Hi-Link HLK-LD2401 24GHz Human Presence Radar Sensor - GPIO/UART/Bluetooth

The HLK-LD2401 uses 24GHz FMCW radar technology, which can detect both moving and stationary human presence, unlike PIR sensors that only sense moving heat sources. It also provides distance information and is less affected by environmental temperature changes, offering more reliable detection for occupancy sensing.

Configuration is performed using the official visual PC tool provided by Hi-Link. Connect the sensor via its UART interface (TX/RX pins) to a USB-to-serial adapter. The software allows you to set specific distance zones (up to 6m), adjust sensitivity levels within each zone, and configure the delay time after detection ends.

The module provides two primary outputs: a GPIO pin that goes HIGH when a target is detected, and a UART (serial) interface that streams detailed JSON-formatted data including target distance and motion status. For Arduino, connect the GPIO to a digital input pin for simple triggers, or connect the sensor's TX/RX to the Arduino's serial pins (using a logic level converter if needed) to read and parse the detailed data stream.

While the sensor's algorithm is optimized for human detection, its primary filtering is based on signal strength and pattern recognition associated with human-sized targets. For best pet immunity, use the configuration tool to set a minimum detection threshold or sensitivity level that reduces the likelihood of triggering on smaller moving objects, though absolute differentiation is not guaranteed.

The module typically operates at 5V DC. Always refer to the official datasheet for precise specifications. Ensure your power source can provide stable, clean power, as voltage noise can affect radar performance. For battery-operated projects, consider using a regulated 5V boost converter or linear regulator.