The discreet charm of the infrastructureless

Early in the morning in a European city, I awoke and wondered for a moment where I was. The room was totally black apart from a small glow from the face of my Casio Lineage watch lying on the bedside table. The luminous dial had absorbed sunlight during the day and was now giving off gentle light in the night; enough brightness to read the time.

Infrastructureless #1: sunlight + chemistry = glow in the dark.

The watch had also absorbed sunlight through its face during the day to recharge its battery. In all the time I've owned this watch I've never seen the battery drop below the what Casio calls HI (there are levels MID and LO but I'd only seen MID once when I took the watch from its original packaging)

Infrastructureless #2: sunlight + semiconductors = electrical power.

Clicking the top right button to illuminate the face further I could see the small LED display showing the local time in the European city (the main hands show my home time zone). And on the LED display a little black rectangle under RCVD indicated that somewhere in the night (it turned out at 02:04) the watch had picked up the signal from the DCF77 transmitter in Germany and set itself.

Infrastructureless #3: radio = correct time.

OK, DCF77 isn't totally without infrastructure, but one of the reasons I became a radio amateur is lack of infrastructure. Sure, you're able to read this because of the Internet but it's an incredibly complex system: layers and layers of technology and cooperating entities just so you can read this. 

On the other hand, radio amateurs just send out electromagnetic waves and talk to each other, no intervening infrastructure (well, ok, maybe you can count the ionosphere as infrastructure allowing long distance reception). And that's what DCF77, and the other five transmitters the Casio can receive in the US, UK, China and Japan, are doing: sending waves into the night to be picked up and decoded by whoever is listening.

Also, I'm just fascinated by radio propagation: my ancient Sharper Image clock sometimes picks up the US WWVB in Portugal.

Low-background Steel: content without AI contamination

Somehow I forgot to blog my site: https://lowbackgroundsteel.ai/. I created it back in March 2023 as a clearinghouse for online resources that hadn't been contaminated with AI-generated content. 

Low-background Steel (and lead) is a type of metal uncontaminated by radioactive isotopes from nuclear testing. That steel and lead is usually recovered from ships that sunk before the Trinity Test in 1945. The site is about uncontaminated content that I'm terming "Low-background Steel". The idea is to point to sources of text, images and video that were created prior to the explosion of AI-generated content that occurred in 2022.

It currently contains pointers to a Wikipedia dump from prior to the release of ChatGPT, the Arctic Code Vault, Project Gutenberg, and more.

If you know of other sources of non-contaminated content plus submit them!

It was time for a dim bulb current limiter

One of my Minitels (the one that I modified a few years ago to run new firmware) started having power supply problems: the LED was on but nothing else was working. I suspected that the main power/CRT board needed new capacitors and so I recapped it:

Alas, despite some of the older capacitors measuring poorly compared to their specs, that wasn't the problem and so I need to go deeper. The only problem is there are a ton of nasty voltages on this board. Notably the 230V AC input and then the tens of kilovolts generated for the CRT.

Also the board seems to have a short somewhere.

So, it's time to a dim bulb current limiter. Which I didn't have. So I made one. Here it is:

It's a remarkably simple device which plugs into a standard power outlet (230V AC) and puts a lightbulb in series with one of the connections. The two wires coming in then go to a standard socket. Thus you plug your device (e.g. my Minitel) into the socket and the lightbulb limits the current.

These things were super common in the past for anyone working with mains voltages.

Works great if you have an incandescent bulb at, say, 100W. A 100W bulb on 230V AC would have a current running through it of I = V/P -> I = 100/230 (approximately 430mA). Limiting the current that way means you're less likely to damage the device you're working on if there's a short. Naturally, using a different bulb would give you a different current. 60W would give you around 230mA. 150W around 650mA. 

As the Minitel's input fuse is 630mA, my current limiter will keep things well under its blowing current. Also, if there's a complete short then the bulb will glow brightly. 

Here's a look inside:

Power comes in at the top, and goes to a DPST switch. I'm using DPST because it's not easy to know which input wire is live and which is neutral because the European Schuko/Type F plug/socket is not polarized and I like knowing that when I switch something off, it's off! And the DPST has an integrated lamp that gives me a visual reminder that it's on.

Because local power sockets aren't polarised, the power strip I am using for my bench gear uses DPST switches for each socket. It's relatively hard to find one that does this (and says it does). Thanks, Brennenstuhl!

But I digress.

To make my dim bulb current limiter do the right thing, I need a 100W incandescent bulb. These have been on their way to oblivion in the EU since 2009 and were, I believe, eliminated for home use in 2016. It is still possible to buy them, labelled for "industrial use", from some locations.

 

So, that limits the current and protects the device I'm working on, but what about protecting me? For that, I pair it with an isolating transformer. If you're not familiar with this then here's the basics. In a house the neutral line is connected to ground (typically at the point at which power comes into your house). This means that the 230V coming out the live wire is relative to ground. If I touch it the power will flow through me to ground. 

The isolating transformer eliminates the link between live, neutral and ground. It's still outputting 230V but that voltage isn't relative to ground and so I won't get a shock if I touch one of the wires coming from the transformer's socket. Of course, touching both would send 230V through me.

So, having built that I can go back to understanding why my Minitel isn't powering on.