OpenHAB and Open Energy Monitor – emonTH Prototype

So far I have outlined the basic strategy I plan to take regarding building a HAPMaS (Home Automation and Power Management System). Now it is time to get down to actually build something.

In my Open Energy Monitor so far I have:

  • an emonBase (Raspberry Pi and RFM69CW). This takes in data from the sensor units over the 433MHz network and puts it on the emonCMS system.
  • an emonTX unit (Arduino Uno and emonTX Shield with RFM69CW). This senses the power used by the house and generated by the solar PV and sends it to the emonBase.

emonBase also sends the data to where the data is available online. openHAB then picks up that data from and displays it on openHAB.

emonTH as sold in the Open Energy Monitor shop

All this is working well. So now I wanted to start to add to this with additional sensors and to start I would build an emonTH unit. The emonTH is a unit designed for the OEM system which is basically an arduino with a temperature/humidity sensor sending its data to the emonCMS via the RFM69CW and the 433MHz network. These usings are available to buy from the OEM web site but I wanted to build my own as this will then form the basis of many of the sensor units I will add in the future.

My prototype emonTH using a Arduino Pro Mini 3.3V, RFM69CW and DHT22
My prototype emonTH using a Arduino Pro Mini 3.3V, RFM69CW and DHT22

Building a emonTH unit will provide a template for sending data over the 433MHz network and also give me some valuable experience building packaging and testing these small, electronic sensor units.

This then is my prototype. It looks messy but it isn’t really. It is just a Arduino Pro Mini 3.3v ( the blue board), an RFM69CW 433MHz transceiver (green in middle) and a DHT22 temperature/humidity sensor (white on left). Between the DHT22 and the RFM69CW is a AMS1117 3.3V voltage regulator which takes the 9V from the battery and outputs the 3.3V needed for the RFM69CW although this may well be replaced with a Jeelabs Power Board which seems a better way to power these devices. There are also a  couple of resistors (behind the DHT22) as a voltage divider to allow me to measure the battery voltage. When this is mounted on a single board without all the jumper wires it should look almost as tidy as the shop’s single board solution.

I shall publish the high-level system diagram and the device specs when this first module is packaged and deployed.

So this then is now working and publishing the Lounge temperature and humidity along with the battery voltage to emonCMS, and then openHAB is picking that up from emonCMS.

Now to decide how to package it into the emonTH casing.

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