T5's are far cheaper, and mostly more efficient (unless you get high-end LED fixtures from companies like CREE, but even so their CRI can't touch what I can buy in T5 bulbs, and they are just too expensive at this time).

-RoB-

[Alton Root]

always prefer LED light only because CFL lights is the mercury contained in the bulb, Mercury is a dangerous heavy metal, and proper cleanup and disposal of CFL bulbs is critical. Never put a used CFL bulb in with the rest of your trash.