Contactless Hand Sanitiser Dispensing System

The Contactless Hand Sanitiser Dispensing System operates by using an Arduino Uno microcontroller to coordinate distance measurement and mechanical actuation. At the heart of the sensing mechanism is the HC-SR04 ultrasonic sensor, which continuously emits high-frequency sound waves and measures the time it takes for the echo to return after bouncing off an object. When a user places their hands underneath the dispensing spout, the reflected sound wave returns more quickly, signaling to the Arduino that an object has entered the targeted proximity threshold. Once this distance criterion is met, the microcontroller triggers its digital output pin connected to the 5V single-changeover relay module. The relay functions as an electrically operated switch, using a low-power control signal from the Arduino to safely isolate and close the higher-power circuit driving the 12V DC motor. Energizing the relay allows current from the 12V power supply to flow into the 12V DC motor, causing it to spin. This rotational mechanical force is coupled with a sanitiser container mechanism—such as a cam, lever, or pump depressor—which physically pushes the pump to dispense a measured dose of liquid sanitiser. After a pre-programmed delay interval configured in the Arduino IDE, the microcontroller turns off the relay signal, cutting power to the motor and allowing the dispenser mechanism to reset. By utilizing ultrasonic echolocation rather than traditional infrared detection, this system effectively avoids false triggers caused by ambient room lighting or varying skin pigmentation, ensuring reliable, touchless hygiene management in high-traffic environments.