SO I READ THE HOW TOO ABOUT LEDS FOR THE GAUGES AND I THINK I UNDERSTAND BUT IM ALSO GOING TO TRY TO MAKE THE TAIL LIGHTS MYSELF AND SOMTHING NEW. I WANT TO MAKE A STRING OF LEDS THAT MATCH THE COLOR OF MY BIKE AND SECURE THEM ON THE INSIDE OF MY FRAME AND MAYBE SOME OTHER PLACES TOO. I SAW SOME BIKES THAT BOUGHT SOME FLOURESENT BULBS AND PUT THEM WITHIN THE BIKES INARDS AND I LIKE IT, BUT I WANT TO TRY THE LEDS. DOES ANYONE HAVE TIPS FOR MAKEING A STING OF LEDS LIKE HOW MANY RESISTORS PER LED AND WILL I BE ABLE TO SPLICE THEM STRAIT INTO A POSITIVE WIRE OR SHOULD I CONNECT A NEW WIRE TO THE BATTERY? :dunno:  ETC, ETC, ETC. THANKS,
BRANDON

Take 6 LED's in series with about a 200 ohm resistor.  

DO NOT PUT LED'S IN PARALLEL!
and you can just hook them straight up to the battery. (best thing is to get a single pole single throw switch in series with all the branches)  Make sense?

Go get some cheap LED's to test out with before you get the expensive ones.(like from old computers or something) and then play with the good ones.  You can also go buy this stuff called "PERF" board which is just fiberglass with a bizillion holes drilled through it, to build your stuff on.  

IF you have anymore questions, post em up!

Good luck.

how many LED's would you need so you didnt need a resistor? why not in parallel? 2 LED's with a load of .5 v each in Para, should be same in series, only diff would be if one pops on series circut, they both go out. if this isnt right, plz explain.

SO IS THIS WRONG? :dunno:
http://www.uploadit.org/nicebelair/LEDS.jpg

I cant read the photo.  But if -|>- is a diode and -/\/\/\- is a resistor hook them up this way.


(+)-|>--|>--|>--|>--|>--|>--/\/\/\- (put the switch here)(-)


now,  Explaining diodes in parallel.    its not really critical but! if the diodes are not EXACTLY the same one will draw more current than the other, which could cause it to destroy itself, and once that one blows the diode that is in parallel with it will also blow because now it is taking 2times the current.


Also you HAVE! to have a resistor because that is what controls the current.  without the resistor you are running the chance of smoking all the LED's at once.  The resistors cost ~ $0.02 apiece, to give you protection from burning your hard work to pieces.

cool, i got it

don't put the led's in serie, they will die
the current flowing thrue them is to high

i used 4 leds in paralel on 1 680ohm 1Watt resistor

u need the resistor to bring down the voltage from 15 to >2,6(with the led's i used)

if you put them in series every led has to take the current of all the leds
in paralel every led has it's own current flowing thrue them


edit: made pic

http://www.bivar.com/eLetter/driving-la.htm

Quote
Connecting LEDs in Parallel:
You can also connect LEDs in parallel. However, variations in the forward voltage requirements of individual LEDs will result in non-uniform current distribution, and non-uniform current distribution results in non-uniform brightness.

LEDs in series only have one downside - if one blows, all the LEDs in series don't work. But you can still set the current by an appropriate resistor.

(+)----^^^----|>----|>----|>----|>-------(-)

R = ( Ub - n * Ul ) / I

where

Ub=battery voltage (typ. 13.8V)
n=number of LEDs
Ul=LED forward voltage (typ. 2V for super bright LEDs)
I=desired current (typ. 20mA = 0.02A)

So for 5 LEDs, you would use 190 Ohm and for 3 you would use 390 Ohm and for only 1 LED, you would use a 590 Ohm resistor.

You certainly shouldn't put only LEDs in parallel. That's cause LEDs have slightly different forward voltages and the one with the lowest will light up the brightest, the other will be dimmed or not even on.

You should use a separate resistor for each LED.

http://www.superbrightleds.com/

  D.

PS: Before calculating the resistor, you should KNOW the propertios of your LEDs (some have a forward voltage of 3.4V and continuous current of 30mA)...

Quote from: spazdon't put the led's in serie, they will die
the current flowing thrue them is to high

if you put them in series every led has to take the current of all the leds

Wrong. In series, the currents don't add up.

Quote
in paralel every led has it's own current flowing thrue them

The LEDs are NOT exactly the same - they have different forward voltages. So most of the current will flow through the one with the lowest forward voltage - in worst case, if the difference is too big, the rest will not even light up!

  D.

in my first led taillight i put them in series and they slowly died
(must have done something wrong then)

now in parallel they still live and all shine equally bright