1. Raspberry Pi
This project started because I absolutely wanted to make use of something I had lying around for some time: a Raspberry Pi 1 Model B (with a whopping 512MB of RAM !!). This was great a few years ago, though it lacked wireless connectivity.
Nowadays a Pi Zero W would probably replace it perfectly and make the whole build much smaller.
2. Micro motors + driver
Pololu has an extended choice of micro brushed DC motors. I had determined that I wanted the 100:1 version, meaning enough torque to carry a real payload (speed was not so much a priority). I even took the extended shaft option for encoders, since I wanted room for potential evolution.
The DRV8835 page has all the information needed. It is perfect for the selected motors and supports a simple differential drive mode that I wanted. It also states "built-in protection against reverse-voltage, under-voltage, over-current, and over-temperature", so I did not need to add important safety features myself.
3. Power Bank
To power everything up, I opted for a convenient and standard USB power bank. I was able to find one with dual output: One is rated 2.1A max, plenty enough for the Raspberry Pi, the other 2.4A. This covers exactly the continuous 2 x 1.2A per channel that the motor driver can deliver. It does not cover the 2 x 1.5A peak it can reach, but in practice this has been good enough.
4. Camera + micro servomotor
While deciding to get a an embedded camera for the robot, I did not know exactly what I would do with it (video streaming? image processing?). Having no quality-vs-speed criteria yet, and because I definitely wanted good software compatibility from the start, the official camera module from the Raspberry Pi Foundation seemed like the natural choice.
The last component is a simple and standard 5V-compatible analog micro servo, directly power by the Raspberry Pi. It provides the tilt for the camera, thus avoiding any blind spot when teleoperating.
I try to avoid soldering whenever possible, hence making Dupont connectors and crimping pliers my first choice.
2. Putting it all together
The complete wiring diagram:
And the result in action: