Time-of-Flight Sensors: How Do They Work?

January 20, 2025 by Al Williams 15 Comments

With the right conditions, this tiny sensor can measure 12 meters

If you need to measure a distance, it is tempting to reach for the ubiquitous ultrasonic module like an HC-SR04. These work well, and they are reasonably easy to use. However, they aren’t without their problems. So maybe try an IR time of flight sensor. These also work well, are reasonably easy to use, and have a different set of problems. I recently had a project where I needed such a sensor, and I picked up a TF-MiniS, which is a popular IR distance sensor. They aren’t very expensive, and they work serial or I2C. So how did it do?

The unit itself is tiny and has good specifications. You can fit the 42 x 15 x 16 mm module anywhere. It only weighs about five grams — as the manufacturer points out, less than two ping-pong balls. It needs 5 V but communicates using 3.3 V, so integration isn’t much of a problem.

At first glance, the range is impressive. You can read things as close as 10 cm and as far away as 12 m. I found this was a bit optimistic, though. Although the product sometimes gets the name of LiDAR, it doesn’t use a laser. It just uses an IR LED and some fancy optics.

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Forgotten Internet: UUCP

January 16, 2025 by Al Williams 82 Comments

What’s Forgotten Internet? It is the story of parts of the Internet — or Internet precursors — that you might have forgotten about or maybe you missed out on them. This time, we’re looking at Unix-to-Unix Copy, more commonly called UUCP. Developed in the late 1970s, UUCP was a solution for sending messages between systems that were not always connected together. It could also allow remote users to execute commands. By 1979, it was part of the 7th Edition of Unix.

Ken Thompson and Dennis Ritchie may have used UUCP on a PDP-11 like this one. (Photo via Computer History Museum/Gwen Bell)

Operation was simple. Each computer in a UUCP network had a list of neighbor systems. Don’t forget, they weren’t connected, so instead of an IP address, each system had the other’s phone number to connect to a dial up modem. You also needed a login name and password. Almost certainly, by the way, those modems operated at 300 baud or less.

If a computer could dial out, when someone wanted to send something or do a remote execution, the UUCP system would call a neighboring computer. However, some systems couldn’t dial out, so it was also possible for a neighbor to call in and poll to see if there was anything you needed to do. Files would go from one system to another using a variety of protocols.

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No Ham License? Listen Anyway In Your Browser

January 15, 2025 by Al Williams 53 Comments

Full disclosure: ham radio isn’t for everyone, and there are many different facets to it. What appeals to one person might bore another to death. One area of ham radio that has changed a lot in the last few years is more or less local and typically mobile operation on VHF or UHF. Not long ago, hams used HTs (walky-talkies or handi-talkies) or mobile radios via repeaters to talk to each other and — the golden prize back then — make phone calls from their cars. Cell phones have made that much less interesting, but there is still an active community of operators talking on repeaters. However, the traffic has gone digital, the Internet is involved, and people with inexpensive, low-powered radios can talk to each other across the globe. This is nothing new, of course. However, having digital services means that operators with special interests can congregate in what amounts to radio chat rooms organized by region or topic.

There’s a long history of people listening to ham radio conversations with shortwave radios, SDRs, and scanners. But with so much activity now carried on the Internet, you can listen in using nothing more than your web browser or a phone app. I’ll show you how. If you get interested enough, it is easy enough to get your license. You don’t need any Morse code anymore, and a simple Technician class license in the United States is all you need to get going.

A Quick DMR Primer

There are several digital ham networks around and like real networks, you can have different physical transport layers and then build on top of that. For the purposes of this post, I’m going to focus on DMR (digital mobile radio) on the Brandmeister network which is very large and popular ham network. You won’t need a license nor will you need to sign up for anything as long as you are content to just listen.

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The Many Leaning Towers Of Santos, Brazil

January 14, 2025 by Lewin Day 55 Comments

If you’ve ever gazed at the shoreline of Santos, Brazil, and felt like something was tugging at your inner eye level, you’re not alone. In fact, you’ve spotted one of the world’s most bizarre architectural phenomena.

Santos is an interesting contradiction—it’s a sunny coastal city with pristine beaches that also plays host to a bustling port. What draws the eye, however, is the skyline—it’s decidedly askew. This isn’t a Photoshop job or some avant-garde urban planning experiment, either. It’s a consequence of engineering hubris, poor planning, and geology just doing its thing.

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Carnarvon’s Decommissioned NASA Satellite Dish Back In Service After 40 Years

January 12, 2025 by Maya Posch 35 Comments

The OTC Station 29.8 meter dish at Carnarvon, Australia, in need of a bit of paint. (Credit: ABC News Australia)

Recently the 29.8 meter parabolic antenna at the Australian OTC (overseas telecommunications commission) station came back to life again after nearly forty years spent in decommissioning limbo.

This parabolic dish antenna shares an illustrious history together with the older 12.8 meter Casshorn antenna in that together they assisted with many NASA missions over the decades. These not only include the Apollo 11 Moon landing with the small antenna, but joined by the larger parabolic dish (in 1969) the station performed tracking duty for NASA, ESA and many other missions. Yet in 1987 the station was decommissioned, with scrapping mostly averted due to the site being designated a heritage site, with a local museum.

Then in 2022 the 29.8 meter parabolic dish antenna was purchased by by ThothX Australia, who together with the rest of ThothX’s world-wide presence will be integrating this latest addition into a satellite tracking system that seems to have the interest of various (military, sigh) clients.

Putting this decommissioned dish back into service wasn’t simply a matter of flipping a few switches. Having sat mostly neglected for decades it requires extensive refurbishing, but this most recent milestone demonstrates that the dish is capable of locking onto a satellites. This opens the way for a top-to-bottom refurbishment, the installation of new equipment and also a lick of paint on the dish itself, a process that will still take many years but beats watching such a historic landmark rust away by many lightyears.

Featured image: OTC Earth Station. (Credit: Paul Dench)

The Engineer Behind Mine Detection

January 10, 2025 by Al Williams 8 Comments

According to [Joanna Goodrich] in IEEE Spectrum, prior to World War II, soldiers who wanted to find land mines, simply poked at the ground with pointed sticks or bayonets. As you might expect, this wasn’t very safe or reliable. In 1941, a Polish signals officer, [Józef Stanislaw Kosacki], escaped to Britain and created an effective portable mine detector.

[Kosaci] was an electrical engineer trained at the Warsaw University of Technology. He had worked as a manager for the Polish National Telecommunication Institute. In 1937, the government tasked him with developing a machine that could detect unexploded grenades and shells. The machine was never deployed.

When Germany invaded Poland in 1939, [Kosacki] returned to military service (he had done a year of compulsory service earlier). He was captured and kept in a prison camp in Hungary. But he managed to escape in late 1939 and joined the Polish Army Corps in Britain, teaching Morse code to soldiers.

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Front panel of a GPO Brooklyn with cassette player (Credit: VSchagow, Wikimedia)

Physical Media Is Dead, Long Live Physical Media

January 9, 2025 by Maya Posch 132 Comments

Much has been written about the demise of physical media. Long considered the measure of technological progress in audiovisual and computing fields, the 2000s saw this metric seemingly rendered obsolete by the rise of online audiovisual and software distribution services. This has brought us to a period in time where the very idea of buying a new music album, a movie or a piece of software in a physical, or even online, retail store has become largely impossible amidst the rise of digital-only media.

Even so, not all is well in this digital-only paradise, as the problems with having no physical copy of the item which you purportedly purchased are becoming increasingly more evident. From increases in monthly service costs, to items being removed or altered without your consent, as well as concerns over privacy and an inability to resell or lend an album or game to a buddy, there are many reasons why having the performance or software on a piece of off-line, physical media is once again increasing in appeal.

Even if the demise of physical data storage was mostly a trick to extract monthly payments from one’s customer base, what are the chances of this process truly reverting, and to what kind of physical media formats exactly?

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