3 bit optical code scanner

Short description and operation:-  This circuit scans the black and white coded pattern. Then it converts the scanned pattern into digital data which is string of 0's and 1's. In this project white surface is '1' and black surface is '0'. The scanner works on simple principle of  physics that is, a black surface absorbs infrared radiation and white light reflects infrared radiation. The IR led and IR diode are close to one another. Then the IR led is turned on . If the reflected light from the surface is more. Then the resistance of diode in reverse bias falls, allowing more current to pass through it. Now if this current falls below a set threshold then it turns on the transistor. and the output goes high, indicating that a white surface is detected. To make a 3 bit scanner we need three pairs of IR led and IR diode. Each of the pair will detect the color beneath it and convert it into '0' or '1'. The IR led's turn on and off sequen...