This is not a conventional bicycle signaling light as we all know. Instead, it has two 4x4 RGB LED matrices! The maker used the ATmega168 microcontroller to control these matrices. For driving the LEDs, he uses the UDN2981A 8-channel NPN source driver. To operate this gizmo needs 6 to 7 volts, although with 5 volts it still works, but the LEDs are dimmed. He plans to use 4x AA cells or maybe 2 LiPo batteries in series. In the second case scenario, he will need to include a management chip (charging / preventing deep draining). Visit his site for more info.