Simple MQTT Doorbell Notifier

Welcome to the first project of my blog.  It's a doorbell notifier for my smart home.

I'll start out with some of the tech I'm using.  Home Assistant on a Raspberry Pi 3 (Hass.io).  I have an MQTT server on the Hass.io that I like to use for sensors that I build.  I've been using NodeMCU boards recently to make WiFi projects, but I've also played with the Wemos ESP8266 boards as well.

I recently wanted to start tracking when the doorbell has been rung.  After brainstorming and researching many options, I decided to make a battery operated WiFi sensor that would send MQTT messages to Hass.io.

I started the project by heavily paring down some code from BruhAutomation for his multisensor.  That's a brilliant project and have found mine quite useful.  I used the Arduino IDE to load this onto a NodeMCU board:

/*

  .______   .______    __    __   __    __          ___      __    __  .___________.  ______   .___  ___.      ___   .___________. __    ______   .__   __.

  |   _  \  |   _  \  |  |  |  | |  |  |  |        /   \    |  |  |  | |           | /  __  \  |   \/   |     /   \  |           ||  |  /  __  \  |  \ |  |

  |  |_)  | |  |_)  | |  |  |  | |  |__|  |       /  ^  \   |  |  |  | `---|  |----`|  |  |  | |  \  /  |    /  ^  \ `---|  |----`|  | |  |  |  | |   \|  |

  |   _  <  |      /  |  |  |  | |   __   |      /  /_\  \  |  |  |  |     |  |     |  |  |  | |  |\/|  |   /  /_\  \    |  |     |  | |  |  |  | |  . `  |

  |  |_)  | |  |\  \-.|  `--'  | |  |  |  |     /  _____  \ |  `--'  |     |  |     |  `--'  | |  |  |  |  /  _____  \   |  |     |  | |  `--'  | |  |\   |

  |______/  | _| `.__| \______/  |__|  |__|    /__/     \__\ \______/      |__|      \______/  |__|  |__| /__/     \__\  |__|     |__|  \______/  |__| \__|

  Thanks much to @corbanmailloux for providing a great framework for implementing flash/fade with HomeAssistant https://github.com/corbanmailloux/esp-mqtt-rgb-led

  To use this code you will need the following dependancies: 

  

  - Support for the ESP8266 boards. 

        - You can add it to the board manager by going to File -> Preference and pasting http://arduino.esp8266.com/stable/package_esp8266com_index.json into the Additional Board Managers URL field.

        - Next, download the ESP8266 dependancies by going to Tools -> Board -> Board Manager and searching for ESP8266 and installing it.

  

  - You will also need to download the follow libraries by going to Sketch -> Include Libraries -> Manage Libraries

      - DHT sensor library 

      - Adafruit unified sensor

      - PubSubClient

      - ArduinoJSON

    

  UPDATE 16 MAY 2017 by Knutella - Fixed MQTT disconnects when wifi drops by moving around Reconnect and adding a software reset of MCU

             

  UPDATE 23 MAY 2017 - The MQTT_MAX_PACKET_SIZE parameter may not be setting appropriately do to a bug in the PubSub library. If the MQTT messages are not being transmitted as expected please you may need to change the MQTT_MAX_PACKET_SIZE parameter in "PubSubClient.h" directly.

*/

// MODIFIED BY D SMYTH TO DETECT A DOORBELL ELECTROMAGNET

#include <ESP8266WiFi.h>

#include <PubSubClient.h>

#include <ArduinoJson.h>

/************ WIFI and MQTT INFORMATION (CHANGE THESE FOR YOUR SETUP) ******************/

#define wifi_ssid "YOUR_SSID" //type your WIFI information inside the quotes

#define wifi_password "YOUR_PASSWORD"

#define mqtt_server "192.168.X.X"

#define mqtt_user "MQTT_USER" 

#define mqtt_password "MQTT_PASSWORD"

#define mqtt_port 1883

/************* MQTT TOPICS (change these topics as you wish)  **************************/

#define state_topic "home/doorbell/frontdoor"

#define SENSORNAME "doorbell_sensor"

const char* on_cmd = "ON";

const char* off_cmd = "OFF";

/**************************** SENSOR DEFINITIONS *******************************************/

char message_buff[100];

int calibrationTime = 0;

const int BUFFER_SIZE = 300;

#define MQTT_MAX_PACKET_SIZE 512

/******************************** GLOBALS for fade/flash *******************************/

bool stateOn = true;

WiFiClient espClient;

PubSubClient client(espClient);

/********************************** START SETUP*****************************************/

void setup() {

  Serial.begin(115200);

  Serial.println("Starting Node named " + String(SENSORNAME));

  setup_wifi();

  client.setServer(mqtt_server, mqtt_port);

  Serial.println("Ready");

  reconnect();

  sendState();

  delay(1000);

  stateOn = false;

  sendState();

  delay(10);

  ESP.deepSleep(1);

}

/********************************** START SETUP WIFI*****************************************/

void setup_wifi() {

  delay(10);

  Serial.println();

  Serial.print("Connecting to ");

  Serial.println(wifi_ssid);

  WiFi.mode(WIFI_STA);

  WiFi.begin(wifi_ssid, wifi_password);

  while (WiFi.status() != WL_CONNECTED) {

    delay(500);

    Serial.print(".");

  }

  Serial.println("");

  Serial.println("WiFi connected");

  Serial.println("IP address: ");

  Serial.println(WiFi.localIP());

}

/********************************** START SEND STATE*****************************************/

void sendState() {

  StaticJsonBuffer<BUFFER_SIZE> jsonBuffer;

  JsonObject& root = jsonBuffer.createObject();

  root["state"] = (stateOn) ? on_cmd : off_cmd;

  char buffer[root.measureLength() + 1];

  root.printTo(buffer, sizeof(buffer));

  Serial.println(buffer);

  client.publish(state_topic, buffer, true);

}

/********************************** START RECONNECT*****************************************/

void reconnect() {

  // Loop until we're reconnected

  while (!client.connected()) {

    Serial.print("Attempting MQTT connection...");

    // Attempt to connect

    if (client.connect(SENSORNAME, mqtt_user, mqtt_password)) {

      Serial.println("connected");

    } else {

      Serial.print("failed, rc=");

      Serial.print(client.state());

      Serial.println(" try again in 5 seconds");

      // Wait 5 seconds before retrying

      delay(5000);

    }

  }

}

/********************************** START MAIN LOOP***************************************/

void loop() {

}

/****reset***/

void software_Reset() // Restarts program from beginning but does not reset the peripherals and registers

{

Serial.print("resetting");

ESP.reset(); 

}

Then I had to add a few lines to the "configuration.yaml" file on Hass.io.

binary_sensor:
  - platform: mqtt
    state_topic: "home/doorbell/frontdoor"
    name: "Doorbell"
    value_template: '{{ value_json.state }}'

This completed the programming for the board.  When the NodeMCU powered up, it sends an "ON" message to the MQTT server and then after a second it sends an "OFF" message.  I connected a simple reed switch between the RST and GND pins on the NodeMCU board to reset the code any time the doorbell rings.

I have some Z-wave sensors that I use and work on battery, so I had some extra 123 batteries around and wanted to use one to power the sensor.  I connected the battery directly to the GND and 3V3 pins and found that it worked great!

Then I measured the current draw and found that the battery had a 30mA drain on it while the ESP8266 was in deep sleep.  :(

A little googling later, I found this blog and followed it to disconnect the voltage regulator and the USB-to-serial adapter using a quick touch of the soldering iron, an exacto knife and a resistor.  I had to play with the resistor value because the board still didn't start correctly with a 1 Mohm resistor.  In the end, I left the deep sleep current around 80 microAmps.  That should be low enough to keep it going for a year or so.

I used my 3D printer to print a holder for the 123 battery and will print another to hold the whole sensor.  I will hang it up next to my doorbell and my home will be that much smarter.

That was fun!

I'm sure I skipped over a lot of details of what to do and such.  If you feel really lost, but want to learn more, I would recommend starting with the BruhAutomation guides.

Good Luck!