LED Flashlight--Off topic

I have all sorts of things that all seme to use the 357 size cells. I don't have a dollar store around that carries them, but you can save a budle over Radio Shack prices if you buy them in boxes of 10 from McMaster Carr. They want a little over a buck a cell, and Radio Shack is over twice that.

Doug White

Actually, all white LEDs use blue, not UV. It's quite a violet blue, but it's not UV. ("real" UV LEDs are very expensive)

That doesn't match with what my reading on various web sites seems to say is the case. It also doesn't match "real-world" as far as I'm aware: Last I'd heard, there's still no LED available that puts out "blue"

*DIRECTLY* - Blue-appearing LEDs are (again, based on my reading) spewing some other wavelength (UV is most commonly mentioned) into a phosphor-like substance, which then spits out the desired blue light. Supposedly, white LEDs are a refinement of the same concept, using a mix of phosphor material to give an output that's more or less white. (personally, I find it far *LESS* than white - Not a single white LED I've laid eyes on actually makes light I'd consider to be "white". Dunno what, if any, proper term there might be for the color, but I flatly refuse to call it "white" - Plain and simple, it isn't! Not according to what I see, and DEFINITELY not by the technical definition of white light.)

Which makes me ponder... I really need to point this thing at a prism and see just what color(s) it's lacking/rich in... Maybe that'll help me figure out a "why" for the "haze" effect I get from them. Going purely "by eyeball", the beam

*DESPERATELY* needs AT LEAST some red to swing it toward what I could consider calling "white".

More pondering... Would the LED flashlights benefit from, for instance, 6 whites in a circle around a red? Might need to be fairly picky about the red that gets chosen (and/or how much power it gets fed) to balance the beam, but it would seem to me that throwing a bit more red in the mix would at least help some with the haze problem I've got.

I read someplace that red is missing from white LED and there is no reflections from red unlit taillight. I made a cluster with banks of 4 LED with 12 volt supply, no resistor. I have 8 green LED and 32 white LED. I am happy with the result.

N40° 3.744' W75° 6.180'

LEDtronics makes warm LED lamps that work very nicely for video. I purchased a 42 LED array in a MR-16 housing ($62) that I've used for a couple of Model Engineer Exhibition videos. Just enough light to pop the colors and open up the shadows. This company makes arrays up to around 400 if you need a street light.

2004.

I knew the number sounded fammiliar Like a CR2, but longer. Commonly used in cameras. Pricy little devils, but they CAN be recharged several times if you have the right charger, The "New discovery 109000 handles them very well. It is a microprocessor controlled charger

The websites you are reading are wrong, currently UV LEDs are very expensive, around $200 for a .1W device, compared with blue emitters which are about $7 for 1W.

Nope. I can confirm this absolutely because I have dissasembled white LEDs and removed the phosphor layer, to expose the blue behind, and measured the wavelength. It's also mentioned in nearly all datasheets.

I suggest you have a look at

has better information.

The 'white' that most white LEDs produce is not a very good white, but a layer of yellow phosphor that's thin enough for quite a bit of blue to shine through. This blue + yellow means that you get a sort-of white. There is little red or green.

There are 'warm white' LEDs available, but these produce about 80% of the apparent brightness of ordinary ones.

If you do that experiment you will see the blue resolve into a single band - of blue. I've done that with the R/S leds.

And you don't need much red to get the white appearence - this is how so-called "Cool-White" phosphor works in fluorescent lamps. It's a physiological trick of the human eye, which percieves a mix of yellow and blue as "white."

If you look carefully at a white led, you will see that the plastic lense focusses the two different colors at slightly different planes - so you can see a ring of different color around the outside.

The neat thing with the blue leds is they will drive most hot pink or red pigments to fluoresce. Red gage needles and so on light up great wtih those.

Jim

A pig is smart enough to test an electic fence everyday to make sure its working. If its not, there out for a walk! I have seen ponies and cows that you cannot force to walk where an electric fense use to be! Takes them years to figure out the wire is gone!

cs

I've seen similar from ponies/horses in regards to just a normal "not electric" fence. Recently, in fact. Knocked the dividing fence (two "walls" of 5 strands of high-tensile wire on T-posts) out from between two adjacent pens after the occupant of one of them finally succumbed to old age. Once the demolition was completed, the group of ponies from "next door" took the better part of a week to cross the old fenceline and start exploring their expanded digs. For several days, they behaved exactly as if there was a solid wall where the old fenceline was. I actually saw one of them do an ass-over-teakettle crash when they got to playing "chase me" with each other, and she got herself lined up to head for the far end of the new expansion - She got close to where the fenceused to be, hit the brakes to avoid crashing into it, and ended up eating dirt right at the point where she would likely have stopped if the had still been there. Picked herself up, shook the dust off, snorted at the former fenceline, then took off like her tail was on fire and her ass was catching - heading AWAY from where the fence used to be.

Equines... Go figure...

They came up with an actual blue LED in teh mid 1990's. Near UV leds (395nm) sell for a buck or two.

The high powered LEDs (brand name Luxeon) are extremely bright and can be very white. They use a blue light source that shines through a yellow emitting phosphor. Yellow is a mixture of red LIGHT and green LIGHT, so the result is white. I have a luxeon light (a modified 2 C Maglite) that will throw a beam that can be seen on a palm tree 300 feet away. Reflectors and lenses are available to concentrate the light.

The small lights that use a lot of little LEDs are NOT in the same class as the Luxeons. The little LEDs are typically fed too much power and that makes that blue tint.

There's a lot more information on discussion groups like

Some of us "flashaholics" use get into machining to build our toys.

Enjoy,

Daniel

Actually, yellow light is just yellow light. The human eye perceives a combination of yellow and blue as being white. Strange but there it is. This is what makes cool-white such an economical phosphor for fluorescent lamps.

I have a luxeon light (a modified 2 C Maglite)

The luxeons are great - my favorite is the one watt version inside Underwater Kinetics 4AA light.

JIm

Current project is a 1AA 1W luxeon light. I was going to do a 1AAA 1W luxeon light refit for a mini-maglite, but even NiMH AAA cells can't really do 1W.

Whose electronics are you using for voltage boost?

Jerry and I are making single CR123 (2/3AA) 1-watt lights using Teralux elex. I haven't seen the Teralux module yet, but I suspect it uses the Zetex 310 chip. That chip doesn't work very well below

1.8 volts or so.

A single AAA could do 1 watt with the right elex, but it'd have to be a circuit where peak current is about the same as avg current. The "LED driver chips" use flyback topology with peak current > 2X avg current.

On 11 Nov 2004 17:45:04 GMT, Ian Stirling wrote.

My wife has one of those blue/violet keychain LED lights and I can confirm that it puts out plenty of UV. We were at a museum display of antique syrup pitchers. I pointed at one and commented that it looked like uranium glass. My wife pulled out her light and pointed it at the pitcher. It lit up with the beautiful yellow glow you see from uranium glass under UV light. Our guide was rather startled to say the least. :-)

Alan

Way off topic now, but look into the everready L92 AAA lithium battery. It can do 1 watt. It's a touch above 1.5 volts when fresh. It has a shelf life of 15 years! It's also much lighter than an equivilent alkaline cell.

There are an awful lot of good LED based lights now. I have 20 or so, and I don't have all the good ones. The UK 4AA eLed is a nice emergency light with it's 10 hours of full power per set of batteries, but it's not super bright.

Now I'm making my own. Turning them on a 7x10 lathe. My current light is an aluminum 3 part light; head; body and tailcap. The body's just a touch bigger than a CR123A, and it drives a LUX III at .35 amps (about

1 watt). It's brighter than a 3 D-cell maglite. It fits in my pocket.

Daniel

My own.

In tests, 1AAA NiMH cells diddn't really want to.

There are low-power near-UV LEDs, they are not the ones used in white LEDs. Lots of things glow under blue light.

Hardly matters for AAA cells. Also, I'd like it to work with reasonably available cells, not special ones.

Tests I did with NiMH cells that were lying around indicated that 1W was pushing it.

I'm looking at variable power, from 1W down to about .05W, for a life with

1 AA NiMH cell of about 2-40 hours. (in addition to a 1W/for 1/1000th of a second per second mode, to aid finding in dark)

Don't have a (functional) metal lathe :(