In article ,
slepax wrote:
Short description of the problem: I want to use a series of LEDs to
replace the turn signal indicator globe on my bike.

My bike battery outputs 12.5V, and currently, the bike uses a 12V/10W
globe (on each side). I intend to replace each globe by connecting 6
LEDs in a row, so that way the total voltage required for all LEDs
would be ~13.8V (a single LED consumes 2.0-2.6V, so 6x~2.3V=13.8V).

LEDs are actually current driven, so this isn't that good an idea.

So here comes my first question. Am I assuming correctly that because
I have a total of 6 LEDs in a row (~13.8V) I
dont need a resistor
[b:6e8628ea4d]before[/b:6e8628ea4d] the LEDs?

Given that resistors are cheap, I'd use one per LED, and drive them in
parallel. Then if one fails, you'll not overload the others as would
happen with one common resistor, or end up with no light, as when in
series. You should be able to use 0.25 watt resistors which are pretty
small and cheap. If it's a bayonet fitting bulb, then simply break away
the glass and use the bayonet plug for the resistors, and bend the LEDs so
they point in the right direction. After checking it works, pot the
resistors in car body filler, etc, to give some mechanical strength.

Next, a single globe consumes 0.83A (10W/12V=0.83A) while all the LEDs
together consume less than half (~0.05Ax6=0.30A). So here comes my
second question, do I need to put a high-power resistor in
[b:6e8628ea4d]parallel[/b:6e8628ea4d] to the LEDs to match the
current consumption compared to the globe?

Standard LEDs driven at 50mA are likely to have a short life. And six
standard ones will be brighter on axis than a 10 watt tungsten, when
driven at 20mA. Where they should last forever.

But you may be able to buy an LED replacement anyway. Not the same fun,
though.;-)

Sorry its long, but I would appreciate you help.

--
*I don't suffer from insanity -- I'm a carrier

Dave Plowman London SW
To e-mail, change noise into sound.