Thursday, December 21, 2017

Very good offer for books and videos from Packt Pub. On eBook $5

Packt Publishing has a new offer, for $5 you can get a lot of eBooks and videos.

Click here for a list. There are over 4000 books and over 1000 videos to choose from.

Saturday, December 2, 2017

New book on how to made a complete ready-to-sell home automated system with ESP8266

I've been busy in the latest months writing a book  to cover some key aspects of the ESP8266 ecosystem, the chip, the cloud and a mobile application.

The book will teach you and will give you a ready-to-sell solution for an IoT product.

You will discover how to work with the GPIOs on the ESP8266, how to build your basic thermostat for your house, how to control it from your mobile with your own cloud system based on MQTT.

Securing the data using authentication at the broker level and SSL is explained in a special chapter. 

Real-time communication has a dedicated chapter where you will learn how to send real-time data from an ESP8266 to an nodejs server.

You can buy the book from Amazon

I hope that you will enjoy the book.

BME280 and ESP8266

Latest environmental sensor from Bosh is the BME280 which can measure:

  • temperature
  • humidity
  • pressure

and can be found in mobile phones (Nexus 5). There are rumors  that the BMP280 is a BME280 which couldn't be calibrated for humidity, but I have no confirmation on this.


Can be used for:

  • Indoor navigation (based on changing the measured altitude - pressure)
  • Outdoor navigation
  • Weather forecast
  • Home application control
  • Context awareness ( change room detection)  
  • Internet of Things.

Temperature precision is ± 1 C degree in 0-60C range.

Can be found in multiple modules, from SPI connectivity to I2C.

Make sure that if you are using the I2C version  to change the I2C address to 0x76. ( Default value for I2C address in Adafruit's library is 0x77).

I2C version

The SPI version can be found around USD 5 here.

Code is similar with the BMP280 , just read the humidity

 * Catalin Batrinu 
 * Read temperature, humidity and pressure from BME280
 * and send it to

#include <Wire.h>
#include <SPI.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BMP280.h>
#include <ESP8266WiFi.h>

Adafruit_BME280 bme; // I2C
// replace with your channel’s thingspeak API key,
String apiKey = "YOUR-API-KEY";
const char* ssid = "YOUR-SSID";
const char* password = "YOUR-ROUTER-PASSWORD";
const char* server = "";
WiFiClient client;

 *   S E T U P
void setup() {
  Serial.println(F("BMP280 test"));
  if (!bme.begin()) {  
    Serial.println("Could not find a valid BME280 sensor, check wiring!");
    while (1);
  WiFi.begin(ssid, password);
  Serial.print("Connecting to ");
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) 
  Serial.println("WiFi connected");  

 *  L O O P
void loop() {

    if (client.connect(server,80))  // "" or
        String postStr = apiKey;
        postStr +="&field1=";
        postStr += String(bme.readTemperature());
        postStr +="&field2=";
        postStr += String(bme.readHumidity());
        postStr +="&field3=";
        postStr += String(bme.readPressure() / 100.0F);
        postStr += "\r\n\r\n";
        client.print("POST /update HTTP/1.1\n");
        client.print("Connection: close\n");
        client.print("X-THINGSPEAKAPIKEY: "+apiKey+"\n");
        client.print("Content-Type: application/x-www-form-urlencoded\n");
        client.print("Content-Length: ");
    //every 20 sec   

If your readings are with almost 2 degrees more than the expected value is because the BME280 is to close to the ESP8266. Try to keep at least 10 cm between the BME280 and ESP8266 to eliminate the RF heating and heating produced by ESP8266. 

Also is possible that you run the BME280 in normal mode ( more samples per second) versus forced mode when you are reading the values exactly when you need them ( here the drift is around 0.6 degrees Celsius).

The complete datasheet can be found here.

Sunday, November 12, 2017

Getting air quality with ESP8266 and Amazon Alexa

If last week I've managed to get the temperature and humidity with ESP8266 and Alexa, now it's time to integrate the air quality sensor GP2Y1010AU0F from Sharp.

The GP2Y1010AU0F it is a compact optical dust sensor that has an infrared emitting diode and a phototransistor that are diagonally arranged. It detects in fact the reflected light of the present dust in the air. It is effective to detect very fine particle like cigarette smoke and it can distinguish from the house smoke from the house dust.

GP2Y1010AU0F sensor.
It has 6 pins and the electronic inside is split in two parts, the IRED emitting part and the phototransistor (receiving part)

Internal schematic
For the Air quality module I've used an wemos D1 board. The datasheet for the GP2Y1010AU0F is referring as VCC and the provided output by using a 5V power supply. Since the ESP8266 on analog input is limited to 1V and the wemos D1 is having an 220K and a 100K divider, I've choose to power the transmitter part to 5V and the receiver part with 3V3.

According to the specification in the datasheet also you will need an 150 ohm resistor and a 220uF capacitor, both came with the package.

Connect them according to the datasheet.

Resistor and capacitor

The provided analog output is proportional with the number of the dust particle in the air. Powering the phototransistor part with 3V3 will not get exact the output graph from the datasheet unless you will not use the 5V Vcc. If you need to be 100% to the datasheet and you are using an wemos D1, add a resistor in series with the output VO (pin 5) so the maximum voltage on the A0 input will not exceed 1V. Probably an 180k resistor will be fine.

Output voltage vs dust density

Based on the output voltage you can setup some steps for the air quality like excellent, very good, good, fair or dusty.

Here is a video clip on how is working with platform and Amazon Alexa.

Now eNVi-A is online. Total cost: 18.50 euro.

Thursday, November 9, 2017

Getting temperature from ESP8266 over MQTT with Amazon Alexa

With the help of the platform now I can get room temperature or outside temperature with just an ESP8266 and a temperature sensor like DHT22 or DS18B20 or BMP280.

The Alexa is questioning the server that will ask my local broker that will publish a message the the ESP8266 to ask the temperature for my room. The values for temperature and humidity will travel the other way around to Alexa, that is so nice and is letting me know about them.

On you will find also a demoapp ( source code on git) for a plug, but you can convert it easy to other IoT device. Also there is a mobile application in Google Play named Homy4( source is on git) that connects to the and allows you to turn on/off the plug device from demoapp.

Let me know what you think and what modules do you want to integrate on, on Alexa, ESP8266  and on the mobile application.

Everything is done encrypted and authenticated against 2 servers, so the entire communication is secured.

I will publish soon this skill to Amazon so any of you can have it. Just use the demoapp from and adapt it to send temperature. Maybe will be a good option to create also a demoapp for the temperature, not only for a plug.

The final box is small and compact. I've choose the DS18B20 since it can be integrated well in the box I have. To bad that there are not some enclosures for wemos D1 or nodeMcu which are most popular boards on the market. A printed 3D one it is an option, but takes time and I don't know if they can be produced in a large number.

Final box with eNVi - Alexa thermometer

So now the eNVi-T is up and running in 3 rooms. Next will be an air quality module and maybe an thermostat.

Total cost:10 euro.