Normally general bicycle will systematically give the light at night with a light bulb. By will receive the electric energy from the dynamo. But this system is defective straight that when stop spin a bicycle. As a result will make a light bulb switches off problem this solution so. There is the battery upwards. For the electric energy replaces the dynamo which certainly this system has to have fire package gives with the battery with. Come to see model the plan is or work system circuit Bicycle Power supply regulator. Follow the circuit see not difficult already by this system designs to come to for voltage source 6V. See the detail in the circuit or seek you want to read the detail more than this as a result can see from http://www.nscl.msu.edu/~daniel/regulator.html