Monitoring your appliances’ power

This is a work-in-progress because so many people have asked me about it that I decided to write up some notes early. Keep checking back for updates.

I recently posted about real-time data from your smart meter and all was good, but then thread by Robin Hawkes on Twitter caught my eye:

These devices connect to your WiFi network and allow you to switch a connected device on or off, on a schedule if you require, and also monitor power consumption. That last bit is the most important for me – knowing how much energy I’m consuming.

After researching Tasmota, an open firmware for simple home automation devices, and checking a bunch of reviews on the TP-Link Tapo P110‘s firmware, it looked like these P110s would do just what I needed – simple power monitoring for not much of an initial outlay.

LocalBytes were out of stock of both of these items when I looked, so I took the plunge and ordered one from elsewhere. Well, I ordered eight because I was feeling quite bold.

Initial setup

Trivial. Download the Android (or iOS presumably) app, plug in a device, find its wireless network and configure it to connect to your wireless network. It reboots and that’s about it.

Firmware updates can be scheduled automatically, but I don’t know whether this will switch the power off to any connected device or not. Something to check later.

Control and monitoring

The mobile app makes it quite easy to switch a device on and off, to set a schedule, and to see power consumption. But it’s a mobile app, and I want the data somewhere I can analyse it easily.

Home Assistant to the rescue! Running HA under Docker is really easy if you know Docker. I could have re-purposed one of my Raspberry Pi as I can’t get a new OpenVMS Community licence for VAX any more, but I wanted to try HA quickly to see if it fitted my needs.

Support for the P110 devices doesn’t come as standard, but there’s a community-written workaround for that. A little fiddly and not really what I’d expect, but it works.

Next steps

Oh boy, there’s a lot I want to do.

First off, I want to push the sensor data out from these devices in to an MQTT server such as Mosquitto and have Telegraf pull this data in to a time-series database so I can visualise it with Grafana.

Other things I want to do include automatically checking my Google Calendar and setting the heating to come up early when I’m doing a morning clinic, or having it come on a bit later when I’m at home that day. I want to get an inline power switch for my porch light and turn that on between dusk and sometime around midnight.

Real-time Smart Meter data

A year or two ago, I took the plunge and had a smart meter installed. I naively thought that being able to read energy usage was a simple case of connecting a ConBee-II or similar to the ZigBee HAN.

To save anyone else from going through the same range of emotions as I did, here’s how you can read your own smart meter data.

Technology primer

Your electricity meter has two parts – a metering device, and a communications device located at the top. The electricity meter periodically sends energy usage information over a communications network to your supplier. It’s easy when you have a continual supply of electricity.

If you have a gas meter, it doesn’t have its own communications device. To do so would require a power supply to the gas meter – readily available on an electricity meter. Instead, the gas meter sends energy usage to the electricity meter every 30 minutes and therefore only has a long-life battery installed.

Getting access to the data

There are two ways to get access to real-time electricity and real-ish time gas usage data. Neither of them involve pairing your own device.

The quickest and simplest is to use an intermediary such as Glowmarkt, who are a DCC Other User and can request your metering data from the Data Communications Company, then make it available to you. This is a straightforward process, although you need to go through an industry-mandated security process to prove you are requesting access to your data and not somebody else’s.

The other option, a lot better from my point of view, is to buy a combined In-Home Display (IHD) and Customer Access Device (CAD) from Glow (Hildebrand Technology) sell a combined in-home display (IHD) and Customer Access Device (CAD) for around £65. This arrives already paired with your smart meter, and you connect it to your home wireless network, and it sends out data from your smart meter to an MQTT server (which can be on your local network too), ready for you to consume yourself.

The data

You can use the CAD as a simple IHD – it’s a lot prettier than the one supplied by my energy supplier (which I can still use). Electricity usage arrives every few seconds, with gas usage as and when the metering equipment makes it available.

The real power comes when you work with data in real-time, or at least as close to real-time as it’ll give you. Want to work out how much the tumble dryer cost to run? Or find out whether you’re OK with having your home a little cooler to save a bunch of energy?

Data format

The MQTT messages you receive are in JSON format, and contain data for three ‘clusters’ – Metering (0x0702), Prepayment (0x0705) and Device Management (0x0708). Each of these clusters has an attribute set – the Metering cluster presents the Reading Information Set (0x00), Formatting (0x03) and Historical Consumption (0x04). Finally, each attribute set has a set of key/value pairs. From this, you can decode that cluster 0x0708 (Device Management), attribute set 0x01 (Supplier Control Attribute Set) value 0x01 is the provider name.

Since the data is sent in JSON format, it’s quite easy to parse. If you want to dive straight in to the detail about what clusters and attribute sets are, the ZigBee Smart Energy Standard is available, although at 628 pages, it’s a heavy read.

Problems

The entire process was quick – the CAD arrived within a day or two of placing my order and was ready to use the moment I plugged it in. Getting my data in real-time took a little longer – it’s a manual process for the staff at Glow, but once it’s set up, that’s it.

The only problem is that there’s no formal support. For the first six months, the CAD disconnected itself from my WiFi network for no reason. Despite posting about my issue, there’s was no progress on it – but out of the blue, a firmware update arrived which fixed the issue.

Is the lack of formal support a problem? Likely not – unless you’re having an issue. Since the firmware update, I’ve had no problems with the IHD, other than a lack of time to play with and analyse the data.

Recommendation: go buy one!

Installing a LetsEncrypt certificate on an HPE iLO 5

Once again, I’ve spent far too long trying to work out how the heck to get a LetsEncrypt X.509 certificate on to the HPE Integrated Lights-Out 5 board.

To save me some time in three months, and to save you some time since you’re already here, the instructions are really straightforward. Be aware that this method uses a DNS-based challenge which may be tricky for you to do unless you can automate DNS updates.

First, from the iLO web interface, select Security and SSL Certificate, and click Customize Certificiate.

Next, Click Generate CSR and go back to the page in a few minutes when the certificate signing request (CSR) has been generated.

Copy the CSR in to a file on a machine with the ‘certbot’ client installed and run the following command:

certbot certonly --csr request.csr --preferred-challenges dns

When the certificate has been issued, select Import Certificate and paste in the entire PEM-formatted file.

And it’s really as straightforward as that.

Let’s Encrypt and Zabbix Agents

A week or two ago, some of a number of servers became unreachable via Zabbix. Both pairs of servers (as we run everything in pairs) showed the same problem, and no other host did.

Looking in the Zabbix log showed this rather cryptic error:

SSL_shutdown() with 172.31.16.32 set result code to 6

That’s not very helpful, and several hours of head-scratching went by before we finally stumbled across what was happening.

The X.509 (or SSL) certificate on the target machine is issued by Let’s Encrypt, who are in the process of signing new certificates with a new key. Within Zabbix, we check that the certificate presented by the client when we connect is issued by a specific issuer and since this had changed, the server was refusing to connect.

How did we fix it? Really easily – by going in to the host configuration in Zabbix, and setting the issuer to:

CN=R3,O=Let's Encrypt,C=US

Ridiculously straightforward, and if you hover over the red ‘ZBX’ status box, you’ll see an error saying that the wrong issuer was found on the certificate.

That’s a few hours we’ll never get back, but it’s great to have solved the problem. And as it happens, there was a correlation between the servers affected – two pairs were built at the same time, and the remaining pair was built just about 90 days before the others. Let’s Encrypt certificates have a lifetime of 90 days.

We’re expecting further servers to drop off Zabbix, but at least we know why and we can fix it.