🔹 Overview Type: Ultrasonic distance sensor (waterproof version) Principle: Measures distance by sending an ultrasonic pulse and measuring the time it takes to reflect back from an object. Waterproof: Can be used in wet environments, rain, or even submerged in shallow water (housing protects electronics). Applications: Liquid level detection, obstacle avoidance, robotic sensing, tank water level monitoring. 🔹 Key Features Waterproof design – sensor head is sealed; suitable for outdoor and wet environments. Operating voltage: 3.3–5 V DC Distance measurement range: ~20 cm to 600 cm (varies slightly by model) Accuracy: ±1 cm to ±2 cm Interface: Digital trigger (input) and echo (output) pins, compatible with microcontrollers (Arduino, ESP32, Raspberry Pi, etc.) Ultrasonic frequency: ~40 kHz (standard for ultrasonic distance sensors) 🔹 Pinout Most JSN-SR04T / AJ-SR04T modules have 4 pins: Pin Function Description VCC Power supply 3.3–5 V DC GND Ground Connect to system ground TRIG Trigger input Send a 10 µs HIGH pulse to start measurement ECHO Echo output Output pulse width proportional to distance 🔹 Working Principle Trigger pulse: MCU sends a short HIGH pulse (typically 10 µs) to TRIG pin. Ultrasonic burst: Sensor emits an ultrasonic pulse at ~40 kHz. Echo detection: The sensor receives the reflected pulse from the object. Pulse width measurement: ECHO pin goes HIGH for a duration proportional to the distance. Formula: Distance (cm) = Time (µs) × 0.0343 2 Distance (cm)= 2 Time (µs)×0.0343 ​ (0.0343 cm/µs = speed of sound in air; divide by 2 for round-trip) 🔹 Applications Water tank level monitoring (waterproof) Outdoor robots / obstacle avoidance Rain or flood detection systems Automated liquid dispensing systems 🔹 Advantages Waterproof, suitable for wet or outdoor environments Long-range distance measurement (up to ~6 m) Easy to interface with microcontrollers using simple digital pins Reliable and low-cost