I ride my bike allot at night and sometimes I'm not sure if people can see me. This circuit will flash an incandescent light that you can purchase from Radio Shack. Adjust the VR's for your flash requirements and make sure that the lamp you use is designed to put out high brightness. The enclosure should be water tight. The Batteries can be replaced by a bike wheel generator and a diode. If you add the generator then you can still use rechargeable batteries and the batteries will charge while you are riding your bike.