Case 94: Bill Bowden: Night Rider

To see and be seen after dark on his bicycle, Bill designed this 40-LED light. He configured a 555 timer IC to generate a continuous on/off timing cycle to alternately flash two groups of 20 LEDs. The device operates on four AA batteries, keeping things bright for even the longest night rides. You can extend battery life with a second circuit Bill designed that uses a short duty cycle to flash a single group of 30 LEDs .