Author: Al Williams

4454 Articles

In Praise Of Old Meters

January 12, 2024 by 54 Comments

We are spoiled with multimeters today. Even the cheapest meter you will get these days is almost surely digital with a tremendous input impedance. But a few decades ago, meters were almost always analog affairs. To make a precise measurement, you needed a mirror under the meter to ensure you read the needle correctly. Moreover, a common meter wouldn’t have that high of an input impedance. If you spent more, you could get a VTVM and, later, one that used FETs to provide high input impedance. [Peter AA2VG] just picked up a vintage Micronta FET volt-ohm meter to join some of the other new and old meters in his shack. You can check it out in the video below.

[Peter] already has a Simpson and a more modern Fluke meter. The Simpson, however, doesn’t have a tube or FET amplifier. The Fluke is nice, but there is something about the needle on an analog meter. If you aren’t old enough to remember, the Micronta brand was a Radio Shack label.

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Linux Fu: Name That Tune

January 11, 2024 by 9 Comments

If you aren’t old enough to remember, the title of this post refers to an old game show where contestants would try to name a tune using the fewest possible notes. What can we say? Entertainment options were sparse before the Internet. However, using audio fingerprinting, computers are very good at pulling this off. The real problem is having a substantial library of fingerprints to compare with. You can probably already do this with your phone, and now you can do it with your Linux computer.

In all fairness, your computer isn’t doing the actual work. In fact, SongRec — the program in question — is just a client for Shazam, a service that can identify many songs. While this is mildly interesting if you use a Linux desktop, we could also see using the same technique with a Raspberry Pi to get some interesting projects. For example, imagine identifying a song playing and adjusting mood lighting to match. A robot that could display song information could be the hit of a nerdy party.

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19th Century Copy Machine: The Cyclostyle

January 10, 2024 by 15 Comments

In the 2020s photocopiers are getting a bit exotic, although they are not gone yet. But these days, you are more likely to simply print multiple copies of a document. However, it wasn’t long ago that making a copy of a document was a tall order. Carbon paper was fine if you were typing and only needed a few copies. But in the late 1800s to early 1900s, several solutions were available, including a beautiful early mimeograph known as the Cyclostyle at [Our Own Devices], examined in the video below.

The Cyclostyle was possibly inspired by a hectograph (something we looked at before). The Cyclostyle was originally a special stylus used to remove wax from a paper stencil. Then, a process similar to screen printing would make copies for you.

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Another Tesla Coil Starts

January 8, 2024 by 5 Comments

Everyone interested in electronics should build at least one Tesla coil. But be careful. Sure, the high voltage can be dangerous, but the urge to build lots of coils is even worse. [Learnelectronics] shows how to build a slayer exciter using a 3D-printed core, and lots of wire of course. You can see the coil, an explanation of the design, and a comparison to a cheap kit in the video below.

Of course, you hear about Tesla coils, but it is really more of a Tesla transformer. The 3D-printed core holds the many turns of the secondary coil. The larger Tesla coil, amusingly, upset the camera which made it hard to get close-up shots.

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Putting The C In C64

January 8, 2024 by 43 Comments

Older CPUs and some fairly modern microcontrollers are not made to readily support C compilers. Among those are the 1802, some 8-bit PICs, and the 6502 at the heart of the Commodore 64. That’s not to say you can’t make a C compiler for any of them, but the tricks required to handle the odd word sizes, lack of stack manipulation, or whatever other reason C isn’t a good fit tends to make compiled code bloated and possibly slower. [Dr. Mortal Wombat] took a different approach. The oscar64 compiler takes C source code and compiles it to a virtual machine code or native machine code for cases where performance might be important.

Turns out, the penalty for using native code isn’t as much as predicted, at least in some cases, The performance penalty for using the interpreter, however, can be significant in many common cases. The 6502 has a small stack that is hard to address, and indexing into a user-maintained stack is slow. The word size problem also produces lots of code as you have to break 16-bit operations into multiple 8-bit ones. The compiler aims to be C99-compliant, including floating point, recursion, multiple dimensions for arrays, and pointers to structures.

There are a few things left to hammer out. The linker doesn’t support external libraries, and the floating point code doesn’t understand NaN. On the other hand, many C++ features are available, like namespaces, reference types, templates, and more. The compiler can target several Commodore machines from the C128 to the PET. It also works with some Nintendo and Atari systems and can create various cartridge formats.

If you are writing code for any kind of 6502, it is probably worth checking out. Compiling C for the 6502 is no small feat, but then, so it is targeting PowerPoint. Don’t have a C64? Build one.

Image: [MOS6502], CC-BY-SA 3.0

Recreating The Jupiter ACE

January 7, 2024 by 26 Comments

What looks like a Sinclair ZX81 but runs Forth? If you said a Jupiter ACE, you get a gold star. These are rare because ordinary people in 1982 didn’t want Forth, so only about 5,000 of the devices were sold. [Cees Meijer] assumes they are unaffordable, so he built a replica and shows you how you can, too. [Scott Baker] built one recently; you can see his video below.

The resemblance to the Sinclair computer wasn’t just a coincidence. Richard Altwasser and Steven Vickers were behind the computer, and both had worked for Sinclair previously. In addition to being famous for using Forth, the machine initially had a badly manufactured case and an unreliable keyboard. A later version tried to correct these issues, but there were fewer than 1,000 made. [Cees’] replica used a design from [Grant Searle] with some modifications.

We liked the realistic look of the 3D printed keyboard. The keyboard uses white plastic with raised letters. A quick black spray paint followed by sanding gives the appearance of black keys with white printed text.

Overall, this is a good-looking build of a computer you probably won’t see in person. We wish Forth had caught on in the early PC world, but it didn’t. [Grant] was prolific with replica computers, and [Cees] isn’t the only one who used that work as a starting point for their own projects. If you want real old-school Forth, you have to go back a few more years.

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[Thomas Sanladerer] Gets New Threads

January 6, 2024 by 18 Comments

If you do much practical 3D printing, you eventually need some sort of fastener. You can use a screw to bite into plastic. You can create a clearance hole to accommodate a bolt and a nut or even build in a nut trap. You can also heat-set threaded inserts. Which is the best? [Thomas] does his usual complete examination and testing of the options in a recent video you can watch below.

[Thomas] uses inserts from [CNCKitchen] and some cheap inserts for 3D printing and some for injection molding. There are differences in the configuration of the teeth that bite into the plastic. [Thomas] also experimented with thread adapters that grab a 3D-printed thread.

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