And a resistor... which i will tell you how to figure out what value you need!
My led's package says that its voltage is 3.1-3.4v at .02 amps
First we need to figure out the leds internal resistance
Through V=IR we get 3.4v= (.02A)(Resistance) = 170 ohm
Now our bikes when running can peak (at a number to be safe) 15v
Now when you know that use the voltage divider calculator http://www.raltron.com/cust/tools/voltage_divider.asp or do it by hand
plug in 15v for the input voltage
leave r1 blank (thats what were solving for)
r2 = the resistance of the led (calculated above)
V out = (should be specified) mine is 3.4v
and you should get a value for r2, mine was 580 ohm
(i dont exactly have a 580ohm resistor, so i used a 1000ohm resistor)
the idea is as follows
1.jpg
The circuit works by supplying one + rail to 6 grounds (the gears on the bike)
Start by de-soldering the old connectors (sorry i dont have a picture of what it looked like before)
but the connectors look like this
![](http://i.imgur.com/MBqj5fK.jpg)
Now place the leds onto the board(mine was a common 12v and 6 grounds, the orange wire supplied the power)
the longer leg on the leds is the positive side (very important)
place the leds onto the board like this
![](http://i.imgur.com/1i6anbt.jpg)
Solder them up and trim the leads (should look similar to this when done)
![](http://i.imgur.com/hY0ReE0.jpg)
(i crimped the resistor in parallel with the voltage supply, dont have a picture of that sorry)
and here is what the final result looks like
![](http://i.imgur.com/LGaiCY6.jpg)
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