The advantages of dynamo powered bicycle LED light:
- lots of light!
- always available - You can not forget to take it with You
- unlimited burn time
- no cells, batteries, chargers (think of costs and environment)
- unattractive to thieves.
I use this light for daily bike commuting since one year. The instructable misses some photos, because I didn't took many when I was building the light :) The circuit idea comes from the page http://pilom.com/BicycleElectronics/DynamoCircuits.htm (highly recommended!!)
Step 1: Electrical schema
The circuit is super simple - the graetz bridge rectifer, some smoothing capacitors and power LED diode.
Red LED diodes for the tail light are put as one branch of the rectifier. 13 diodes are connected in parallel - that multiplication gives more light and splits the current on more diodes (as You know, one diode can take only 20 ~ 25 mA current).
Please note, that the bicycle frame is usually used as the ground in AC dynamo circuit. The rectifier on the AC side is connected with the dynamo and with bike frame. The DC circuit needs 2 wire cable for its connections - there mustn't be any electrical contact with the frame.