HLK-LD2412 24GHz Human Presence Radar Sensor Module (9m Range, Bluetooth App Config)

Specifications

• Technology: 24GHz Millimetre-Wave Radar (FMCW)

• Detection Type: Presence (Static) and Motion (Dynamic)

• Max Distance: 9 Meters (Adjustable)

• Detection Angle: ±75°

• Interface: UART (115200 Baud) & GPIO (High/Low Level)

• Configuration: Bluetooth (via HLKRadarTool App) or Serial Command

• Operating Voltage: 5V DC

• Logic Voltage: 3.3V (UART)

• Dimensions: Compact ~35mm x 7mm (excluding pins)

Project Evolution: From Motion to Presence

• Your Past Projects: You've likely used a PIR Sensor (HC-SR501) to turn on a hallway light when someone walks by. Simple, effective, but limited.

• The Upgrade: The HLK-LD2412 unlocks True Presence Automation. It allows you to create "Occupancy Zones."

  • Scenario: The lights in your study stay ON while you are coding or reading, without you needing to wave your hand every 5 minutes.

• Effort Level: Intermediate. Requires soldering header pins and basic UART communication skills (or using ESPHome/Home Assistant).

• Hardware Needed: Any microcontroller (ESP32 recommended for WiFi integration) and a Logic Level Converter.

Key Applications

• Smart Lighting: Lights that never turn off while a room is occupied.

• Elderly Care: Non-intrusive monitoring to detect if a person is active or has fallen (requires algorithm tuning).

• Security Systems: Detects intruders through thin non-metallic walls (drywall/plastic).

• Energy Management: Turn off AC/Heaters immediately when a room is truly empty.

Virtual Technician: Wiring & Safety

Probots™ Logic-Safe ⚡ Warning: The HLK-LD2412 requires 5V Power to operate correctly but its UART communication pins (TX/RX) typically operate at 3.3V Logic.

• If using Arduino UNO (5V Logic): You MUST use a Logic Level Converter for the RX pin to prevent damage.

• If using ESP32/RPi (3.3V Logic): Direct connection is usually safe, but check your specific board's tolerance.

Pinout Guide:

1. VCC: 5V DC Input

2. GND: Ground

3. TX: Connect to MCU RX

4. RX: Connect to MCU TX

5. OUT: GPIO Output (High = Presence, Low = Absent)

Helpful Tutorials & Resources

• HLK-LD2412 human presence - Radar Sensor Documentation
• HLK-LD2412 human presence - Buying Guide
  
• HLK-LD2412 human presence - Starter Guide

Package Includes: 1 x HLK-LD2412 24GHz Human Presence Radar Sensor Module

Frequently Asked Questions (FAQ)

• How is the LD2412 different from the older LD2410? The LD2412 features a significantly wider detection angle (±75° vs ±60°) and a longer maximum range (9m vs 6m), making it superior for covering large rooms.
• Is this compatible with Home Assistant? Yes, it is fully supported in ESPHome using the standard ld2410 component (works for 2412 via UART) or via Bluetooth proxies.
• Does it work with Arduino IDE? Yes, you can use existing libraries (like the HLK-LD2410 library) or parse the serial data manually.
• Can I use it without a microcontroller? Yes, the OUT pin provides a simple High/Low (3.3V) signal indicating presence, which can directly drive a relay module or logic circuit.
• Is it compatible with Raspberry Pi? Yes, connect it to the Pi's GPIO UART pins. Note: The Pi provides 5V power, but ensure the RX pin on the Pi handles the 3.3V logic (which is safe).
• What is the Logic Level of the UART pins? The TX/RX pins operate at 3.3V. If using a 5V Arduino (Uno/Nano), you MUST use a Logic Level Converter for the RX pin.
• How much current does it consume? The module typically draws between 80mA and 100mA.
• Why does the module get hot? FMCW radar chips process high-frequency signals continuously, generating heat. Operating temperatures up to 60°C are normal.
• Can I extend the wires between the sensor and ESP32? UART signals degrade over distance. Keep wires under 20cm. For longer runs (e.g., ceiling mount), use an RS485 converter or shielded cable.
• Can it detect through walls? Yes, 24GHz radar penetrates drywall, plastic, wood, and glass. It cannot see through metal or concrete.
• Will a ceiling fan trigger false detections? Yes, moving fans or curtains are detected as motion. You must use the App to set "Gate Sensitivity" to ignore the specific distance zone where the fan is located.
• Does it work in total darkness? Yes, unlike cameras or PIRs, radar relies on radio waves and works perfectly in dark, smoky, or dusty environments.
• Does it interfere with my WiFi? No, it operates at 24GHz, which is far removed from the 2.4GHz and 5GHz WiFi bands.
• Can I mount it behind a mirror? Yes, provided the mirror uses a non-metallic backing. Traditional silver-backed mirrors will block the signal.
• How do I configure the sensing distance? Download the HLKRadarTool App (Android/iOS), connect via Bluetooth, and adjust the "Max Detection Distance" slider.
• Can I disable the Bluetooth after setup? Yes, for security, you can send a serial command to turn off the Bluetooth radio.
• Why is the output stuck on "Detected"? Check the "Energy Map" in the App. You likely have a static object causing reflection or the sensitivity floor is set too low.
• What is the default baud rate? The default baud rate is 115200 bps.
• Does it save my settings if power is cut? Yes, all sensitivity and distance parameters are saved in the module's non-volatile memory.