2026-01-05 08:00:00
The other day I took apart an old smoke detector. I looked at it for a bit until I thought I'd figured out how it works, and then I thought, hey, why not write a quick blog post about it, maybe someone else will find it interesting, too. And so I did and I put the post online.
Small problem though: I completely misunderstood how the thing actually works. Whoops.
Thankfully some folks on Mastodon pointed it out to me, so I did some research, realised what I'd gotten wrong, and corrected my post. Fixed and done, problem solved. But a bit of an uncomfortable feeling remained with me.
At the end of the day this is really no big deal, and arguably I learned more by posting the wrong thing than if I hadn't written about it at all, because now people corrected me and so I was, let's say, encouraged to look into it a bit more, which I probably wouldn't have done if I hadn't written the post because I would have just assumed that I was right. So ultimately this worked out well for me, even though I have to admit I was a pretty embarrassed when I realised my mistake.
This got me thinking though how easy it is to spread misinformation online, unintentionally or otherwise. We live in a world where everything from AI chat bots to Facebook tinfoil-hatters all the way to the richest and most powerful people in the world are spitting out a constant stream of misinformation and straight up lies all day long, and by now the web is absolutely drowning in it. And I hate it with a passion.
So my takeaway is this: In a world that's increasingly fake, filled with slop and misinformation and lies and where you can't be sure anymore about what's real and what isn't, I want to make sure that the things I post to the internet are correct. Even if they're as inconsequential and ultimately meaningless as explaining how a smoke detector works. I feel like I owe this to myself, and I also owe it to you, the reader.
It might not make a difference in the grand scheme of things, but it does make a difference to me.
2026-01-04 08:00:00
Last month I've lived in my current apartment for exactly 10 years, which means it's now time to replace the smoke alarms, which you're supposed to do after 10 years. When I was a kid, I always took everything I could get my hands on apart to see what it looked like on the inside, much to the dismay of my parents at times. Now, several decades later, things haven't really changed all that much. So, before bringing the old smoke alarms in for recycling, I decided to take one apart to see what's inside. 1
Here's what the smoke alarm looks like intact, and after prying it open (and almost losing an eye in the process because a piece of plastic snapped off and shot right past my face - oops!) we can see that there isn't very much in there at all.
(1) is the battery (I already snipped the wires so the thing wouldn't accidentally go off in my face), (2) is the piezoelectric speaker (the thing that goes "beep"), and (3) is the smoke detector itself on a small circuit board. Here's a closer look at the internals:
There's also (3) a button to test the functionality and (4) an LED which blinks in regular intervals to indicate that the device is still working. And there are a few electronic components on the back of the board.
So what's inside the smoke detector?
Surprisingly, almost nothing! In fact, there are only two things in there: (1) an LED, which is a light source (infrared, I assume) and (2) a photo sensor, which is a light detector.
So how does it work?
The photo sensor sees a certain amount of light that the LED emits. Since the chamber is black and largely closed with just a few openings around the sides, almost no ambient light can get inside and the amount of light that the photo sensor registers is always the same, no matter if the smoke alarm is in a bright or dark room.
Except when the chamber fills with smoke. Then the photo sensor will see less light than when the chamber is filled with clear air, and that's when the alarm will go off.
I got that completely backwards! Here's how it actually works: The photo sensor and the LED are misaligned, and the path from the LED to the sensor is blocked, which means the sensor can't see much, if any, light from the LED during normal operation. However, when smoke enters the chamber the smoke particles scatter the light, so the sensor can now detect more light from the LED than before, and this causes the alarm to go off. Damn. I should have checked this before writing the post.
Thanks to Lapo Luchini and ClickyMcTicker on Mastodon for correcting me!
It's such a simple thing, and yet it does exactly what it's supposed to do. I love seeing well-engineered solutions like this!
I should mention, there are smoke detectors that are filled with a radioactive material. I double and triple checked to make sure that this wasn't one of those before taking it apart. If you take one apart, make sure you know what you're doing!
2026-01-02 08:00:00
Over the last few days I read a lot of end-of-year blog posts around the small web, and I noticed that by reading personal blogs you get the full range of human experiences. Some people are doing really well and are in a good place, and some are unfortunately struggling due to health issues, financial uncertainty or the loss of a loved one. Life is unpredictable, sometimes things are great and sometimes they really aren't. I haven't written a 2025 roundup this year, but there have been some challenges for me as well, mostly regarding my health which hasn't been great these last few months, and it still isn't where I'd like it to be. There are also some changes in my professional life. But these are topics that I might talk about at some other time; suffice it to say that 2026 is going to be a challenging and interesting year for me.
I hope you are doing well, I wish you a happy new year wherever you are and whatever 2026 has in store for us all, we'll deal with it to the best of our abilities.
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2025-12-26 08:00:00
Last Linkdump of 2025! And maybe last post of this year too, I don't know yet. I just checked, and this is the 108th blog post I'm writing this year. I'm too lazy to do it now, but if I stitched them all together I would get at least a small book out of it. Which means I've written a book this year! Granted, a very confusing and disjointed book, but still. I always wondered how people write books, because it takes so long to write anything and a book is a lot of text. Well, this is how. Write consistently over a long period of time. In fact, this is how you do anything worthwhile, isn't it? Do it consistently over a long period of time. Wait, did I just learn a life lesson here?
Anyway, I think this is a good opportunity to say a big thank you to you all for reading my ramblings week after week, and for getting in touch with me via e-mail or Mastodon. Writing this blog has become one of my favourite hobbies, and this is in no small part thanks to the community of fellow bloggers, readers and online friends that has developed around it. Thinking about it, this year I received messages from people in both North and South America, Europe, Asia and Australia/New Zealand, which is absolutely mind-blowing!
I hope you're all having a great holiday season wherever you are in the world, and I'm looking forward to continuing this in 2026.
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2025-12-22 08:00:00
A few weeks ago a copy of Unix V4 which was thought to be lost was discovered on a storage tape at the University of Utah. It was then sent to the Home Computer Museum in California, and well, they managed to read it out and put its contents on the Internet Archive.
I haven't seen any news articles about this yet, but fellow Mastodonian Flexion gave it a try and posted about it, which is how I came across this. So I had to try it, too.
Thankfully someone put up a tutorial with the necessary files here. All that's needed is a pdp11 emulator. I'm using the one from the Open SIMH project which I could easily download on Arch Linux from the repos, it's just called simh.
And from there it was just a matter of following the tutorial. I had to get four files:
I put them all in the same folder and started the pdp11 emulator with the ini script:
$ simh-pdp11 install.ini
Then I followed the tutorial by typing out the following commands:
=mcopy
'p' for rp; 'k' for rk
k
disk offset
0
tape offset
75
count
4000
=uboot
k
unix
mem = 64530
login: root
# sync
# sync
# sync
# ^E ; end emulation
After Ctrl+E the emulator can be quit with Ctrl+C and then restarted with the boot script:
$ simh-pdp11 boot.ini
After typing k and unix I got the login prompt and could log in as root:
k
unix
mem = 64530
login: root
#
And there we go, Unix V4 from 1974!
So what can we do with that?
Honestly, I have no idea. Not too much probably, but it's really cool to explore and just to see it running. This system is almost a decade older than I am, and it feels kind of alien and still familiar at the same time. It was made at a time when computers were the size of refrigerators and often didn't even have monitors yet but instead printed their output on a piece of paper. And yet It's the ancestor to all modern day Unix systems (including MacOS) and also at least the spiritual ancestor to Linux, and that's exacty what it feels like using it. Like an early version of these systems. Relatively primitive and missing a lot of features that make using the modern systems easy, but definitely familiar.
It's fascinating to see how much it has changed in the last 50 years, but also how much has stayed the same. It's a bit like driving in a car from the 60s or 70s. They are incredibly barebones by today's standards, but still unmistakably just an earlier version of what we have today and if you know how to drive a modern car, you will also be able to drive one from 1974, just like you are able to navigate around a Unix system from 1974 if you're familiar with it's modern descendants.
2025-12-19 08:00:00
In 1981, a new TV station dedicated to playing music videos appeared in the US. It famously started its programme by playing The Buggles' Video Killed the Radio Star. In 1987, MTV Europe began its broadcast with an equally fitting video: the Dire Straits song Money for Nothing, which opens with the line "I want my MTV", sung by Sting. I was too young to have been around for this, but I remember watching MTV and its German counterpart VIVA a lot when they were at their peak during my teenage years in the 90s.
I also remember them playing less and less music and more and more "reality TV" shows in the 2000s, which caused me (and everybody else) to lose interest in watching them. Today, VIVA has been dead for years, and now MTV at least over here will stop playing music altogether, which means its spirit is also gone. Nothing lasts forever I guess, and since YouTube appeared on the scene this development was probably inevitable, but it's still kind of sad to see. Today of course you can see any music video you like at any time online, but it's just not the same, is it? Rest In Peace, MTV!
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