LiPo-Powered Halogen Bike Light with AVR Light Controller

Overview

The purpose of the project is to build a power controller based on a small ATtiny45 AVR microcontroller which uses PWM to achieved the desired output power of a LiPo battery power source.

Details

The use of a microcontroller in this project does not only control the output power but also provides smooth transition between power levels. A low battery or when the light is not connected provides a warning using the control LED. The LED could show the battery voltage level by holding the input button when the light is OFF. The light can be turned ON using the button on the remote which can also toggle between BRIGHT and DIMMED power mode. The light turns OFF by holding the button for a second. The strap of a bike pack can be used for attaching the remote control with a single button and an LED.

A 5V VCC is provided for the ATtiny45 by the 7805 regulator along with two capacitors. To prevent the battery voltage from being noisy as it drops when the light is turned ON and raises when turned OFF by the PWM, a low-pass filter was created.