Line follower robot without microcontroller

This line follower robot without microcontroller is compossed of 2 CNY70 sensors, 2 motors with reduction, 1 ULN2803, 2 10 K adjust resistors and 4 220ohm resistors.

Each CNY70 sensor when is over white causes the opposite side motor run slower, this causes the robot comming back to the black line.

The sensors excite both groups of 4 darlington transistors in parallel (in order to increase the output current to 2A), and 2 motors with reduction.

The way to adjust the robot is:
- Place the robot over the white surface to run.
- Switch on the robot while stopping it with the hand.
- Adjust one of the adjust resistors through one of the small holes over the robot until the opposite side motor stops.
- Perform the same adjust for the other adjust resistor.

All the components on this robot are cheap and very easy to find in most of the countries.