The HC-SR501 PIR Motion Sensor Module is a passive infrared sensor designed for human body motion detection. It detects infrared radiation emitted by moving objects and triggers an output signal, making it ideal for security systems, automatic lighting, and motion-activated projects.

The IR Infrared Obstacle Avoidance Sensor is a photoelectric switch module designed for proximity detection and obstacle avoidance in robotics and automation projects. It features an IR transmitting and receiving tube that detects objects by reflecting infrared light, making it ideal for robot navigation, object detection, and smart automation systems.

The YF-S201 Hall Effect Water Flow Sensor is a high-precision flowmeter designed to measure water flow rates from 1 to 30 liters per minute (L/min). With a durable plastic body, G1/2" (1/2 inch) inlet/outlet ports, and a Hall-effect sensor, this sensor provides accurate flow rate readings in water dispensing systems, industrial automation, and IoT applications.

The HC-SR04 Ultrasonic Sensor is a high-precision distance measurement module that uses ultrasonic sound waves to detect objects and measure distances ranging from 2cm to 400cm with an accuracy of ±3mm. It is ideal for robotics, obstacle detection, automation, and IoT applications.