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The Case of the Unchanging Config

2026-04-09T00:00:00Z

Last week I was attempting to make it so I could share pictures on IRC directly from my client. This sounds simple, but it involves a bouncer¹ that proxies the request to a standalone image hosting service that I had to modify to be compatible. At one point my testing loop was:

Make a change to the hosting service
Commit it
Tag a new release
Wait for it to build
Update the version I’m running on my server
Reconfigure the bouncer to pass the new parameter or change the URL or whatever
Try uploading a photo from my phone
Realise I’ve overlooked something and go back to step one

I could have set up a local copy of everything and tested it sensibly. I should have set up a local copy of everything and tested it sensibly. But it seemed like such a trivial change, and setting up the whole environment seemed like such a pain. After the third or so iteration of failure I was pretty annoyed with myself, computers, and basically everything.

My biggest annoyance was that my bouncer would not pick up the new URL from the config when I changed it. It’s meant to reload the config when it receives a SIGHUP, and it claimed to in the logs, but I could clearly see it was still hitting the old URL. Restarting the bouncer to update the config is a pain, as it disconnects me from all the IRC networks, and has to reconnect to them all, reauthenticate, etc. It also mildly spams everyone who shares a channel with me².

When I finally got everything working I had a look at the bouncer source, and thought I’d spotted the issue. I raised a bug report, ending in this remark:

It looks like the config is reloaded properly, but the handler for uploads is created once at startup and has its own copy of the uploader, so effectively snapshots the config to whatever it is at startup:

fileUploadHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    cfg := srv.Config()
    h := fileupload.Handler{
        Uploader:    cfg.FileUploader,
        DB:          db,
        Auth:        cfg.Auth,
        HTTPOrigins: cfg.HTTPOrigins,
    }
    h.ServeHTTP(w, r)
})

I’m not quite sure what I thought I saw there, but that’s not right. I want to call it a hallucination, but that feels like a very overloaded word these days. I guess I was just seeing what I wanted to see, and that was a good excuse to stop investigating. Still, even if I misidentified the cause, the bug was still present, right? … Right?

The Science of Deduction

When the developer got back and said he couldn’t reproduce my issue, I went back to my install and immediately reproduced it. With a calmer head, I figured it was probably something with my particular set up. First thing to check: am I actually running the version I think I am?

Unfortunately the bouncer doesn’t actually seem to expose the version anywhere that I can see. It’s not in the logs, it doesn’t have a -version flag, and none of the IRC-based status commands seem to include it. But I know it’s a Go app, and I know Go embeds the version information. go version -m <binary> will dump it all out, but the binary is inside a Docker image, and the Docker image is one of my nice, minimal, artisanal ones so doesn’t ship a go binary. No problem, docker compose cp bouncer:/bnc ./bnc yoinks the binary out of the container, and then dumping the version shows that, yes, I am running the version I thought I was. Hmm.

The next tool I reached for in my toolbox was strace. Maybe it’s not actually reading the file for some reason? I immediately executed strace -p <pid> -e trace=openat,open,read,pread64 -f without having to look any part of that up. Yep. Definitely. Then I edited the config, HUP’d the bouncer, and saw that it was… reading the config file. As it’s meant to. By default strace truncates strings to 32 bytes, so I couldn’t actually see the line I’d changed. Some more definitely-not-RTFMing later, and rerunning it with an extra -s 65536 let me see the full config. Surprise! The config hadn’t changed!

To confirm my findings, I used docker compose cp again, this time yoinking the config file from inside the container. The inside config file was definitely different to the outside config file. What? My hypothesis at this point was “something something Docker nonsense”. I mount the config as read-only, and was wondering if that meant that Docker was doing something weird instead of just bind mounting it. A quick trip to /proc/<pid>/mounts showed that it was, in fact, not doing anything weird, and was just bind mounting it.

If the file is bind mounted, then surely it’s the same file? I ran stat on the file on the host, noted the inode number, then pondered how to actually run stat on the file inside the container, given the aforementioned awkwardly minimal image. The solution was easy: access it via /proc/<pid>/root/. I could’ve saved myself a bunch of docker compose cp if I’d thought about that earlier. Oh well. The inode of that file was different. What?

The answer was DNS. It’s always DNS. Oh, sorry, force of habit. I meant the answer was vim. I was editing the config in vim, and when it saves files, by default, it writes the new content to a temporary file and does an atomic rename. That’s normally a good thing: it prevents corruption if the write fails midway through³. In this case, though, that means the new file has a new inode. Bind mounting a file binds to the inode, so the container just keeps clutching onto the original config from when it was started, blissfully unaware that the party has relocated down the street.

This problem is likely to happen whenever you bind mount a file into a container. When I mentioned this to a friend, he immediately responded “oh yeah, never do that”, and went on to describe the horrible hacks he’s had to add to Ansible to sidestep the issue. The nicer solution is to just bind mount an entire directory if you can, as then it doesn’t matter what happens to the files within it. I really like having the config files sat alongside the Docker compose files, though; having to create a directory just to work around some bind mount weirdness upsets me.

Now I knew what the problem was, I found there was an issue raised against Docker twelve years ago⁴. The first response was “that’s expected”, and I fully agree with the author: “respectfully, that might be expected by you, but it was not expected by me”!⁵ As a result of the issue they added a nice note to the docs:

Note: Many tools used to edit files including vi and sed --in-place may result in an inode change. Since Docker v1.1.0, this will produce an error such as “sed: cannot rename ./sedKdJ9Dy: Device or resource busy”. In the case where you want to edit the mounted file, it is often easiest to instead mount the parent directory.

But in the intervening twelve years, both the note and the functionality described have gone missing. Ho-hum.

I found it interesting how I’ve only just hit this problem, given how long I’ve used Docker. But I realised that almost everything I run I’m happy to just restart. Cattle, not pets, and so on. My IRC bouncer is one of the few exceptions to that. The only other thing I regularly hot reloaded was Centauri, my reverse proxy, but that had a whole config directory mounted because it was shared between containers, so nicely sidestepped the foot-gun.

So lesson learnt: check for weird bind mount issues before raising issues about config hot reloading. It’ll join the esteemed company of “maybe the drive is full and causing completely unrelated problems?”, “perhaps everything is dog slow because the kernel ran out of entropy?”, and “did systemd sneakily take over that functionality while you weren’t looking?” in the troubleshooting checklist.

An IRC bouncer is basically an always-on proxy. It connects to the IRC networks for you, then your clients connect to your bouncer. The bouncer can then send incoming messages to all your different clients, cache them when you’re offline and replay them later, and lots of other nice things people take for granted in their chat apps these days. ↩︎
Join/part/quit spam is part of IRC, and clients have ways of handling it, but I still feel bad about doing it excessively. ↩︎
You can disable this in vim by setting backupcopy=yes. Good luck redoing all the debugging if you ever accidentally remove that from your vimrc, though! ↩︎
Which is weird, because Docker can’t possibly be that old. That would make me much older than I’m prepared to accept. ↩︎
If you read the thread they didn’t actually mean to sound so dismissive, but it’s still pretty funny. “Yes, it’s expected that the foot-gun causes your foot to hurt. Duh. What did you expect?” ↩︎

Monthly Meanderings: March 2026

2026-04-01T00:00:00Z

Since last month’s update I’ve been unpleasantly reminded that I’m middle aged, through the medium of a dodgy knee. There’s nothing quite like not being able to stand up without groaning to underscore that you’re not young any more. The ongoing game of “will this seemingly mundane activity make my knee go funny again?” is a delight to play, too. I’m great at it.

Website updates

Two new blog posts this month: the longest way to represent a date is a short thought experiment on absurd date formats, and modern CSS is fun goes through some neat new CSS features I’ve used recently for this site.

I did some design tweaks this month: headers now have a blue background behind them¹, and a lot of components have been redesigned to have a consistent style. You can see that component in action in the new “now playing” widget I’ve added:

VersaEmerge — Redesign Me Fixed at Zero Scrobbled 12m ago

Instead of each component defining its own styles (which were mostly copied and pasted), there’s now a single class that handles the drop shadow, border, background colour, and the optional title. It also applies a consistent format to elements that are clickable: they use the blue accent colour for their borders, and have a glow effect shown on hover.

The now playing widget is part of a larger bit of work I did on importing some music stats. I’m pulling in the data from my Navidrome instance. A new music page shows my most listened albums and artists. Navidrome doesn’t store a complete play history, just the last play and the count, so I can’t do “what I listened to last month” stats until next month.

Other projects

Other than a minor bug-fix update to contempt, my Dockerfile templating/updating tool, I’ve not done much on my other open source projects. I’ve got a bit more work to do finish migrating all my repositories from GitHub to my private Forgejo instance. I’ve also been thinking about mirroring my public repositories to Codeberg so there’s a non-GitHub way to access them.

Entertainment

I apparently only watched a single film in March:

The Substance

2026-03-18

I really didn’t get on with this. It’s too long for what it is, and over-the-top in a way that just didn’t work for me.

Demi Moore and Margaret Qualley were great, but nothing else really was. The cinematography and sound design were too affected, the plot was pretty shallow and obvious, most of the body horror fell into the uncanny CGI valley for me.

It’s not completely without merit: there were around 40 minutes in the middle where I was really into it, but that’s not really enough given it’s closing in on a 2.5 hour runtime.

There’s something to be said for the message it’s presenting about women in Hollywood, too, but it was very heavy handed. Dennis Quaid’s character is even called Harvey; it’s not so much a subtle nod as a sledgehammer to the face.

Instead of films, I’ve been watching a bunch of TV. After devouring The Pitt last month, I struggled to find something to fill the hole it left. I settled on catching up on Chicago Fire and Chicago P.D.. They’re both mostly about getting things done without personal drama becoming the primary focus. They’re not quite as grounded as The Pitt, but at least they’ve not completely gone off the deep end like 9-1-1 where the first responders end up in space somehow?

I’ve also watched the first two episodes of SNL UK. I didn’t have very high expectations, and it gave me a pleasant surprise. Both episodes so far have some hilarious sketches, and are obviously written by British comics with the typical darker, more sardonic humour that separates us from the USA.

Last but not least, board games! I spent a weekend at a tabletop/LAN event with friends, so got to physically play some games for a change. I also kept up with some turn-based games on Board Game Arena, as usual.

6 plays
4 plays
4 plays
4 plays
3 plays
3 plays
3 plays
2 plays
2 plays
2 plays
2 plays
2 plays
1 play

Around the web

Warranty Void if Regenerated

Some really cool speculative fiction about a future where all software is written by LLMs, and the social effects that may have. Unfortunately the story itself is written with an LLM, and that becomes painfully obvious about a third of the way in. By that point I was already hooked, though.

My 2-step process for AI-free blogging

Speaking of LLM-generated text, this short piece by Manuel Moreale made me laugh. I’m by no means anti-LLM, but I really hate people publishing the output like it’s their own work. It breaks the social assumption that the writer put more effort in than the reader, and makes me wonder how much is hallucinated.

25 Years of Eggs

An interesting applied use of coding agents. I’m a sucker for personal statistics. I have no explicit desire to keep my receipts, or generate graphs of my egg consumption, but seeing the graphs makes me question that. The journey to get there is a great read, too.

I made a one-page notebook

The clever paper folding is interesting, but I really like some of the small touches on the page. There’s a nice little “in reply to” callout providing context at the top of the page, you can click to rotate the image further down, and there’s a details element containing a textual version of it. It has that great ‘small web’ vibe of someone who really cares about what they’re doing.

Workers who love ‘synergizing paradigms’ might be bad at their jobs

I haven’t read the full paper, but the summary given by the article is equal parts interesting and amusing. They developed a “Corporate Bullshit Receptivity Scale”, what more is there to say?

It’s meant to resemble painter’s tape, but I’m not sure quite how well it works. ↩︎

Modern CSS is fun

2026-03-17T00:00:00Z

I’ve been doing a bunch of CSS tweaking recently, and keep being surprised by how nice modern CSS is to work with. As someone grey-haired enough to remember writing HTML without CSS, it’s amazing to think how far along web technology has come¹. I wanted to demonstrate some of the handy bits and pieces I’ve used recently.

:has

The :has selector allows you to effectively query for child elements. While a span will match a <span> within an <a>, a:has(span) will match an <a> that contains a <span>. This really shines when combined with more complex selectors, for example:

input {
    border-radius: var(--border-radius);

    &:has(+ .results:not(:empty)) {
        border-bottom-left-radius: 0;
        border-bottom-right-radius: 0;
    }
}

This is part of the styling for my film search box. When the search box is presented initially it has fully rounded corners. But when it is followed by a non-empty results element, it removes the rounding on the bottom corners so that the border continues in a straight line down into the results. You can see it in action below; just enter a few characters (like “the”) to get some results:

You could achieve the same effect by having JavaScript add a class to the <input> element, but I’ll take a CSS solution over a JavaScript solution any day.

Nested rules

You probably spotted this in the example above. It’s what finally made me switch from SCSS to plain CSS. If you have a rule for .foo and a rule for .foo .bar you can just nest them. Not only does it save repeating yourself an awful lot, it keeps everything organised nicely. For example, the CSS for my film list embeds looks like this:

a.film-list {
    display: grid;
    grid-template-areas: "header images" "description images" "meta images";
    grid-template-columns: 1fr auto;
    grid-template-rows: auto 1fr auto;
    row-gap: var(--small-space);

    @media (width <= 800px) {
        grid-template-areas: "header" "description" "images" "meta";
        grid-template-columns: 1fr;
        grid-template-rows: auto auto auto auto;
    }

    & + & {
        margin-top: var(--medium-space);
    }

    h3 {
        font-size: var(--font-size-xxlarge);
    }

    .description {
        /* ... */
    }
}

Everything is wrapped up in a single bundle, including the @media rules for changing the layout on smaller screens, the lovely little & + & rule that adds some extra margin if there are two lists in a row, etc. The & syntax refers to the parent selector, so & + & in this case is the same as a.film-list + a.film-list: it’s very handy! The best part about this is that it’s the exact same syntax as SCSS, so converting is easy². The styled element looks like this:

Watched films ranked

Every film I’ve watched since I started logging, ranked.

Obviously super subjective, and subject to change often and arbitrarily.

264 films

Media range syntax

Once again, you might have spotted this in the previous snippet. I’m not deliberately teasing things, I promise! Back in the day, you did media queries like so:

@media (min-width: 1000px) and (max-width: 2000px) {
    /* some rules that work for screens at least 1000px wide and at most 2000px wide */
}

I always hated this syntax. I always got muddled up as to whether I wanted “min” or “max”, and whether they were inclusive or not. It’s easy to reason through, but it never came naturally. Fortunately you can now just use ranges:

@media (1000px <= width <= 2000px) {
    /* some rules that work for screens at least 1000px wide and at most 2000px wide */
}

I find this style so much easier to write and understand.

Anchor positioning

Trying to dynamically position one element next to another used to exclusively fall within the purview of JavaScript. Fortunately anchor positioning fixes all this. I use this in the film search field I showed above:

.film-search {
    input {
        anchor-name: --film-search-box;
    }
    .results {
        position: absolute;
        position-anchor: --film-search-box;
        position-area: bottom center;
        position-visibility: always;
        width: anchor-size();
    }
}

This does lots of fun things. The .results element is anchored to the input field (via the --film-search-box name), and it’s positioned on the bottom, directly under the anchor. The position-area rule describes a 3x3 grid, with the anchor at the center, so top left would put it diagonally adjacent to the anchor. Next, position-visibility keeps the .results element visible when the anchor isn’t; otherwise when you scroll the anchor off the screen the results would immediately vanish. Finally, the special anchor-size() function makes the .results element take up the same exact width as the anchor.

All-in-all, this puts the results exactly where I want them, without having to deal with any JavaScript at all. I can see how it’d also be amazingly useful trying to do tooltips or other forms of ‘floating’ content too. You can even leave the positioning up to the browser, giving it hints about which order to try, or what property to optimise for (e.g. you can say “anchor to the left or right, whichever has more horizontal space”).

attr() function

This one blew my mind a little. In some of the elements on the site, I’ve added a little label to the top. It looks something like this:

It’s meant to just be a visual flourish, not a semantic title or anything, so I initially just added a ::before selector to each element, customising the content to have the right value. I didn’t like the duplication, though. Now, instead, I do this:

&::before {
    content: attr(data-title);
}

Each component defines its title in a data attribute: <div class="raised-box" data-title="an example">, and the attr function plucks it out and puts it in the content rule. It’s worth noting that this is only widely supported for the content rule, you can’t yet use it for colours or dimensions or other things. It still feels a bit magical, though. Like you’re making a reusable, customisable component with just HTML and CSS.

layers

I’d come across layers a few times, but I never found a need for them. It seemed like something you’d only really need with complicated design systems, or something. Then I had a problem and layers were the perfect solution!

The headings on this site have a whole bunch of CSS attached to them. Currently they look a bit like blue painter’s tape with handwriting on them. This style is applied to all headers, and then the various places that don’t want it had to manually reset everything. I got fed up with that, so decided to add a plain-header class which would “disable” the extra styling:

h2,
h3,
h4,
h5,
h6 {
    /* common styles for all headers, regardless */
    font-family: "Chris Hand", sans-serif;
    font-size: var(--font-size-xxlarge);
    color: var(--text-highlight-colour);
    margin: var(--medium-space) 0;
    line-height: 1;

    &:not(.plain-header) {
        /* do fancy stuff if it _doesn't_ have the .plain-header class */
        transform: rotate(-0.15deg);
        padding: var(--smedium-space);
        font-weight: 800;
        filter: drop-shadow(3px 3px 5px rgb(0, 0, 0));

        a {
            background: none;
            text-decoration-skip-ink: auto;
        }
    }
}

This might seem a bit backwards but I want the default to be styled, as those are far more common. I added this change, sprinkled around some “plain-header” classes, tidied up a lot of duplicate CSS, and things mostly worked. Mostly. Some things stopped working. In a few places the headers had slight tweaks, and they stopped working entirely.

It turns out in moving the rules from a plain h2 selector to a h2:not(.plain-header), I’d made them more specific. Previously a selector like h2.special would have been more specific, so its properties would override those from the less specific h2 selector. My first reaction was to try and hack around it. Changing all the overrides to body h2.special would make them more specific again, but I didn’t want to have to remember to do that forever more.

Instead, I defined some custom layers, and put the header definitions in one:

@layer reset, links, headings

@layer headings {
    h2,
    h3 {
        /* etc */
    }
}

The first @layer rule defines some layers that will be handled in a specific order: first the “reset” layer, then the “links” layer, then the “headings” layer, and then anything not in a layer after that. Rules in one layer don’t have to worry about beating the specificity of rules in another layer, because they’re handled separately.

Note that I couldn’t just put the headings in a layer and call it a day: their rules have to come after the CSS reset, and after the normal link styles, as headers have a bit of extra styling for nested links. If the CSS reset weren’t in a layer, then the * { margin: 0; padding: 0; } type reset would apply over the rules from the headings layer.

Using layers is definitely a bit fiddly, and is not necessary for a lot of sites, but it’s a much cleaner alternative to ugly specificity hacking.

Things I’m looking forward to

There are a few things that aren’t (widely) available yet, that particularly interest me:

sibling-index() and sibling-count()

These new functions are available in WebKit and Blink based browsers, but not Firefox. They give you the index of the element within its siblings, or the count of siblings. For the film list component above, I currently have this abomination for the overlapping posters:

&:nth-child(1) {
    z-index: 5;
    left: 0;
}
&:nth-child(2) {
    z-index: 4;
    left: calc(133px * var(--overlap) * 1);
}
&:nth-child(3) {
    z-index: 3;
    left: calc(133px * var(--overlap) * 2);
}
&:nth-child(4) {
    z-index: 2;
    left: calc(133px * var(--overlap) * 3);
}
&:nth-child(5) {
    z-index: 1;
    left: calc(133px * var(--overlap) * 4);
}

These could be replaced with something like:

z-index: calc(1 + sibling-count() - sibling-index());
left: calc(133px * var(--overlap) * (sibling-index() - 1));

As an added bonus, it would scale to any number of posters. index being 1-based not 0-based is a bit unfortunate as it makes using it in calculations awkward (see 1 offset in both of those rules!), but it’s leagues better than writing 5 separate rules.

random()

Currently only available in Safari. There are a few places where I’d like to have slight random variations of the style. Things like elements that are rotated slightly for aesthetics; they look a bit silly if they’re all identically positioned. I also randomise the icons and positions of my rating stars to break up the visual monotony. Here are a few examples:

Currently I do the stars by hardcoding a bunch of classes and having the backend randomly apply one when it generates the markup for stars. Being able to do it in CSS would be great, though.

Mixins

This one’s so far off it’s not even listed on caniuse.com yet. Mixins are another handy feature of SCSS, that allow you to define reusable blocks of rules, then import them when needed:

@mixin fancy-background {
    background: /*...*/;
}

.some-element {
    @include fancy-background;
}

#other-element {
    @include fancy-background;
}

This would be particularly useful if you can’t easily control the markup to add classes to everything. For example, my footnotes are rendered by a markdown plugin, and don’t easily have a way to add extra classes to them. To style it the same as another element, I currently duplicate a bunch of rules between them both. Mixins would allow me to define those rules once, and then import them in both places.

Aside from JavaScript, which seems to just endlessly reinvent new frameworks and ways to make the most sprawling dependency tree possible. ↩︎
It also means that if your website’s syntax highlighting library doesn’t seem to understand nested rules, you can just pretend your perfectly valid CSS is actually SCSS and it’ll magically work. Grumble, grumble. ↩︎

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. ↩︎