System Essentially Contradicting American Methods

July 5, 2023 by 36 Comments

Today, acronyms such as PAL and initialisms such as NTSC are used as a lazy shorthand for 625 and 525-line video signals, but back in the days of analogue TV broadcasting they were much more than that, indeed much more than simply colour encoding schemes. They became political statements of technological prowess as nations vied with each other to demonstrate that they could provide their citizens with something essentially home-grown. In France, there was the daddy of all televisual symbols of national pride, as their SECAM system was like nothing else. [Matt’s TV Barn] took a deep dive into video standards to find out about it with an impressive rack of test pattern generation equipment.

At its simplest, a video signal consists of the black-and-while, or luminance, information to make a monochrome picture, along with a set of line and frame sync pulses. It becomes a composite video signal with the addition of a colour subcarrier at a frequency carefully selected to fall between harmonics of the line frequency and modulated in some form with the colour, or chrominance, information. In this instance, PAL is a natural progression from NTSC, having a colour subcarrier that’s amplitude modulated and with some nifty tricks using a delay line to cancel out colour shifting due to phase errors.

SECAM has the same line and frame frequency as PAL, but its colour subcarrier is frequency modulated instead of amplitude modulated. It completely avoids the NTSC and PAL phase errors by not being susceptible to them, at the cost of a more complex decoder in which the previous line’s colour information must be stored in a delay line to complete the decoding process. Any video processing equipment must also, by necessity, be more complex, something that provided the genesis of the SCART audiovisual connector standard as manufacturers opted for RGB interconnects instead. It’s even more unexpected at the transmission end, for unlike PAL or NTSC, the colour subcarrier is never absent, and to make things more French, it inverted the video modulation found in competing standards.

The video below takes us deep into the system and is well worth a watch. Meanwhile, if you fancy a further wallow in Gallic technology, peer inside a Minitel terminal.

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A man next to a robot with animatronic eyes and a CRT display showing an audio waveform

Animatronic Alexa Gives Amazon’s Echo A Face

July 5, 2023 by 17 Comments

Today, we’re surrounded by talking computers and clever AI systems that a few decades ago only existed in science fiction. But they definitely looked different back then: instead of a disembodied voice like ChatGPT, classic sci-fi movies typically featured robots that had something resembling a human body, with an actual face you could talk to. [Thomas] over at Workshop Nation thought this human touch was missing from his Amazon Echo, and therefore set out to give Alexa a face in a project he christened Alexatron.

The basic idea was to design a device that would somehow make the Echo’s voice visible and, at the same time, provide a pair of eyes that move in a lifelike manner. For the voice, [Thomas] decided to use the CRT from a small black-and-white TV. By hooking up the Echo’s audio signal to the TV’s vertical deflection circuitry, he turned it into a rudimentary oscilloscope that shows Alexa’s waveform in real time. An acrylic enclosure shields the CRT’s high voltage while keeping everything inside clearly visible.

To complete the face, [Thomas] made a pair of animatronic eyes according to a design by [Will Cogley]. Consisting of just a handful of 3D-printed parts and six servos, it forms a pair of eyes that can move in all directions and blink just like a real person. Thanks to a “person sensor,” which is basically a smart camera that detects faces, the eyes will automatically follow anyone standing in front of the system. The eyes are closed when the system is dormant, but they will open and start looking for faces nearby when the Echo hears its wake word, just like a human or animal responds to its name.

The end result absolutely looks the part: we especially like the eye tracking feature, which gives it that human-like appearance that [Thomas] was aiming for. He isn’t the first person trying to give Alexa a face, though: there are already cute Furbys and creepy bunnies powered by Amazon’s AI, and we’ve even seen Alexa hooked up to an animatronic fish.

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Minimal Mods Make Commodity LNBs Work For QO-100 Reception

July 4, 2023 by 15 Comments

A word of advice: If you see an old direct satellite TV dish put out to the curb, grab it before the trash collector does. Like microwave ovens, satellite dishes are an e-waste wonderland, and just throwing them away before taking out the good stuff would be a shame. And with dishes, the good stuff basically amounts to the bit at the end of the arm that contains the feedhorn and low-noise block downconverter (LNB).

But what does one do with such a thing once it’s harvested? Lots of stuff, including modifying it for use with the QO-100 geosynchronous satellite (German link). That’s what [Sebastian Westerhold] and [Celin Matlinski] did with a commodity LNB, although it seems more like something scored on the cheap from one of the usual sources rather than picking through trash. Either way, these LNBs are highly integrated devices that at built specifically for satellite TV use, but with just a little persuasion can be nudged into the K-band to receive the downlink signals from hams using QO-100 as a repeater.

The mods are simple — snipping out the 25 MHz reference crystal on the LNB board and replacing it with a simple LC bandpass filter. This allows the local oscillator on the LNB to be referenced to an external signal generator; when fed with a 25.78 MHz signal, it’s enough to goose the LNB up to 10,490 MHz — right about the downlink frequency. [Sebastian] and [Celin] tested the mods and found that it was easily able to detect the third harmonics of a 3.5-ish GHz signal.

As for testing on actual downlink signals from the satellite, that’ll have to wait. For now, if you’re interested in satellite comms, and you live on the third of the planet covered by QO-100, keep an eye out for those e-waste LNBs and get to work.

Saying Goodbye To Don Lancaster

July 2, 2023 by 63 Comments

The electronics world has lost a guru. On June 7th this year, Don Lancaster passed away. [Brad] from Tech Time Traveller paid tribute to Don in a recent video. Don Lancaster was perhaps best known as the designer of the TV Typewriter.  The Typewriter drew characters on a TV screen when the user typed on a keyboard. It was the fundamental part of a simple terminal. This was quite an accomplishment in 1973 when the article was first published.

Don embodied the hacker spirit by figuring out low-cost (cheap) ways to overcome obstacles. His genius was his ability to communicate his methods in a way even non-technical people could understand. Keyboards are a great example. Back in the 1970’s a simple keyboard cost hundreds of dollars. Don figured out how to build one from scratch and published an article explaining how to do it.

Like many people we cover here on Hackaday, Don was quite a character. His website layout hasn’t changed much since the 1990’s, but the content has grown. To say he was a prolific writer would be an understatement. PostScript, Magic Sinewaves, and patents are just a few of his favorite topics. Don’s recent work involved the research of prehistoric canals in the American Southwest.

Everyone here at Hackaday sends our deepest condolences to Don’s family.

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Meshtastic For The Greater Good

June 26, 2023 by 62 Comments

Last week, my city was hit by a tornado. That’s not surprising here in Oklahoma, and thankfully this event was an F0 or possibly even an EF0 — a really weak tornado. Only a couple roofs collapsed, though probably half the houses in town are going to need roof repairs, thanks to the combination of huge hail and high winds. While it wasn’t too bad, power did go down in a few places around town, and this led to an interesting series of events.

Chat messages were coming in like this: “That was a [power] flicker, yeah. Even took down my Internet.” Followed by “Whee, [fiber Internet] got knocked out and now Starlink has too many clouds in the way.” And after ten minutes of silence, we got a bit worried to see “Time to hide under a bed. … Is cell service back?” It is a bit spooky to think about trying to help neighbors and friends after a disaster, in the midst of the communication breakdown that often follows. If he had needed help, and had no working communications, how long would it have taken for us to go check on him?
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A More Conspicuous Computer Assistant

June 25, 2023 by 11 Comments

Back in the last century, especially in the ’40s to the ’60s, one of the major home decor trends was to install various home appliances, like the television or stereo, into its own piece of furniture. These were usually bulky, awkward, and incredibly heavy. And, since real life inspires art, most of the futuristic sci-fi technology we saw in movies and TV of the time was similarly conspicuous and physical. Not so with modern technology, though, where the trend now is to hide it out of the way and forget it exists. But [dermbrian] wanted some of his modern technology to have some of the mid-century visibility aesthetic so he made some modifications to his Amazon Echo.

The Echo itself remains largely unmodified, other than placing it inside a much larger cookie tin with some supporting electronics. For that, [dermbrian] found a relay board with a built-in microphone which switches the relay off when it detects sound so that when the Echo is activated, the sound from its speaker activates the module. From there it drives a series of blinkenlights which mimic the 60s computer aesthetic. Some custom fabrication and light diffusion methods were needed to get it to look just right, and a switch on the outside can disable the mechanism if it is getting triggered by background noise like music from his stereo.

While the appeal of this style may be lost on anyone who wasn’t a fan of the original Lost in Space, Star Trek, or Jetsons, it certainly holds a special significance for those who grew up in that era. It’s certainly not the first project we’ve seen to take a look back at the aesthetics of bygone eras, either. Take a look at this project which adds lenses to modern displays to give them the impression of antiquated CRT displays.

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A glass plate holds a translucent set of silver electrodes. The plate appears to be suspended across two petri dishes, so the scale must be small.

Hydrogels For Bioelectronic Interfaces

June 25, 2023 by 1 Comment

Interfacing biological and electrical systems has traditionally been done with metal electrodes, but something flexible can be more biocompatible. One possible option is 3D-printed bioelectric hydrogels.

Electrically conductive hydrogels based on conducting polymers have mechanical, electrical, and chemical stability properties in a fully organic package that makes them more biocompatible than other systems using metals, ionic salts, or carbon nanomaterials. Researchers have now found a way to formulate bi-continuous conducting polymer hydrogels (BC-CPH) that are a phase-separated system that can be used in a variety of manufacturing techniques including 3D printing.

To make the BC-CPH, a PEDOT:PSS electrical phase and a hydrophilic polyurethane mechanical phase are mixed with an ethanol/water solvent. Since the phase separation occurs in the ink before deposition, when the solvent is evaporated, the two phases remain continuous and interspersed, allowing for high mechanical stability and high electrical conductivity which had previously been properties at odds with each other. This opens up new avenues for printed all-hydrogel bioelectronic interfaces that are more robust and biocompatible than what is currently available.

If you want to try another kind of squishy electrode gel, try growing it.