The Pacemaker Patch

A pacemaker is implanted to send signals that regulate a patient’s heartbeat, and to do that, you need power. That means they require battery changes, and when the device in question happens to be inside your chest, that means surgery. Sometimes as often as every five years. [Alex Music] writing in Spectrum notes that researchers have a new paper discussing a possible alternative: a tiny patch stuck to the outside of the chest that uses ultrasound to pace the heart rhythm.

Rats, pigs, and human heart cell samples have all responded to the system. You might wonder how ultrasound could make your heart beat, but the new pacemaker relies on gene therapy to sensitize your heart cells to the high-frequency waves. The therapy is delivered by a simple injection.

In addition to the chest patch, the patient would need a data and power module that they could keep in their pocket. The gene therapy doesn’t alter your DNA but introduces RNA to make heart cells produce a sound-sensitive protein in the cell’s ion channels. When stimulated, the ion channels admit calcium, which causes the heart to beat.

Pacemakers are nothing less than a modern technological marvel. Maybe if this catches on, cheap junked pacemakers will show up on the surplus market. They could be useful.

Custom Watch Is On The Case

We were excited to see [Z0hn]’s project about 3D printing a custom watch from scratch — both because it was an exciting idea, and because the pictures looked great. While we still liked the project, we quickly realized it wasn’t really printing a watch so much as it was printing a case that holds an off-the-shelf movement. But it still looked great.

Many homebrew watches are cool and fine to wear to your next hackerspace board meeting. But this watch wouldn’t raise an eyebrow out among the normal public. Conventional watches use press-fit backs, tiny screws, or make the back screw into the housing. None of those are great for 3D printing, so this watch uses a bayonet connector, which is easy to create, robust, and reliable.

The watch looks easy to modify, so if you don’t like, for example, the unusual crown placement, you can change it. The movement is a Miyota 8N24 and, of course, the crystal is off-the-shelf, too.

While not exactly a printed watch, it was still pretty cool, and there are lessons to be learned here if you want to pull off the same feat. Or just go full on hacker. You could, too, try your hand with an open source movement.

Homebrew Macropad Looks Good

We are fans of macro pads and especially homebrew ones. The Apna Dost project by [np_vishwakarma] ticks most of our boxes. In addition to a few buttons, there’s an encoder, an OLED display, and it runs QMK firmware. Plus, it looks good, too.

We like that the system uses an RP2040. It is possible you have everything you need to put one of these together right now. We would wish for a few more keys, but it wouldn’t be hard to add them, either.

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The Air Position Indicator For The B-29

When you think of a computer, you probably don’t think of a tube full of motors and mechanics. However, as [Our Own Devices] shows, the Bendix AN5841 API Computer, an air position indicator computer, is exactly that. Using mechanical integrators and data from other analog systems on an airplane to provide key flight data to a pilot. You can see the video below.

These devices were made for military aircraft, including the B-29. It is odd that speed data can be derived from a pump that balances pressures using a fan. The video does a good job of explaining exactly how that works.

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A Peek Inside The Secret Lagercrantz Suitcase Radio

What counts as portable is somewhat a matter of opinion, especially over the years. [Helge Fykse] has a portable spy radio of Swedish origin. For its time, it was considered very portable, crammed into a good-sized suitcase.

You can see the large crystal that sets the transmit frequency and a key to send Morse code. The receiver has a VFO, so it was more agile. Based on the regenerative knob, it appears the receiver was of the regenerative type. The suitcase had its own battery, and with tubes, it could probably put out some kind of signal if connected to anything metal, like bedsprings, a clothesline, or anything. There was a lightbulb to let you see when you were transmitting maximum power.

Speaking of tubes, there were five inside, two for the transmitter and three for the receiver. The radio had storage for spare tubes, and the agent could maintain the radio in the field.

You not only get a peek inside the suitcase, but a look at the schematic. The radio is a model of simplicity, but we are certain it did its job.

We love looking at exotic spy gear, especially radios.

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So Many Analog To Digital Converters

An old algebra teacher used to say, “You have to take what you know and use it to get what you don’t know.” You might say the same thing about converting analog signals into digital. Computers know how to count and keep time. [Eric Explains] has a video purporting to explain “every type of analog-to-digital converter.” We aren’t sure he got every possible method, but there’s still a lot of information in the video, which you can see below.

From the flash ADC, using a ton of comparators to the successive approximation converter, which essentially plays a game of hi/lo, guessing the answer and figuring out if the real answer is higher or lower.

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Deep Dive Into Sputnik

If you are an American of a certain age, you know the Soviet Union launched the first satellite, Sputnik, beating the United States to orbit. You might even remember ham radio operators tuning into the satellites beeping. But you probably haven’t heard much about the team that built the vehicle, the problems they had, or the clever design choices they made. [Hoog] has a video that details the birth of Sputnik. You can see the video below.

The original plan was to launch a massive space lab, but it proved too ambitious. Keep in mind that in the late 1950s, you didn’t have tiny computers, high-density power sources, or advanced materials, and no one really knew what to expect in the Earth orbit environment. Even the viability of radio from the ground to orbit wasn’t a given. But Sputnik’s 1-watt transmitter did the job.

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