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Toys

LED Flashlights 113

Daniel Rutter writes: "LED flashlights are better than incandescent, but not for the reasons you might think. I've done a couple of hefty LED flashlight comparisons, now. The latest one, just finished, is here. It covers the neat little Streamlight Stylus 3, five Tektite lights (four of which are waterproof to 1000 feet...), and a couple of old-fashioned filament-bulb Maglites, so you can see how the new technology stacks up. My first comparison is here; it covers a few of LEDCorp's cheap but tough lights, and some of the very, very Star-Trekky EternaLights. They've got microprocessor control, baby!" Nifty. Birthday presents galore.
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LED Flashlights

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  • by Anonymous Coward
    If you were to actually cool your spiffy new LED flashlight to some low temperature, you might actually be able to get a factor of two brightness increase out of it.

    Incidentally, check out www.lumileds.com (spin-off of Phillips lighting and Agilent (spin-off of HP)) where they make *monstrous* LEDs with 1mmx1mm dies that can handle a good fraction of a watt input. A couple of these would be equivalent to a tail-light, and they're aiming for even brighter ones in the next couple years. I think you can buy them for $5 if you are willing to buy in the 100's.
  • by Anonymous Coward
    Here is a site [att.net] that has tested pretty much every LED flashlight produced.

  • by Anonymous Coward on Friday June 08, 2001 @01:52PM (#165197)
    And an infra-red model, which may come in handy for those among us whose hobbies include telling something to put the lotion in the basket or it'll get the hose again.

    What the hell is he talking about?
  • He's probably trying to infer that his wife/girlfriend/teenage daughter is a bit too shy of the sun ... infrared ... etc...

    Weird Aussie humor. I don't get it, and I'm Australian.
  • running around the net with javascript enabled. . . for that matter, for using a non-lynx browser :)


    hawk

  • by tzanger ( 1575 ) on Friday June 08, 2001 @02:45PM (#165200) Homepage

    A friend of mine has made several flashlights out of LEDs, potentiometers (as dimmers), and short lengths of PVC.

    Good idea but I would suggest building a small CMOS oscillator or using a 12C509 PIC and Pulse Width Modulate (PWM) the LED instead of burning up the excess energy in a potentiometer. The batter(y|ies) will last much longer.

  • This is obviously the definition of someone with too much timeon his hands.
  • Cannot focus the beam, as the reflector is inside the LED itself

    One of the very first lights reviewed in this article does focus the LED much like a normal flash light. It is true that very few others do though.

    The "white" light, while impressive and cool, is not that great for night-time viewing. It can ruin your night vision, and does not display contrast as well as the yellow light. (of course, no one wants to put a yellow LED in their flashlight, even if they exist, because it's not "cool")

    The white is definitely easier to read by though, at least for me. It does reduce your night vision though. Works well for finding cables under a desk in a dim office though.

    P.S. I'm sure I have seen yellow LED lights, they might just be micro light sized though. You can definitely get the red ones full size. Good for preserving night vision. I don't really like the way red ones make things look though.

    So.. my advice is to find a local outdoors retailer that has these lights, or better yet -- look for a flashlight freak like me that has these lights, borrow them, and try them out before you plonk down $20+.

    If $20 is a lot of money, definitely borrow first. If it isn't march right out and buy a Proton and put it on your key chain. Proudly declare your flashlight geeakery. Maybe later you can buy a real LED light too :-) I haven't gotten anything bigger then the CCTrek, it is good to read by, and my wife uses it to watch the dog in the backyard. It probably has almost saved it's own cost in bulbs and batteries yet. It would be a bad hiking light though.

  • However, am I the only person who thinks it is a little bizarre to test flashlights as a hobby? Somehow this behavior does not strike me as beneficial to the evolution of the species as a whole.

    Well, after the metetor hits/nuclear war breaks out/other awful event happens, only those people who know flashlights well will survive and have offspring.
  • >Somehow this behavior
    >does not strike me as beneficial to the
    >evolution of the species as a whole.

    Versus being a vegetable in front of the TV
    and/or computer monitor?

    I think it's interesting. The world needs more
    people who do things other than just become
    sheep.

    -Kevin
  • ...a lot of newer motorcycles are coming with LED turn signals and brake lights. I have seen some, and they are very effective.

  • From the article:

    The Freudian behemoth in the middle is Mag Instrument's Club With A Bulb, the six-D-cell Special Police Brutality Edition.

    The "Police Brutality Edition"?

    LOL!


    --
  • If you want to replace the Maglite Solitaire, get the LED light from Arc Flashlight [yahoo.com]. This is slightly smaller than the Solitaire and also uses only one AAA. They also have infra-red [yahoo.com] and ultra-violet [yahoo.com] LED versions.
  • I just received my eternaLight [techass.com] Xray [techass.com] and I can't stop playing with it, it's so cool! It's got bright-dim, flash, strobe, SOS, and other modes. As well as a blue LED that flashes very 2s so you can locate it in the dark. I can't wait for night; I'm going down to the basement to test this baby.

    I got mine from theLedLight.com [theledlight.com]; they've got them on special [theledlight.com]. You can also get them from Glow-Bug [glow-bug.com].

  • I have one of these an I love it.
    Built like a tank but very light(considering it has 6 bateries in it!)
    Each battery is 3V so it has the equivalant of 12 penlights in it!
    Comes with 2 bulbs so you can chose between BRIGHT and ^@@#@%^BRIGHT!
    Cost me an arm and a leg(and 2 elbows,) but was worth it.
    Surefire makes the best (conventional) flashlights I have ever used, and I collect them.
  • These lights are so bright that you cannot force yourself to look in their direction at night(and it HURTS even on a sunny day!) You can feel the heat from across the room! And yes, they have IR filters to make these a strong source of IR.
    Where full auto fire is avaliable(or you are facing multiple advosaries that are spread out,) I agree. The enemy can just spray the area you are in with supressing fire and either you get hit by the fire or an area weapon like a gernade.
    Police action is USUALLY quite a bit different.
    As the expression goes: 'You cannot hit what you cannot see.' And trust me, it this light is shined in you eyes unexpectedly, you can not help but turn your head(closing your eyes is usually not enough even in daylight,) and by the time you can look back, you can be filled with holes.

  • Well, considering (when compared to you lot) we EUian's burn half as much energy as you do per head of population, produce far less emissions, and actually stick to deals we make to reduce world polution (ever heard of Kyoto!) .. I don't see what's at all self-righeous about being me.

    Wake up and smell the coffee. Keep putting the needs of your economy first like this, and you'll end up choking on your own success. Unfortunately, so with the rest of us. Thanks very much!!!!!!


  • No of cause it's not my job. I also know it's Offtopic, and it's the first time I've ever said anything political on /.

    But I have to say, it really scratches an itch. I'm genuinely pissed off about Bush's behaviour over world polution. And I'm not alone either. The majority of Europians are not impressed with Bush's pro-polution policies, or the pro Star Wars initiative (but that's another topic entirely).


  • > Burn half as much energy? Prove it

    Pointers to text evidence I don't have right now. I've just seen it stated so many times on UK TV News and Documentary programs (like Panorama) that I know it to be a fact.

    It wouldn't surprise me to find that most Europeans know this too. Nor would it surprise me to know that most USAnians don't.

    And who gives a rats ass about your taxes. We're talking about polution of the air we breath, and destruction of the natural protection this planet has against solar radiation.

    Or does a few more dollars in your pocket each month mean more to you than that? You're already the richest country in the world. Don't be so dam greedy!

  • by kzinti ( 9651 ) on Friday June 08, 2001 @02:12PM (#165214) Homepage Journal
    It's a quote from Silence of the Lambs

    Yup. To elucidate further, the serial killer "Buffalo Bill" used IR goggles to see in the dark, so the reviewer must think he needed an IR flashlight.

    At one point in the movie (though he's not using the IR goggles at this point), he has a victim he's holding prisoner in his house. She's being held in what appears to be a dry well dug in the cellar. He's starving her so her skin will loosen, and he wants her to put lotion on her skin to keep it from drying out. He lowers a basket into the well with a rope, and tells the girl to apply the lotion. But instead of speaking to her directly, he speaks in the 3rd person and refers to her as "it":

    It puts the lotion on its skin, then it puts the lotion back in the basket.

    This is what the reviewer was referring to, though it was pretty obscure and I didn't get it until reading the previous post.

    --Jim
  • It is not my intention to dismiss anyones hobbies with this post. To the contrary, I think the review is kind of cool in a geeky sort of way. =] However, am I the only person who thinks it is a little bizarre to test flashlights as a hobby? Somehow this behavior does not strike me as beneficial to the evolution of the species as a whole.

    Anyway, shine on you crazy diode...
  • I think it is interesting also....I even said so. Everyone has something that turns their crank, for example, I build networks (big, medium, small), backpack, and bicycle among other things. My comment was that I found it a unique way to spend ones time. Perhaps I was flippant....alas, another pastime of mine.

    Yours truly,

    Mrs Premis -or- Mrs Conclusion (to your liking)
  • It seems to me that I saw a /. article about a year ago which was talking about LED flashlites, and one of the links I followed was to a website which touted an LED array that had something like 256 LEDs, each of which could be computer-controlled to set a specific RGB frequency.

    Essentially, this LED spotlight had the ability to cast millions of colors, and was an interesting substitute for a PAR can and gels.

    Anyone know any kinds of products out there that might fit this description? I find myself out in remote locations often, having to film subjects in the dark, and dragging old-fashioned spotlights out there is getting annoying.
  • colorkinetics.com: Bingo! Thanks 1meg!
  • One good thing about LEDs is that they simply grow dimmer as the battery runs down, unlike incandescents which have a tendency not to glow at all once the voltage falls below a critical point.

    Umm, LED stands for Light Emmiting Diode. Diodes need to overcome a certain critical voltage (the reverse bias voltage) before they let more than nanoamps of current through (~ .7 volts for silicon at room temperature). Less than that and they act as a close to ideal break. Much more and they closely approximate a short.

    Perhaps you meant to say that they work well at low currents.

  • by Lumpish Scholar ( 17107 ) on Friday June 08, 2001 @01:52PM (#165221) Homepage Journal
    A friend of mine has made several flashlights out of LEDs, potentiometers (as dimmers), and short lengths of PVC. They're great for providing very low levels of light during star watching parties; you can read maps, tweak screws, etc., without destroying your night vision (or that of the people around you). Some people prefer red (lowest energy wavelength); some prefer green (dim light goes further).
  • by mindstrm ( 20013 ) on Friday June 08, 2001 @02:52PM (#165222)
    is in diving magazines. Apparently they are really good for diving (good under high pressure, very low chance of burnout, basically impossible).
    You can whack them around and not get burned out.... which is rather important when you're a hundred feet under water in the dark.
  • No, a TFT monitor is an LCD (i.e. a light gate with individual holes for each colour of each pixel). It differs from cheaper LCDs in that it has an active switching element (Thin Film Transistor) mounted on the glass at every pixel.

    Other types switch the cells using a complex multi-level drive waveform in X any Y directions which result in a large polarizing voltage on selected cells and a small voltage on others. The low duty cycle required to multiplex all those pixels has the disadvantage of low contrast.
  • Check http://ledmuseum.home.att.net. Dude must spend hours every day playing with LEDs of all shapes, sizes, and colors.

  • It's a quote from Silence of the Lambs
  • I paid the usual early adopter price and bought a few of the Holly Solar lights -- while they're nice enough, a) they were expensive and b) the one-LED brinkman blows away even the 3-LED Holly light for beam quality.

    I understand that Holly's lights now have better reflectors (mine are around 2 years old), but boy, for what I paid for those, I wish I had a brinkman to give to all my friends;)

    Minor gripes about the brinkman (and most flashlights, really):

    a) too round -- rolls away easily. I have not yet added any sort of bumper system to prevent this, and hey, round is aesthetically pleasing, I must admit.

    b) a screw-in filter adapter would be nice. White light is at least a good choice to start from, and I suppose it wouldn't be hard to jury-rig in an amber or red filter ... but it would be a nice improvement to have a decent system for that built in.

    c) the bottom mounted switch is not recessed enough, and the thing can't be set upright as a "candle mode."

    d) the diameter. It's not a bad feel, but hard to use headmounted etc.

    timothy

  • Just use an LED flasher chip: they will act as a charge pump, allowing higher voltage to the LED from a lower-voltage battery. If you set the flash rate to a couple of kilohertz you won't notice the flashing in normal use (although it makes a cool effect if you move the light around: lots of little spots of light), and the flasher chip plus LED will burn WAY less power than a PIC.

    You can even adjust the duty cycle to vary the brightness. Furthur, even DratShack carries LED flasher chips.

    I've built a number of adjustible LED flashlights over the years for my amateur astronomer friends. A couple of points: First, PICs are CMOS RISC microcontrollers that can operate from DC up to their rated clock speed (32 kHz, or 1, 4, 20, or 40 MHz). Even the standard PICs don't draw much power when under-clocked, and the low power models consume very dern little. Sure, a LM3909 LED flasher doesn't take much power either, but it's a bipolar chip designed in the early '70s. The state of the art has progressed just a bit since then.

    Now, a LM3909 can be operated in voltage boost mode (it's usual operating mode) using just one capacitor. I was never able to get a 3909 to both be adjustible over a 100:1 brightness range and still use capacitive voltage boost. Maybe you've managed it, but I never could. I got my best results by operating it as a DC-to-DC boost converter using an inductor, a much smaller capacitor, and two extra resistors to increase the cycle rate up to around 100 kHz. See the National Semiconductor application guide for the LM3909 for lots of circuits that use the 3909 for everything from blinking LEDs, to an audio amplifier, to a coil tester for motorcycles.

    Secondly, you're right that a switching power supply is much superior to just burning the excess power in a potentiometer. I've had the best results using DC-to-DC converter chips from Maxim or Linear Technologies. The chips designed for single cell operation are already optimized for low power. Just pick the adjustible output voltage ones, use them in current controlled mode, and you're in business. Choose the right chips and you've got minimal external components and a nice clean surface mount design that can drive the LEDs until the battery is dead, dead, dead. (Some single cell chips can self-start from 0.8 V and operate down to 0.7 V. An alkaline cell is considered dead at around 0.9 V or so.)
    --

  • This picture [utah.edu] nicely shows the receptivity of the four kinds of receivers in the human eye.

    Nice picture. OK, so if the goal is to fire up the cone cells (which, occupying the fovea, give the sharpest vision) without futzing up the night adaptation of the rods, then we should pick a color that the rods are least sensitive to, while maximizing the cone sensitivityj. This is so we don't have to pump out too much light.

    I'd say that means something in the orange through red-orange to red range. Right?
    --

  • At most hardware stores you can purchase a small keychain light that uses two watch cell batteries and an LED in a flexible rubber shell. They come with a red LED in most cases; go to Radio Shack and get a white LED to replace the red. I use it all the time, and the batteries last for months. You get a wide bright circle of crisp white illumination. The white is much easier than pure red - I suppose the human vision system relies on color differentiation.

    This is good advice except for one thing: All the red LED rubber squeeze lights I ever bought contained alkaline coin cells, which put out 1.5 V each. A red LED can reach its rated current (and brightness) at around 1.85 V, so the 3 V from the batteries is more than enough. (These squeeze lights don't have current limiting resistors. They rely on the batteries' internal resistance to limit current. With watch batteries, that seems to work pretty well.)

    So, everthing is fine for red LEDs. White LEDs need about 3.5 V to max out. Their voltage/current curve isn't as sharp as a red LED's, so they will emit some light at 3.0 V, but you aren't seeing them at their best. As the batteries run down, you'll get exponentially less light. Bad juju.

    For best results in your squeeze light conversion, remove the two alkaline cells and put in two lithium cells of the same size. The combined 6.0 V output along with lithium cells' ability to sustain nearly 3.0 V over most of the cell's life will keep your light shining brilliantly for a long time. In fact, a Photon Microlight II is just a squeeze light with a better case (hard plastic) and one or two lithium coin cells (depending on which LED you choose).

    So, by converting a squeeze light youself you can save lots of cash vs. the Photon's cost of USD $15-$20.
    --

  • by coyote-san ( 38515 ) on Friday June 08, 2001 @03:01PM (#165230)
    Isn't this covered in some scientific urban legends page?

    IIRC, the reason red light doesn't disturb night vision isn't because it's the "lowest energy wavelength," it's because the color receptors contain organic dyes that only respond to a band of frequencies. If the photon is out of that range, too low *or* too high, the receptor won't fire.

    Red is outside of the frequency range of two dyes, and on the edge of the third. (If it weren't, we would see infrared and call *it* "red"). With high intensity red light those cells still fire, and other psychological changes would cause the (brain? eye?) to respond mostly with the color receptors. But with a dim red light the dye-free receptors dominate and there's no loss of night vision.
  • by coyote-san ( 38515 ) on Friday June 08, 2001 @03:12PM (#165231)
    An important safety tip about LED flashlights, learned through experience.

    If you're driving in an unfamiliar area, e.g., the Olympic Penisula, and pull over to the side of the road to figure out where everything else is (since you know exactly where you are, so many miles south of the National Park on the only major street in the area), do NOT use a red LED flashlight.

    It makes major roads disappear from the map.

    I got *very* confused, since I knew I had driven on some of those missing roads just days earlier. I swear I started to hear the music from the _Twilight Zone_. But turning on the overhead lights revealed the missing road. Red lines illuminated by a red light disappear, and presumably the same thing happens with the other colors as well.
  • On the same topic (LEDs) here is a site [att.net] that was (to me) pretty impressive. Lots of LED info if you are into that sort of thing. And this guy also evaluates flashlight....LEDs in particular :)
  • No, I'd rather club him for pimping his website to Slashdot when its so weak it gets slashdotted before theres 3-4 comments posted.

  • Night vision is done with the rods, not the blue cones.
  • by thogard ( 43403 ) on Friday June 08, 2001 @05:07PM (#165235) Homepage
    When I fly, I tend to use a white LED Photon Micro light to read the multi-colored charts. Its not too bright and I haven't replaced its battery yet after 3 years.

    I also carry a Eveready 2AA light with lith Lithium batteries. Its light and very bright. It will light up reflectors at over a 1.5 miles. I also carry a one that has normal Alkaline batteries if I need a semi-bright light.

    I've given up on the mag light junk. Sure the case is strong but any little bump and the light bulbs go out. You can't hold them in your teeth (sometimes you need to do that in a small plane). I'm not impressed with their switches and if you have a problem, you can't fix them in the dark. Once they get wet inside, they die. Other than use as weapon, I can't see any good. I have had several maglights and they all failed. The plastic everready is something like 10 years old.

    For Diving, I like the Underwater Kenetics 4D cell model and have an 8 AA dual circut light bade by Technisub. Most dive lights use magnetic reed switches so they are completely sealed but if they don't have transistor switches, you burn out the reeds but if you have transistors, they are never off.

    Out in the bush, the photon is great. It is easy to carry around (just clip to to your shirt) and it lights up about a 1m circle in complete darkness. Its not too bright so you don't lose your night vision.
  • Night vision mostly occurs with the 'blue' receptors. Red, besides being as far away from the blue as possible, wouldn't normally fire under low light conditions. That way, you don't eat up the retinal resources normally used for night vision when you use red light. Green, is also a non-night vision color, but it probably 'bleeds' into the blue receptors a bit more (which some people may find useful for looking at some things).
    --
  • I don't think the link is incorrect... I got it eventually, but I had to screw around a bit to get it to work... I went to the home page, then reviews, then LED #2. Rediculous.

    He has this whole long review with "scientific" pictures, to get to this conclusion:

    • There is a very,
    • very big difference in brightness between one LED and 14!

    Say... one is roughly 14 times brighter?
    --

  • That's his first LED flashlight review. It's not quite as rambling and verbose as his second.
    --
  • slashdotted faster than the speed of light

  • Out of curiousity, do you have the plans for the 4 Dcell mag light on the web anywhere?
  • modded you up

    i have lived in the US for all of my life. I agree that most people that live here are self-centered greedy bastards. The greed factor comes in through our media. USAnians (an interesting word, thanks to the coiner) are taught by our media, that we will all be famouse millionares when we grow up. Many children are sacrificed to the god of TV by their parents, who are too busy trying to bring home more and more money each day, so they can feed their zombie children more and more media. The TV god tells us that everyone is famous and happy and makes lots of money and children believe this. It is sad really.

    I try to do my part to reduce the destruction of the planet, I drive an Insight, have a compost pile, recycle, and try not to shop at stores that treat their employees like garbage. I try to talk with other people, sometimes I think it helps, but mostly I think it is too late.

    I think we are doing an efficient job at desroying the planet, but other countries help out too. I think the only cure for this planet is Human Genocide. It is already too late for our culture (or lack there of), maybe the next will strive. Or maybe if we're really lucky, we'll make it to Mars and strip-mine the motherfucker too.

    --
    microsoft, it's what's for dinner

    bq--3b7y4vyll6xi5x2rnrj7q.com
  • Check out this...
    http://www.streamlight.com/2001/cuffmate.htm
  • by ahertz ( 68721 )
    What kind of masochist would submit his own site for slashdotting?
  • Just use an LED flasher chip: they will act as a charge pump, allowing higher voltage to the LED from a lower-voltage battery. If you set the flash rate to a couple of kilohertz you won't notice the flashing in normal use (although it makes a cool effect if you move the light around: lots of little spots of light), and the flasher chip plus LED will burn WAY less power than a PIC.

    You can even adjust the duty cycle to vary the brightness. Furthur, even DratShack carries LED flasher chips.
  • Fluorescence always red-shifts things

    Not quite true: there are some modes of fluorescence that involve the adsorption of two photons to yield one higher-energy photon. I have a card in my wallet that adsorbs visible light and IR to give off an orange glow. It's used to detect the output from IR LEDs in things like "electric eye" beams and remote control. It's a lot handier than getting my Starlight gear out.
  • Yeah we all know LEDs rule. but I want an LED monitor. That'd be awsome. I'm rigging up my brightlite sets to the computer, i'll set up a site once i've got it figured out.
  • yes, in the theatre i've mostly given up on maglights (i still carry one for emergencies, though). my main lights are two photon ii microlights (red and blue) and a princeton tec matrix headlamp. the matrix is awesome, uses three white leds but the module can be switched with an (included) incandescent module for long range vision.

    i'm just waiting for cheaper leds so i can replace the lights in my house. $20USD/photon ii and $50USD/matrix is mighty expensive.
  • by BlueUnderwear ( 73957 ) on Saturday June 09, 2001 @04:00AM (#165248)
    > Red is outside of the frequency range of two dyes, and on the edge of the third.

    And most importantly, it is outside of the range of the un-dyed cells, called the rods ;-). Night-vision is mostly done with the rods, whereas color-vision is done with the cones. That's the reason why, in low-lit conditions, you see everything in shades of grey

    > (If it weren't, we would see infrared and call *it* "red").

    Actually, the reason why red is near the edge of the receptivity of red cones, is because there is a significant overlap between the ranges of the red and green cones. The wavelength at the maximum of the red cone's sensitivity (564 nm) is also well within the green's range, and is thus seen as yellow (red+green) rather than "pure" red. If sensitity ranges were more evenly spread (i.e. the green range closer to the blue, but further away from the red), we would see 564nm as red, and still not see any infrared...

    This picture [utah.edu] nicely shows the receptivity of the four kinds of receivers in the human eye.

  • Cannot focus the beam, as the reflector is inside the LED itself

    Couldn't they just point the LED the "wrong" way (toward the batteries) and an external reflector? Then just twist to change the position of the LED relative the reflector . . .


  • Actually, the typical discrete "white LED" component uses a blue LED to excite a phosphor which reemits over a broad spectrum of wavelengths, rather than separate blue, red, and green chips (though that would also get you white light, providing you regulated the current through each chip correctly -- the differing bias voltages required might make it a little tricky).

    I have never actually seen an LED flashlight but I assume that most of the white ones use the phosphor-type white LEDs, just because those are the readily available components, and they are very efficient white-light sources.
  • by Zaphod B ( 94313 ) on Friday June 08, 2001 @02:33PM (#165251) Journal

    I have several "photon lights" (which are just bright LED lights), but I don't use them for illumination as for dancing, particularly in rave clubs, which I would suspect is the most common current use for these things.

    The blue is by far the brightest. The red is OK, but the white is disappointingly dim. Now if they could just have a purple one that didn't explode on first touch of current... it would be hopelessly dim but quite pretty :)


    Zaphod B
  • You really haven't experienced the stunning joy of holding a real flashlight in your hand until you've used the new Surefire Millenium M6 Magnum Assault Flashlight.

    That's right, Assault Flashlight.

    500 lumens of blinding power.

    Of course, it runs through 6 Lithium batterys in 20 minutes, which makes it a bit expensive to run, but when you need to blind every last motherfucker in the room... accept no substitute. Check it out [uws.com]

  • This isn't that silly. Many years ago (1983), before high power LED, a friend an myself knocked up an RS232 transmitter using LEDS. To get extra range we ran them in liquid nitrogen. usual current consumption, 20mA. With LN, 1A(!!)without burnout, with room lighting brightness to match. Semiconductors work *much* better cold. :-)
  • Was this the US Army? Because US military maps are designed with 5 colors that are viewable under a red light.
  • by Bill Daras ( 102772 ) on Friday June 08, 2001 @03:46PM (#165255) Homepage
    I'm gonna order me some dry ice and overclock the hell out of my flashlight!

    Woohoo!
  • >>What kind of masochist would submit his own site for slashdotting?

    The same idiot that is making a fraction of a dollar from those damn anoying ads on his sight.

    pop-ups suck.


    mr.
  • Check out Color Kinetics, http://www.colorkinetics.com
  • http://www.glow-bug.com/main.html for the goat-paranoid

    3C
  • Unfortunately, I haven't written it up. Maybe I'll get around to it someday. The hardest part was disassembling the Maglite: you have to pry out the rubber button over the power switch, and then stick a long Allen (hex) key through the hole in the button and loosen a set screw. This frees the switch/bulb holder assembly, which can then be slid out the bottom of the tube (the end where you put in batteries). I learned this the hard way by removing the snap ring above the switch assembly and driving it out from below! Needless to say, that ruined it, but I learned what to do the next time.
  • Diodes need to overcome a certain critical voltage (the reverse bias voltage) before they let more than nanoamps of current through (~ .7 volts for silicon at room temperature).
    (It's 'forward voltage drop', but we understand.)

    I was actually referring to the weird properties of tungsten-filament incandescent lamps: First, their resistance increases as the filament gets hotter. Second, their ability to get hot (and therefore produce light) depends on having a sufficiently high resistance. When one is first turned on, it has a low resistance because it's cold and therefore draws a large current. As it warms up, the resistance goes up, and the current drops to a more reasonable level. Unfortunately, this means that if the battery doesn't have enough 'ooomph' to supply the large startup current, the filament will never get hot enough to glow.

    What happens with LEDs is that, as the battery nears exhaustion and starts approaching the forward voltage drop, less and less current flows through the LEDs and they become fainter. However, the forward voltage drop isn't the cause: the battery running out of juice is.

    The cool thing is that if you matched the LEDs and resistors to the battery, the current will start to drop just as the battery is getting dangerously low, which reduces the load on the battery just when it is running out of energy. This means that the LEDs get dim towards the end, and make that last little bit of energy last a long time. (BTW, this holds for regular alkaline batteries only. Ni-cads will die much faster.)

    Perhaps you meant to say that they work well at low currents.
    That's true too: LEDs usually have the highest quantum efficiency (photons per electron) at the lowest currents. This is a double bonus: not only do they preserve the last little bit of energy in the battery, they use it more efficiently. The net effect is that LED lamps gradually dim over tens of hours, while incandescent lamps just suddenly go dead over the course of maybe 15 minutes.
  • by sigwinch ( 115375 ) on Friday June 08, 2001 @03:50PM (#165261) Homepage
    Ha! Yes, LEDs are very monochromatic. For map reading (or working on electrical wiring, etc.) you'd be wise to get a lamp with multiple colors of LEDs. I've seen the 'disappearing ink' effect with the LED flashlight I built (4 D cell Maglite case, 56 ultra-bright red LEDs from Digi-Key [digi-key.com]). In a dimly lit room, I drew a red, a green, and a blue dot on a whiteboard. When I light them with the LED flashlight, the red dot totally disappears. It's a very cool effect.

    Somebody asked above how well LED flashlights work. Mine is blindingly bright: looking into the beam at close range produces a dazzle effect like a flashbulb, complete with sparkly afterglow. I used highly-focused LEDs: it makes a beam about 2 feet across at a distance of 10 feet. Unfortunately, since the human eye isn't very sensitive to red, the beam doesn't appear very bright, but it's plenty good enough to see with at night. Battery life is very good: I gave up trying to run it down after 24 hours, although there was noticeable dimming by that point. One good thing about LEDs is that they simply grow dimmer as the battery runs down, unlike incandescents which have a tendency not to glow at all once the voltage falls below a critical point.

  • by dara ( 119068 ) on Friday June 08, 2001 @02:06PM (#165262)
    A reason that LED lamps are great that is often not mentioned is that they have a very uniform illumination pattern. This is great for reading books in the tent, maps, etc. Most incandescent bulbs simply cannot focus as cleanly. Mine's quite adequate for what I use it for (see my review of the Princeton Tec Matrix on http://www.outdoorreview.com/reviews/Headlamps/pro duct_2333.asp) and it runs around 40 hours on 2 AA's. I never use my Petzl Micro or Zoom these days (anybody want them cheap?)

    Dara
  • LEDs aren't as bright as incandescent flashlight bulbs, so most LED flashlights use multiple LEDs.

    There's only a couple ways to change the focus on something like that, and the most practical method so far is to use LEDs with a variety of focal lengths and alternate between them in various duty cycles using oscillator circuits. The article discusses that.

  • I don't know why people couldn't get to my site for a while (it's fine now); I presume the server just decided to have a depressive episode at that moment. It's on a Hostpro (used to be VServers) box, and I've had Slashdot mentions a few times before (who remembers Pornsweeper [dansdata.com]? :-) and never had an overload problem.

    So get it straight - the server's unreliable, not underpowered :-).

  • Very important for fibre optic.It allows about 8-10 time more data to be transmitted. Not really designed for flashlight use.
  • I never understand why anyone would mount a flashlight on there weapon. in vietnam they called those people dead. repates after me "Hold light away from body,Hold light away from body,Hold light away from body"
  • I'm pretty sure that's what a TFT display is.
  • by deglr6328 ( 150198 ) on Friday June 08, 2001 @04:19PM (#165268)
    take a look at this [dialight.com] page especially this [dialight.com] graph. LED's surpassed incandescents long ago in terms of efficiency, the only hurdle left is to increase the brightness. When Nick Holonyak (inventor of the LED) won the Japan Prize(the Japanese equivalent of the Nobel Prize) in 1995 and was asked to say a few words, he simply pointed to the celing lights and said "all this is going". I think we'll see this happen within 20 years or so.

  • You know, you'd think that if you're going to submit a story to /., you'd have enough sense to use a server that won't get slashdotted. This article was posted at quarter of six, and I still can't get the site at 7:30!

  • Don't know if its just me, but that site would appear to be down. I don't think the /. effect would have happened quite so quickly?
  • Fun stuff. I got one of the White LCD flashlites and (applies to other LCD stuff, too) my mom left it on overnight, under stuff so it wasn't discovered until later that morning, 18 hrs or so, and there wasn't very much difference at all (with a second one that wasn't on)

    I have made some White LCD-5.99 at radio shack. plus some surplus wires, and electrical tape. Use some watch batteries and you have one less than 3 cm long by 1 cm around. (If you do, don't look right at it) the box recommends 4v but 4.5v (3 AA, AAA, etc) work just fine.

  • The LEDs on his network cards woke up the neighbors ;)
  • What kind of masochist would submit his own site for slashdotting?

    The kind who'd call in an air strike on his own unit's position. That's Medal of Honor material, man. Show some respect.

  • (Are you sure you included a URL? Didja test them for typos?)
    Seems like the second link is either dead, or slashdotted.

    Anyways, led flashlights are cool, but make them yourself and save $$. Shit, I've seen lamps for over $40!!

    OK. Speaking of LED's - does anyone know where to get these things that plug into cat-5 hub/switches ports - sorta like really primitive, really compact testers? They light up differently depending on whether the outlet is wired right/wrong/has data on it. Look like cable ends?


    The slashdot 2 minute between postings limit:
    Pissing off hyper caffeineated /.'ers since Spring 2001.

  • I tried making them, but they aren't as nice and finished as the ones I saw. Sure, send me your specs too. Mine are um.. a bit crude.

    loraksussr@hotmail.com

    are you also trying to imply that radio shack was hertz-so-good?

    I'll try your email if you don't respond, I can't exactly believe its real.

    The slashdot 2 minute between postings limit:
    Pissing off hyper caffeineated /.'ers since Spring 2001.

  • hmmm thats a cool cable tester, (got one sorta like it) but I was looking for a simple thing (well, alot of them) that I could plug into a patch panel, and see which ports are active.

    Thanks anyways.

    The slashdot 2 minute between postings limit:
    Pissing off hyper caffeineated /.'ers since Spring 2001.

  • You need green blue and red LEDs to make white light since LED's are monochromatic. The Blue ones seem to be the most expensive ones and I am guessing the other LED's get much brighter (this means you need more blue ones than greens or reds.) The Blue ones don't last as long as the lower frequency ones do either. I am guessing these won't really catch on until the blue ones are almost as cheap as the red.
  • by Alien54 ( 180860 ) on Friday June 08, 2001 @02:47PM (#165278) Journal
    C. Crane company (www.ccrane.com [ccrane.com]) has had this and other nifty stuff for years and years. They sold bucketfuls of this stuff along with the hand crank radios [ccrane.com] and night scopes and other geeky survivor type stuff [ccrane.com] before the Y2k crunch.

    One of my favorite toys they have is the radio set wall clock . It checks itself every hour, and is great for things like daylight savings time, etc.

    I am sure that this is not the only place to get this stuff, but a second source is always nice.

    Check out the Vinny the Vampire [eplugz.com] comic strip

  • A very simple, low-tech answer to this problem... Even my 24-year-old Volvosaurus has this. If you look up and towards the middle of the car, somewhere, either in the middle of the roof, or just aft of the rear view mirror mounting, will be a simple incandescent light, around 4/5 watts, but perfectly adequate for map reading...
  • Screw that, get a Cine 60 movie light. 40 volt nicad pack with a built in charger, and a 250w halogen lamp, in a 5" housing with a daylight correction dichroic on the front. Very bright, very blue.
    Just like daylight. Saved my backside while filming, saved my backside when the car broke down in the dark, coming back from filming.

  • So when can i buy one of these from Thinkgeek?
  • > He has this whole long review with "scientific" pictures...

    If he had called it a "two dimensional InGaAs/GaAs digital light integrator" and shown proof that it's light-capture efficiency was repeatable and constant to within N%, would you have been more suitably impressed?

    Say... one is roughly 14 times brighter?

    Nope, apparently you didn't read the simple electronics (aka physics) that he was explaining in certain parts. If you want proof, just run a numeric analysis of the images yourself to determine the total light output. The 14 LED version is not exactly proportionally brighter than the 1, 4, or 7 LED versions.

  • I can't say I knwo where to buy them off hand, but I've mad dozens of them for pennies a piece. Go to Radio Shack (nee Hertz-So-Good) and pick up a few LEDs and a couple RJ45's.

    I have a crimper (what good geek doesn't), so I can email you a copy of it. Maybe fax one instead? ;)

    --
  • are you also trying to imply that radio shack was hertz-so-good?

    That's a reference to Space Quest 4. In the original version of the game, one place you had to go was a place called Radio Shock. Radio Shack didn't like that, especially since the sign for Radio Shock looked exactly like the radio Shack signs of the day. So, Sierra (the game's maker) changed it to Hz-So-Good as a play on words.

    --

  • In my area (eastern Phoenix Metro area), they have already replaced many, if not most, of the traffic signal bulbs with high-intensity LED arrays. They appear to be just as bright as the incandescent bulbs, are much more energy-efficient, and have a longer MTBF, resulting in a big savings in maintanance costs. The company I work for makes GPS guidance systems for agriculture ("crop duster" aircraft and ground spray rigs). We use high-intensity LEDs for our steering "lightbar" displays, and actually have to dim them down, even in sunlight, as they can be painful to look at directly at full brightness.
  • by Sodakar ( 205398 ) on Friday June 08, 2001 @02:06PM (#165286)
    Hmm. I think there are more sites that deserve recognition. My favorite site is Brock's LED comparison page [uwgb.edu], which I used to get a good idea before making purchases.

    Having purchased a ton of flashlights myself, here are some things you should realize before making a LED light purchse. Most flashlight review sites fail to point out the disadvantages of LED lights:
    • Cannot focus the beam, as the reflector is inside the LED itself
    • Thus... the beam must be either non-focused, or too focused. Short focus LED lights have a very small range of 30 feet or so, while exceptions (like the PAL light) have such a focused beam that it is useless in close range)
    • The "white" light, while impressive and cool, is not that great for night-time viewing. It can ruin your night vision, and does not display contrast as well as the yellow light. (of course, no one wants to put a yellow LED in their flashlight, even if they exist, because it's not "cool")
    • pricey. (new technology is always pricey)
    So.. my advice is to find a local outdoors retailer that has these lights, or better yet -- look for a flashlight freak like me that has these lights, borrow them, and try them out before you plonk down $20+. Personally, I find that the headlamp Tekka (from Petzl) [petzl.com] works wonderfully for proximity lighting, and combined with a conventional Xenon lamp like the Bison [theledlight.com], you have your long range covered as well.

    Just my 2 cents.
  • Well, after the metetor hits/nuclear war breaks out/other awful event happens, only those people who know flashlights well will survive and have offspring.

    But the /. folks will die off as soon as they realize their photon light has fallen victim to the EM pulse...

  • by JohnTheFisherman ( 225485 ) on Friday June 08, 2001 @02:48PM (#165288)
    They're actually blue LEDs with a mixture of different fluorescent materials on the front. Shine it about 3" away from a piece of paper and you'll probably see a distinct blue ring. Fluorescence always red-shifts things, so you shine a blue light on some which absorbs some of the blue and emits blue-green, some of which gets absorbed and emits green....

    They must have also done some silly stuff with the LED selection, wiring and/or batteries, because you can get reds much brighter and cheaper than any blue, and in many different wavelengths.

  • When Nick Holonyak (inventor of the LED) won the Japan Prize(the Japanese equivalent of the Nobel Prize)

    I thought the Nobel was international, prizes like "The Japan prize' would be a sort of subset of all Nobel-Prize-space, I think...

    --

  • This may be more than you're looking for, but here goes...

    http://wirescope.comms.agilent.com/products/ws350/ default.htm [agilent.com]
    ---
    nuclear presidential echelon assassination encryption virulent strain
  • At most hardware stores you can purchase a small keychain light that uses two watch cell batteries and an LED in a flexible rubber shell. They come with a red LED in most cases; go to Radio Shack and get a white LED to replace the red. I use it all the time, and the batteries last for months. You get a wide bright circle of crisp white illumination. The white is much easier than pure red - I suppose the human vision system relies on color differentiation.

    There's no switch - the LED leads are spread so you have to press the flexible sides together to make them contact the battery.

    (The interesting thing is that you can buy the keychain for one dollar. If you want to replace the batteries you would have to pay about four dollars at the same store. I guess the manufacturers found a way to ditch substandard batteries and still make a buck.)

    Total cost: about five dollars, one time; about a dollar to replace the batteries (by buying a new keychain). And it fits on your keychain for easy instant access.
    --Brandon
  • As a couple other posters pointed out, most U.S. produced topographic maps are red light readable, the "red" ink actually being kinda brownish, but I have seen some topo maps made outside the US that had red markings that weren't red light readable. The simple solution to this is to cut a small notch in one of the red lenses that allows a feeble sliver of white light to illuminate the map to make the red lines stand out. Then, when done, cover the notch with a small square of 100 M.P.H. tape (the green duct tape the Army uses for everything from patching rain gear to taping helicopters back together.)
  • by KupekKupoppo ( 266229 ) on Friday June 08, 2001 @01:49PM (#165298)
    I'm referring to the big, heavy kind. Just so that I can club "Daniel Rutter" in the head, for having that damned popup ad on his site.

    -k.
  • LED flashlight industry insiders have leaked that this whole story was designed to improve the sales on the thinkgeek site. Apparently they aren't selling as well as the bawls, chimp, and mp3 jukeboxes.

    --

I have the simplest tastes. I am always satisfied with the best. -- Oscar Wilde

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