Any LED Experts?

[FieroBUZZ]

Anyone familiar with making LED's?  I'm considering a modded taillight which would need several small 2x4 boards with LED's suitable for running/stop light use.

[JetJumper]

I have played with lots of LEDs in the past..

I have about 400-500 of them right now in Blue/UV/White/Pink.

nothing red though for stop lights

I get mine from EBAY.  $20 for around 100 shipped from Hong Kong and they come with Resistors for 12V.

[dguy]

I get mine from EBAY.  $20 for around 100 shipped from Hong Kong and they come with Resistors for 12V.

For brake/tail functionality though you need different levels of brightness, not a single fixed resistor like the ones you're describing.  It's usually accomplished using a higher resistance on the line which drives the running lights than the brake lights, a pair of diodes to prevent cross-feed between the brake & tail circuits, and a blast of wide-angle LEDs.

Gary I'd like to say that I could mock something up for you, but I have way too many things on the go at the moment as it stands.   

[JetJumper]

One thing you can do, is it will take more LED's but they are not that expensive when you buy in bulk, is have 2 strings.  1 string is your Running lights at half power, the other half only come on when you press the brake, and have a different resistor so that they go full power.  you will still have the other ones running, but these will be brighter off the bat and over power them.

I took some quick pictures...

One is 4 LEDS on a 12V line no resistors.  In series.
Two is 4 LEDS on a 12V line, 1 resistor, In series, but should be parr.  Just didn't bother

[JetJumper]

sorry about the big pictures.. didn't know my phone took that big :|

Anywho, you can see the brightness difference on the bottom picture

[dguy]

Only catch with your solution Chris, is that you need double the number of LEDs for the same functionality.

i.e.  If due to space constraints you're limited to a circuit board which can hold 50 LEDs max, your design would have 25 LEDs for the brake light, and 25 for the tail.

My suggestion would have all 50 work for both the tail & brake functions.  Given the relatively narrow field of view for LED output, I'll take 50 over 25 for important stuff like brake lights. 

Been there, done that with a custom LED insert on one of our motorcycles.  There's a huge visual difference to following drivers between a small count of LEDs and a larger one.