# LED tail lights for motorcycle

R

#### Rust

Jan 1, 1970
0
I am currently working on adding LED turn signals and tail lights to my
motorcycle.

I have already built the turn signals using 5 20v, 30mA, orange LEDs and a
50 ohm resistor on each side. Pretty simple actually.

My problem is now that I want to do the same for my tail lights. I'd like
to use 10mm red LEDs. I was thinking about using 24 (4 rows of 6 each) - 12
for my rear lights, and 12 for my brake lights. The problem i'm running
into is that the amount of voltage seams too low. I have seen LED clusters
with 30+ LEDs and they work fine on a standard 12v system. Is there some
device that boosts the voltage? Am I missing something?

I'd appreciate anything y'all could offer. Thank you.

Trey

S

#### soundman

Jan 1, 1970
0
Rust said:
I am currently working on adding LED turn signals and tail lights to my
motorcycle.

I have already built the turn signals using 5 20v, 30mA, orange LEDs and a
50 ohm resistor on each side. Pretty simple actually.

My problem is now that I want to do the same for my tail lights. I'd like
to use 10mm red LEDs. I was thinking about using 24 (4 rows of 6 each) - 12
for my rear lights, and 12 for my brake lights. The problem i'm running
into is that the amount of voltage seams too low. I have seen LED clusters
with 30+ LEDs and they work fine on a standard 12v system. Is there some
device that boosts the voltage? Am I missing something?

I'd appreciate anything y'all could offer. Thank you.

Trey

Instead of trying to drive all 12 in one circuit, separate them into three
sets of 4 and use a separate current limiting resistor with each set of 4.

With a forward voltage of 2V for each, the 4 will drop 8V leaving 5V - 6V to
drop across the resistor. You should end up with a resistor in the range of
220R.

Take care to avoid over driving the LEDs. They will lose performance
quickly if the current is allowed to remain higher than the stated maximum.
Personally I would reduce the current level by 10 - 20% below the maximum.
Also, unlike the turn indicators, these LEDs are likely to be on for a long
time and there can be a significant heat build up. Generally LEDs don't
like getting warm. I know that there is only a 2W power rating with all 24
LEDs on, but there does need to be some means for the heat to be dissipated.
For differentiation, you will probably need to drive the tail light at a
lower current than the brake light, so this will probably solve the problem
of heat build up.

Good luck

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