Fetchbot Hardware
I primarily work in theory and software development, so when I wanted to test my theories in an implementation of robot software, I became severely out of my comfort zone. I was hoping that I could purchase a simple rover bot with motors and a camera programmable in my choice of platform (and in a hobbyist price range.)
Most robot kits are meant for hardware experimentation, but I wanted a stable and simple set of components so I could focus on software. Many of the ready-made robots can only be programmed in a proprietary language—often a "kids" development platform where you drag blocks around. This is completely inappropriate for exploring advanced AI. I also found the other extreme: robots meant to be programmed in C. It's a great language for embedded development like writing hardware drivers, but I needed a very high level language for natively manipulating complex data structures. (I had been exploring proof of concepts in Python, Node.js, and Erlang.) These are the reasons I grudgingly decided that I had to build my own Fetchbot
When I am confident in a stable kit of hardware, I'd love to share it with other robot programmers who are in a similar situation. I'll publish a comprehensive parts list and instructions, and I am considering compiling a crowd-funded kit so you can order everything in one box, including an SD card with core software and tools already installed.
News
State of the Hardware - August 2018
Version 2 of Fetchbot has been stalled for a while due to an issue with my chosen motor driver (I think.) 4 alkaline cells are not sufficient to power the motors of the Runt Rover. However, when I increase the power to 6 cells, the motor controller stops working. I am doing some troubleshooting to try and fix this as soon as I can, but I am not experienced at this sort of thing.
Fetchbot 2 Parts
Parts
- Actobotics Whippersnapper Runt Rover Kit (chassis, wheels, motor) $29.99
- Raspberry Pi Zero W $10.00 ($5.00 on sale)
- 16GB micro SD card with Raspbian image $7.99
- Velleman L298N Dual Bridge DC Stepper Controller Board $11.99
- Inland 2,600mAh Power Bank Battery Charger for Mobile Devices for remote power to the Raspberry Pi. $5.00
- 4 AA cells and case
- Raspberry Pi camera module $24.99
- Raspberry Pi Zero case $4.99
- GPIO Hammer Header $6.50
- Jumper wires. I started with M/M and F/F because I can make an M/F with two of them.
Tie wraps, electrical tape, twist ties, and other miscellaneous kludge tools.
Total Cost
About $95.00
Summary
With batteries, jumpers, and other parts you should plan on spending about $100.00 on this project, not including necessary tools like screwdrivers, a computer, and for setting up the Pi Zero: a keyboard, mouse or touchpad, HDMI monitor, and mini HDMI cable or adapter.
Fetchbot 1 Parts
Parts
- Actobotics Kit - Actobitty 2 $29.95
- Raspberry Pi 2 $29.99
- Raspberry Pi Camera Module $29.99
- “Power Bank” battery charger for mobile devices $5.99
- Actobotics Pi Channel Mount $1.95
- L9110 dual H-bridge ~$3.00
- USB WiFi dongle ~$3.00
- 16GB micro SD card with Raspbian image $7.99
- Female to female jumper wires
- Male to female jumper wires
- Nylon cable ties
- Electrical tape
- 4 AA cells
Total Cost
About $120.00
Tools
For working with the Raspberry Pi
- Raspberry Pi power supply
- HDMI monitor
- Bluetooth keyboard
Summary
This was my first attempt at building my own robot and it worked, but I spent more money than I wanted. I think the cost could be brought down with a less expensive single-board computer (maybe a Raspberry Pi Zero) and USB camera.
The Actobitty has 2 rear wheels and a single front plastic runner so it is only capable of movement on a smooth, flat surface.
Assembly of the robot hardware is easy - a 12 year old should be able to handle it. Working with the Raspberry Pi is harder. Make sure you have the tools and experience needed for a Pi before you start.