Final Design

Light Source Circuit

                                                     Final Circuit Diagram

The circuit takes Arduino PWM signal voltage as input. The input voltage passes through a low-pass filter with gain approximately 0.44 to produce DC voltage in the range of 0 to 2.2 V. It is then used as input of a voltage controlled current source (VCCS) which consists of an Op-Amp and a transistor. As the result, changing PWM command could directly change the current in the load circuit, which powers up LEDs by 12 V external power source. Since LED intensity is linearly proportional to current through it, changing PWM command would proportionally change the light source intensity.