How to include the battery measurement?

  • I am trying to build a sensor with a DHT22 and for now on a solar panel and a battery.
    I want to see the battery level within Domoticz.
    I cannot seem to merge both the battery sketch and the DHT sketch together.
    Most of the times i get an error about a { being in a place where it should not belong.
    I think i lost it 😃 and i am going mad soon.
    Also how to send the battery level to Domoticz? i tried the battery sketch alone and nothing happens.

  • Hardware Contributor


    Most of the times i get an error about a { being in a place where it should not belong.

    Its easier for us if you post the code so we can have a look if you want help 🙂

    Also how to send the battery level to Domoticz?

    Well, before 2.0 it was gw.sendBatteryLevel(batteryPcnt); and now it is sendBatteryLevel(batteryPcnt);
    The battery% needs to be attached to a sensor - so it will be displayed in the deviced tab if you look at the device/sensor.

  • sendBatteryLevel doesn't do anything.
    I have modified it a bit and now i have some readings.
    I will do a bit more playing to see where i will end.

  • Hardware Contributor

    @tlpeter - it does, but it needs to be together with a sensor. You will find it in "devices".

  • Hardware Contributor


  • I have voltage now (utility) and a percentage under devices.
    I have read somewhere that the percentage is depending on the last sensors poll so i will now try to add the DHT part in to the sketch.

  • I have the voltage part working and i think also the battery percentage with it.
    I build the sketch like this. Can you have a little look?

     * The MySensors Arduino library handles the wireless radio link and protocol
     * between your home built sensors/actuators and HA controller of choice.
     * The sensors forms a self healing radio network with optional repeaters. Each
     * repeater and gateway builds a routing tables in EEPROM which keeps track of the
     * network topology allowing messages to be routed to nodes.
     * Created by Henrik Ekblad <>
     * Copyright (C) 2013-2015 Sensnology AB
     * Full contributor list:
     * Documentation:
     * Support Forum:
     * This program is free software; you can redistribute it and/or
     * modify it under the terms of the GNU General Public License
     * version 2 as published by the Free Software Foundation.
     * This is an example that demonstrates how to report the battery level for a sensor
     * Instructions for measuring battery capacity on A0 are available here:
    // Enable debug prints to serial monitor
    #define MY_DEBUG 
    // Enable and select radio type attached
    #define MY_RADIO_NRF24
    //#define MY_RADIO_RFM69
    #include <SPI.h>
    #include <MySensors.h>
    #include <DHT.h>
    #define CHILD_ID_BATT 0
    #define CHILD_ID_HUM 1
    #define CHILD_ID_TEMP 2
    #define DHT_DATA_PIN 3 // Set this to the pin you connected the DHT's data pin to
    int BATTERY_SENSE_PIN = A0;  // select the input pin for the battery sense point
    // Set this offset if the sensor has a permanent small offset to the real temperatures
    #define SENSOR_TEMP_OFFSET 0
    static const uint64_t UPDATE_INTERVAL = 30000;
    // 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;
    //unsigned long SLEEP_TIME = 9000;  // sleep time between reads (seconds * 1000 milliseconds)
    int oldBatteryPcnt = 0;
    float lastTemp;
    float lastHum;
    uint8_t nNoUpdatesTemp;
    uint8_t nNoUpdatesHum;
    boolean metric = true; 
    MyMessage msgBatt(CHILD_ID_BATT, V_VOLTAGE);
    MyMessage msgHum(CHILD_ID_HUM, V_HUM);
    MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);
    DHT dht;
    void setup()  
       // use the 1.1 V internal reference
    #if defined(__AVR_ATmega2560__)
    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 presentation() {
       // Send the sketch version information to the gateway and Controller
       sendSketchInfo("Battery Meter", "1.0");
       present(CHILD_ID_BATT, S_MULTIMETER);
       present(CHILD_ID_HUM, S_HUM);
       present(CHILD_ID_TEMP, S_TEMP);
       metric = getConfig().isMetric;
    void loop()
       // get the battery Voltage
       int sensorValue = analogRead(BATTERY_SENSE_PIN);
       #ifdef MY_DEBUG
       // 1M, 470K divider across battery and using internal ADC ref of 1.1V
       // Sense point is bypassed with 0.1 uF cap to reduce noise at that point
       // ((1e6+470e3)/470e3)*1.1 = Vmax = 3.44 Volts
       // 3.44/1023 = Volts per bit = 0.003363075
       int batteryPcnt = sensorValue / 10;
       #ifdef MY_DEBUG
       float batteryV  = sensorValue * 0.003363075;
       Serial.print("Battery Voltage: ");
       Serial.println(" V");
       Serial.print("Battery percent: ");
       Serial.println(" %");
       if (oldBatteryPcnt != batteryPcnt) {
         // Power up radio after sleep
         send(msgBatt.set(batteryV, 1));
         oldBatteryPcnt = batteryPcnt;
      // 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

  • Hardware Contributor

    @tlpeter - Im not a coding guy, but it looks good to me.
    Myself i build my sketches, test and look at serial output and Domoticz output. When im happy with the result - i go for it.

    This is going to create two devices i think, one humidity/temp and one voltage. The batterypct and voltage will be seperated from humidity/temp i think even if they belong together. If you want the procentage in devices for the right device you just skip the voltage part.

  • I have voltage now and a percentage at the devices.
    Hum and temp do work fine.
    I only sucked all the juice out of the battery so it is charging now by the little solar panel.
    I found out that 2,4V was really the lowest voltage that worked 😄

  • Hardware Contributor

    @tlpeter If you want to suck more juice out of the batteries use a DC-DC step up booster: then you can go down to 0.9V 🙂

  • I will buy one later 😄
    This is just to play with as i wanted to know how the battery measurement works.

  • @tlpeter said:

    if (oldBatteryPcnt != batteryPcnt) {
    // Power up radio after sleep
    send(msgBatt.set(batteryV, 1));
    oldBatteryPcnt = batteryPcnt;

    Hi, This part should not have been updated

    this part is icluded in the lib
    So leave it like the exsample
    if (oldBatteryPcnt != batteryPcnt) {
    // Power up radio after sleep
    oldBatteryPcnt = batteryPcnt;

    For sending over your voltage you need one additional

    send(msgBatt.set(batteryV, 1));

    Good luck

Log in to reply

Suggested Topics