Build a Robot¶
Everything so far has lived on your desk. Now it's time to build something that moves around on its own. In this section you'll build a two-wheeled robot car from a cheap chassis kit, wire it up to your ESP32, and teach it, one step at a time, to:
- drive in patterns, and even dance,
- see obstacles with an ultrasonic sensor and steer around them,
- follow a line of black tape around a track, and
- take orders from your phone over Wi-Fi.
This is mechatronics: mechanical parts (motors, wheels, gears), electronics (drivers, sensors, batteries) and code, all working together. It's exactly how real robots work, from warehouse robots to robot vacuums and Mars rovers. They're just bigger.
Before you start
The robot uses skills from across the guide. You should be comfortable with saving programs and library files to the board, Buttons, and ideally Ultrasonic Sensors and Servo Motors.
What you'll need¶
Robot parts:
- 2WD robot car chassis kit. These are sold under names like "2WD smart robot car chassis" and usually include: an acrylic base plate, 2 × yellow TT gear motors (3–6 V), 2 wheels, a caster wheel, a 4 × AA battery holder with an on/off switch, and screws.
- DRV8833 dual motor driver module
- HC-SR04P ultrasonic sensor, the 3.3 V version. A classic 5 V HC-SR04 works too, but needs the voltage divider from the Ultrasonic Sensors lesson.
- 2 × TCRT5000 line-tracking modules
- Half-size breadboard
- Jumper wires, male-to-male and male-to-female
- 4 × AA batteries (rechargeable NiMH are fine)
- A small USB power bank and a short USB cable
- Your ESP32 DevKit board
Optional extras:
- SG90 servo and a small bracket, for the scanning "head"
- Piezo buzzer and a push button (you already have these)
- Black electrical tape, for a line-following track
Why a power bank?
The robot uses two power supplies: the AA batteries drive the motors, and a USB power bank runs the ESP32. Motors are electrically "noisy" and can pull the battery voltage down when they start, which would make the ESP32 restart. Keeping them apart avoids that whole class of problem. Build the Robot explains how the two are connected.
The robot's pin plan¶
| Part | GPIO | Notes |
|---|---|---|
| Left motor (DRV8833 AIN1 / AIN2) | 16 / 17 | |
| Right motor (DRV8833 BIN1 / BIN2) | 18 / 19 | |
| Ultrasonic sensor TRIG / ECHO | 5 / 39 | Same as the desk lessons |
| Left line sensor | 34 | |
| Right line sensor | 35 | |
| Servo (optional scanning head) | 13 | Same as the desk lessons |
| Buzzer (optional) | 26 | Same as the desk lessons |
| Start button (Button A) | 14 | Same as the desk lessons |
The plan¶
Work through these pages in order. Each one adds one new skill, and ends with something working.
| Step | Page | What happens |
|---|---|---|
| 1 | DC Motors | Spin a single motor on your desk, forwards, backwards, fast and slow. |
| 2 | Line Sensors | Learn how the robot can "see" a black line. |
| 3 | Build the Robot | Put the chassis together, wire everything up, and test each wheel. |
| 4 | First Drive | Use the robot.py library to drive, turn, trace a square and dance. |
| 5 | Obstacle Avoider | Let the robot roam and steer around anything in its way. |
| 6 | Line Follower | Build a tape track and have the robot follow it. |
| 7 | Wi-Fi Remote Control | Drive the robot from your phone. |
Safety first¶
Batteries
- Only use the battery pack for the motors. Never connect it to the ESP32's 3V3 pin.
- Don't mix old and new batteries, or rechargeable and non-rechargeable ones, in the same holder.
- If anything gets hot or smells like burning, switch the battery pack off straight away and check the wiring for shorts.
- Switch the battery pack off whenever you're not driving. The switch is there for a reason!
Testing on the desk
When you're trying out new code, prop the robot up on a small box or a roll of tape so its wheels spin in the air. It's much easier than chasing it off the edge of the table.
Let's go: start with DC Motors.