Build simple colour detector circuit for line tracking robots.

The given circuit is tested by myself in NCE Robotics Club ( www.facebook.com/ncerobotics ) many times with various modifications, the given circuit works very effectively.

Figure: Verified circuit diagram of color detector

The circuit can detect two different colors comparing the light reflecting capacity of those colors. As we know the light reflecting capacity of brighter color is higher than dark one, thus the different intensity of light reflected by different color surface will cause the different value of resistance in LDR ( Light Dependent Resistor ) sensor, which is converted into voltage levels by implementing LDR and a fixed resistor in voltage divider arrangement (but as fixed resistor we use preset to change the sensitivity as our desire and required level).

Specifications and features of line following robots:

• The robot can follow both black and white lines.
• It has uses an LDR (light depending resistor) sensor array to follow the line.
• It is controlled by an Atmega32 running at 1 MHz.
• The program is written in C using WinAVR as given below for two sensors arrangement.

Figure :- Logic development process

How to run two 7segment display with a single port of microcontroller.

For this purpose we can alternatively display the different data at different time repetitively from same port. Since there is some delay need to turn off the glowing LED of 7 segment display so by alternative display of different data in different segments we  can show as they are continuously displaying the data.