Volts and mcd??

Does volts on an led have anything to do with the brightness or output?I was looking at some bulbs at Radio shack and noticed one 3.7 volt and one 2.1 volt.Both had similiar mcd ratings and I am curious as to the brighter of the two.Will a led bulb with a lower volt but higher mcd rating be brighter than a led with a higher volt and lower mcd?....Probably a stupid question but radioshack is my only option until I can learn the ropes here and place an on-line order for some good led bulbs...Thanks for any help

Whichever mcd rating is the highest is the highest. Voltage and current don't matter.

However..

If you want to know which one is the most efficient (brightest for the least amount of power) you have to know how much power (in a DC circuit- voltage times current) is used to get that mcd rating. Whichever is the brightest for the least power used is the most efficient. The most efficient will run the longest time on a set of batteries and therefore be the cheapest to run.

GregR

I think I understand most of it now and thanks for the help.
I was just curious as how the 4 dollar bulb(blue)I bought was much dimmer than the one taken from a 1.99 key chain light bought at wal mart.I ran them both on the 12 volt battery and just swapped them out to check the output.
I like this little mod but I think I am going to purchase the Arc AA or AAA...seems to be the favorite here
Thanks again

Robocop-

All electronic parts have maximum ratings (voltage and current) running them above that rating will shorten or kill them, sometimes in an instant, sometimes their lifespan is severely shortened.

Are you running a 3.7 volt LED directly off a 12volt battery? without a resistor to drop the voltage and limit the power running through the LED?

Wires connected directly to the battery will cause your LED to blow shortly after it goes superbright.

Running an LED with just a resistor to limit voltage and current is called "direct drive". The value for the resistor can be changed slightly up or down to vary the brightness. Running brighter than it's rated for however will greatly shorten the LEDs life and is called "overdriving"

The best LED flashlights used tiny electronic circuits to regulate the amount of power used, boosting it up or bucking it down as needed. This will produce a constant even light output and usually squeeze the most juice of of a set of batteries. Downside however is higher cost of flashlight.

GregR

Yes I am running the led off of a 12 volt battery for now.See I did the mod similiar to the one I found on here with the short 12 volt batt.and 1 5mm led to convert a Solitaire.I changed the directions a little to use both a resistor and also without if I wanted.I used a section of wood to place behind the battery as a filler.I drilled a hole straight through to allow a small extension spring from a standard writing pen to pass through.I have two springs that make the contact.One spring has a 100 ohm resistor threaded through it and rests in the middle of the wood filler when in place.The other spring is bare without a resistor.I can interchange them but did not know if I had to use a resistor.Does the resistor effect the brightness of the led?I also did not understand the resistor conversion chart so I guessed and picked the 100 ohm resistor.The light works with both the springs and I can not tell much difference in output.I have not ran the light for more than 30 seconds at one time but so far no problems.This entire thing is very interesting to me but I see now that there is much more involved with lights than I ever knew.Glad you are helping me otherwise I would probably blow myself up..hehe...Thanks

One more thing ...the bulb I settled on came from a keychain light that I tore apart so I do not know the volts or mcd.The extra bulb I bought was rated at 3.7 volts but was much dimmer so I did not use it.The key chain was a photon look a like with a white led and cost under 2 bucks...what a deal huh..

You're not blowing the led because of the internal resistance of the 12 volt battery. I have seen the mod you are talking about. I haven't tried it myself though. If you wanna experiment with leds like that...you should get the really bright ones from www.lsdiodes.com. Radioshack leds are not very bright compared to modern high output 5mm leds. They are LOT'S more expensive there too. You can get them at lsdiodes from as low as 60 cents a piece for the white ones...and they are MUCH brighter than the ones you find at radioshack for more money.

Thank you for the link.That is much better than Radio Shack but I was in a hurry to try this and that was my first and only option.Now that I know a little more I plan on trying some future mods with much better pieces.I like the stuff by Mr.Bulk but man that stuff is way out of my league.I would love to have some of those lights.Lots of great stuff on here.

No problem. I know what you mean about the mods Mr. Bulk produces. I wish I could get my hands on one of em, but too expensive for me presently. Don't get me wrong. The modders on cpf are probably charging too LITTLE for the amount of effort and time that goes into their creations. Worth every penny and then some... /ubbthreads/images/graemlins/wink.gif

I've been "playing" with 5mm leds for a few months now. I'm kind of addicted to them. They are cheap, small(very bright for their size) and easily found. I've just recently been playing with the high output leds like the Luxeon Star. A CPFer gave me a great deal. These guys(and gals) on here are some of the best people that I've ever had the pleasure of posting with...hehe. If they can help you...then they will. /ubbthreads/images/graemlins/wink.gif

Yes the prices are excellent and there are just so many great ideas and products here.It is highly addicting...just something about a quality light that can make so much light from such a small package.I like the idea of modding a light but will probably only do it for fun.I will purchase any real light I use as I would not rely on any of my creations.I would like my next purchase to be a Luxeon Star but once again there are just so many choices.Thanks again for your replies...

Indeed /ubbthreads/images/graemlins/wink.gif