Advanced Line Following Robot - Step 4: The Electronics



In this parts I will be explaining the constuction of the sensor array and the main controll board.


The Sensor Array

The sensor board consists of 8 IR sensors. The sensors are placed 1.2 cm apart from each other.Two on oboard LM324 onboard convert the anaglog signals from the IR photodiode and convert them to digital signals. There is a onboard preset to calibrate the sensors. The sensor board PCB is shown below. I used EaglePCB for the designing because it is quite easy to learn and comes free. The sensor board is single sided so it should be possible to etch at home. Just print the board to size and etch it.


The solder side (the board is 10cm x 4.5 cm)


The silkscreen side


R1 - 120 ohms

R2 to R9 - 10K

L1 to L8 are IR LEDs

PD1 to PD8 are photodiodes


The final sensor board is shown below



I attached two l brackets on both sides of the sensor board to mount it to the robot chassis.


The Main Board

The main board consists of the microcontroller and the motor driver. The microcontroller I used is the Atmega16. The motor driver I used is the L293D. I used the L293d because it is quite cheap and also you can control the motor speed with its enable feature. 

The main board's PCB is shown below. It is also single sided. It is 10 cm x 4.5 cm.

The solder side

The silkscreen side


Photobucket Photobucket

The final board


Note: The motor driver I have used, the L293D, can drive motors which consume upto 600 ma of current. If your motor requires more current, you can use the L239NE which can drive motors upto 1 A. It is pin compatible with the L293D so you can use the same circuit.


Visit to view the schematic. You can also download the Eagle schematic files below.


Lotl Schematic.png91.98 KB