Chameth.com - posts like further-adventures-in-3d-printing but not adventures-in-3d-printing, why-you-should-be-using-https

Home Automation Without the Megacorps

2025-05-21T00:00:00Z

I first experimented with home automation in 2016, by picking up a Samsung “SmartThings” hub. It was terrible. The UI to configure things was slow and clunky, firmware updates were applied whether you wanted them or not, and everything stopped working if their cloud services stopped. You were also locked into whatever integrations they deigned to support, of course. After that broke for the umpteenth time I scaled back and for years the closest I got to home automation was a couple of Hue bulbs.

Recently I’ve been building it out again, though. This time using off-the-shelf components that interop using Zigbee, open-source software, and some code I wrote myself. It’s great; it runs entirely locally and has had basically zero downtime. The Zigbee ecosystem lets me integrate all sorts of things without having to spend lots of money on “smart” alternatives. I think I’ve spent less on this incarnation than I did on the original SmartThings hub all those years ago (even without adjusting for inflation!).

My current setup

I run everything on a Raspberry Pi 4, with a Sonoff USB Zigbee adapter based on the CC2652P chipset¹. Interfacing with the Zigbee stack is handled by zigbee2mqtt (z2m for short), an open-source project that basically bridges your devices to an MQTT broker². When a device reports some data, it will send a new message over MQTT; when you want to make a device do something you just post a message back. It’s incredibly lightweight, but supports a huge array of devices out of the box. And as it’s just using MQTT, it’s trivial to integrate with other software or build on top of.

I know a lot of people building out this kind of home automation use Home Assistant, but I don’t get on with it terribly well. It felt incredibly sluggish, and the entire project is just a bit… much. I want a binary or package or docker image I can just run, not an entire operating system. That’s not how computers are meant to work! In contrast, z2m is simple to set up, super light weight and responsive.

Anyway. z2m exposes Zigbee devices over MQTT, so I wrote some code in Go to connect to the MQTT broker, and listen to the messages. It’s grown a bit beyond this now, and I’m skipping some boring bits like error handling and JSON parsing, but at first I had something like:

for {
    message, topic, err := c.ReadSlices()
    
    if string(topic) == "zigbee2mqtt/desk-button" {
        if strings.Contains(message, "single") {
            c.Publish(nil, []byte("{\"state\": \"TOGGLE\"}"), "zigbee2mqtt/room-lights/set")
        }
    }
}

I think I actually made this harder to read by trying to simplify it here, but hopefully you can follow that it was relatively straight forward to listen for a particular action to happen (in this case me “single”-pressing on the device called “desk-button”) and then make another device do something in response (toggling the state of the “room-lights” device).

So what actually are these devices? At present in z2m I have the following:

Some generic buttons
An air quality sensor (USB powered), and a separate temperature sensor (battery powered)
A light switch
Some 240V relay modules, that I use to turn non-smart devices on and off
Some USB relay modules, for the same purpose
Some “smart” plugs that I mostly use to monitor power usage
A motorised blind roller

I think all of these are either Tuya or Moes branded, and were all sourced from AliExpress. You can get the same things from Amazon or elsewhere, but they tend to be 3-4x more expensive for the same product.

One of the cool things about Zigbee devices is that the powered ones work together to create a mesh network, so you don’t have to worry about network repeaters or signal strength like you do with Wi-Fi networks. z2m even makes a map showing the connections:

The network map produced by z2m. You can see how all the powered devices form a mesh that the lower power ones can connect to.

Some interesting automations

A Zigbee relay spliced into the power cable for the fan

So what do I actually do with all of this? Some of it is just what I’ll call “laziness automation”: I want to be able to turn on the lights without getting up and walking to the light switch. So there’s a Zigbee button on my desk that does it. Then there are some less manual automations: my blinds are automatically closed at sunset³, for example. It feels a bit trivial, but it’s surprisingly nice just not to have to think about that at all.

Another nice quality of life automation is the light I have above my monitor. It’s USB powered, and I now have it going through a Zigbee USB relay that lets it be toggled on and off. Then I have a small agent running on my desktop that turns the light on when the computer is unlocked, and off when it locks or shuts down. I keep meaning to make a “film mode” that detects when I’m watching a film, and turning all the lights and blinds down, but I haven’t got around to it yet.

The most complex automation is probably for a window fan. It’s not smart in any way, so I cut the power cable and inserted a Zigbee relay. The whole thing is housed in a little project box to keep it secure. The relay basically acts as a switch: the live wire leading to the fan runs to the “normally open”⁴ contact, while the upstream power goes to “common”. When the relay is told to turn the fan on, the two get connected and the fan gets power. Oh, it’s also not actually a window fan, but I designed and 3D printed some adapters so that it sits right in the window.

So now we have a window fan that can be turned off and on automatically. But I don’t want to have to press a button to do that. I’m lazy, remember? Instead, I made it so that the Go code constantly monitors the temperature reported by the air quality sensor, and queries the free OpenWeatherMap API to get the rough temperature outside. It can then turn the fan on if the room is too hot, and outside is cool enough to make a difference (there’s no point in blowing hotter air in!).

A graph of room temperature, showing the effect of the fan being turned on and off

I don’t want it to do that all the time though. The room doesn’t need to be cooled if I’m not around. There are various Zigbee presence sensors you can get, but the cheaper ones seem to be of dubious quality. Instead, I wrote some code to guess whether I’m present. It uses the state of the monitor light as a proxy for “is the computer in use”, and then makes some guesses based on the last time the computer was used and the current time (if I turn the computer off at midnight it probably means I’m going to sleep; if I turn it off at 2pm it probably means I’m going out somewhere).

You can see in the graph that the fan has a decent impact on temperature. I coded it to cool the room to 19 degrees, but then not turn on again until it was above 20. This prevents it flip-flopping on and off constantly. You can clearly see the pattern in the graph, as it actively cools and then slowly the room warms back up. This arrangement is much better than being woken up at 5am because it’s painfully cold. Trust me.

Bonuses: metrics and 3D printer

One of the things my custom Go code does is collate all the various stats reported by the Zigbee devices, and inserts them into a VictoriaMetrics database. I originally hosted this on the Pi itself, and it performed fine, but I’ve since moved it onto a server so that I can use it for some other things as well.

I set up Grafana to point to VM, and can create dashboards showing power usage, what devices are turned on when, and a bunch of environmental conditions. This also makes it easy to spot how good the data coming from the devices are. For example, the air quality sensor reports a figure for the amount of Carbon Dioxide in the air, as well as the amount of Volatile Organic Compounds (VOCs). The graphs are basically identical, but on a different scale. It turns out this particular device has no actual way of detecting CO₂, so it just “calculates” it from the VOCs figure. Useful to know if you want to actually use that data.

Recently I came across a go library for interacting with Bambu Lab printers, so I’ve also hooked that into my automation. It exports metrics about the printer, so I now have a way of seeing what’s going on when I’m not physically present⁵. I even added a HTTP endpoint (exposed over Tailscale) that shows pictures from the built-in camera.

On the automation front, I’ve made it automatically turn off the printer’s light when it finishes a print, and also added push notifications via PushOver whenever the state changes. No longer will I be sat in another room blissfully unaware it ran out of filament seconds after I walked out the door!

Was it worth it?

These days you could probably just buy some kind of ‘smart home’ hub that works well enough, and do most of what I’ve done with a lot less effort and no coding. I’m still of the opinion that for something so essentially local, it should itself be managed entirely locally. I don’t trust companies like Google or Amazon not to kill their products, or change or remove an API I rely on.

Obviously the “Not Invented Here” approach of coding everything yourself doesn’t suit everyone, but as someone who enjoys coding and enjoys having things work just so it works very well for me.

It turns out the chipset is important. I initially used a similar Sonoff dongle that used a CC2531 chipset, and its performance wasn’t great. It often failed to pair with new devices, and dropped links to existing ones. The zigbee2mqtt docs do explicitly advise against the CC2531 chips for that reason. At the time they recommended CC2652Ps, so that’s what I went with. If you’re starting new I’d go with whatever their latest recommendation was. ↩︎
MQTT is basically a network protocol for publishing and subscribing to arbitrary messages. A broker is the thing that sits in the middle and routes the messages. I use Mosquitto but any will do. ↩︎
They originally also re-opened at sunrise but that was a terrible mistake. Who knew the sun rose so early?! ↩︎
“open” meaning “there’s a gap so it doesn’t work” not “open for business”. This confusion in terminology also extends to drawbridges. ↩︎
I use the printer in LAN mode, which means there’s no way to monitor it from a phone, even if you’re connected to the same network still. ↩︎

Further adventures in 3D printing

2024-08-04T00:00:00Z

The Bambu Labs P1S.

Not quite a year ago, I bought a Sovol SV06 3D printer and wrote about my initial experiences. At the end I joked:

I’m sure there will be more problems, but hopefully I get at least a week or so before anything else goes wrong. Maybe I’ll print an “X days since the last SV06 problem” counter…

That turned out to be more prophetic than I expected. It became a running joke that I’d flip the imaginary “days since” sign back to 0 almost every time I printed. I still really enjoyed having a printer, though: it’s so useful to be able to be able to go from an idea to a CAD drawing to a physical object in the space of minutes or hours. So when Bambu Labs reduced the price of the P1S — a printer generally regarded as about as trouble free as you can get — to £522 including shipping, I splurged on one.

Concerns

I make it sound like that was an easy decision, but I actually ummed and ahed a lot before pulling the trigger. I had a lot of objections to a Bambu Labs printer, and wasn’t quite sure if the price made up for them.

The Bambu Labs printers are designed to be more consumer friendly than most previous 3D printers. You can start a model printing directly from their website or mobile app, which employs a cloud-based slicer that then sends the model down to your printer. This is one of those things that sounds amazing for consumers, but should terrify anyone who works with computers. There are so many ways for a “cloud-connected” printer to go wrong, and with such potentially disastrous results it gives me anxiety just thinking about it.

This is not just theoretical, either. In a blog post with the rather under-stated title of “Initial Investigation in the Bambu Cloud Temporary Outage”, Bambu describe how a server-side error caused printers to start printing unprompted. Users on Reddit reported printers starting in the middle of the night, trying to print on top of other objects that were left on the build plate, and so on. 3D printers can easily start fires; having them cloud controlled is frankly insane.

As a result of that “temporary outage”, Bambu further improved the “LAN mode” for their printers, which allows you to sever its connection from their servers and control it over the network. That’s basically how my old printer worked anyway, so I was happy enough that I could enable LAN mode and ignore all the cloud nonsense.

My other objection to Bambu was more nebulous. Almost all 3D printers are built upon open source software, and some companies like Prusa go out of their way to make their products more open to give back to the community. Bambu don’t really do any of that: I’d be very surprised if they hadn’t incorporated a bunch of open source software into their printers and just ignored the licences¹. I’d much rather give my money to a company doing good, but the only equivalent printer was the Prusa MK4 which was double the price and didn’t come with an enclosure. To add an enclosure kit would have made it £800 more expensive than the P1S, and I just can’t justify that.

Experience

The initial setup of the P1S was a breeze. While the SV06 shipped in parts, the P1S came fully assembled and just needed some packaging and retaining screws removed. These were all clearly marked with large coloured arrows. It’s very much designed so anyone can do it.

I ran through the initial calibration, firmware update, and then put it in LAN mode. Then I just started printing and it went fine. No messing around levelling a bed, or using a sheet of paper to try and set the Z-offset properly; it just worked. It was really loud though. After talking a bit with a friend who’d also bought a P1S, I realised that most of his noise was from the fans, while most of mine was from the servos. A bit of research later and I found out they added servo noise compensation in a firmware update, but I hadn’t run the calibration for it because the initial calibration happened before the update. After doing that, the printer went from sounding like it was impersonating a continental police siren to just being a bit fan-y.

The biggest difference over the SV06 is the speed. I’d swapped the nozzle on the SV06 to a 0.6mm one, and generally printed at a layer height of 0.4mm. The P1S still has its 0.4mm nozzle, and I mostly print at a layer height of 0.2mm. So it’s laying down twice the number of layers, with a nozzle that can extrude half the amount of plastic… And it’s at least twice as fast! Prints that I previously wouldn’t have even attempted on the SV06 are now 8-10 hours on the P1S, without even adjusting the speed or lowering the quality. Here’s a side-by-side comparison:

P1S vs SV06.

The P1S can print eight objects because of its slightly larger bed, while the SV06 can only manage three. The P1S is also printing at a much higher quality. Yet somehow it still ends up being faster. It’s mind blowing.

The other big difference I’ve not mentioned yet is that the P1S is a “core XY” printer rather than a “bed slinger”. That means in order to move along the Y-axis (from the front of the bed to the back), the P1S moves the extruder while the SV06 moves the bed. This makes a big difference when printing tall objects, as they’re far more likely to wobble and come loose when the bed is moving back and forth. It also presumably makes the kinematics a lot easier as the mass of the moving parts is constant, instead of gradually becoming heavier as more and more plastic gets added.

The only failures

I’ve only had a handful of failures since getting the P1S. I had one weird issue where the slicer decided to print some parts extremely slowly, and the print just didn’t work out in those parts; that’s more of a slicer issue, though: after tweaking the model to stop the weird behaviour it printed fine.

The only failure I can directly attribute to the printer was when I tried ironing. This is a process where after printing the top layer, the printer slowly goes back over it at the same height while extruding a small amount of plastic. This is meant to fill in the small gaps between extrusions and give a smooth finish. In my case, though, it just clogged the nozzle and extruder.

At first I thought it was because I was printing too hot: the profile I was using was designed for fast printing, so had to melt the filament rapidly, but there was no way to turn that temperature down just for the ironing pass. I tried another run at a lower temperature and everything clogged again. I then swore off ironing, did a normal print, and everything clogged once more.

At this point I was getting exceedingly good at disassembling the hot end, but also fairly annoyed. It felt like I was using an SV06 again²! I’d previously read some recommendations that you should leave the door or top of the enclosure open when printing PLA, but had never really had any issues so hadn’t bothered. I tried a print with the top propped open and everything worked smoothly again. In hindsight all these clogging issues happened when it was particularly hot and humid outside, which was probably a factor.

Summary

Upgrading to the P1S has made the 3D printer feel more like a tool and less like an additional ongoing project. The speed increase continues to amaze me, as does the increase in quality.

I still think it was valuable to have the SV06 to learn how printers work — you definitely don’t get as much of that from using something so consumer-focused as the P1S — and figure out if I was actually going to use it long-term or whether it was just a fad for me. So it served its purpose, but I’m rather glad to see the back of it in favour of something better in pretty much every way.

And if they did there’s nothing anyone can do about it because copyright doesn’t exist in the same way in China. ↩︎
Although taking apart the P1S (which is a proprietary machine you might not expect to be very user-servicable) was orders of magnitude easier than taking apart the SV06 (which was an open source design). Everything is just much nicer: the connectors are easier to attach and detach, the screws are all a consistent size instead of needing a whole suite of allen keys, and so on. ↩︎