MQTT Based Energy Meter with OpenHAB

Overall Architecture:

Libraries Used:

1. ArduinoJSON
2. Autoconnect
3. PageBuilder
4. U8glib Library for OLED
5. SoftwareSerial

ESP32 Pin Diagram:-

Connection Diagram:-

Setting up with OpenHAB

If MQTT addon is not installed, Goto OpenHAB Paper UI -> Ad-ons -> Bindings and search for mqtt. Make sure to install the 2.x listing of it.

Create required Things/Items

There are 2 ways of creating the required things/items in OpenHAB, using the paper UI and through text files. Over here I am going to use the text files way, as this makes managing and backing up easy.

If you have not created a broker already,

Navigate to things folder in your OpenHAB installation. For OpenHabian it is /etc/openhab2/things.

Create a new file boker.things and paste the following content.

Bridge mqtt:broker:localMosquitto "Mosquitto" [ host="192.168.0.7", port="1883", secure=false, username="", password="", clientID="A_RANDOM_String" ]

Make sure to change the content (host,port, username, password) as per your setup/installation.

Create Thing/Channels for Energy Meter

Navigate to things folder in your OpenHAB installation. For OpenHabian it is /etc/openhab2/things.

Create a new file energy_meter.things and paste the following contents,

Thing mqtt:topic:localMosquitto:EnergyMeter "Energy Meter" (mqtt:broker:localMosquitto)  {
    Channels:
        Type number : power "Power" [ stateTopic="home/energymeter/93/data", transformationPattern="JSONPATH:$.POWER" ]
        Type number : voltage "Voltage" [ stateTopic="home/energymeter/93/data", transformationPattern="JSONPATH:$.VOLT" ]
        Type number : current "Current" [ stateTopic="home/energymeter/93/data", transformationPattern="JSONPATH:$.AMP" ]
        Type number : energy "Energy" [ stateTopic="home/energymeter/93/data", transformationPattern="JSONPATH:$.ENERGY" ]
}

Make sure to change the mqtt topic as per your conveneince. I have subsribed to smae topic and using JSONPath Transformation to parse the incoming JSON data. To use this however you need to have JSONPath Transformation add on for OpenHAB installed. This can be done from TRANSFORMATIONS tab in Add-ons in PAPER UI.

Create Items

Navigate to  `items` folder in your OpenHAB installation. For `OpenHabian` it is `/etc/openhab2/items`.

Create a new file energy_meter.items and paste the following contents,

Group gEnergyMeter
Number  EnergyMeterPower "Power [%.2f Watt]" <alarm> (gEnergyMeter) { channel="mqtt:topic:localMosquitto:EnergyMeter:power" }
Number  EnergyMeterVoltage "Voltage [%.2f Volt]" <poweroutlet_au>(gEnergyMeter) { channel="mqtt:topic:localMosquitto:EnergyMeter:voltage" }
Number  EnergyMeterCurrent "Current [%.2f Amp]" <cistern> (gEnergyMeter) { channel="mqtt:topic:localMosquitto:EnergyMeter:current" }
Number  EnergyMeterEnergy "Energy [%.2f Kwh]" <energy> (gEnergyMeter)  { channel="mqtt:topic:localMosquitto:EnergyMeter:energy" }

I have added icons which are available by default with OpenHAB, which donot justify the parameters. You can change that and add icons of your choice.

Add the items to a sitemap

You can either add the items individually or add the group straight away to the sitemaps file.

Navigate to sitemaps folder in your OpenHAB installation. For OpenHabian it is /etc/openhab2/sitemaps. Create a file energy_meter.sitemap and pasgte the following contents,

sitemap test label="Energy Meters"
{	
    Frame label="Mains Meter"{
        Text item=EnergyMeterPower
        Text item=EnergyMeterVoltage
        Text item=EnergyMeterCurrent
        Text item=EnergyMeterEnergy
    }
}

Enjoy !!