Arduino based Automatic Water Dispenser for Washing Hands

This automated touchless water dispenser uses an Arduino microcontroller to coordinate distance detection, audio feedback, and water flow control. The core of the system is the ultrasonic sensor, which constantly emits high-frequency sound waves and measures the time it takes for the echo to return, thereby calculating the distance of a user's hands. When hands are placed within the target range, the Arduino registers this trigger and initiates the hand-washing routine. First, it activates the buzzer to provide an audible cue or timer aligned with hygiene guidelines. Simultaneously, because the Arduino's digital pins cannot supply enough current or voltage directly to a high-power motor, the control signal is sent through a 1kOhm resistor to the base of a BC548 transistor. This transistor acts as a solid-state switch, allowing a small current to control a larger one that triggers the 5V relay. The relay functions as an electromechanical switch, safely bridging the 12V 1A adapter power to turn on the cooler water pump. Once the designated washing time elapses or the hands are removed, the Arduino cuts the transistor base current, causing the relay to open and the pump to instantly shut off, conserving water and maintaining a completely touch-free experience.