L.E.D. Info Wanted

[Frosty_47]

Dear Komrades,

Being a total hobo, I would like to build my own L.E.D. flashlight. Before I can proceed, I would like to better understand the following LED ratings:

LUMINOUS INTENSITY
VIEWING ANGLE
WAVE LENGTH

I realize that the intensity on most LED's decreases as viewing angle increases. This sounds like common sense as the beam of light widens so the intensity decreases proportionally. But what in the world is WAVE LENGTH? And what are the benefits of having shorter/longer wavelength?

Thanks

 

[blueroomelectronics]

Brightness
How wide the beam is
Color

 

[Frosty_47]

Brightness
How wide the beam is
Color

Thanks. With this info, I now know what LED's to use for my flashlight. Hopefully it will yield benefit to my nightly food searches...

 

[audioguru]

Hopefully it will yield benefit to my nightly food searches...

Are you a racoon??
The smart critters knocked down my garbage can for the last time. A heavy concrete slab on top didn't stop them. Now I have a strong bungee cord wrapped around the can and hooked to my house. When the critters learn how to pull and unhook the cord then I will bolt it to my house. When they bring their own tools (they might bite off the cord) then I must figure a better way.

 

[Frosty_47]

Are you a racoon??

No, but I live like one

Eh, why not build a system that will discharge a low-energy defibrillator capacitor into the garbage can whenever a raccoon comes in contact with it. Obviously it would have to be a conductive garbage bin. The lid with some wiring on the inside of it, can serve as a switch to a normally closed relay. As soon as the lid is removed, the current through the relay seizes, and a defibrillator discharges through the bin shocking anything that comes into contact with it. You can activate the defibrillator whenever you go to bed, and deactivate it as needed.

Would the following LED's be a suitable choice for flashlight?


it's MCD = 280, 000
Angle = 40 degrees

**broken link removed**

Just wondering how bright the flashlight would be, if I connect 20 of these LED's.

 

[Andy1845c]

I would think it would be plenty bright, but I don't see how it would have any range to it. It would be more of a flood light type beam. I have an LED flashlight that only uses 1 10mm white led, and is plenty bright, but it also has a refelector and a lense that focuses the light so it will shine aways out.

 

[audioguru]

I don't like "no name-brand" LEDs.
Operate the LEDs at 80mA, with strings of two in series and each string in series with a current limiting resistor. With 20 LEDs the total current will be 0.8A.
Seven 2500mAh AA Ni-MH battery cells will last 3 hours.
The flashlight will be blinding without a reflector.

I think only one of those LEDs would make a good flashlight.

 

[Andy1845c]

The flashlight will be blinding without a reflector.

Blinding, yes, but how much range will it have? I did a project with 36 orange LEDs in a group, and it was blinding to look into, and would almost light a room, but wouldn't make a good flashlight. But I suppose if all you want to do is rummage though trashcans looking for rancid food, a floodlight would be better anyhow.

What about a single 1w or 3w led? **broken link removed**
They have reflectors to go with those.
Would be kinda power hungry though, but bet it would have a better beam then the 20 x 10mm leds.

 

[blueroomelectronics]

You can buy LED flashlights for $1 at many dollar stores, cheaper than you could ever hope to build one. Dan over at Dan's Data - PC hardware and gadget reviews! has a flashlight fixation. Lots and lots of reviews and pretty neat site too.
**broken link removed**

 

[Ubergeek63]

**broken link removed**

Just wondering how bright the flashlight would be, if I connect 20 of these LED's.

I think that is a typo of sorts. There is just no way it is getting 100Lm from 0.5W.. the "m" should be a "u". 280mC @40 is 0.1Lm ... you should look into premounted lighting class LEDs

 

[ronsimpson]

**broken link removed**

 

[MrAl]

Hi there,

Usually when you use high power LEDs you also use some other devices
like 'optics' to direct the beam so it projects a beam instead of just
a wide area light. The Luxeon Star for example has two different
optic director lenses that can be used to make a pretty good flashlight.
There are many other types of LEDs out there these days however.

BTW, for a flashlight, you probably want a 'white' LED, not a colored
one, where the wavelength might come into play. White is made of
many different wavelengths of light but the LEDs are simply called
"White".

 

[audioguru]

We don't know what are the true spec's for the no-name-brand LED.
The "280,000mcd" brightness might actually be only 2,800mcd.
The "40 degrees" viewing angle is probably only 4 degrees.
The unknown manufacturer lied.
Maybe the LED will melt at it rated 100mA of current.

 

[ronsimpson]

Normally 5mm LEDs are good for 20mA max. Running them hotter really shortens their life. I have had problems with white LEDs running too hot and killing the phosphor.
The e-bay LED is rated for 100mA at 3.4 volts that .34 watts not .5 watts.
The .5 watt and up LEDs I use come with a method of heat sinking.
In flashlights I usually use 10 degree LEDs with little to no reflector or wide angle with a reflector. The e-bay LEDs are not 4 degree they look like 40 degree.
The mcd numbers are very questionable even from known sources.
I looked at some other e-bay LED data from the same store and they do not add up. One LED looked to be a 20mA part. Normally all the numbers are based on 20mA (5mm). It has a 40mA absolute maximum current rating and pulse rating of 100mA under very short duty cycle. Then there are other LEDs that look the same to me and have a 100mA rating with much more light. I think they will not last! Some of the LEds have a 100mA rating and a 120mA pulse rating. Normally these two numbers are 5 or 10 or 20:1 different not 1.2x. I really question these numbers.
I would not touch these parts until I got a part number and went back to the source and verified the numbers.

 

[audioguru]

What do you expect from cheap Chinese LEDs?
A few out of 50 might even work.

 

[Frosty_47]

What do you expect from cheap Chinese LEDs?
A few out of 50 might even work.

I agree. It's better to trust a known reputable source such as NTE than some random person on ebay. NTE has high brightness L.E.D.'s but none are near 480,000 mcd.

The brightest LED I found from NTE is 30045.

Angle: 22
Intensity: 16000mcd
Vf: 3.6V
If: 30mA
Pd (max): 120mW

**broken link removed**

Oh, and I forgot to mention that I have a MEGA SIZE metal reflector. And I am using two 6V 12A/hour SLA batteries for the flashlight!

Yes that thing is like 20 pounds of weight!

 

[blueroomelectronics]

With a narrow 22 degree beam the reflector isn't going to add anything to the beam.

 

[Frosty_47]

With a narrow 22 degree beam the reflector isn't going to add anything to the beam.

DAMN IT!

But wut if it's a very LONG BEAM REFLECTOR around 5"-7" ?

And wut if I point the LEDS in an angle so that they face the inner wall of the reflector ?

My reflector is basicaly taken from a motorcycle head light. Like those retro ones u see on hardley davidson motorcycles.

 

[Andy1845c]

DAMN IT!

But wut if it's a very LONG BEAM REFLECTOR around 5"-7" ?

And wut if I point the LEDS in an angle so that they face the inner wall of the reflector ?

My reflector is basicaly taken from a motorcycle head light. Like those retro ones u see on hardley davidson motorcycles.

I would think you would lose efficiency pointing them sideways.

Motorcycle headlight? That sounds like its going to be a huge flashlight