Touchless Arduino Water Dispenser

The Touchless Arduino Water Dispenser functions by utilizing an HC-SR04 ultrasonic sensor to continuously measure the distance of an object, such as a hand, placed beneath the dispensing nozzle. The Arduino Uno processes these distance echoes in real time. When a hand is detected within a predetermined threshold range, the Arduino triggers an output signal to its digital pins. Because the Arduino's digital pins operate at 5V and cannot directly drive higher-power peripheral devices, the control signal is routed through a 1k resistor into the base of a BC547 NPN transistor. This transistor acts as a solid-state switch, allowing a lower-current signal to control the higher-current path required by the 5V relay module and an audible buzzer. When energized, the relay closes its high-power contacts to complete the circuit for the 12V 1A adapter powering the cooler water pump, initiating water flow. Simultaneously, an LED illuminates to provide visual feedback of the active dispensing state. Once the ultrasonic sensor detects that the hand has been removed, the Arduino immediately cuts the control signal, opening the relay, stopping the water pump, and turning off the LED.