LD2410S Low-Power Module

The trick is duty cycling. Rather than transmitting all the time, the S wakes, checks the room and reports at an interval you set. That reporting frequency is configurable, and it is the main lever on battery life: report often and you drain the cells faster, report rarely and presence changes arrive later.

It also reaches further for people on the move:

• Moving people: 0.2–8m, against 5m for the C.
• Stationary people: 0.2–4m, a little shorter than the C's still range.
• Outputs: a GPIO level for present or empty, plus UART data for distance and state.

Where it earns its place:

• A presence sensor in a room with no socket near the ceiling.
• Hallway and stairwell lighting on a battery-powered controller.
• A desk occupancy node that runs for months on a pack of cells.
• Any 3.3V product where adding a 5V boost converter costs space and current.

Pair it with a low-power controller that sleeps between reports, such as an ESP32-C3 in deep sleep woken by the S's GPIO line, or a Zigbee or Thread chip.

1. Take power from a 3.3V regulator or the 3V3 pin of your board, never from VIN or 5V.
2. Share ground with the microcontroller.
3. Cross the serial lines: S TX to board RX, S RX to board TX.
4. Run the GPIO output to a wake-capable pin if the controller sleeps.
5. Check the silkscreen on your board for pad order before the first power-up.

Supply choices by power source:

A fresh Li-ion cell sits above 3.6V, so it cannot feed the S directly. A low-quiescent regulator keeps the saving the S offers; a cheap one with milliamps of idle current throws it away.

The shared power and pin figures for the family sit on the LD2410 pinout page, and the datasheet summary lists the S alongside the others.

What that changes on your build:

• ESPHome: the stock ld2410 component is written for the B/C protocol. For the S, use an S-specific external component, or read the GPIO output as a plain binary sensor.
• Arduino: LD2410 libraries built for the C do not parse S frames. Look for one that names the S, or parse the frames from the protocol document yourself.
• Configuration tools: there is no Bluetooth, so tuning goes over serial with Hi-Link's tool, a USB-serial adapter and a 3.3V supply.

The simplest reliable start skips the UART entirely:

binary_sensor:
  - platform: gpio
    pin: GPIO3
    name: Presence
    device_class: occupancy

Pick a pin that can wake the controller from deep sleep, and let the S do the watching while everything else is off. On an ESP32-C3, the low GPIO numbers can wake it; check your board's documentation for which ones.

That gives you occupancy in Home Assistant with the S's default thresholds. Once it works, add the UART for distance and configuration. Confirm the baud rate against the manual for your firmware before you blame the wiring.

The general ESPHome approach, and where the S differs from the C, is covered on the ESPHome page, with board-by-board UART pins on the wiring page. For the configurator itself, see installing the LD2410 tool.

The S comes as a single module and as a 4-pack. Order one first if you are writing your own firmware, because the protocol work is the slow part and one board is enough to finish it. Move to the 4-pack once one node runs on its battery for a few weeks.

One more trade to weigh: the S reaches further for walking people but holds a shorter range for someone sitting still. In a long hallway that suits it well. Over a sofa four or more metres from the wall, the C's longer still range fits better.

Tick these off on the bench:

• The board is marked LD2410S, not LD2410 or LD2410C; they look alike.
• Your controller has a 3.3V rail, or you have a regulator ready.
• You have a 3.3V USB-serial adapter for configuration.
• Your software stack has S support, or you are ready to write it.

For a mains-powered build, go to the LD2410C. For the full family side by side, see the version comparison.