Design and Implementation of QR Code Based Library Door Access Control System

When a user scan a QR at QR scanner it decode the QR data internally and send a string to esp-32. The esp-32 converts this string into a JSON file and POST it to server , server validate the authentication of QR and send a response to ESP-32 request either true or false .If it send true it means QR is valid and ESP-32 GPIO pin becomes high which activate relay and finally door will open for a fix period of time, after that automatically close. IR sensor is used to detect user presence near the machine when any motion is detected , QR scanner turns on otherwise it always remains in sleep mode to avoid heat up and power saving. We also can put ESP in sleep mode when not in use.