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quick question about LED brightness? Answered

How bright is a 3500 mcd LED? I was planning on using 4 3500 mcd LEDs for a bicycle brake light project, but now I'm thinking that it might not be bright enough. Being as this is my first LED project, I'm not too sure how bright 3500 mcd is relative to others. I'd imagine it would be sufficient, but after lighting one with a 1.5 volt battery, I was kinda disappointed.

If there is a mcd rating that is better for this application please share
thanks for your input


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11 years ago

There is a problem between the lumen output, and candella rating of leds. 1 lumen is roughly equal to 1 candlepower - with a notable exception:
1 candella (candlepower) is a brightness, measured at an angle, and a distance from a light source. for example, a 1000mcd (1 cd) led will be 1000 mcd at zero degrees, and it will logarithmically go down to 500mcd at its rated 'angle' - the 50% angle, where it quickly drops off
1 lumen is an amount of light - total - which includes all light in the entire area illuminated by the source.

For your application, superbright leds are pretty darn bright. If you are only getting a tight beam then try using a dremmel, and grinding off the round lens of the led (carefully) and see if that widens the beam sufficiently for better viewing.

Also - red leds usually need closer to 2 volts, so 1.5 wont be ...bright... -check the rating, and make sure you use the right resistor. http://led.linear1.org/led.wiz can help with that.

If in doubt, use more leds, and make sure to run them at their rated voltage and power.