AWD Lego Custom made Car using Raspberry Pi - Part 1

 Idea

Use Raspberry Pi to control this custom made car model. 

Implementation

Bill of Materials

Hardware

1. Raspberry Pi Zero W
2. Raspberry Pi, 1 to 2 expansion
3. Pi Juice Hat
1. Amazon, very costly but looks like latest model
2. Digikey, fair price but looks like old model
4. Adafruit Motor Bonnet for Raspberry Pi
5. DFrobot RPi zero IO Expansion Hat
6. DFrobot Ultrasonic Sensor, URM09 Analog 
7. DFronot i2c Digital Wattmeter 
8. Mini Breadboard
9. 3mm LED for front light
10. Micro LED 0603 for back light
11. 1.5V AA Batteries
1. I used EBL ones
12. Lego Power Functions Servo Motor
1. One for steering and one for Transmission
13. Lego Power Functions L-Motor
1. I used two
14. Lego Power Functions Battery Box for AA
15. Lego Power Function Extension Cable, 20"
16. Dupont Connector Kit
17. Crimping Tool for Dupont Connectors
18. Ferrule Crimping Toolset
19. Wire Stripping Tool
20. Paper/Utility knife
1. To cut and separate wires of Lego extension cable

Software

1. Raspberry Pi OS Lite, 
1. with no GUI as it's not needed on Car
2. Adafruit python library for Motor Bonnet
1. Edit /usr/local/lib/python3.7/dist-packages/adafruit_motorkit.py or locate adafruit_motorkit.py based on installation
2. Add default parameter, pca_frequence=1600 like this
1. 
   
   
   
   
3. Dfrobot Wattmeter Code
4. PiJuice Code
5. My Test Code. FOR REFERENCE ONLY, DON'T JUST COPY PASTE and USE IT.
1. Controller.py
1. Main file to control the car, it uses curses lib.
2. + is shift up, - is shift down
3. w is steering straight, a is steering left, d is steering right
4. s is to stop
5. UP arrow increase Throttle/power to motor
6. Down arrow decrease Throttle/power to motor
7. q to quit
2. car.py
1. Module which implements Car's functionalities

Wiring

I use Lego Extension cables when connecting Lego motors and motor driver board. This way, Lego motors can be reuse in pure Lego based projects.

Cable for Lego Power Functions Battery

Lego cable has four wires. Wires on each side doesn't change polarity when battery box switch turns to either side. Right outer cable is +ve and left outer is -ve. Use this to attach to desired power source. 

See this picture to get an idea

Caution: Use multi meter to confirm polarity

Cable for Lego Power Functions Motor

Middle two wires are used to power Lego PF motors. 

I prefer to use light grey head side, (which doesn't fit the battery), for motor connection as it can be attached to Lego Buggy Motor. Picture for information 

Cable for Lego Power Functions Servo

Lego PF servo uses all four wires. Side wires are to power and middle two wires are used to set duty cycle and direction. I use breadboard to share battery power with PF Servos.

See picture for idea 

Also see Ideas on how to Control Lego Servo

Setup

My Raspberry Pi Zero W with other boards stacking looks like this

1. Raspberry Pi Zero W
2. 1 to 2 GPIO Expansion Kit
1. Motor Driver board  to the side
2. Pijuice on Top side of GPIO Expansion Kit
3. IO Expansion kit
4. Breadboard attached to the kit

More pictures from different sides

I updated model and attached, camera, distance sensor, lights, though they are not operational yet. Model looks like this

Demo

Without Load

Or 

Youtube Link

Running on floor

Or 

Youtube Link

Note engine speed on shifting to 4th gear, it's slow. Reading motor battery was on 3V. Not sure if batteries were not able to handle such load or was there any other issue.

Next Step

1. Hook up sensors, lights, Camera and Automated Action
2. Use a Remote not laptop, which looks something like this
1. 
   
   
   
   
2. 
   
   
   
   
3. Yep, it has Google Coral