Home Automation System - My first sensors...

After all my experiments, now I'm able to use OpenHAB with familiarity; so now it's time to build my first sensors.

Let's start from the kitchen where I would like to monitor gas, temperature and humidity.

The MCU will be a ESP8266 NodeMcu board. I chose this board because it has wifi, several digital I/O and an analog one, you can write firmware in the same way you could with Arduino and above all...it's very cheap...On Banggood I bought two at only € 2,76 each, not bad...

If you are interested in it, this is the product link:

Geekcreit-Doit-NodeMcu-Lua-ESP8266 on Banggood.com

I will use these sensors:

- MQ-4 gas sensor: for detecting of methane mainly, (I'm interested on it...), propane and butane gas. I already used it months ago. Here is it:

MQ-4 gas sensor on Banggood.com

- Humidity / Temperature sensor DHT11: it'a a very cheap sensor (with about €5 i bought 5); its error is +/- 2°C and it's able to get only positive temperature. Its precision is 1°C, so no decimal number...For these limitations I decided to buy other sensors, the ds18b20 (for internal and external use)...I will use these DHT11 just for humidity

5 pack on Banggood.com

3 Pack on Banggood.com

Single sensor on Banggood.com

- Dallas ds18b20 temperature sensor: compared to the previous one it has a better precision (0,5°C) and it's able to get negative values, so it's ideal for external use

Single sensor on Banggood.com

5 Pack on Banggood.com

External probe on Banggood.com

I built some prototype using a breadboard...

...till I found the right configuration...and so I made a "definitive" board...

I added a led used for the indication of network activity and a connector used for external power. The device will be powered through a little 5V 450mA power adapter, connected to the blue terminal blocks. In this way I could power up the device and also the sensors.

The led, ds18b20 and DHT11 sensors are linked to digital I/O and the MQ-4 gas sensor to the analog one.

Now it's time to write the firmware...I use Visual Studio Code with platformio extension; I think it's better than the Arduino IDE (personal opinion). I chose this IDE because it also has an extension for openHAB that let me edit configuration files in a better way (just like Eclipse SmartHome Designer).

My device will connect to the MQTT broker of OpenHAB through wifi, fetch the data from the sensors and send them as json formatted string with nodemcu/mainfloor/esp8266mcu11/temphumiditygas/state topic.

The sample period is 5 seconds and each 60 seconds the average data will be sent to the MQTT broker. When the data will be sent, the green led will blink twice.

Here is an example of a message sent to the MQTT broker:

{"gas":{"error":"","sensorValue":46.33333,"ppm":0.431016,"percentage":0.000043,"realValue":829.0371},"tempHum":{"error":"","humidity":63.66667,"tempC":22,"tempF":71.59999,"heatIndexC":21.91774,"heatIndexF":71.45234},"temp":{"error":"","tempC":21.66667,"tempF":70.99999}}

The gas object is related to the MQ-4 sensor, the tempHum object is related to the DHT11 sensor and the temp object is related to the ds18b20 sensor.

For now I decided to use both sensors for temperature reading; so I can compare them.

Ok, it seems to work as expected...I put my device in the right place in the kitchen...

Now it's time to setup OpenHAB...and build a new dashboard on Grafana.

In OpenHAB I created a new file called esp8266mcu11.items (esp8266mcu11 is the unique id of the device) in the /etc/openhab2/items folder; in this file I appended the following lines:

Number MainFloor_KitchenTemperature "Kitchen Temperature [%.1f °C]" <temperature>
(gPersistence)
{mqtt="<[openhabianpi-mqtt:nodemcu/mainfloor/esp8266mcu11/temphumiditygas/state:state:JSONPATH($.tempHum.tempC)]" }

Number MainFloor_KitchenTemperatureNew "Kitchen Temperature NEW [%.1f °C]" <temperature>
(gPersistence)
{mqtt="<[openhabianpi-mqtt:nodemcu/mainfloor/esp8266mcu11/temphumiditygas/state:state:JSONPATH($.temp.tempC)]" }

Number MainFloor_KitchenHumidity "Kitchen Humidity [%.1f %%]" <humidity>
(gPersistence)
{mqtt="<[openhabianpi-mqtt:nodemcu/mainfloor/esp8266mcu11/temphumiditygas/state:state:JSONPATH($.tempHum.humidity)]" }

Number MainFloor_KitchenGasPpm "Kitchen Gas [%.2f ppm]" <carbondioxide>
(gPersistence)
{mqtt="<[openhabianpi-mqtt:nodemcu/mainfloor/esp8266mcu11/temphumiditygas/state:state:JSONPATH($.gas.ppm)]" }

Number MainFloor_KitchenGasValue "Kitchen Value [%.2f]" <carbondioxide>
(gPersistence)
{mqtt="<[openhabianpi-mqtt:nodemcu/mainfloor/esp8266mcu11/temphumiditygas/state:state:JSONPATH($.gas.realValue)]" }


Now the sitemap:

Frame label="Gas Detection" {
Text item=MainFloor_KitchenGasPpm valuecolor=[>800="red",>600="orange",<=600="green"]
}

Frame label="Kitchen" {
Text item=MainFloor_KitchenTemperatureNew
Text item=MainFloor_KitchenHumidity
}

And this is the result:

Good, I added a new brick...now I can create the new Grafana dashboard with the gas, humidity and temperature of the kitchen:

Last step: adding the device to the network monitoring...so OpenHAB will notify me when the device will be offline.
So, using PAPERUI I added the device using the Network Binding and create the items. Then I added the gNetworkCheck group to the "status" item, so its network presence will be monitored by OpenHAB.

Home Automation System - Dashboards with Grafana

I chose InfluxDB as persistence engine in OpenHAB also because it is easy to integrate with Grafana, an open source visualization suite that let us build interactive web dashboards.

I installed Grafana on my Raspberry PI3, where already run OpenHAB and InfluxDB, using the Openhabian configuration tool (openhabian-config), choosing "optional components".

Then, I'm able to reach the suite through http on port 3000.

Here you can find a very good guide about Grafana and InfluxDB setup and configuration

https://community.openhab.org/t/influxdb-grafana-persistence-and-graphing/13761#grafana-setup

The process to build dashboards is very easy...as long as you define your InfluxDB data source.

Every dashboard is a set of rows and objects; to fetch your data you have to choose among all the measurements in InfluxDB...

Here is my example dashboard where I put:

- at top left, ping time of my local network devices;
- at top right, speedtest results;
- at bottom, weather data, fetched from the OpenWeatherMap service

Home Automation System - Openhab persistence service with InfluxDB

In the last few days I studied the "persistence" service in OpenHAB v.2, just to store acquired data and be ready to create dashboards.

As usual, official docs are the best choice:

http://docs.openhab.org/configuration/persistence.html

I chose InfluxDB as persistence service, a time series database, easy to integrate in Grafana, a web platform for dashboards creation.

The first thing to do is to install InfluxDB on the RPI3 (the same where OpenHAB is already running) following the official documentation https://docs.influxdata.com/influxdb/v1.3/introduction/installation/

Next, I have to enable the persistence service on OpenHAB v.2, using PaperUI, Add-ons section, Persistence tab

Then, OpenHAB must be configured with the InfluxDB connection info, editing services/influxdb.cfg file in the usual OpenHAB configuration folder. In my case, I used all the default options, so I just entered the password.

This is my configuration file:

# The database URL, e.g. http://127.0.0.1:8086 or https://127.0.0.1:8084 .
# Defaults to: http://127.0.0.1:8086
# url=http(s)://<host>:<port>

# The name of the database user, e.g. openhab.
# Defaults to: openhab
# user=<user>

# The password of the database user.
password=XXXXXXX

# The name of the database, e.g. openhab.
# Defaults to: openhab
# db=<database>

On the official guide you can find all the options: http://docs.openhab.org/addons/persistence/influxdb/readme.html

Now it's time to build the persistence strategy to let OpenHAB knows how store data on InfluxDB; in a few words I have to decided, item for item, when datas will be stored on db. I can choose between many options: on every change, on every update or by time schedule, using Quartz syntax. To do so, I created a new configuration file in the /etc/openhab2/persistence folder, called influxdb.persist. In this file I defined which kind of persistence strategy I will use (Strategies section...) and assigned them to items and groups (Items section).

Official docs:

http://docs.openhab.org/configuration/persistence.html#configuration

My Strategies section is as follow:

Strategies {
everyMinute: "0 * * * * ?"
everyHour: "0 0 * * * ?"
everyDay: "0 0 0 * * ?"
default = everyUpdate, restoreOnStartup
}

I used groups to assign the persistence strategies to items; so I defined new groups in /etc/items/groups.items file

Group gPersistence (gAll)
Group gPersistence1m (gAll)
Group gPersistence1h (gAll)
Group gPersistence1d (gAll)
Group gPersistenceChange (gAll)

then I'll assign them the persistence strategy just defined in the Items section of the influxdb.persist file

Items {
gPersistence* :
gPersistence1d* : strategy = everyDay, restoreOnStartup
gPersistence1h* : strategy = everyHour, restoreOnStartup
gPersistence1m* : strategy = everyMinute, restoreOnStartup
gPersistenceChange* : strategy = everyChange, restoreOnStartup
.........
}

I will easily assign these groups to items to assign a particular persistence strategy

In the next post I will speak about Grafana, a powerful tool to build dashboard.