LD2410D Module

Mounted on a 3m ceiling, the D's motion detection covers a cone whose base is a circle 4m in radius on the floor. That is a circle 8m across, roughly 50 square metres, from one sensor looking straight down. The cone's edge runs at about 53° from vertical.

The D defines its axes for this mount:

• X axis at 0°, along the ceiling.
• Z axis at 90°, also in the ceiling plane.
• Y axis perpendicular to both, pointing straight down at the floor. Hi-Link calls this the normal direction.

On a real ceiling, the antenna face points at the floor and the board lies flat against the ceiling. Tilt it and the cone tilts with it, taking part of the circle up a wall.

Where the ceiling mount pays off:

• Bedrooms: the whole bed sits well inside the cone, and a sleeping person is only a couple of metres from the sensor.
• Offices and studies: a desk anywhere in the room stays covered.
• Living rooms: a sofa against the wall still falls inside a 4m radius from the centre.

A higher ceiling spreads the cone wider but weakens the return from the floor. Plan for 3m, and treat anything well above it as something to check with the D's own manual.

The axes change for a wall mount:

• X axis horizontal, as the reference.
• Z axis pointing up.
• Y axis pointing into the room, the direction the sensor looks.

By default, detection reaches 6m along the Y axis within a cone of ±60° both horizontally and vertically. That wide cone is why height matters. Too low and furniture blocks the lower half; too high and the cone spends much of its angle on the ceiling.

Choosing between the two:

1. Pick the ceiling for rooms where people sit or lie in the middle, like bedrooms.
2. Pick the wall for long rooms, or where the ceiling has no power.
3. On a wall, aim across the room, away from windows, doors and radiators.
4. Keep the sensor off walls shared with a busy neighbouring room, since 24GHz passes through plasterboard.

Fans and moving curtains produce energy that looks like a restless person, and a presence sensor tuned for stillness picks it up readily. Keep them out of the cone where you can. The range and field of view page explains how cone angle and distance play out across the family.

A safe order of work:

1. Read the supply voltage and pin order from the D's own documentation and silkscreen. Do not copy them from a B or C diagram.
2. Power it and watch the IO output with a multimeter or an LED on a transistor. Walk in and out of the cone.
3. Only then connect the UART, with a 3.3V USB-serial adapter, and check what frames arrive.
4. Compare those frames with the manual before you point an existing library at it.

The IO output is the quickest route into Home Assistant, and it needs no protocol support at all:

binary_sensor:
  - platform: gpio
    pin: GPIO4
    name: Bedroom presence
    device_class: occupancy

That gives you occupancy on the D's default settings. Distance readings and tuning come later over the UART, once you know the protocol it speaks.

For the general wiring approach, see ESP32 and Arduino wiring and the pinout reference. Get the configuration software from the LD2410 app and PC tool notes; check that the tool version you download names the D before you connect it.

• 3-pack: bedrooms in a small flat, or one sensor to experiment with and two to install.
• 4-pack: a family house's bedrooms plus a study.
• 1–10 pieces: this bundle covers several quantities and also the LD2410B, so make sure you pick the D and the count you want.

Keep one module on the bench while the rest go in. Working out the protocol and your preferred thresholds on a spare is far easier than on a board already screwed to a ceiling.

How the D compares:

Three boxes to tick for the D:

• The board is marked LD2410D.
• You have the D's manual, or a plan to use the IO output only.
• Your rooms suit a ceiling or 1.5–2m wall mount.

Family specs side by side are on the datasheet summary.