led question
 

Ok, I'm wiring up some led tail lights. What kind of viewing angle should I get for the leds? Would a higher mcd led with small angle, or a lower mcd led with wider angle be better?

Thanks

For tail lights, you're not really trying to illuminate anything, you're just trying to make your presence known. So, you don't really need a huge viewing angle for them. I would go with the higher mcd rating, unless the angle is only like 5 degrees on them. I think most are around 15 degrees though, so a high mcd with that should be alright.

Make sure they're not too bright though, you don't want to blind people at night.

You could have several LEDs in the one lamp, at slightly different angles to spread the overall coverage. Quite a few cars nowdays have twenty or so LEDs instead of a single light.

From the rear, a wider angle is better as long as the light output is good on all angles. A narrow angle can incrase the risk of being rear ended by an inattentive driver.

Funny, I would think "not trying to illuminate anything" would mean you want a wider less-concentrated amout of light. It's always good if someone who isn't directly behind you can still see some red light that denotes where the back of your car is.

I'd go for as wide a viewing as I could reasonably get. Probably with multiple LEDs pointing in different directions, or possibly with a diffuser over them. The more people who can see where my car is, the better!!

-soD

The LED brake light units on school buses, commuter buses, and semi-trucks use 12mm diameter LED in collimator arrays, or 5mm LEDs in diffusion lenses.
You don't really need a wide viewing angle for them to be effective.

I was thinking that since you have to use several LED's anyway, the 'viewing angle' would pretty much be covered by the fact that you're using several in an array. Since you sacrifice brightness when you increase the viewing angle of an individual LED, you might as well get several bright ones in an array rather than several dimmer ones that would hardly increase the overall angle of the light.

Ok cool, so i guess I'll order some 5mm 8000mcd with 30*. I'm going to have about 25 or 30 in each tail with what I think is a diffusing lens. These are the lenses I'm putting leds in:
http://pic16.picturetrail.com/VOL664.../363851137.jpg

Thanks guys.