LED Flashlight--Off topic

I think it depends on the LED. Those Garrity "Glo-Tastic" electric light sticks make the plastic tube that they're made out of flouresce (the blue and green ones both have blue LEDs). The blue LEDs from Radio Shack, while looking exactly the same to the eye, do not make the plastic tube flouresce.

So who finally got to chow down?

The L92 cells are simply lithium AAA cells. They were just introduced. They are sold where-ever the energizer lithium AA cells are found. In the US that's about every other store that sells batteries. They are a bit more expensive but they allow high drain in a small form factor.

Hmmm. There are a few out there that come close. In the last year several new lights have ben introduced with dimming capability. Many have special signaling modes. The 1 AA NiMH makes it real hard, as that's nominally

1.2 volts and the white LEDs tend to be 3.5 to 4 volts. That means the converter must triple the voltage. A 2000mah NiMH at 1.2 volts becomes a 690 mah at 3.6 volts. Add in converter losses and it's hard to get 1 watt out of it for two hours.

Check out the features of the lights at

and you may find what you want.

Most of the more complex lights use 1 or more CR123A batteries. You can buy them for $1.25 each at places like the batterystation.

Boy! Now THAT's off topic!

Let's bring it back a little; I've put a picture of my light at

My light is the silver one. My light is exactly 3 and 7/8 inches tall in that picture. Making it required turning, boring, internal threading and external threading. The dc/dc converter was scrounged out of a $9 light.

The leftmost (model ARC AAA) runs on a single AAA for 5 hours. It runs twice as long on a L92 :) . The second one (model ARC LSH-P) runs on a single CR123A for 2 hours at about 10x the brightness of the AAA. The one on the right (model Surefire L1) runs on a single CR123a for 50 hours (dim) or 2 hours (bright). All three of the bigger lights are brighter than a Maglight.

Daniel

that's about every other store that sells batteries. They are a bit more expensive but

I've never seen them available retail in the UK.

The actual harder bit about the converter is getting it down to size. It's got to be quite high frequency, otherwise the size of the needed caps and inductors balloons.

I'm looking at building, rather than buying. Sapphire front lens, stainless body, optimised optics, thick gold plated contacts. And diameter not much bigger than the batteries.

Yeah, with all the *$&%^# that people eat these days, it is not surprising that it would eventually be toxic to the cat. :-)

This morning's Los Angeles Times reports another "cat in a tree" episode in La Canada / Flintridge, only a few miles from my house. The Dept. of Fish & Game closed off the area and the cat came down after a few hours. I'm glad they didn't try to shoot it -- I think they are magnificant creatures.

Alan

(thanks)

If you want to look into building lights, a good forum is

's the Homemade and Modified lights section of a flashlight discussion board. There's also a Materials/Mechanical/Machining section. The folks there appreciate advice from experienced machinists and are more than happy to share information about building lights.

Daniel

They would be welcome to all the dogs they could snag, around here. And the children are armed anyway. I think big cats around here would do wonders for the deer population, anyhow.

Jim

And I'd love to see your circuit if you don't mind. (Remove the obvious for e-mail.)

Why?

I tried that many years ago. I dismantled the flashlight and gave all contacting surfaces a heavy (brush plated) gold coat. Worked for a while but didn't last well. I'd be inclined to solder in NiMH cells and use an encapsulated reed switch such as 306-1168-ND or HE133-ND available from

. (Digikey seems to go to the effort of dealing conveniently with folk not in the US.) Mount a small bar magnet for actuating the switch.

Ted

The mountain lion is a beautiful sight in the sun as it moves away.

Be aware if cats and or dogs begun to vaporize - think - they all didn't run away.

I've been in deer country just after fauns are dropped. That is when big cats and bears are really dangerous.

In the home site, the wild will almost always win with a kill. That is what they know.

Martin

It's not finished yet.

Because I'm mounting the LED on the lens, and extracting the heat from the LED through it, with a reflector (at a variable distance) behind it, shining back through the lens. This reduces the length of the flashlight a bit.

Brush gold isn't really very good. I was thinking more actual thickly plated buttons.

The switch is going to be totally electronic, it will actually be on constantly in a standby mode, to run the microprocessor.

A micro may not actually be overkill - it's the simplest smallest way I can implement all the things I'd like to include.

I said "with the right elex" which your tests very likely did not use, and for good reason. I agree that a single AAA is not a good choice for 1 watt service.

I think you're on the right track using a micro to get function and features not available in silicon offered by from Zetex et al. Mr Yamaguchi

taken that course as well.

Right. It's probably the only way to get the features and function that you seek.

Ted's discovery of these very small reed switches cracked a code for me on my little LED light project. Electronics is easy peasy, packaging is the challenge. This got my switching function inside the O ring seals I already had designed in. The very small reedswitch is made by Philips, should be readily available in the UK.

I'm not designing a flashlight, though it does use a very bright Luxeon LED. Packaging is an issue because it does need to be all-weather betcherass reliable. There are many very good flashlights available.

Please keep us posted on your progress in making one that is even better. Your use of a sapphire lens as a heatsink is interesting. I don't see much advantage in a retroreflector, but one issue I had with that concept was heat transfer which your scheme neatly solves. Streamlight, I think, offers the "recoil" which is a retroreflector but I wonder how or if they accomplish heatsinking without fragility.

Interesting, though I think a hall/GMR sensor (I'm considering a compass function) might be another way.

True.

The reteroreflector lets you shrink the size, while retaining beam quality. It was the only possible solution for reterofitting a mini-maglite solitare.

With a conventional parabola, you lose a lot of the light out the front, with most designs, meaning you don't get a nice sharp beam, but a lot of light goes round the edges. (this is nice, but sometimes you want the beam to be actually as good a beam as you can get to pierce the darkness) Use a conventional LED with an exterior lens helps, but you've got a big tradeoff between the lens capturing enough light, and light bouncing off the inside of the lens due to extreme angles, again scattering the beam.

I'll see how the prototype optics works.

I used the appropriate resistor, to draw 1W from the cells. The voltage dropped significantly after 10 mins (a fraction of the capacity) and decreasing the resistor value to keep it at 1W meant it died shortly afterwards.

I'm not saying that no NiMH AAA cell can do this, just not one cell of the 4 of varying brands I tested.

Micros are so cheap low power and small nowadays, that even running them all the time on an AA cell will not noticably degrade the shelf life for many technologies. (lithium excluded)

That's somewhat the wrong way to do it. At the end of life, the cell can't provide the power needed to run the light at full brightness, if you try the voltage just falls to 0. If you reduce the output power, you can get significantly more out of the battery that a circuit that demanded 100% all the time can.

And I know I'd prefer a lamp that went dim, or otherwise indicated imminent failure, rather than one that just went out.

You needn't exclude lithium in that assertion.

True if "beam quality" means maximum collimation for long "throw",

So an unconventional parabola would be better? What sort of unconventional parabola might that be? Unconventional focal length perhaps. The trick in a retro is to match the reflector to the feed's radiation pattern so the feed port doesn't block the beam.

I played with this using the radiation pattern of a white Luxeon side-shooter emitter with the constraint of reflecting nearly all emitted light in the beam while blocking nearly none with the emitter in the retro path. Math model. Found a minimum exit aperture and focal length of truncated paraboloid of revolution to make it so.

You're surely well past my primitive level of understanding, but I found it fun to explore. Question for you, pls: how will you make and then reflectorize your reflectors?

I think Ian's point is that with a five to ten year shelf life on lithium it might be hard to keep standby drain low enough to be negligable. Even 1uA is in the 40 to 90mAh over the shelf life.

Ted

You have the right of it there! Graceful degredation rather than sudden catastrophic failure. One of the reasons I neve liked relying on incandescant flashlights for night hiking. (I used to use a carbide lamp with a small pocket flashlight for short term backup.)

Ted