Sensor dht+relay won't send data or present

  • Hi everyone,
    Started a challenging sensor immediately: RF24+relay+dht11.
    Radio seems to work, sensor gets power and the debug-mqtt appears to show all proper presentations. Using Domoticz, the node is seen but only s_hum and s_binary. The humidity sensor wont show in devices, the relay is seen but doesnt respond.
    I think I have a problem with my code. I'm using a millis-counter to send temp+hum every 60s and have the relay at the ready constantly.

    Pls help.

    // Enable debug prints
    #define MY_DEBUG
    // Enable and select radio type attached 
    #define MY_RADIO_NRF24
    //#define MY_RADIO_RFM69
    //#define MY_RS485
    #include <SPI.h>
    #include <MySensors.h>  
    #include <DHT.h>
    // Set this to the pin you connected the DHT's data pin to
    #define DHT_DATA_PIN 4
    // Set this offset if the sensor has a permanent small offset to the real temperatures
    #define SENSOR_TEMP_OFFSET 0
    // Sleep time between sensor updates (in milliseconds)
    // Must be >1000ms for DHT22 and >2000ms for DHT11
    static const uint64_t UPDATE_INTERVAL = 60000;
    // Force sending an update of the temperature after n sensor reads, so a controller showing the
    // timestamp of the last update doesn't show something like 3 hours in the unlikely case, that
    // the value didn't change since;
    // i.e. the sensor would force sending an update every UPDATE_INTERVAL*FORCE_UPDATE_N_READS [ms]
    static const uint8_t FORCE_UPDATE_N_READS = 10;
    #define CHILD_ID_HUM 0
    #define CHILD_ID_TEMP 1
    float lastTemp;
    float lastHum;
    uint8_t nNoUpdatesTemp;
    uint8_t nNoUpdatesHum;
    bool metric = true;
    // Generally, you should use "unsigned long" for variables that hold time
    // The value will quickly become too large for an int to store
    unsigned long previousMillis = 0;        // will store last time DHT was updated
    // constants won't change :
    const long interval = 60000;           // interval at which to read DHT (milliseconds)
    MyMessage msgHum(CHILD_ID_HUM, V_HUM);
    MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);
    DHT dht;
    #define RELAY_1  3  // Arduino Digital I/O pin number for first relay (second on pin+1 etc)
    #define NUMBER_OF_RELAYS 1 // Total number of attached relays
    #define RELAY_ON 0  // GPIO value to write to turn on attached relay
    #define RELAY_OFF 1 // GPIO value to write to turn off attached relay
    void before()
      for (int sensor=1, pin=RELAY_1; sensor<=NUMBER_OF_RELAYS; sensor++, pin++) {
        // Then set relay pins in output mode
        pinMode(pin, OUTPUT);
        // Set relay to last known state (using eeprom storage)
        digitalWrite(pin, loadState(sensor)?RELAY_ON:RELAY_OFF);
    void presentation()  
      // Send the sketch version information to the gateway
      sendSketchInfo("TemperatureAndHumidity", "1.1");
      // Register all sensors to gw (they will be created as child devices)
      present(CHILD_ID_HUM, S_HUM);
      present(CHILD_ID_TEMP, S_TEMP);
      metric = getControllerConfig().isMetric;
      // Send the sketch version information to the gateway and Controller
      sendSketchInfo("Relay", "1.0");
      for (int sensor=1, pin=RELAY_1; sensor<=NUMBER_OF_RELAYS; sensor++, pin++) {
        // Register all sensors to gw (they will be created as child devices)
        present(sensor, S_BINARY);
    void setup()
      dht.setup(DHT_DATA_PIN); // set data pin of DHT sensor
      if (UPDATE_INTERVAL <= dht.getMinimumSamplingPeriod()) {
        Serial.println("Warning: UPDATE_INTERVAL is smaller than supported by the sensor!");
      // Sleep for the time of the minimum sampling period to give the sensor time to power up
      // (otherwise, timeout errors might occure for the first reading)
    void loop()      
     unsigned long currentMillis = millis();
      if (currentMillis - previousMillis >= interval) {
        // save the last time you checked DHT
        previousMillis = currentMillis;
      // Force reading sensor, so it works also after sleep()
      // Get temperature from DHT library
      float temperature = dht.getTemperature();
      if (isnan(temperature)) {
        Serial.println("Failed reading temperature from DHT!");
      } else if (temperature != lastTemp || nNoUpdatesTemp == FORCE_UPDATE_N_READS) {
        // Only send temperature if it changed since the last measurement or if we didn't send an update for n times
        lastTemp = temperature;
        if (!metric) {
          temperature = dht.toFahrenheit(temperature);
        // Reset no updates counter
        nNoUpdatesTemp = 0;
        temperature += SENSOR_TEMP_OFFSET;
        send(msgTemp.set(temperature, 1));
        #ifdef MY_DEBUG
        Serial.print("T: ");
      } else {
        // Increase no update counter if the temperature stayed the same
      // Get humidity from DHT library
      float humidity = dht.getHumidity();
      if (isnan(humidity)) {
        Serial.println("Failed reading humidity from DHT");
      } else if (humidity != lastHum || nNoUpdatesHum == FORCE_UPDATE_N_READS) {
        // Only send humidity if it changed since the last measurement or if we didn't send an update for n times
        lastHum = humidity;
        // Reset no updates counter
        nNoUpdatesHum = 0;
        send(msgHum.set(humidity, 1));
        #ifdef MY_DEBUG
        Serial.print("H: ");
      } else {
        // Increase no update counter if the humidity stayed the same
      // Sleep for a while to save energy
    void receive(const MyMessage &message)
      // We only expect one type of message from controller. But we better check anyway.
      if (message.type==V_STATUS) {
        // Change relay state
        digitalWrite(message.sensor-1+RELAY_1, message.getBool()?RELAY_ON:RELAY_OFF);
        // Store state in eeprom
        saveState(message.sensor, message.getBool());
        // Write some debug info
        Serial.print("Incoming change for sensor:");
        Serial.print(", New status: ");

  • Mod

    On my Domoticz the dht11 shows as a combined temphum and it shows both data even if I present it separately

  • I think there's a bigger clitch in my code somewhere that is causing that. I'm not sure if the millis-timer is properly used here or if that is somehow interfering with the other code.

  • Mod

    I'd use a wait (500) or (1000) at the end of the loop, to slow things down a bit

  • @gohan you mean "delay(500)"? Will that not affect the radio function if it is waiting for a command for the relay for example?

  • The startup serial "seems" OK, but the relay function is not there. The MQTT log appears to send empty strings "" rather than 0 or 1 when I attempt to activate the relay from Domoticz.
    Just in case, the startup serial is as follows:

    4 TSM:INIT
    5 TSF:WUR:MS=0
    14 TSF:SID:OK,ID=1
    16 TSM:FPAR
    52 TSF:MSG:SEND,1-1-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
    319 TSF:MSG:READ,0-0-1,s=255,c=3,t=8,pt=1,l=1,sg=0:0
    324 TSF:MSG:FPAR OK,ID=0,D=1
    2059 TSM:FPAR:OK
    2060 TSM:ID
    2061 TSM:ID:OK
    2063 TSM:UPL
    2068 TSF:MSG:SEND,1-1-0-0,s=255,c=3,t=24,pt=1,l=1,sg=0,ft=0,st=OK:1
    2075 TSF:MSG:READ,0-0-1,s=255,c=3,t=25,pt=1,l=1,sg=0:1
    2082 TSM:UPL:OK
    2084 TSM:READY:ID=1,PAR=0,DIS=1
    2089 TSF:MSG:SEND,1-1-0-0,s=255,c=3,t=15,pt=6,l=2,sg=0,ft=0,st=OK:0100
    2098 TSF:MSG:READ,0-0-1,s=255,c=3,t=15,pt=6,l=2,sg=0:0100
    2105 TSF:MSG:SEND,1-1-0-0,s=255,c=0,t=17,pt=0,l=5,sg=0,ft=0,st=OK:2.1.1
    2113 TSF:MSG:SEND,1-1-0-0,s=255,c=3,t=6,pt=1,l=1,sg=0,ft=0,st=OK:0
    2240 TSF:MSG:READ,0-0-1,s=255,c=3,t=6,pt=0,l=1,sg=0:M
    2247 TSF:MSG:SEND,1-1-0-0,s=255,c=3,t=11,pt=0,l=22,sg=0,ft=0,st=OK:TemperatureAndHumidity
    2257 TSF:MSG:SEND,1-1-0-0,s=255,c=3,t=12,pt=0,l=3,sg=0,ft=0,st=OK:1.1
    2266 TSF:MSG:SEND,1-1-0-0,s=0,c=0,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
    2273 TSF:MSG:SEND,1-1-0-0,s=1,c=0,t=6,pt=0,l=0,sg=0,ft=0,st=OK:
    2281 TSF:MSG:SEND,1-1-0-0,s=255,c=3,t=11,pt=0,l=5,sg=0,ft=0,st=OK:Relay
    2289 TSF:MSG:SEND,1-1-0-0,s=255,c=3,t=12,pt=0,l=3,sg=0,ft=0,st=OK:1.0
    2297 TSF:MSG:SEND,1-1-0-0,s=1,c=0,t=3,pt=0,l=0,sg=0,ft=0,st=OK:
    2304 MCO:REG:REQ
    2307 TSF:MSG:SEND,1-1-0-0,s=255,c=3,t=26,pt=1,l=1,sg=0,ft=0,st=OK:2
    2345 TSF:MSG:READ,0-0-1,s=255,c=3,t=27,pt=1,l=1,sg=0:1
    2351 MCO:PIM:NODE REG=1
    2353 MCO:BGN:STP
    2355 MCO:SLP:MS=2000,SMS=0,I1=255,M1=255,I2=255,M2=255
    2360 MCO:SLP:TPD
    2362 MCO:SLP:WUP=-1
    2364 MCO:BGN:INIT OK,TSP=1```

  • @MasMat said in Sensor dht+relay won't send data or present:

    @gohan you mean "delay(500)"? Will that not affect the radio function if it is waiting for a command for the relay for example?

    That's what wait() is for (mysensors specific) , it will not interfere with the radio commumication.

  • Thanks for the tip. Good to learn these things as I go.

    I'm to the point of rebuilding the sensor (or building a duplicate really) to see if this could be a hardware glitch.

  • Mod

    You could try ethernet gateway instead of mqtt if it works better and move to mqtt later on

  • @gohan I cant see the upside to going back since I couldnt get the Ethernet gw working but the mqtt appears to be working AND Domoticz supports it apparently.
    I did a quick breadboard setup and it seems the problem might be hardware rather than sketch.

    Question about the wait command: could I use wait (=soooo simple) rather than a millis timer to have a sensor/node be ready to activate a relay at any time but to only send DHT data every 60s or so?

  • Mod

    sure you can use the wait()

  • To follow up. It was hardware: broken vcc pin on the dht11 corrupted the whole sensor code badly. Resolder and added wait-code, inverted the on-off 0-vs-1 and I have a good working sensor. The duplicate is also installed and working reliably.
    A 6-relay board is also working nicely and Domoticz is great. My old system is nearly replaced and I couldnt be happier.

    Respect and thanks all around!

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