Ten days, one robot, three control loops. How our ESP32 balancing robot on brushed motors learned to stand, to come back after a push, to hold its spot and to drive over Wi-Fi, with the numbers from its logs and the firmware that made it work.
Brushed motors, an ESP32 and an MPU-6500 — and three control loops, each one fixing what the one before couldn't. The angle loop (PID, 500 times a second) keeps it upright, but it rolls 27 cm away. The speed loop brings it back to a 30 cm band. The position loop brings it home within 3 cm — then it drives over Wi-Fi and jumps off a bathroom scale. Three loops, one LQR, or a neural net — which would you bet on?
A level and a compass: your phone has both, so naturally I built my own. One case printed on a Creality Ender-3 V3 KE, four brass inserts, three boards (a TTGO T-Display with an ESP32, an MPU-6500 accelerometer and gyro, a BMM150 magnetometer) and one 18650 cell charged over USB-C. Within half a degree of level it turns green and beeps once. The lesson: a magnetometer notices everything, from the buzzer's magnet to the charging cable and a phone nearby. So: buy one, or build one?
I push, it comes back. This frame balances in one plane on the thrust of a single propeller: an MPU-6500 sensor measures the tilt, and an ESP32 runs a PID controller (Kp 8 · Ki 2 · Kd 2.2 in this test) that drives the motor through a DRV8833. Bluetooth sends the tilt and the motor command to a page on my computer, where I can adjust the PID settings. Earlier attempts? Gravity was consistent. What next: two planes, or wheels?
The original ESP32, S2, S3, C3, C6 and P4 side by side: cores, memory, radios, motor-control peripherals, ADC, USB and sleep currents, checked against Espressif datasheets — and which chip to pick for motors, sensors, USB devices, cameras or Thread.
Six wires, 100 readings a second, and three calibration tries — I used all three. An MPU-6500 (3-axis accelerometer + 3-axis gyroscope in a 3 × 3 mm chip) talks over SPI to an ESP32 (LILYGO T-Display), and a page in the browser turns its readings into a 3D model, a paper plane and a ball maze. What should the robot get next: wheels or eyes?
Three parts, five wires, 35 solder joints. An ESP32 (LILYGO T-Display) receives music over Bluetooth A2DP, a MAX98357A I2S amp drives a tiny 2 W speaker, and the screen runs a live spectrum analyzer. What should I add next: a 3D-printed case or an SD card player?
An ESP32-S3 board with a 5 MP OV5640 camera, two USB-C ports, microSD, 16 MB of flash and 8 MB of PSRAM. What is wired to what, which of its 36 GPIOs are really free, how to set up Arduino so the camera behaves, and a pin reference to download.
An ESP32 board with a 1.14-inch colour screen already wired to it. What is connected where, which GPIOs are safe to use, how long it lasts on a battery — and where the classic T-Display ends and the S3 begins.
