A low cost energy meter

  • I am curious to know if my heat pump is actually saving energy. To know this, I would need an energy meter. So I designed and built one. You can see my projoect and I believe it is sufficiently documented for you to build your own. See Energy Meter

    My nephew has done the same and is as curious as I. But he knows nothing of MySensors, and how to get the data presented in a reasonable way. I explained to him it is a small matter. This turns out to be not so. Beyond the aforementioned energy meter, it involves an Arduino MySensors Gateway (hardware and software), Home Assistant (software), Virtual Box (Software), and an i86 computer (hardware) which is running linux (software). Just writing that makes the project sound intimidating. It is not, if you break it down to its constituent parts.

    The Arduino Serial Gateway (GatewaySerial) can be found as an example in the Arduino IDE, once the Arduino library is loaded. This probrammed Arduino will be connected to the target computer vie the same USB cable used to program the arduino. For my environment, I have some modifications. The wiring of the radio to the Arduino Nano is slightly different. CE is wired to D10 and CS is wired to D9. Also, I am using radio channel 86. These changes are reflected in the following three lines which are added after the line #define MY_RADIO_RF24

    #define MY_RF24_CS_PIN 9    // for compatibility with RF-Nano
    #define MY_RF24_CE_PIN 10   // for compatibility with RF-Nano
    #define MY_RF24_CHANNEL 86  // 86 is the development channel 121 is the production channel

    Acquiring an adequate computer for the task can be as simple ordering one from Amazon for around UD$85. Discarded laptops can be found for as little $10 sans battery and power supply. The only important requirement is more than 2GB RAM.

    See information about SSH below

    Installing Ubuntu on the computer is tedious but easily done. These instructions are for the server version of the operating system (OS). This version has no graphical user interface (GUI). You will need a monitor and a keyboard. If network manager is not installed (nmcli d doesn’t work) or nmcli d doesn’t indicate a wireless network, the internet port will have to be used. If there is only WiFi, a network client device, which connects to the internet port, will have to be used. Official instructions

    Installing Virtual Box is also a tedious task. By this time you’re pretty used to using the command line.

    Finally, installing Home Assistant will be the training session for working with Home Assistant.

    Information about SSH
    SSH is programs running on your usual desktop computer and the target computer. When you installed the operating system on the target computer, you entered a username and and password. Once the target computer is up and running, and you’ve found it’s IP address (ip address) you can “ssh” from your usual desktop with “ssh username@xxx.xxx.xxx.xxx (the IP address you just found) You will be prompted for the password.

    This is just like being at the keyboard and monitor of your target computer. EXCEPT, you can now copy and paste from your usual desktop computer into the window of the target computer. That is, you don’t have to fret about typing in all those commands.

    Challenge yourself! 🙂 It's all do-able and you can do it!


    The answer to your first question is, "Yes, you can do it!"

  • Hi OldSurferDude,
    I just read through your Energy Meter documentation. Nice work. It gives basic theory and calculations. I've been thinking about building an energy meter for a while now. I'll use this as a reference. Thanks.

  • @KevinT you welcome 🙂

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