Another common occurrence is not having enough water for afore mentioned bath.
Our hot water is provided by a system boiler/unvented cylinder arrangement and I use a Nest to control the hot water (more on that later). The current schedule has it running the boiler for thirty minutes each day.
What is very annoying is that on some bath days we have ample hot water and on others, we don’t. We end up boiling the kettle to make up the difference. I don’t like the idea of just turning on the hot water as we might just be heating water that is already hot enough.
How much hot water do we have?
The first thing to figure out is how much how water we actually have. As I’ve mentioned, one some days we have ample and on other days we run out. Why does this happen?
Here are a few of the main factors that spring to mind:
The duration of the showers in the morning.
The ambient temperature in the loft.
How much washing up we’ve done.
The image above shows the basic operation of an unvented cylinder. Cold water enters the tank at the bottom and hot water exits at the top. The coil inside the tank is connected to the boiler and is responsible for actually heating the water in the tank. The whole thing works off the principal that the hot water will sit on top of the cold water and be pushed out the top.
My plan, therefore, was to attach temperature probes to the cold water entry and hot water exit and see what I could measure.
I was also interested in trying to measure the effect of the loft temperature on heat loss.
With my requirement of three sensors, I set about building a circuit that included an ESP-8266 and three DS18B20 temperature probes.
For power, I wanted to use an off the shelf power supply. As these are mostly 5v, I added an LV1117V33 LDO. This little device accepts up to 7v input and outputs 3.3v, which was perfect to power the D1 and the sensors. To this, I connected a barrel input.
I had originally planning on writing my own software to read the values from the sensors and send via MQTT to my HA instance. I actually did write my own software and even got the auto-discovery working, but as I wanted a web UI running on the device, so I could change easily change WiFi and MQTT settings, going down the custom road made little sense.
I was vagly aware that the excellent Tasmota Firmware (which I use in lots of smart sockets) did have some form of sensor support, so I did some reading. It turns out that not only did it support the DS18B20 sensor, it supported multiple ones 🙂
I flashed it onto the D1 mini and, after setup, navigated to the Configuration page.
You can select Module type as Generic (18) to gain access to the various GPIO pins on the device. I had connected the data wire of my sensors to D4, which is GPIO2. I choose teh DS18x20 option.
Once I hit save, the device rebooted and, lo and behold, the temperature started flowing into the UI!
I drilled four holes. One for each of the temperature probes and one for the power connector. The probes are held by three IP68 glands. Not necessary at all, but I just had them and thought they’d suit.
Once I had it all assembled, I plugged it in. It was at this point I wished I had some sort of indicator light to tell me it was powered or connected to the internet. I had to wait a minute, but eventually the Tasmota appeared on my list of connected clients.
I have a pretty standard unvented cylinder. There are two pipes entering at the bottom, the cold water inlet and the hot water return to the boiler. The hot water outlet is at the top.
The third probe I just left hanging in the air, supported by a piece of furniture. My loft really is full of junk!
From the three probes, I could have a guess as to which probe was were!
The 15.8 was the ambient temperature in the loft, with the 19 and 48 degree measures pointing to the inline and outlets.
My hot water turns on for 30 minutes each morning (30 mins because the Nest Thermostat won’t let me do anything shorter). I looked at the temperatures when I got up around 7am and I could see the top temp was at almost 60 degrees.
I’m going to let this setup run for a few weeks and note the days we run low/out of hot water.
Combined with better control of my hot water (I’m thinking of replacing my Nest’s control), I think there is an opportunity to reduce the time my hot water needs to actually be turned on.
Other things might be possible, such as extra hot water when we have guests over (using their connection to the house WiFi as an indicator of presence). Or ensuring these is hot water for washing the dishes at 6pm each night.
I’ll post an update, once I’ve got some findings!
Update 24th Feb
With the sensor installed for over a week, I pulled a graph from Home Assistant.
The green line, which reaches the highest values is the outlet temperature. You can see the rather pronounced peaks and troughs. The orange line represents the inlet temp and that does spike a little, each morning, when the heating is turned on. The red line is the ambient temp of the loft. It does vary by a few degrees.
From the graph, it’s very obvious when we’re very low on hot water!
I also find the temperature loss over the course of the day to be interesting. This is obviously a function of the ambient temperature in the loft, but also, I suppose, of the temperature of the incoming water.
I’m in the process of upgrading my Home Assistant instance and I hope to be able to retain more data than I can do right now. I’d like to be able to compare summer months to winter months, so I need a few months of stored data to perform that comparison.
With Den Automation facing immanent demise, I’ve been looking at alternatives.
I came across the Shelly 1 relay, quite by accident, whilst looking at some Sonoff stuff. It immediately piqued my interest, mostly because it taught me that I didn’t know anything about lighting circuits in the UK.
I’ve installed my fair share of lighting fixtures during the rennovation of my home and whilst I was astonished at the number of connections in a ceiling rose, I never really took any time to investigate why.
I had made my own attempts at automating lighting when I first moved in. This was a crude affair, which involved putting a Sonoff Basic relay in between the rose and bulb.
Whilst functional, the downside was that flipping the physical switch turned the relay off. Bye, bye, remote switching.
Essentially, the Shelly 1 is connected to the permanent supply, so it’s always on, regardless of the physical switch. The Shelly is also connected to the physical switch, so it knows when it’s been flipped.
This means that the light can be turned on and off via an API *and* by the existing light switch! I immediately ordered some.
My order included two Sonoff Minis, but I choose the Shelly1 to begin with as it supports MQTT control out of the box (which bypasses the Shelly Cloud – local control all the way). I know the Minis have to be flashed with Tasmota firmware to support MQTT and I didn’t want to get distracted!
WARNING! Please don’t attempt anything related to mains electricity unless your confident in your ability. Always remember to isolate circuits from the fuse board before doing anything!!I am not responsible if anything happens.
Installation was very straight forward with the help of the excellent WAGO connectors. Following the diagram, I installed the Shelly 1.
Once I’d restored power from the fuse board, I went through the configuration process. This followed the standard pattern of connecting to the Shelly’s WiFi network, connecting to my own WiFi network and then entering the MQTT server address and credentials.
It worked first time!
I set it’s Switched Live mode to edge, so that means that any change in the physical switch will turn it on or off, perfect for my needs.
Adding the Shelly to my Home Assistant required the addition of an MQTT entity with the appropriate topics.
A few months ago, Den Automation Ltd appeared to drop off the face of the earth. My hub disconnected from the internet and the Den app would only work whilst I was at home.
I should point out that I invested in Den via Seedrs.
Continued Operation is possible
I took time to try and understand the protocol and eventually managed to write some code that allowed me to continuing using them. I created a Flow in my Home Automation installation using NodeRed. This essentially bridged messages from my Hass over to my Den Hub.
This has been reasonable successful, but there are some issues.
#1 The Den Hub needs to be restarted every week or so. I don’t know what’s happening, but I suspect the MQTT server they are using has a memory leak. After a few days of successful operation, it disconnects from NodeRed and refuses new connections. A restart clears this.
#2 Speed is inconsistent. Sometimes operating a light or socket from within HA will result in speedy action from the Den unit. Sometimes it takes several seconds and sometimes nothing happens.
#3 Disconnections from the switches and sockets. This has happened my bathroom switch. It just no longer operates or sends its state. I guess it has lost contact with the Hub. I might try and reset it, but I think that’s probably a crap shoot since I have no App to guide the process.
Den Automation Ltd. are officially in liquidation.
As somebody who invested in both shares and product, I’ve been hit twice.
I’m also in the process of trying to recover some of the money I spend on pre-orders, as some of the items were never delivered. I’ve submitted the paperwork, but I have yet to get a response.
End of the line
With Den officially in Liquidation, there is no longer any hope for the company.
I’ve also decided to start the process of removing all their products from my home. First to go was the double socket connected to my Kitchen’s TV. I’ve replaced this with a Sonoff switch (flashed with Tasmota).
I’ve had a great experience with the Shelly 1 relay product, so my plan is to remove all the Den light switches upstairs and restore the original switches, with Shelly relays going into the lights.
The loss of Den’s cloud crippled the product for most people who had purchased it. I was lucky that I was had the knowledge and tools to determine the local protocol and leverage it from my own ends. Sadly, I wasn’t able to help anyone else.
Den’s local control ability was the primary thing that attracted me to their product line. The relied on the Cloud for user account’s and when that went, their app became useless, actually logging the users out. Not as “local” as I had hoped.
Sonos’s recent announcement about their hardware has made me come to the conclusion that any hardware that needs a Cloud is bad. It’s hardware you own, but don’t own. I’ve got £250 of Den products that I can’t really use because a company was poorly managed, despite the product itself being fully operational.
With the very sad news that Den Automation is having financial troubles, I decided it was time to revisit my investigation into the protocol that Den uses.
I had read on their website that they used both a cloud based and local network approach. In fact, this was one of the things that appealed to me most. Offering local control is an important aspect in any smart home as it insulates you from internet outages.
I had looked into their protocol a few weeks after setting up my Den hub, but it turned up a dead end for me.
Based on what I’d learned my own adventures in IoT, I started working under the assumption that the local protocol would be HTTP based and use probably use mDNS. Using Charles, the populate iOS proxy, I was able to capture some of the traffic from my phone whilst using the Den app.
Unfortunately, all the requests were targeted at Den’s cloud. I was able to see the details of my deployment, the various switches and sockets, but I wasn’t too interested in taking this approach, since I had Google Home and Alexa integrations already setup.
After more digging around, I eventually capture the Publish command used to control the state of the individual devices.
This enabled me to update the state and thus turn the switches on and off.
I’ve created a simple web app – https://denclient.azurewebsites.net/ – which can be used to control the connected hardware. You just need to use the same process as I did to sniff the packets.
At the time of writing this, the Den app was still working for me, which enabled me to perform some basic packet sniffing. Since I performed this investigation, the Den App is no longer working. I presume that AWS/Azure have killed the Den backend due to unpaid bills.
I carried on through the developer study guy and implemented the basic Light. The messaging flow is now making sense to me. I knew the Microbit’s 16KB of RAM wasn’t going to be enough for any real project, so I decided to bite the bulled and pick up a Adafruit nRF52832 device.
Ordered from www.coolcomponents.co.uk, they arrived pretty quickly. I plugged it in, downloaded the Bluefruit app from the app store and was able to discover and connect to the device pretty quickly. So far, so good.
Unfortunately, I couldn’t flash it my Zephyr project. More digging around, using the Nordic Tools and I discovered that the West tool couldn’t detect the device. Strange, as I could flash it with simple Arduino sketches. I trawled the documentation. Tried changing drivers. Updated the bootloader. Nothing had any effect.
During the umpteenth reading of the Zephyr docs, I finally realised why:
Flashing Zephyr onto the nrf52_adafruit_feather board requires an external J-Link programmer. The programmer is attached to the X1 SWD header.
I have emphasized external in the quote above. I totally missed that key piece of information. More googling and I learn that Segger J-Link is a special protocol and that a small unit is required to interface your computer with the board! Everything fell into the place. The different drivers and the talk of the SWD header.
Unfortunately, my Adafruit boards don’t have a SWD header. Fortunately, the board has space and solder pads for one to be added.
I found a J-LINK device on The PiHut which I ordered, along with a short cable. I’ll wait for that to arrive before I attempt to solder this header onto the board. I’m going to need some steady hands!!
J-Link Device arrived and connected up. Managed to solder on the header without any issue.
I think hooked up my newly purchased J-LINK device. Side node here – I ordered a serial cable with this as PiHut said it was recommended. One came in the box, so the extra one I ordered was redundant! I’ll be writing to them about that.
Running the nordic command shows it has found the J-LINK connector!
I was aware that the Expressif ESP32 supports the new Bluetooth LE Mesh protocol, and as Bluetooth Low Energy would help stretch battery life, it seemed like the natural place to start my investigations.
I was initially going to try the WiFi mesh, but it didn’t really seem to suit devices like temperature sensor as they are actually asleep most of the time. If nodes in the mesh keep turning on and off, the other devices in the mesh would be constantly reorganizing themselves to plug the gaps. I do want to learn about ESP’s WiFi mesh, but for now, I’ll focus on Bluetooth
Documenting my progress
Rather than try and put a post together at the end, I’m going to try and document my progress as I go, with additions to this post each time I do something significant.
I’ve already got the ESP-IDF environment setup and have two different dev boards. I’m going to try and approach this in stages
Copy one of the sample projects and get it running
Add another node
Send data from one node to another
Add MQTT and WiFi to get data out of the mesh
9th July 2019
I pulled down the ESP-IDF code from their mesh branch and spun up on the samples. After faffing around with the menuconfig settings, I got the Node example compiled and deployed onto the device. It also appeared appeared in the Nordic iOS Mesh App.
Once I tapped on the node, I was able to tap “Identify”, which pulled back more information. I think this is what novelbits called “Invitation”. I then tapped “Provision” and after a few seconds, and a lot of logging from the device, I had the first Node in my mesh!
Now that I had my first mesh node, I quickly realised why the Expressif code was only at version 0.6 – none of the provisioning data was being saved. This meant that each time I flashed the device, I had to provision it again. This became annoying after the fifth time, so I started digging into the actual provisioning process, to see if I could put in something temporary.
I was digging around on google and I came across the Zephyr RTOS. In their examples, they had a simple 2 node mesh demo. The readme page states that no provisioning is required, and whilst it’s insecure, it’s sufficient for the demo. In their code, I could see a few lines of code where they manually provision the device with their own network and device keys.
This seemed ideal for my tinkering. I also found reference to the Zephyr code in Expressif’s news release about their BLE Mesh, where they state they are basing their implementation on top of the Zephyr . This meant I could probably find simple code in the esp-idf repo.
Running this code on the device resulted in it saying that provisioning was complete.
After more digging around the ESP-IDF examples, I came across some testing code, which appeared to provision using the esp code.
Try as I might, I couldn’t get that to work. Just kept reporting an error of -22.
UPDATE 13th August: During some experimenting with how to bridge the mesh network with MQTT, I managed to get this code working eventually, meaning:
After more attempts to provision the device directly, I’ve decided to kinda give up. As I mentioned, the Zephyr code is easier for me to understand at this stage, so I’m going to try and get a build of the Zephyr samples running on my ESP32 boards.
After hours of playing around trying to get the Zephyr SDK compiling against the ESP32 toolchain, I decided to stop. I found an excellent resource at over on the Bluetooth SIG website, called “An Introduction to Bluetooth Mesh Networking“. The samples in their course use the Zephyr SDK and the BBC Microbit. I had a glance though it and most of the main concepts are covered, so I think I’ll order some BBC Microbits and run through it.
I also came across an interest post at https://hutscape.com/, which is worth checking out. The author, Sayanee, uses an Adafruit board to build a UV sensor. Pretty cool. At £26 (and no Friend Node support in the Nordic SDK), I decided against buying any for the time being.
I got a BBC Microbit and tried the Zephyr mesh_demo code. After more mucking around, I managed to flash it with their code.
As suggested by the Bluetooth study guide, I turned on the logging and then
Hardware development is tough! That said, these microbits are perfect for me to dabble in the fundamentals of Bluetooth Mesh and to get to grips with the models. Hopefully there is enough space for me to try my own code. Perhaps it’s possible to compress the Zephyr RTOS runtime down a little??
Been reading about how to figure out the size of the runtime. You just run the command ninja rom_report
I don’t know what those numbers actually mean. I had assumed bytes, but that would mean the bluetooth library, if measured in bytes, was around 50KB and I know that’s not right.
I experimented with the Zephyr mesh_demo sample, but couldn’t make it work. Kept getting error codes when trying to send messages. I tried to tweak it here and there, but I was just strumbling around in the dark. I returned, instead, to the Bluetooth developer guide and gave that go. The guide starts at the Switch module.
The sample code wasn’t up-to-date with the latest Zephyr code, so I had to tweak it somewhat, but I got it to compile and, amazingly, it worked.