MQTT Publish And subscribe Using RaspberryPi,Esp8266,And Particle Photon

     



  

Current trend in DIY is IoT based projects. The present professional  electronics engineering industry is also now focusing to IoT.There are many existing protocols are there for making connection with your device with Web.If we need real time data in every second or less than that,We will need a fast internet connectivity protocol.And it should use very little bandwidth.Here we have MQTT.

MQTT is an extreamly light weight connectivity protocol which is mainly used for machine to machine /IoT applications.It was formerly known as MQ Telemetry Transport.it is a publish/subscribe based messaging protocol for use on the top of TCP/IP protocol.MQTT is very helpful where network bandwidth is limited.Many IoT companies uses MQTT for their applications.

There are several MQTT brokers are available In this example we are using mosquitto broker.In MQTT there is several methods are defined like

1.Connect

2. Disconnect

3.Subscribe

4.Unsubscribe

5.Publish

As DIY hackers we also make use of MQTT in our projects .Many of the boards supporting WiFi is also supports MQTT.Here I am going to discribe MQTT broker in Raspberry Pi.And MOTT Client in Raspberry Pi,Particle Photon,esp8266.

I have no plan to explain the MQTT protocol ,but i would like to explain how it can be implemented  in our DIY project.In MQTT protocol we will have broker and clients.clients are those which can publish and subscribe to some topics created in broker.Broker is responsible for all fitering and all.ie broker will receive all messages and it will send those messages to corresponding subscribed clients.MQTT client libraries are easly available for many devices and in many coding languages.

It is very easy to set up a MQTT broker in linux system.As this blog is mainly explaining DIY projects I would like to Explain how to install MQTT broker in Raspberry Pi,which is one of the best toy of an electronics hobbyists.And I will be sharing how to set up MQTT clients(publish/subscribe) in Raspberry pi, Particle photon,esp8266,which are main tools in IoT hardware prototyping.All these are inspired from community.So I would like to thank all bloggers in community.

First we can Setup a MQTT broker in our Raspberry pi.For installing Mosquitto broker follow the steps below.

How to install MQTT broker in Raspberry pi

First we have to import repository package for mosquitto into our raspberry pi.For that  open the Raspberry pi terminal and run below commands.I used a Raspberry Pi 3 in jessie with 16GB microSD card 

wget http://repo.mosquitto.org/debian/mosquitto-repo.gpg.key

sudo apt-key add mosquitto-repo.gpg.key

Now we have to make available this repository to apt by using below command

cd /etc/apt/sources.list.d/

Now follow below commands

sudo wget http://repo.mosquitto.org/debian/mosquitto-wheezy.list

sudo -i

for updating pi

sudo apt-get update

apt-get update

After updating we can install mosquitto MQTT broker running below command

apt-get install mosquitto

How to install MQTT Client in Raspberry pi

So  now we successfully installed MQTT broker in our Raspberry Pi.Now we can install MQTT client by below command

apt-get install mosquitto-clients

Now the client library for MQTT is installed

So we successfully installed MQTT.Now we can start publishing and subscribing to some topics.

How to use MQTT client as Publisher

To publish a data “wiring_it _my _way ” to  a topic named “color”we can use the below commands

If the broker is installed in the same Raspberry pi

mosquitto_pub -h localhost -t color -m wiring_it_my_way

If the broker is installed in different Raspberry pi

mosquitto_pub -h 192.168.0.114 -t value -m wiring_it_my_way

How to use MQTT client as Subscriber

If the broker is installed in a different system then for subscribing a topic named “color” just run the below command

mosquitto_sub -h 192.168.0.114 -t color             

Here the IP in the command is lP of broker  raspberry pi/system

if the client is running in the same raspberry pi where broker is installed then use the below command for subscribing a topic named “color”

mosquitto_sub -h localhost -t color

ESP8266 as MQTT client

   As we know  ESP8266 WiFi Module is a self contained SOC with integrated TCP/IP protocol stack that can give any micro controller access to our WiFi network.Also we can program the ESP8266 directly from our arduino IDE.There many libraries available for ESP8266 in the community.I am sharing two code snippets .One is for publishing using ESP8266 and the other is for publishing and subscription.

Here our broker is set upped in raspberry pi so we have to note the IP of the raspberry pi and include in our ESP8266 arduino code.

Here given code is only basic code please make your own variety with sensors and actuators have fun.And please share in comments  I used an ESP8266-12

 

 

 

 

 

 Particle Photon as MQTT client

In one of my previous post we have discussed about the particle module,which is one of the best choice for IoT based prototyping.Particle web IDE contains MQTT libraries in it.By including those libraries we can easly subscribe or publish to a MQTT topic.Here also we have to give IP address of our pi in Particle code.

.

// This #include statement was automatically added by the Particle IDE.
#include "MQTT/MQTT.h"

// This #include statement was automatically added by the Particle IDE.
#include "MQTT/MQTT.h"

#include "MQTT/MQTT.h"
String sensor;
byte server[] = { 192,168,0,115 };//the IP of broker
void callback(char* topic, byte* payload, unsigned int length);
MQTT client(server, 1883, callback);

void callback(char* topic, byte* payload, unsigned int length) {
    char p[length + 1];
    memcpy(p, payload, length);
    p[length] = NULL;
    String message(p);

    if (message.equals("RED"))   
        RGB.color(255, 0, 0);
       
    else if (message.equals("GREEN"))   
        RGB.color(0, 255, 0);
    else if (message.equals("BLUE"))   
        RGB.color(0, 0, 255);
    else if (message.equals("wiring_it_my_way"))   
        {RGB.color(255, 0, 0);
        delay(1000);
        RGB.color(0, 255, 0);
        delay(1000);
        RGB.color(0, 0, 255);  
        delay(1000);}
    else   
        RGB.color(255, 255, 255);
    delay(1000);
}

void setup() {
    pinMode(A0,INPUT);
    RGB.control(true);
    client.connect(System.deviceID());
    if (client.isConnected()) {
        client.subscribe("color");//color is the topic that photon is subscribed
        client.publish("fun", "hello");//publishing a data "hello" to the topic "fun"
       
    }
}

void loop() {
    int sensor_value =analogRead(A0);
    sensor =String (sensor_value);
    if (client.isConnected())
        client.loop();
         client.publish("value", sensor);//publishing a sensor data  to the topic "value"
        
   
     
}   

when i heard the name MQTT for the first time i thought it will be very difficult for a hardware geek like me.But the broker set up was very easy and straight forward.It makes MQTT very easy.Regarding quality there are methods in MQTT to retain messages,confirmation etc.I don't have a plan to explain those in this post.Now make your own project in MQTT in whichever platform you like and please let me know your ideas in comments.  


 you can find the hackster project here







Ambient Light Sensor For Microcontroller Based Projects

TEMT6000 ambient light sensor is just another analog sensor.It is compatible with micro-controllers which supports analog data input.This sensor is working like a transistor.As light falling on sensor increases the analog output(SIGNAL)will increase.

                                                 If the light is very low then the SIG will be also very low as light increases the SIG will also goes high.

       We can useTEMT6000 ambient light sensor from spark fun electronics in various applications that includes ambient light sensing.Like if you want to control your bulb according to ambient light then TEMT6000 ambient light sensor  is best choice over simple LDRs.This one is more reliable that LDRs

       TEMT6000 is a silicon NPN epitaxial planar photo transistor .The device is sensitive to the visible spectrum.TEMT6000 is used as ambient light sensor for display back light dimming in mobile phones,Notebook computers ,cameras etc.

      The below circuit and code is for demonstrating basic working of TEMT6000 Ambient light sensor.Here we are  using Arduino Pro Mini as our microcontroller.You can use either a battery or FTDI+USB for powering the board.Anyway if we want to see the data on serial monitor we need to use FTDI and USB.In the below code i am just reading the data and printing it into percentage of Ambient light.And arduino inbuilt LED will ON if the analog value from the sensor goes beyond certain value.

CONNECTION

ARDUINO PRO MINI                  SENSOR

VCC                                               VCC

GND                                              GND

A0                                                   SIG

You can find  fritzing files here
you can find the hackster project here

Arduino Code

Purchase links
Sparkfun electronics 
Rhydolabz 

Playing With HC-SR04 Ultrasonic Ranging Module

 Introduction

 HC-SR04 is a ultrasonic  ranging module which is working like bats.ie it uses sonar technique for ranging.This module is widely used in between arduino hackers and diy enthusiast.The main attraction of this module is it is one of the simplest module and can be recommend to any newbie

 

 

 Applications

HC-SR04 is a module which can be used in various applications in our DIY projects.

• As obstacle detector in obstacle avoiding robot.
• In walking assistant system for visually impaired people.
• As parking sensor in vehicles. 
• As sensor in bugler alarm type projects.

 

 

Example project

Arduino based ultrasonic obstacle detector 

components needed

1.  Arduino ProMini x 1
2. HC-SR04 x1
3. Buzzer x 1
4. LED x 1
5. 220 ohm resistor x1

 Connections 

Arduino                                                 HC-SR04

pin 9                                                         trig

  pin8                                                          echo

  vcc                                                           vcc

  gnd                                                           gnd 

arduino pin 6 is connected to LED.

arduino pin A3 is connected to a buzzer.

arduino can be power via usb/ftdi or a 5v battery

working 

 In this demo project HC-SR04 is used as simple obstacle detector.it detects objects in front and will reply how far the obstacle is from the sensor.If an obstacle is detected it will alarm with a buzzer.If the obstacle is very close the led will ON.

Arduino code

//http://anasdalintakam.blogspot.com/2016/06/playing-with-hc-sr04-ultrasonic-ranging.html
//this is a simple project to demo working of HC-SR04
//connctions
//pin9-hcsr04 trig
//pin8-hcsr04 echo
//vcc-hcsr04 vcc
//gnd-hcsr04 gnd
//pin6-led
//pin A3-buzzer



int trig=9;
int echo=8;
int duration;       
float distance;
int val; 
float meter;      
void setup()
{
  Serial.begin(9600);
  pinMode(trig, OUTPUT);//trigger to hcsr04
  pinMode(echo, INPUT);//echo from hcsr04
  pinMode(6,OUTPUT);// led pin
  pinMode(A3,OUTPUT);// buzzer pin
  digitalWrite(trig, LOW);
  delayMicroseconds(2);
 
  delay(6000);
  Serial.println("Distance:");
}
void loop()
{ 
  digitalWrite(trig, HIGH);   
  delayMicroseconds(10);              
  digitalWrite(trig, LOW);   

  duration = pulseIn(echo, HIGH);

  if(duration>=38000){
      Serial.print("Out range"); 
      }    

  else{
      distance = duration/58;
      val=200-distance;  
      Serial.print("value:");
      Serial.print(val);
      Serial.print("\n");
      Serial.print(distance);   
      Serial.print("cm");
      meter=distance/100;
      Serial.print("\t");
      Serial.print(meter);
      Serial.println("m");
   if (distance >10){
   digitalWrite(6,LOW);
    }
    else {
   digitalWrite(6,HIGH);
      }
analogWrite(A3,val);
     
      }
  //   delay(1000);  
}