Solar-Powered RFID Water Vending Machine Based on ESP32

Building an Autonomous Water Dispensing System for Rural and Public Installations.

Abstract

Providing safe drinking water in remote and public locations often requires a reliable dispensing system capable of operating without a stable electrical grid. This modern world we see there has so many industries, buildings and other public infrastructures it is essential for purifying water in public places. This project presents a solar-powered water vending machine built around the ESP32 microcontroller.
The system combines Smart Vending Software, RFID authentication, cashless payment support, real-time monitoring, and intelligent power management into a compact embedded platform.

Introduction

Water vending systems have become increasingly common in public spaces, but many installations depend on continuous AC power and require frequent maintenance. Remote deployments demand an alternative architecture that minimizes power consumption while ensuring reliable operation. This smart vending machine is able to manage the real time inventory system and this vending machine allows users to access it with a web app.

The objective of this project was to develop an embedded controller capable of:

Authenticating users through RFID cards
Controlling water dispensing electronically
Logging transactions
Reporting operational data remotely
Reducing maintenance requirements

The ESP32 was selected because it integrates Wi-Fi, sufficient GPIO resources, multiple communication interfaces, and low-power operating modes.

System Architecture

The controller consists of the following functional blocks:

RFID Reader (RC522)
Solar Charge Controller
12 V Battery Pack
Solenoid Valve Driver
Relay Module
LCD Display
Water Flow Control
Wi-Fi Communication
Cloud Dashboard (MQTT)

The firmware coordinates every subsystem while monitoring battery voltage and communication status.

Hardware Design

The electronics are divided into three primary sections.

Power System

PWM/MPPT Charge Controller
12 V Sealed Battery
5 V Buck Converter
3.3 V LDO for ESP32

The battery ensures continuous operation during nighttime or cloudy weather.

User Interface

Users authenticate using an RFID card.

The display shows:

Water quantity
Dispensing status
Error messages
Network status

LED indicators provide immediate visual feedback during operation.

Water Dispensing Circuit

A MOSFET-driven relay controls a 12 V solenoid valve connected to the filtration system.

The dispensing duration determines the delivered water quantity.

Optional flow sensors may be integrated for precise volume measurement.

Firmware Design

The firmware follows a modular architecture.

Main software modules include:

Payment Interface
Display Manager
Water Control
MQTT Client
Wi-Fi Manager
Power Monitoring
Data Logger
OTA Firmware Update

Each module operates independently, simplifying maintenance and future expansion.

Operating Sequence

The vending process follows these steps:

System startup
Initialize peripherals
Connect to Wi-Fi
Wait for RFID authentication
Validate user credentials
Verify payment or account balance
Activate solenoid valve
Dispense programmed water quantity
Store transaction locally
Upload data to cloud server
Return to standby mode

Remote Monitoring

The ESP32 periodically publishes operational parameters through MQTT.

Typical monitored data includes:

Solar charging status
Daily water consumption
Number of transactions
Valve operating time
Device uptime
Network signal strength
System alarms

A cloud dashboard enables maintenance personnel to supervise multiple installations remotely.

Power Optimization

Because the machine relies entirely on solar energy, several power-saving strategies were implemented.

These include:

Wi-Fi activation only when required
LCD backlight timeout
Low-power peripheral management
Battery voltage monitoring

These techniques significantly reduce overall energy consumption.

Applications

The controller is suitable for:

Schools
Industrial facilities
Public parks
Bus terminals
Railway stations
Highway rest areas
Smart city infrastructure

Future Improvements

Potential enhancements include:

UPI integration
GSM/LTE communication
Water quality monitoring
Predictive maintenance
Mobile application support
Remote firmware updates
AI-based usage analytics

Conclusion

This project demonstrates how an ESP32 can serve as the core of a fully autonomous solar-powered water vending system. By integrating RFID authentication, remote monitoring, intelligent power management, and wireless connectivity, the design provides a scalable solution for reliable drinking water distribution in locations where conventional infrastructure is unavailable.

The modular hardware architecture and firmware design also make the controller suitable for future expansion with additional payment methods, environmental sensors, and cloud-based management services, offering a practical embedded solution for modern smart infrastructure.