White LEDs as tail/etc lights.

[jcmassey@netspace.net.au]

Hello list, me again.

Has anyone else been playing around with the white 6000mCd LEDs.

I have found the following:

A matrix of 150 3500mCd amber LEDs (consuming 0.6A from 12V) has similar
intensity (to my eyes and to those I have shown it to) as a matrix of only
18 white LEDs of 6000mCd (9 paralell of series pairs consuming 0.18A total
from 12V). This is without any lenses in front of the matricies.

Due to the forward voltage drop amber LEDs can have 5 in series with a
current limiting resistor, but white require a little over 10 volts for
three in series - too close to a nominal 12V battery voltage for use of a
current limiting resistor - can use a resistor and a LDO 3-terminal voltage
regulator, but probably not a good idea (get a low battery and - no
lights). Better to only use 2 in series and a resistor.

That was to encourage anyone who has looked at using LEDs and dismissed
them as a waste of time to take another look.

However, there are some things that I have not tried with these LEDs. The
most obvious one is: are they still as comparably bright once put in an
orange or red lens assembly? I know that some light will be absorbed, etc.,
so no lectures on optics, please (I've done the optics module in the B.
Tech I'm working on).

Has anyone put white LEDs into a tail-light assembly and done a comparative
test to standard incandecents? If so, how did they go?

If no-one has, then I'll do some tests in  the next few weeks and post the
results.

James Massey