question about 5mm and 8mm LED

[spaspeckerthedull]

I am currently into a lighting project using leds and have a question.

My project is to pass light through a clear plastic rod that has been bent into various shapes, the idea is to put 1 led at each end of the rod and make the shaped rod light up. I need to be able to see my leds in daytime as well as at night. I have seen various led's for sale but need to know a few things before committing to buy. The led's I have seen are 5mm white with an estimated output of 55,000mcd and an 8mm white with an estimated output of 100,000mcd. How much heat would be generated by these different led's bearing in mind that they will be completely encased in heatshrink to "focus" all the generated light forward into the rod? They will be wired in pairs in series from a 12v dc supply (car battery) using a correctly calculated resistor.

Any help or advice will be gratefully accepted!!

 

[Fallingwater]

55cd 5mm LEDs and 100cd 8/10mm ones use the same die. Candela readings change as does the tightness of the beam, and the larger lenses on the bigger LEDs concentrate it more. Hence, higher readings.

As for the heat... well, I'll let someone more knowledgeable than me answer that one.

 

[Changchung]

If the led current in a 8mm led is 20ma is just a 5mm led, maybe the max mcd is because the view angle is very close, maybe 15º or 20º if you are looking for some bright leds you have to check the current, 80ma or 100ma is your best choice...