Last Updated or created 2025-10-18

December is coming, time for candles.

The plan is to make a flame sensor, with in combination with my presence sensor will alert me when we leave the room and candles are on, give us a notification.

Above is the schematic. A Wemos mini (left over from another project), an analog multiplexer and a cheap 5 times flame detector.
There is a potentiometer on this board to change the sensitivity.

Search “Infrared Ir Flame Sensor Detector Fire Detection Module 5 Channel” on Aliexpress. These are 1 euro.

Presence sensor:

HLK-LD2410B with a Wemos Mini D1 (v4) connected to Home Assistant using ESPHome

ESPHome code will follow, here is some Arduino code.
(esphome code is not complete yet, 5 sensor reading needs to trigger single switch.)

#define MUX_A D5
#define MUX_B D6
#define MUX_C D7
#define ENABLE D1

#define ANALOG_INPUT A0


void setup() {
    Serial.begin(9600);

  //Define output pins for Mux
  pinMode(MUX_A, OUTPUT);
  pinMode(MUX_B, OUTPUT);     
  pinMode(MUX_C, OUTPUT);     
  pinMode(ENABLE, OUTPUT);     
  digitalWrite(ENABLE, LOW); // No need to switch, can be permanenty low
  
}

void changeMux(int c, int b, int a) {
  digitalWrite(MUX_A, a);
  digitalWrite(MUX_B, b);
  digitalWrite(MUX_C, c);
}

void loop() {
  float value;
  
  
  changeMux(LOW, LOW, HIGH);
  value = analogRead(ANALOG_INPUT); //Value of the sensor connected Option 1 pin of Mux
  Serial.print("Variable_1:");
  Serial.print(value);
  Serial.print(",");

  changeMux(LOW, HIGH, LOW);
  value = analogRead(ANALOG_INPUT); //Value of the sensor connected Option 2 pin of Mux
  Serial.print("Variable_2:");
  Serial.print(value);
  Serial.print(",");

  changeMux(LOW, HIGH, HIGH);
  value = analogRead(ANALOG_INPUT); //Value of the sensor connected Option 3 pin of Mux
  Serial.print("Variable_3:");
  Serial.print(value);
  Serial.print(",");

  changeMux(HIGH, LOW, LOW);
  value = analogRead(ANALOG_INPUT); //Value of the sensor connected Option 4 pin of Mux
  Serial.print("Variable_4:");
  Serial.print(value);
  Serial.print(",");

  changeMux(HIGH, LOW, HIGH);
  value = analogRead(ANALOG_INPUT); //Value of the sensor connected Option 5 pin of Mux
  Serial.print("Variable_5:");
  Serial.println(value);
}