As a new generation energy-saving lighting source, LED is applied widely in various technology and industry fields.
The requirement of its adaptive lighting technology is more and more rigorous, especially in the automatic on-line
detecting system. In this paper, a closed loop feedback LED adaptive dimming lighting system based on incremental PID
controller is designed, which consists of MEGA16 chip as a Micro-controller Unit (MCU), the ambient light sensor
BH1750 chip with Inter-Integrated Circuit (I2C), and constant-current driving circuit. A given value of light intensity
required for the on-line detecting environment need to be saved to the register of MCU. The optical intensity, detected
by BH1750 chip in real time, is converted to digital signal by AD converter of the BH1750 chip, and then transmitted to
MEGA16 chip through I2C serial bus. Since the variation law of light intensity in the on-line detecting environment is
usually not easy to be established, incremental Proportional-Integral-Differential (PID) algorithm is applied in this
system. Control variable obtained by the incremental PID determines duty cycle of Pulse-Width Modulation (PWM).
Consequently, LED's forward current is adjusted by PWM, and the luminous intensity of the detection environment is
stabilized by self-adaptation. The coefficients of incremental PID are obtained respectively after experiments. Compared
with the traditional LED dimming system, it has advantages of anti-interference, simple construction, fast response, and
high stability by the use of incremental PID algorithm and BH1750 chip with I2C serial bus. Therefore, it is suitable for
the adaptive on-line detecting applications.