LD2410 — 24GHz mmWave Human Presence Radar Sensor

Overview

The LD2410 (along with variants LD2410B with Bluetooth and LD2410C with 2.0 mm connector) is a high-sensitivity 24 GHz Frequency-Modulated Continuous Wave (FMCW) radar human presence sensing module manufactured by Hi-Link.

Unlike traditional PIR motion sensors that rely on thermal infrared movement and fail when a person sits still, the LD2410 transmits 24 GHz radio waves capable of penetrating plastic enclosures and detecting microscopic chest movements caused by human breathing. It divides its range into 8 distance gates (0.75 m resolution up to 6.0 m) and reports moving presence, static presence, and distance metrics via a 256,000 bps UART interface or a simple digital High/Low OUT pin. It is the leading presence sensor choice for Home Assistant and ESPHome smart home lighting systems.

Quick reference


Operating voltage (`VCC`)	5.0 V to 12.0 V DC (5 V nominal)
Operating frequency	24.00 GHz to 24.25 GHz (ISM band)
Detection distance	0.75 m to 6.0 m (divided into 8 gate zones)
Detection angle	$\pm 60^\circ$ Azimuth / $\pm 60^\circ$ Elevation
Interface	UART (256,000 bps) & Digital GPIO Output (`OUT`)
Logic level	3.3 V TTL logic on `TX`/`RX` and `OUT`
Operating current	79 mA typical at 5.0 V
Configuration tool	HLKRadarTool mobile app (Bluetooth variant) or serial commands

Pinout

5-pin 0.1" (2.54 mm) connector header:

Pin	Name	Type	Description
1	`VCC`	Power	Supply input (+5.0 V to +12.0 V DC)
2	`GND`	Power	Ground (0 V)
3	`OUT`	Digital Output	High = Human presence detected, Low = No presence
4	`TX`	Digital Output	UART Transmit data pin (3.3V logic, default 256,000 bps)
5	`RX`	Digital Input	UART Receive command pin (3.3V logic)

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Supply Voltage	$V_{CC}$	4.75	5.0	12.0	V	DC supply
Operating Current	$I_{CC}$	70	79	120	mA	Active radar transmission
Transmit Frequency	$f_{radar}$	24.00	24.125	24.25	GHz	ISM ISM band
Max Detection Range	$D_{max}$	0.75	5.0	6.0	m	Configurable per gate
Range Gate Resolution	$D_{gate}$	—	0.75	—	m	8 configurable distance gates
Detection Angle	$\theta$	-60	$\pm 60$	+60	°	Conical radiation pattern
UART Baud Rate	$Baud$	—	256000	—	bps	8 data bits, 1 stop bit, no parity
Operating Temperature	$T_{opr}$	-40	—	85	°C	Ambient

UART Frame Structure & Protocol

The LD2410 streams binary status frames at 256,000 baud every 100 ms:

Header: F4 F3 F2 F1
Data length & Command: 0D 00 02 AA
Target Status Byte: 00 (No target), 01 (Moving target), 02 (Static target), 03 (Moving & Static targets).
Moving Target Distance: 2 bytes (in cm).
Moving Target Energy: 1 byte (0–100%).
Static Target Distance: 2 bytes (in cm).
Static Target Energy: 1 byte (0–100%).
Detection Distance: 2 bytes (in cm).
Footer: F8 F7 F6 F5

Sensitivity Calibration per Gate

The LD2410 allows setting motion and static sensitivity thresholds (0–100) independently for each of the 8 distance gates (Gate 0 = $0–0.75\text{ m}$ , Gate 1 = $0.75–1.5\text{ m}$ , up to Gate 7 = $5.25–6.0\text{ m}$ ). Lowering sensitivity on distant gates prevents false triggers caused by ceiling fans, swaying curtains, or air conditioners.

Wiring

LD2410 Pin	ESP32	Arduino (Hardware Serial)	Notes
`VCC`	5V	5V	Requires 5V power supply
`GND`	GND	GND	System ground
`OUT`	GPIO 15	Digital Pin D2	Simple binary presence pin
`TX`	GPIO 16 (RX2)	Hardware RX (Serial1)	3.3V logic output
`RX`	GPIO 17 (TX2)	Hardware TX (Serial1)	3.3V logic input

Warning

High baud rate requirement:

The default UART baud rate is 256,000 bps. Standard 8-bit Arduino microcontrollers using SoftwareSerial cannot reliably receive 256,000 baud.
Always connect TX/RX to a 32-bit MCU with hardware UART peripherals (such as ESP32, ESP8266, or STM32) or rely strictly on the binary OUT pin.

Example (ESPHome Configuration)

yaml

uart:
  id: uart_bus
  tx_pin: GPIO17
  rx_pin: GPIO16
  baud_rate: 256000

ld2410:
  id: my_ld2410

binary_sensor:
  - platform: ld2410
    has_target:
      name: "Human Presence Detected"
    has_moving_target:
      name: "Moving Target Detected"
    has_still_target:
      name: "Static Target Detected"

sensor:
  - platform: ld2410
    moving_target_distance:
      name: "Moving Target Distance"
    still_target_distance:
      name: "Static Target Distance"

Common mistakes

Attempting to use SoftwareSerial at 256,000 baud: Causes garbage bytes and continuous packet parsing failures.
Powering from weak 3.3V rails: The LD2410 requires a stable 5.0V supply rail and draws up to 120 mA during active radar bursts.
False triggers from metallic objects: Placing the radar probe directly facing metal surfaces or mirrors causes multipath microwave reflections.
Vibrating mounting surface: Mounting the radar on a flimsy partition wall that vibrates when doors close triggers false motion detection.

Notes

LD2410 vs PIR: PIR sensors cannot detect stationary seated people; the LD2410 continuously detects stationary breathing targets without needing movement.

Interface	UART, Digital GPIO Output
Supply	5–12 V
Package	Compact PCB Module (5-pin 0.1" header)