HC-SR04 Ultrasonic sensor is a 4 pin module used in many applications where measuring distance or sensing objects are required. Check out this article to find more details about ultrasonic sensor like pinout, datasheet and technical specifications.

Water level controllers are useful devices. In this water level indicator and controller project we are going to use an Arduino board and ultrasonic sensor to measure the water level in a tank. We will also start the water pump automatically when water level goes low below a certain preset level.