The $40 Line Follower - Step 4: Putting everything together

In this part of the tutorial I will explain the process of connecting the sensor to the main circuit board and mounting them to the robot’s chassis.


There will be 7 wires coming out of your sensor module. Solder the two black wires and one red wire to the black wire and red wire of the battery cap respectively. The remaining four blue wires should be connected to each presets wiper as shown below. Note that wires from the left sensors and right sensors should be connected to the presets to the left and right of the DIP socket respectively.


I advice you to add a 270 ohms resistor between the red wire from the sensor board and Vcc(red wire of the battery clip) to limit the current reaching the LEDs. I have not fried a single LED but some SOR members have fried their LEDs for not having used the resistor. 


Solder the motor wires as shown in the image below (Refer to the circuit diagram if you are confused about the connection).


Next mount the sensor module and the circuit board to the robot’s base through the spacers. Before mounting the main circuit board make sure that you have attached the 9V battery to the base.


Sensor board mounted to the base


The main circuit board mounted to the base


This completes the construction of the robot. But there is still one step left , which I call “Pin Plugging”. You may have noticed (if you have gone through the circuit diagram) that all the input pins of the L293D are left unconnected (apart from being connected to a header pin) in the circuit board. The reason I did this was because the connections change every time you want the robot to achieve a different task (line following, obstacle avoiding etc. )  

To use the robot as a black line follower, obstacle avoider and photophobe, make the following connections in the main circuit board.



To use the robot as a white line follower and photovore  make the following connections.




Time taken to build the robot - 


Research :-10-15 hours

Designing:-  4 hours

Building the chassis:-  < 1 hour

Electronics :- 3 hours

Click here to view the shake test.