mmWave - C4001 24GHz Human Presence Detection Sensor for Arduino & ESPHome (25 Meters, UART)

The C4001 is a 24GHz millimeter-wave radar sensor designed for high-precision human presence and motion tracking over distances up to 25 metres. Utilising FMCW radar technology, it detects micro-movements such as breathing to reliably identify stationary occupants where standard PIR sensors fail. It is well-suited for makers, educators, and hobbyists building occupancy-based automation, smart bathroom controls, and security projects with Arduino or ESPHome.

Extended 25-metre detection range

The sensor provides motion tracking up to 25 metres and static human presence detection up to 16 metres across a 100° by 40° beam angle. It also measures target distance from 1.2 to 25 metres and velocity from 0.1 to 10 metres per second.

FMCW micro-motion detection

Unlike traditional PIR sensors that require large movements, 24GHz FMCW radar continuously analyses frequency shifts to register subtle movements like breathing. The sensing mechanism is immune to environmental disturbances such as ambient temperature, dust, light, noise, and humidity.

UART and digital IO connectivity

The board provides both digital high and low I/O output control and serial communication running at a default 9600 baud rate. With support for 3.3V and 5V operating voltages, it integrates seamlessly into Arduino, ESPHome, and Home Assistant setups.

Flexible installation options

The module supports top-down ceiling mounting for broad room coverage as well as horizontal or tilted orientations for directional zone monitoring. Its compact 26mm by 30mm dimensions make it easy to embed into custom enclosures and smart fixtures.

Occupancy and security automation

The sensor enables automated lighting, HVAC, and exhaust fan control that remains active as long as a room is occupied, eliminating false shutoffs. It also serves security setups by alerting when individuals linger in protected areas across temperatures from -40°C to 85°C.

Included package contents

The package includes one C4001 mmWave presence sensor module and one 5-pin header for wiring and prototyping.

Downloads & documentation

• Product wiki (DFRobot)