This robot was made to enter the Minecraft challenge, the Epilog Challenge IX and the first time author contest. It 's based upon one of the most iconic Minecraft mobs: the Creeper. This robot uses a 3d-printed shell, so you need to have access to a 3d-printer to build it.
** My 12 year old son designed the robot and assembled it and wrote the python code, I only helped a little with the drilling, he also wrote this tutorial, but he had to use my account because of the minimum age requirements of the challenge, so really it's his project ** .
Step 1: Bill of Materials (BOM)
To build this robot, you will need
-a complete Raspberry Pi Zero setup(keyboard, mouse, monitor, fresh install of raspbian, internet access) whith soldered pins
-HC-SR04 Ultrasonic sensor
-2 2BYJ-48 stepper motors with the ULN2003APG stepper motor driver
-1 1KΩ resistor
-1 2KΩ resistor
-Female and Male jumper wires
-3d printed creeper shell (files in this step)
-Hot Glue Gun
-some extra pins
-battery pack (preferabbly a squid)
Step 2: Making the Power Bus
This is easy, cut a bit of protoboard (3 squares min) and solder some pins to it and between them, coat the soldered zone with hot glue to avoid shortcuts. You'll need three of these to substitute the breadboard and make the elctronics more compact.
Step 3: Electronics
If you can't see the resistors' color codes, the left resistor is 2KΩ and the right one is 1KΩ. When you need to use the breadboard, use the power bus instead.
Step 4: Mounting the Electronics Into the Shell
Normally, the head clicks into the body, but if it doesn't, you'll need to sand a bit the top part of the body till the head clicks. The body slots into the base, but it's loose, so put a bit of hot glue to hold it in place. The body has an opening for the Pi Zero usb and hdmi ports. Here you have an arrangement to put the 2 stepper motor drivers together and save space, the only thing you have to do is to put them horizontally and hot-glue them to a piece of plastic (if you have a 3d printer if one of these prints goes badly, you can cut it out with a dremmel tool) . To put the Pi Zero in place, you'll need to drill some holes and put them through the pcb holes on the pizero. Hot glue the ulstrasonic sensor to the eye holes (pre printed). To fit in the stepper motors you'll need to drill some screw holes (the axis has a printed hole). Fix the crazy wheel into the back part of the base with pcb holders until it's at the wheels' level. Fix the squid on top of the back part of the base.
Step 5: Programming
You'll need to open a command prompt in Raspbian (for this step you need internet access on your Pi Zero) and type : sudo pip3 install gpiozero hcsr04sensor if you don't have pip installed install it.
Step 6: You're Finished!
If you want to dedicate this pi to this and only this (your raspbian data). Open a command prompt and type:
sudo nano etc/rc.local
Next, scroll down through the code and add the following line before exit 0:
python3 /home/pi/Directory_where_the_program_is_stored/CreeperBot_Ultrasonic.py &
Here it is in action .... https://youtu.be/0t8IxYl8KcY
Step 7: Creeperbot in Action
He's mean, he's green and he ultrasonically avoids obstacles!