IoT-Enabled Smart Sanitary Pad Vending Machine with Dual-Mode Payment and AI-Based Predictive Restocking

Availability of menstrual hygiene products with the public spaces remains a critical challenge in developing countries, particularly in educational institutions and rural areas. This paper presents a smart vending machine for sanitary pads that was designed, constructed and tested. The system includes a number of technical features: IR (infrared)-enabled contactless activation at the point of use, two digital payment options (UPI/QR ) and one coin-based payment, real time WI-FI based payment verification, AI-enabled stock deletion prediction, and GSM-based remote alerting. A microcontroller-based ESP32 board is the core component and its firmware is developed using the Arduino framework. Transaction logging, stock monitoring, multi-machine dashboard visualization, etc., are handled through the Firebase Realtime Database with which the system is connected. A linear regression model that is trained using Firebase usage logs can predict when stock will run out. This enables planned restocking and minimizing stock-outs. The vending machine dispenses the product within 1.2 s of receiving a valid payment. (payment to dispensing), a dispensing accuracy of 95% was achieved over 20 dispensing trails, Firebase verification delay is 310ms, total hardware costs amount to about ₹2,045. The system developed here brings a low-cost, sanitary, and easy-to-maintain solution to the automated distribution of menstrual hygiene products