Presence-Based Room Lighting

Overview

PIR sensors switch the lights off when you sit still at a desk. The ET-S06 carries the Hi-Link LD2410C 24 GHz radar, which detects breathing-level micro-movement, so the room stays lit while someone is in it.

The ET-S03 lux sensor stops the lights from coming on in daylight. The ESP32 combines both and switches an output after a short off-delay.

• Detects still people, not just motion
• Lights only below a lux threshold
• Adjustable off-delay
• Output for a relay or LED-strip MOSFET module

What you need

ElectroTrical boards

ET-S06LD2410C mmWave Presence Carrier24 GHz mmWave human-presence radar

AED 15.00Out of stock

ET-S03VEML7700 Ambient Light SensorAmbient light level

AED 15.00Out of stock

Boards total: AED 30.00

These boards are being manufactured. Open a board's page to see when it's back, or ask us about a kit.

You'll also need

• ESP32-S3 DevKitC-1 (or any ESP32-S3 board) with a USB-C data cable. Not sold by ElectroTrical.
• Hi-Link LD2410C radar module (fits the ET-S06 carrier)
• A 3.3 V-logic relay module or logic-level MOSFET module for your lamp or 12 V LED strip
• Jumper wires

Wiring

Mains lamps: use a certified relay module in a closed enclosure, or a smart plug. If you are not trained to work with 230 V, control a 12 V LED strip instead.

Build it

1. 01

   Fit the radar module

   Plug the LD2410C into the ET-S06 carrier. The radar sees through plastic but not metal — don't put it in a metal box.

2. 02

   Wire and power

   Wire as in the tables. The radar needs 5 V; the ESP32's 5V pin supplies it when the ESP32 is on USB.

3. 03

   Set up the Arduino IDE

   Install Arduino IDE 2, add the Espressif ESP32 board package (Boards Manager → “esp32” by Espressif), select “ESP32S3 Dev Module” and turn on USB CDC On Boot so Serial prints over USB. Install the libraries listed above the sketch from Library Manager.

4. 04

   Set the lux threshold

   Watch the lux value in Serial Monitor at dusk and set DARK_LUX to the point where you'd want the light on.

5. 05

   Aim the sensor

   Mount it at 1–2 m height facing the seating area. Avoid pointing it at fans, curtains or AC vents, which can look like movement.

6. 06

   Fine-tune (optional)

   Hi-Link's free HLKRadarTool phone app connects to the LD2410C over Bluetooth to set range gates and sensitivity.

Arduino code

Written for the ESP32-S3 DevKitC-1 with the Espressif Arduino core. Install these libraries from the Arduino Library Manager:

• Adafruit VEML7700 Library

#include <Wire.h>
#include <Adafruit_VEML7700.h>

const int   PRESENCE_PIN = 5;     // ET-S06 OUT
const int   LIGHT_PIN    = 6;     // relay / MOSFET module
const float DARK_LUX     = 80;    // turn on below this
const unsigned long OFF_DELAY_MS = 60 * 1000UL;

Adafruit_VEML7700 veml;
bool lightOn = false;
unsigned long lastSeen = 0;

void setup() {
  Serial.begin(115200);
  pinMode(PRESENCE_PIN, INPUT);
  pinMode(LIGHT_PIN, OUTPUT);
  digitalWrite(LIGHT_PIN, LOW);
  Wire.begin(8, 9);
  if (!veml.begin()) Serial.println("VEML7700 not found");
}

void loop() {
  bool present = digitalRead(PRESENCE_PIN);
  float lux = veml.readLux();
  if (present) lastSeen = millis();

  if (!lightOn && present && lux < DARK_LUX) {
    lightOn = true;                       // check lux only before switching on,
  }                                       // so our own lamp can't switch itself off
  if (lightOn && millis() - lastSeen > OFF_DELAY_MS) {
    lightOn = false;
  }
  digitalWrite(LIGHT_PIN, lightOn);

  Serial.printf("present=%d lux=%.0f light=%s\n", present, lux, lightOn ? "ON" : "off");
  delay(500);
}

Troubleshooting

Take it further

• Read distance and energy over UART for zone control (desk vs sofa)
• Use ESPHome's ld2410 component to expose presence to Home Assistant
• Add the ET-S34 PIR carrier at the door for a faster first trigger