MeroSathi Smart Sanitary Pad Vending Machine

Overview

MeroSathi is a smart sanitary pad vending machine developed to make menstrual hygiene products more accessible through a simple, automated, and remotely monitorable system.

The machine uses an ESP32 microcontroller as the main controller. Users access the service by tapping an authorized RFID card, after which the system controls a stepper-motor-based dispensing mechanism to release a sanitary pad.

The product combines embedded electronics, mechanical dispensing, user identification, local information display, backup power, and remote monitoring in a strong metal enclosure suitable for installation in different public or institutional environments.

Problem

Access to sanitary pads can be difficult in schools, offices, public institutions, and other shared spaces, especially when products are not immediately available when needed.

A practical vending system should therefore be:

• easy to use
• secure and controlled
• mechanically reliable
• able to show product availability
• capable of operating during temporary power failure
• remotely monitorable for refill and operational status
• physically robust enough for regular public use

MeroSathi was developed around these requirements.

Solution

The system integrates an ESP32-based embedded controller with RFID authentication and an electromechanical dispensing mechanism.

A user taps an RFID card on the reader. After the card is recognized, the controller operates a stepper motor connected to a spring-based dispensing mechanism. The rotating spring advances one sanitary pad toward the dispensing outlet.

A local display provides information such as machine status and available pad information, while operational data can also be sent to a remote dashboard for monitoring.

The complete system is installed inside a strong metal structure designed for practical long-term use.

System Architecture

The overall system follows this flow:

RFID Card → RFID Reader → ESP32 Controller → Stepper Motor Driver → Stepper Motor → Spring Dispensing Mechanism

Supporting subsystems include:

ESP32 → Local Display

ESP32 → Network / IoT Communication → Remote Monitoring Dashboard

AC Supply → Power System → Machine

Battery Backup → Power System → Machine

Hardware

The main hardware elements include:

• ESP32 microcontroller
• RFID card reader
• RFID cards
• stepper motor
• stepper motor driver
• spring-based dispensing mechanism
• local information display
• AC power supply section
• rechargeable battery backup system
• dispensing outlet
• internal storage mechanism
• metal enclosure/frame

Embedded Control

The ESP32 manages the main operating logic of the vending machine.

Its responsibilities include:

• reading RFID cards
• validating user access
• controlling the dispensing sequence
• driving the stepper-motor mechanism
• updating local information on the display
• tracking machine operation
• supporting remote monitoring
• coordinating the machine’s electronic subsystems

The embedded architecture allows the dispensing logic, user access, display, and monitoring functions to operate as one integrated system.

RFID-Based Access

Users interact with the machine by tapping an RFID card.

The RFID system provides a controlled way to access the vending service and allows usage events to be associated with authorized cards or users where required by the system configuration.

This avoids the need for complicated physical controls and makes the interaction simple for users.

Dispensing Mechanism

Sanitary pads are stored inside the machine using a spring-based mechanical arrangement.

A stepper motor rotates the spring by a controlled amount during each valid dispensing operation. This movement advances the stored sanitary pad and releases one unit through the dispensing section.

Using a stepper motor allows the controller to manage the dispensing movement in defined steps rather than relying on an uncontrolled continuous motor rotation.

Local Display

The machine includes a local display for communicating useful information to users and operators.

Depending on the operating state, the display can provide information such as:

• machine status
• pad availability
• user interaction information
• dispensing status
• service-related messages

This gives immediate feedback without requiring access to the remote dashboard.

Remote Monitoring

MeroSathi includes IoT monitoring capability so important operational data can be viewed remotely through a dashboard.

The remote monitoring system can be used to observe information such as:

• machine operational status
• pad availability
• usage information
• refill requirements
• device condition

This reduces the need to physically inspect the machine simply to determine whether it requires attention.

Power System

The machine is primarily powered from an AC supply.

A rechargeable backup power system is also included so the machine can continue operating during temporary power interruptions.

The designed backup capacity is approximately two days under the intended operating conditions, although actual backup duration depends on usage frequency, battery condition, and system load.

Mechanical Design

The electronics and dispensing mechanism are housed inside a strong metal enclosure.

The enclosure provides:

• mechanical protection
• rigidity
• support for the internal dispensing mechanism
• protection for electronics
• suitability for wall or fixed installation
• durability for regular use

The robust construction was an important part of making the prototype suitable for practical installation rather than limiting it to a laboratory demonstration.

Key Features

• ESP32-based embedded controller
• RFID card access
• automated sanitary pad dispensing
• stepper-motor control
• spring-based storage and dispensing mechanism
• local information display
• remote IoT monitoring dashboard
• pad availability monitoring
• AC-powered operation
• rechargeable battery backup
• approximately two-day backup capability under intended conditions
• robust metal enclosure
• designed for public and institutional use

Engineering Challenges

The project required integration across multiple engineering areas rather than only firmware development.

Important challenges included:

• coordinating RFID access with the dispensing sequence
• controlling the stepper motor accurately
• designing a reliable spring-based mechanical release mechanism
• integrating mechanical and electronic components inside one enclosure
• maintaining pad storage and dispensing alignment
• providing useful local feedback to users
• supporting remote monitoring
• designing backup power for continued operation during outages
• making the enclosure strong enough for practical installation

Implementation

The prototype was developed by integrating the embedded controller, RFID interface, motor-control electronics, mechanical spring assembly, local display, power system, and remote monitoring functionality.

The dispensing operation is triggered only after the required user interaction. The ESP32 then coordinates the motor movement and system status while the monitoring layer provides visibility into the machine’s operation.

The project demonstrates the integration of embedded systems, IoT connectivity, automation, electromechanical design, and product prototyping in a single practical system.

Testing

Testing focused on the complete vending workflow, including:

• RFID card detection
• dispensing activation
• stepper motor movement
• single-pad release behavior
• local display operation
• power operation
• backup-power operation
• remote monitoring
• repeated mechanical operation

Mechanical dispensing and alignment are especially important because reliable operation depends on both the firmware and the physical storage mechanism working together.

Current Status

MeroSathi was developed as a completed working product prototype integrating the electronic, mechanical, power, access-control, and monitoring subsystems.

It represents one of the early product-oriented systems developed with a focus on solving a practical social need through embedded and IoT engineering.

Social Purpose

Beyond its technical design, the purpose of MeroSathi is to support easier access to menstrual hygiene products.

Automated sanitary pad availability can be useful in environments such as:

• schools and colleges
• offices
• public institutions
• health facilities
• community facilities
• workplaces

The project demonstrates how connected embedded systems can be applied not only to industrial monitoring or automation, but also to practical products with a direct social purpose.

Technologies Used

• ESP32
• RFID
• embedded firmware
• stepper motor control
• motor driver
• electromechanical dispensing
• local display
• battery backup
• IoT communication
• remote dashboard
• metal enclosure design

Related Engineering Areas

This project combines several IoTSolutions capability areas:

• IoT system development
• embedded systems development
• hardware prototyping
• automation
• remote monitoring
• dashboard integration
• electromechanical system integration