嵌入式系统导论-实验课-proj2-PCBDesign.pdfVIP

SMIE-141: Introduction to Embedded Systems Project 2: PCB Design Tutorial: Line Tracking Circuit Board Gang Chen, Kai Huang December 10, 2014 1 Goals ? Introducing to the PCB design. ? Creating a schematic of line tracking circuit and designing a Printed circuit board for it. 2 Keywords Printed circuit board, Schematic, Altium Designer 3 Reference /display/ADOH/Tutorial+-+Getting+Started+with+PCB+Design .vn/det/upload/files/introducingproteldxp.pdf 1 4 Required Instruments PC with a free-trial version of Altium Designer 5 Laboratory Exercises 5.1 Line Tracking Circuit During this laboratory exercise, a circuit will be created to implement line tracking for the small car or robot. Line tracking circuit, as shown in Figure 1, can guide the car or robot can follow the line to move, which is the basic component in the smart car or robot. The circuit is consist of of three component: ? IR LED (Emitter) ? Photodiode (Detector) ? Op-Amp (Comparator IC) 1The old version of Altium Designer is called Protel DXP 1 Figure 1: Line tracking circuit Figure 2: Difference between the black surface and while surface 5.1.1 How do we identify the black surface and while surface As shown in figure 2, we know that the white surface reflects all the radiations falls on it whereas the black surface absorbs all of them. When the supply is given to IR sensor, IR LED starts emitting infrared light radiations. If the surface is of white color, then it reflects all the radiations falling on them. As these radiations starts falling on the photodiode (which is placed just near the side of IR LED, sidewise) which is connected in reverse bias condition, the resistance of the photodiode starts decreasing rapidly and the voltage drop across the diode also decreases (VERIFY IT???). Thus, the voltage at Pin 3 (see Pin 3 in 1) starts increasing and we call it as high-level voltage at Pin 3. In case of the black surface, LED emits light but it is not reflected by the surface, so the photodiode detects no