[Ken Shirriff] likes to take chips apart and this time his target is an NFC chip used in Montreal transit system tickets. As you might expect, the tickets are tiny, cheap, and don’t have any batteries. So how does it work?
The chip itself is tiny at 570 µm × 485 µm. [Ken] compares it to a grain of salt. The ticket has a thin plastic core with a comparatively giant antenna onboard.
It is funny how sometimes things you think are bad turn out to be good in retrospect. Like many of us, when I was a kid, I was fascinated by science of all kinds. As I got older, I focused a bit more, but that would come later. Living in a small town, there weren’t many recent science and technology books, so you tended to read through the same ones over and over. One day, my library got a copy of the relatively recent book “The Amateur Scientist,” which was a collection of [C. L. Stong’s] Scientific American columns of the same name. [Stong] was an electrical engineer with wide interests, and those columns were amazing. The book only had a snapshot of projects, but they were awesome. The magazine, of course, had even more projects, most of which were outside my budget and even more of them outside my skill set at the time.
If you clicked on the links, you probably went down a very deep rabbit hole, so… welcome back. The book was published in 1960, but the projects were mostly from the 1950s. The 57 projects ranged from building a telescope — the original topic of the column before [Stong] took it over — to using a bathtub to study aerodynamics of model airplanes.
You needed a few items. An Oudin coil, sort of like a Tesla coil in an autotransformer configuration, generated the necessary high voltage. In fact, it was the Ouidn coil that started the whole thing. [Harry] was using it to power a UV light to test minerals for flourescence. Out of idle curiosity, he replaced the UV bulb with an 01 radio tube. These old tubes had a magnesium coating — a getter — that absorbs stray gas left inside the tube.
If you are used to writing software for modern machines, you probably don’t think much about computing something like one divided by three. Modern computers handle floating point quite well. However, in constrained systems, there is a trap you should be aware of. While modern compilers are happy to let you use and abuse floating point numbers, the hardware is often woefully slow. It also tends to eat up lots of resources. So what do you do? Well, as [Low Byte Productions] explains, you can opt for fixed-point math.
In theory, the idea is simple. Just put an arbitrary decimal point in your integers. So, for example, if we have two numbers, say 123 and 456, we could remember that we really mean 1.23 and 4.56. Adding, then, becomes trivial since 123+456=579, which is, of course, 5.79.
[Joel] picked up a wireless mouse kit. The idea is you get some 3D printing files and hardware. You can print the shell or make modifications to it. You can even design your own shell from scratch. But [Joel] took a different approach. He created a case with transparent resin. You can see the impressive result in the video below.
While the idea of buying the mouse as a kit simplifies things, we would be more inclined to just gut a mouse and design a new case for it if we were so inclined. We were more impressed with the results with the transparent resin.
[Jason Dookeran] reminded us of something we don’t like to think about. Your printer probably adds barely noticeable dots to everything you print. It does it on purpose, so that if you print something naughty, the good guys can figure out what printer it came from. This is the machine identification code and it has been around since the days that the US government feared that color copiers would allow wholesale counterfiting.
The technology dates back to Xerox and Canon devices from the mid-80s, but it was only publicly acknowledged in 2004. With color printers, the MIC — machine identification code — is a series of tiny yellow dots. Typically, each dot is about 10 microns across and spaced about a millimeter from each other. The pattern prints all over the page so that even a fragment of, say, a ransom note can be identified.
In an excerpt from his book The Chinese Computer: A Global History of the Information Age, [Thomas Mullaney] explains how 1980s computer tech — at least the stuff that was developed in the West — was stubbornly rooted in the Latin alphabet. After all, ASCII was king, and with 60,000 symbols, Chinese was decidedly difficult to shoehorn into 8 bits. Unicode was years in the future so, of course, ingenious hackers did what they do best: hack!
The subject of the post is the dot matrix printer. Early printers had nine pins, which was sufficient to make Latin characters in one pass. To print Chinese, each character required at least two passes of the print head. This was slow, of course, but it was also subject to confusing variations due to ink inconsistency and registration problems. It also made the Chinese characters twice as big as English text.
Initial attempts were made to use finer pins to pack twice as many dots in the same space. But this made the pins too thin and subject to bending and breaking. Instead, some engineers would retain the two passes but move the print head just slightly lower so the second pass left dots in the gaps between the first pass dots. Obviously, the first pass would print even-numbered dots (0, 2, 4,…), and the second pass would catch the odd-numbered dots. This wasn’t faster, of course, but it did produce better-looking characters.
While international languages still sometimes pose challenges, we’ve come a long way, as you can tell from this story. Of course, Chinese isn’t the only non-Latin language computers have to worry about.
If you want to read something from magnetic tape, you need a tape head, right? Or you could do like [Igor Brichkov] and make your own. It looks surprisingly simple. He used a washer with a small slot cut in it and a coil of wire.
The first experiment, in the first video below, is using a commercial tape head connected to a preamp. Music playing “through” the homemade head is readable by the commercial tape reader. This is a prelude to creating an entire tape deck using the head, which you can see in the second video below.
