Getting temperature from ESP8266 over MQTT with Amazon Alexa

With the help of the Iotcentral.eu 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 iotcentral.eu 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 Iotcentral.eu 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 iotcentral.eu 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 iotcentral.eu, 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 iotentral.eu 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.

E-ink display Part I

Finally my e-ink display arrived and I had some time to test it.

At the first look it redraw the screen in about 1 second, consume very little when changing the display and nothing between the changes.

I will connect it to my battery operated Temperature and humidity sender so I can see the values during the sleep time.

E-ink aka E-paper display

 Features:

• Ultra low power consumption
• Super wide viewing angle - near 180°
• Extra thin & light
• High Resolution
• SPI interface
• Four gray shade colors
• All necessary component included
• Integrating boosted circuit

Specifications:

• Resolution: 172x72
• Display thickness: 1.18mm
• Display Dimension: 2.04inch,
• Module dimension: 30.13x60.26mm
• Pixel Pitch (mm): 0.28(H) X 0.28(V) / 95dpi
• Contrast Ratio: 10:1
• Display Color: 4 gray shade colors, White, Gray, Deep gray, Black
• Refresh Time (room temp.): 1 sec
• Interface: SPI
• Operation Temperature: 0~50°C
• Storage Temperature: -20~60°C
• Module Weight: 15g
• VCC 3.3V

DHT22 versus BMP180. The winner is ....

For my chronothermostat  project I have evaluated the 5.11USD DHT22 and 2.20 USD BMP180.

I've let them work in parallel for few days and the winner is ..... BMP180.

This is a graph for BMP180.

BMP180

This is a graph for DHT22.

DHT22

As you can see the DHT22 had few unwanted spikes which leads to false triggers.

DHT22 has the advantage of using one pin,  BMP180 is i2c so is using 2 pins, but the temperature has no spikes. 

Both sensors:

•  are reading the same temperature
•  both are showing a lower value as my current chronothermostat which is responding more quickly on changing the temperature.

If you know other sensors that are more precise and are more temperature responsive, please let me know.