Tis The Season

December 7, 2024 by Elliot Williams 16 Comments

’Tis the season for soldering! At least at my house. My son and I made some fairly LED-laden gifts for the immediate relatives last year, and he’s got the blinky bug. We were brainstorming what we could make this year, and his response was “I don’t care, but it needs to have lots of LEDs”.

It’s also the season for reverse engineering, apparently, because we’re using a string of WS2812-alike “fairy lights”. These are actually really neat, they look good and are relatively cheap. It’s a string of RGB LEDs with drivers, each dipped in epoxy, and run on a common three-enameled-wire bus. Unlike WS2812s, which pass the data on to the next unit in the line and then display them with a latching pulse at the end of a sequence, these LED drivers seem to count how many RGB packets have been sent down the wire, and only respond to their own number.

This means that if you cut up a string of 200 LEDs, it behaves like a string of 200 WS2812s. But if you cut say 10 LEDs off the string, where you cut them matters. If you cut it off the front of the string, you only have to send 10 color packets. If you cut them off the other end, you need to send 290 dummy packets before they even start listening. Bizarre, but ’tis the season for bizarre hacks.

And finally, ’tis the season for first steps into “software architecture”. Which is to say that my son is appreciating functions for the first time in his life. Controlling one LED is easy, but making a light show is about two more abstraction layers on top of that. We’ve been having fun making them dim, twinkle, and chase so far. We only have two more weekends, though, and we don’t have a final light show figured out yet, but after all, ’tis the season for last minute present hacking.

Printing In Multi-material? Use These Filament Combos

December 7, 2024 by Donald Papp 15 Comments

If one has a multi-material printer there are more options than simply printing in different colors of the same filament. [Thomas Sanladerer] explores combinations of different filaments in a fantastic article that covers not just which materials make good removable support interfaces, but also which ones stick to each other well enough together to make a multi-material print feasible. He tested an array of PLA, PETG, ASA, ABS, and Flex filaments with each in both top (printed object) and bottom (support) roles.

A zero-clearance support where the object prints directly on the support structure can result in a very clean bottom surface. But only if the support can be removed easily.

People had already discovered that PETG and PLA make pretty good support for each other. [Thomas] expands on this to demonstrate that PLA doesn’t really stick very well to anything but itself, and PETG by contrast sticks really well to just about anything other than PLA.

One mild surprise was that flexible filament conforms very well to PLA, but doesn’t truly stick to it. Flex can be peeled away from PLA without too much trouble, leaving a very nice finish. That means using flex filament as a zero-clearance support interface — that is to say, the layer between the support structure and the PLA print — seems like it has potential.

Flex and PETG by contrast pretty much permanently weld themselves together, which means that making something like a box out of PETG with a little living hinge section out of flex would be doable without adhesives or fasteners. Ditto for giving a PETG object a grippy base. [Thomas] notes that flexible filaments all have different formulations, but broadly speaking they behave similarly enough in terms of what they stick to.

[Thomas] leaves us with some tips that are worth keeping in mind when it comes to supported models. One is that supports can leave tiny bits of material on the model, so try to use same or similar colors for both support and model so there’s no visual blemish. Another tip is that PLA softens slightly in hot water, so if PLA supports are clinging stubbornly to a model printed in a higher-temperature material like PETG or ABS/ASA, use some hot water to make the job a little easier. The PLA will soften first, giving you an edge. Give the video below a watch to see for yourself how the combinations act.

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FlatMac: Building The 1980’s Apple IPad Concept

December 7, 2024 by Maya Posch 17 Comments

The Apple FlatMac was one of those 1980s concepts by designer [Hartmut Esslingers] that remained just a concept with no more than some physical prototypes created. That is, until [Kevin Noki] came across it in an Apple design book and contacted [Hartmut] to ask whether he would be okay with providing detailed measurements so that he could create his own.

Inside the 3D printed enclosure is a Raspberry Pi 4 running an appropriately emulated Macintosh, with a few modern features on the I/O side, including HDMI and USB. Ironically, the screen is from a 3rd generation iPad, which [Kevin] bought broken on EBay. There’s also an internal floppy drive that’s had its eject mechanism cleverly motorized, along with a modified USB battery bank that should keep the whole show running for about an hour. The enclosure itself is carefully glued, painted and sculpted to make it look as close to the original design as possible, which includes custom keycaps for the mechanical switches.

As far as DIY projects go, this one is definitely not for the faint of heart, but it’s fascinating to contrast this kind of project that’s possible for any determined hobbyist with the effort it would have taken forty years ago. The only question that’s left is whether or not the FlatMac would have actually been a practical system if it had made it to production. Although the keyboard seems decent, the ergonomics feel somewhat questionable compared to something more laptop-like.

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3D Printed Caliper Extensions Make Hole Measurement Easier

December 6, 2024 by Dan Maloney 21 Comments

If there’s anything more frustrating than mounting holes that don’t line up with the thing you’re mounting, we don’t know what it could be. You measure as carefully as possible, you drill the holes, and yet at least one hole ends up being just out of place. Sometimes you can fudge it, but other times you’ve got to start over again. It’s maddening.

Getting solid measurements of the distance between holes would help, which is where these neat snap-on attachments for digital calipers come in. [Chris Long] came up with the 3D printed tools to make this common shop task a little easier, and they look promising. The extensions have cone-shaped tips that align perfectly with the inside edge of the caliper jaws, which lines the jaws up with the center of each hole. You read the center-to-center distance directly off the caliper display, easy peasy.

Of course, there’s also the old machinist’s trick (last item) about zeroing out the calipers after reading the diameter of one of the holes and then measuring the outside-to-outside distance between the two holes. That works great when you’ve got plenty of clearance, but the shorter inside jaws might make measuring something like a populated PCB with this method tricky. For the price of a little filament and some print time, these might be just the tool to get you out of a bind.

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Antenna Measurement In Theory And Practice

December 6, 2024 by Al Williams 9 Comments

If you want to analyze an antenna, you can use simulation software or you can build an antenna and make measurements. [All Electroncs Channel] does both and show you how you can do it, too, in the video below.

The antenna in question is a loop antenna. He uses a professional VNA (Vector Network Analyzer) but you could get away with a hobby-grade VNA, too. The software for simulation is 4NEC2.

The VNA shows the electrical characteristics of the antenna, which is one of the things you can pull from the simulation software. You can also get a lot of other information. You’d need to use a field strength meter or something similar to get some of the other information in the real world.

The antenna simulation software is a powerful engine and 4NEC2 gives you an easy way to use it with a GUI. You can see all the graphs and plots easily, too. Unfortunately, it is Windows software, but we hear it will run under Wine.

The practical measurement is a little different from the simulation, often because the simulation is perfect and the real antenna has non-ideal elements. [Grégory] points out that changing simulation parameters is a great way to develop intuition about — in this case — antennas.

Want to dive into antennas? We can help with that. Or, you can start with a simple explanation.

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Retro Computer Goes Back To The 1950s

December 6, 2024 by Bryan Cockfield 24 Comments

When thinking of retrocomputing, many of us will imagine machines such as the Commodore 64 or Apple II. These computers were very popular and have plenty of parts and documentation available. Fewer will go back to the Intel 8008 or even 4004 era which were the first integrated circuit chips commercially available. But before even those transistor-based computers is a retrocomputing era rarely touched on: the era of programmable vacuum tube machines. [Mike] has gone back to the 1950s with this computer which uses vacuum tubes instead of transistors.

The computer has an eight-bit architecture and features most of the components of any modern transistor-based computer of similar computational ability. Memory, I/O, an arithmetic logic unit including a carry bit that allows it to do 16-bit arithmetic, are all implemented using 6N3P dual triode tubes that date to the 50s and 60s and would have been used in similar computers like the IBM 700. All of this drives a flight simulator program or a Fibonacci number generator, demonstrating its general purpose computing capabilities.

Of course, tubes were generally phased out in favor of transistors largely due to their power and space requirements; [Mike] needs a stepladder to maintain this computer as well as around ten minutes each time he starts it up to allow the tubes to warm up, with each module needing over three amps of current each. It’s a hugely impressive build and we’d recommend checking out the video linked below to get more details on its operation. If you’re looking for something a little more accessible to get into the world of vacuum tubes, this single-board tube computer fits the bill.

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VNAs And Crystals

December 6, 2024 by Al Williams 7 Comments

Oscillators may use crystals as precise tuned circuits. If you have a vector network analyzer (VNA) — or even some basic test equipment — you can use it to learn the parameters of a crystal. [All Electronics Channel] has the details, and you can see how in the video below.

There was a time when a VNA was an exotic piece of gear, but these days they are relatively common. Crystal parameters are important because crystals have a series resonance and a parallel resonance and they are not at the same frequency. You also may need to know how much loading capacitance you have to supply to get the crystal at the right frequency.

Sometimes, you want to pull the crystal frequency, and the parameters will help you figure that out, too. It can also help if you have a crystal specified as series in a parallel-mode oscillator or vice versa.

If you don’t have a VNA, you can use a tracking signal generator, as [Grégory] shows towards the middle of the video. The quality of a tuned circuit depends on the Q factor, and crystals have a very high Q factor.

We did something similar in 2018. The other way to pull a crystal frequency is a bit extreme.

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