This project presents a complete 3D CAD model of the HC-SR501 PIR Motion Sensor, created with Autodesk Inventor. The HC-SR501 is one of the most popular passive infrared (PIR) motion detectors, widely used in home automation, security systems, and IoT applications. The purpose of this project is to provide a highly detailed and accurate digital version of the sensor that can be used for design integration, prototyping, and educational purposes.

The modeling process began with a careful study of the physical HC-SR501 module, focusing on replicating its essential features. The design includes the main Fresnel lens dome, which allows the sensor to capture infrared radiation changes in the environment. Beneath the lens, the PCB structure has been modeled, showing the layout and proportions of key components. Important details such as the potentiometers for delay time and sensitivity adjustment, the pin header connector, and the mounting holes are all represented in the CAD model. This makes the model suitable for engineers who need precise dimensions to create enclosures or to integrate the sensor into larger electronic assemblies.

One of the main goals of this project is to bridge the gap between mechanical design and electronic prototyping. By using CAD tools such as Autodesk Inventor, it becomes possible to visualize how the sensor will fit into a complete IoT product. For example, designers can test different enclosures, evaluate mechanical tolerances, and plan the placement of other modules before committing to physical prototypes. This helps save both time and resources in the development process.

The HC-SR501 itself is a simple yet powerful module. It operates by detecting infrared radiation emitted by human bodies or moving objects. When a change in infrared energy is detected, the sensor outputs a signal that can trigger lights, alarms, or data logging systems. Because of its low cost, compact size, and reliability, it has become one of the most frequently used PIR sensors for IoT projects.

By combining this PIR sensor with a LoRa wireless module, new possibilities open up for long-range IoT applications. For instance, the sensor could be deployed in large agricultural fields to monitor movement, in outdoor facilities for security purposes, or in smart cities for pedestrian activity tracking. LoRa technology allows data from the sensor to be transmitted over distances of several kilometers with very low power consumption, making it ideal for scenarios where Wi-Fi or Bluetooth would not be practical.

Potential applications include:

• Smart Homes: automatic lighting or intrusion detection.

• Warehouses: monitoring unauthorized access in large storage areas.

• Agriculture: detecting human or animal movement across large farmland.

• Public Spaces: analyzing pedestrian flow in urban areas.

In summary, this project delivers a precise 3D CAD model of the HC-SR501 sensor that is not only useful for mechanical design but also demonstrates how a common sensor can be adapted into modern IoT systems. When paired with LoRa technology, it has the potential to become part of an energy-efficient, long-range motion detection network. This combination of accurate digital modeling and practical IoT application showcases how engineering design tools can bring value to real-world innovation.