Autonomous Light-Following Flower Robot

info

Author: Serban Lidia-Andreea
GitHub Project Link: https://github.com/UPB-PMRust-Students/fils-project-2026-lidiaserban

Description

The Autonomous Light-Following Flower Robot is a bio-inspired system that mimics plant phototropism by navigating toward the strongest light source using dual photoresistors and an STM32 Nucleo U545RE-Q. Built with the Embassy framework for asynchronous control, it balances light-seeking with active obstacle avoidance via ultrasonic sensors while monitoring environmental conditions through a DHT22 sensor and LCD. The robot utilizes a dual-rail power strategy to isolate high-torque motor noise from sensitive logic, ensuring stable, real-time performance in a standalone package.

Motivation

My motivation for this project is to apply embedded systems engineering to a nature-inspired concept. I chose a light-following robot because it provides a practical way to learn how the STM32 Nucleo U545RE-Q handles real-time sensor data and motor control. The project requires me to use the Embassy framework to solve a specific technical challenge: prioritizing obstacle avoidance while concurrently tracking light sources. Additionally, implementing a dual-rail power system with a DC-DC converter allows me to explore power management and noise isolation between high-current motors and sensitive logic circuitry.

Architecture

       ┌───────────────────────────┐
       │   PRIMARY POWER SOURCE    │
       │      (4x Batteries)       │
       └─────┬───────────────┬─────┘
             │               │
             │        ┌──────▼──────────────────────────┐
             │        │    DC-DC VOLTAGE CONVERTER      │
             │        │   (High-Current / Motor Rail)   │
             │        └──────────────┬──────────────────┘
             │                       │
             │                       ▼
┌────────────▼────────────┐  ┌──────────────────────────┐
│      STM32 U545RE-Q     │  │      L9110S DRIVER       │
│   (Logic / Brain Rail)  │  │   (Motor Control H-Bridge)│
└────────────┬────────────┘  └──────────────▲───────────┘
             │                              │
             ├──────────────────────────────┘
             │      (PWM Speed Control)
             │
     ┌───────┴───────┬───────────────┬───────────────┐
     │               │               │               │
┌────▼────┐    ┌─────▼─────┐   ┌─────▼─────┐   ┌─────▼─────┐
│  LIGHT  │    │ DISTANCE  │   │   DHT22   │   │ LCD 16x2  │
│ SENSORS │    │ (HC-SR04) │   │ (Temp/Hum)│   │ (Status)  │
└─────────┘    └───────────┘   └───────────┘   └───────────┘ 

Log

Week 5 - 11 May

Week 12 - 18 May

Week 19 - 25 May

Hardware

The system is based on the STM32 Nucleo U545RE-Q microcontroller, which manages data processing and control. Light detection is performed using photoresistors, while an ultrasonic sensor provides obstacle detection and a temperature–humidity sensor monitors environmental conditions. Movement is achieved using DC motors controlled by an H-bridge driver with PWM signals. The structure includes wheels and a caster for stability. Power is supplied by a battery and regulated with a DC-DC converter. An LCD display is used to present system data.

Schematics

Place your KiCAD or similar schematics here in SVG format.

Bill of Materials

Device	Usage	Price
STM32 Nucleo U545RE-Q	The microcontroller	~130 RON
DC Motors	The DC motors	~15 RON
Ultrasonic sensor	Distance sensors	~11 RON
Photo rezistors	Light sensors	~10 RON
Movement	Wheels	~11 RON
Support caster ball	Caster	~4 RON
Baterry case	Baterry holder	~5 RON
Driver for motor	H-Driver for motors	~8 RON
Module for humidity sensor	Humidity sensor module	~7 RON
Humidity and temperature sensor	Humidity and temperature sensor	~18 RON
Adjustable DC voltage reducer module	DC-DC voltage converter module	~28 RON
LCD	LCD Display	~23RON
		Total ~= 275RON

Software

Library	Description	Usage
embassy-stm32	Hardware Abstraction Layer (HAL) for STM32	Configures GPIO, ADC for light sensors, and PWM for motors
embassy-executor	Async runtime for embedded systems	Manages concurrent tasks like obstacle detection and movement
hd44780-driver	LCD Controller library	Displays temperature, humidity, and status on the 16x2 LCD screen
dht-sensor	DHT22 Driver	Specifically used to parse the digital signal from the DHT22 temperature and humidity sensor
panic-probe	Debugging tool	Helps you see errors in VS Code if the sensor fails to initialize
embassy-time	Timekeeping and delays	Provides the microsecond-precision delays needed to "handshake" with the DHT22 and measure its data pulses

Links

1. Embassy Book
2. link ...