Note-to-Coin
Converter

Fare collection on Sri Lankan public buses often involves non-rounded values, leading to transaction delays and disputes when passengers do not possess the exact change. Relying purely on cash transactions creates inefficiencies for conductors, and existing cashless solutions are limited by unreliable mobile network coverage in certain areas. The root problem is the lack of an efficient, offline system that allows passengers to exchange higher-value notes into exact coin amounts.

Our team designed and prototyped a standalone, low-cost electromechanical system to automate this process. The device operates completely offline and integrates several subsystems.

• An optical color sensor system (TCS34725) to detect and validate the inserted Sri Lankan currency notes.
• An Arduino Uno microcontroller to process sensor data, calculate the required change, and control system outputs.
• A gravity-fed cylindrical coin dispensing mechanism operated by servo motors for reliable, low-power coin delivery.
• A user-friendly interface featuring an LCD screen and physical push buttons.