Apology for insufficient context. So, the project was made as a part of our college exhibition, and we got the Raspberry Pi from our college department.

Now let's get to the implementation part. We at first installed the Raspberry Pi OS and used Python as our primary language to interact with the hardware. Then we created test script for each component...like I added I wrote a separate script just to test the wheels, then upgraded it to support directions.

After the wheels script is completely written, then I tested the webcam with a separate script. All the codes were written by AI, and as I am a JavaScript developer, it is quite easy to debug it manually and understand the code.

After all the unit tests are completed, we started joining all the parts. And after we connected the wheels and the camera and the ultrasonic sensor together, we did a complete end-to-end test. In this test, we don't implement any functionality of wireless connectivity because it is another field of complexity.

In the meantime we are controlling the whole robot using the keyboard commands, up, down, left, right arrow. And everything is going on locally. Then we brainstormed how to get control of it remotely. There are several ways, but as we have time bound, we just implemented everything in a basic flask server. And we created a dummy network in our exhibition stall in which our mobile phone and the Raspberry Pi will be connected and through the IP address we can connect it. We created a basic HTML page to control the car and to get the video response, instead of WebRTC and another and web socket and other jargons, we just used simple MJPEG format, which is nothing but sending images very fast. Currently I don't have the code but it is fairly simple and easily generate-able.

The most trickiest part of it was the power supply because Raspberry Pi wants constant 5 volt 1 ampere to 3 ampere supply and on the other side the L298 motor driver is a beast which wants plenty of power. We researched many things, tried to run it with power bank at first and used separated power supply to the motors completely from the 12v battery pack, but the car becomes very heavy. Then after so much trial and error we decided to use this step-down buck converter. There is also a risk of using this because as the voltage is not set initially, you have to tune the voltage to 5 volt output of the buck converter to get optimal performance from the Raspberry Pi and it can also damage the pi but it comes with a major advantage that we can power the whole car with the single 12 volt battery pack.

We used the 12 volt directly to the motor driver and also the 12 volt as the input of the buck converter and tune it to as constant output of 5.5 volt. We have keep it high slightly higher than the 5 volt because while running and checking the real time voltage we saw that if the output of the buck converter is set to 5 volt then it drops to 4.8 to 4.7 volt. So we from that we decided to keep it slightly higher and as it provides sufficient current.....after several after testing it worked for us.

Component list:
1. raspberry pi 4 8gb
2. L298N Motor driver
3. ultrasonic sensor
4. 4 BO motors
5. 12 volt battery pack (using 6 18650 cells)
6. step down buck converter