Repurposing Moving Coil Meters to Monitor Server Performance

Snazzy analog meters can lend a retro flair to almost any project, but these days they often seem to be retasked as indicators for completely different purposes than originally intended. That’s true for these Vu meters repurposed as gauges for a Raspberry Pi server, and we think the build log is as informative as the finished product is good-looking.

As [MrWunderbar] admits, the dancing needles of moving-coil meters lend hipster cred to a project, but getting his Vu meters to cooperate and display network utilization and disk I/O on his Raspberry Pi NAS server was no mean feat. His build log is full of nice details on how to measure the internal resistance of the meter and determine a proper series resistor. He also has a lengthy discussion of the relative merits of driving the meters using a PWM signal or using a DAC; in the end, [MrWunderbar] chose to go the DAC route, and the video below shows the desired rapid but smooth swings as disk and network usage change. He also goes into great depth on pulling usage parameters from psutil and parsing the results for display on the meters.

Looking for more analog meter goodness? We saw a similar CPU load meter a few months back, and there was this mash-up of Nixies and old meters for a solar energy CEO’s desk.

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Wood Finish from old Records

Next time you’re working on a project that needs a durable wood finish, don’t grab the polyurethane. Follow [Victor Ola’s] advice and raid your grandparent’s record cabinet for some old 78 records. Modern records are made from vinyl. The stiff, brittle old 78’s from the 1960’s and earlier were made from shellac. Shellac is a natural material secreted by the female lac bug. It can be thought of as a natural form of plastic and was used as such for years until man-made plastics became commodity items.

Older 78 RPM phonograph albums are usually made entirely from shellac. [Victor] started by taking a few old cracked records and pulverizing them with a hammer. The shellac crumbs were then poured into a mason jar along with some isopropyl alcohol. The alcohol dissolves the shellac, creating a thick goo. More alcohol will thin the slurry down to a paintable consistency. The mixture is then ready to be painted on any wood surface. Wiping off the excess will reveal the wood grain.

Shellac is normally amber in color. Records are black because carbon is added to the mix. This makes the shellac stain dark and makes it a flat finish. While it would be fine to leave it this way, [Victor] added a coat of lacquer over his shellac stain to achieve a glossy finish on his upcycled gramophone.

If you’re getting into woodworking, don’t worry – anyone can do it. Just make sure you have sharp tools.

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This 6502 Computer Project Is A Work Of Art

If you were a home constructor in the 8-bit era, the chances are that if you built a microcomputer system you would have ended up with a bare printed circuit board and a terminal. If you were on a budget you might have had a piece of stripboard as well, or maybe even wire-wrap. Beautiful cases were out of reach, they came with expensive commercial computers that were not the preserve of impoverished hobbyists.

Constructing an 8-bit machine in 2017 is a much easier process, there are many more options at your disposal. There is no need to make a bare PCB when you have a 3D printer, and this is demonstrated perfectly by [Dirk Grappendorf]’s 6502 computer project. He’s built from scratch an entire 6502 system, with a text LCD display, and housed it in a case with a keyboard that would put to shame all but the most expensive commercial machines from back in the day.

But this is more than just a hobby project thrown together that just happens to have a nice case, he’s gone the extra mile to the extent that this is professional enough that it could have been a product. If you’d been offered [Dirk]’s machine in 1980 alongside the competitors from Apple and Commodore, you’d certainly have given it some consideration.

We’ve seen retrocomputers too numerous to mention on these pages over the years, so if they are your thing perhaps it’s time to draw your attention to our VCF West reports, and to our reviews of computer museums in Germany, and Cambridge or Bletchley, UK.

Thanks [Colin] for the tip.

The Best Stereo Valve Amp In The World

There are few greater follies in the world of electronics than that of an electronic engineering student who has just discovered the world of hi-fi audio. I was once that electronic engineering student and here follows a tale of one of my follies. One that incidentally taught me a lot about my craft, and I am thankful to say at least did not cost me much money.

Construction more suited to 1962 than 1992.
Construction more suited to 1962 than 1992.

It must have been some time in the winter of 1991/92, and being immersed in student radio and sound-and-light I was party to an intense hi-fi arms race among the similarly afflicted. Some of my friends had rich parents or jobs on the side and could thus afford shiny amplifiers and the like, but I had neither of those and an elderly Mini to support. My only option therefore was to get creative and build my own. And since the ultimate object of audio desire a quarter century ago was a valve (tube) amp, that was what I decided to tackle.

Nowadays, building a valve amp is a surprisingly straightforward process, as there are many online suppliers who will sell you a kit of parts from the other side of the world. Transformer manufacturers produce readily available products for your HT supply and your audio output matching, so to a certain extent your choice of amp is simply a case of picking your preferred circuit and assembling it. Back then however the world of electronics had extricated itself from the world of valves a couple of decades earlier, so getting your hands on the components was something of a challenge. I cut out the power supply by using a scrap Dymar Electronics instrument enclosure which had built-in HT and heater rails ready to go, but the choice of transformers and high-voltage capacitors was something of a challenge.

Pulling the amplifier out of storage in 2017, I’m going in blind. I remember roughly what I did, but the details have been obscured by decades of other concerns. So in an odd meeting with my barely-adult self, it’s time to take a look at what I made. Where did I get it right, and just how badly did I get it wrong?

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A Tiny Sharp MZ-80K That Really Works!

If you were a computer enthusiast in the late 1970s and early 1980s, one of your objects of desire may well have been a Sharp MZ-80K. This was an all-in-one machine from the Japanese electronics giant, and like Commodore’s PET line it included a CRT monitor, full alphanumeric keyboard and cassette tape drive in a smart console.

[Yasushi Enari] is a modeller of miniatures, and while at high school back in 1981 he made a perfect 1/5 scale model of an MZ-80K as an art project. Fast-forward to 2017, and with the help of a Raspberry Pi Zero, a miniature LCD composite video screen, and a Li-Po battery, he’s turned his 1981 model into a functioning computer.

Sadly he was not able to make his tiny 1981 plastic keyboard work, so an external Bluetooth unit is required to perform that function. And he makes no mention of running an MZ-80K emulator on the little machine, either. But the result is a work of art, and an odd collaboration between his adult and teenage self, something we are guessing most readers would be proud to own.

This isn’t the first tiny replica computer we’ve shown you, an Odroid W went into making this tiny Powermac from an American Girl doll’s toy computer.

Thanks [RC2014] for the tip.

CRT Cataract Surgery

Back in the good old days, people got their information by staring into particle accelerators that could implode at any moment, and we liked it that way, by gum! To protect against disaster, CRT monitors were equipped with a safety screen laminated to the front of the tube. Decades of use often resulted in degradation of the glue used to hold the safety glass on, leading to the dread disease of “CRT cataracts.”

Luckily for aficionados of vintage terminals, [John Sutley] has come up with a cure for CRT cataracts. The video below shows the straightforward but still somewhat fussy process from start to finish. You’ll want to follow [John]’s advice on discharging the high-voltage flyback section of any stored charge; we speak from painful experience on this. With the CRT removed from the case, removing the safety screen is as simple as melting the glue with a hot air gun and applying gentle leverage with a putty knife. We’d think a plastic tool would be less likely to scratch the glass, but [John] managed to get them apart without incident. Acetone and elbow grease cleaned off the old glue, and the restored CRT looks great when reassembled.

With its cataracts cured, [John] says his next step is to restore the wonky keyboard on his Lear Siegler ADM-3A terminal. Perhaps he should look over this VT220 keyboard repair for ideas.

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Do You Have An Endangered Craft?

It is probably fair to say that as Hackaday readers, you will all be people with the ability to make things. Some of you can make incredible things, as your writers we are in constant awe of the projects that pass through our hands. But even if you feel that your skills in the maker department aren’t particularly elite, you’ll have a propensity for work in this direction or you wouldn’t be here.

Most of the craft we feature involves technologies that are still very modern indeed to the majority of the population. We for example know that the first 3D printers were built decades ago and that we take them for granted on our benches, but to the Man In The Street they are still right up there with flying cars and time-travelling police telephone boxes.

We use 3D printers and microcontrollers because they are the tools of our age, but how different might our crafts have been if we’d been born a few centuries ago? Apprenticed to a master craftsman as teenagers, we (well, at least you boys!) would have learned  a single craft to a high level of expertise, making by hand the day-to-day products of life in those times.

The Industrial Revolution brought mechanisation and mass production, and today very few of the products you use will be hand-made. There may still be a few craftsmen with the skills to produce them by hand, but in the face of the mass-produced alternative there is little business for them and they are in inevitable decline. In an effort to do something about this and save what skills remain, the Heritage Crafts Association in the UK has published a list of dying crafts, that you can view either alphabetically, or by category of risk.

It’s a list with a British flavour as you might expect from the organisation behind it, after all for example hand stitched cricket balls are not in high demand in the Americas. But it serves also as a catalogue of some fascinating crafts, as well as plenty that will undoubtedly be of interest to Hackaday readers. Making hand-made planes, saws, or spades, for example, or at least where this is being written, coracle making.

As your Hackaday scribe this is close to home, a blacksmith carrying on her father’s business can’t earn enough to live in Southern England while an electronic engineer and technical journalist can. Eventually there will be one less blacksmith plying the craft, and though his tools and some of his skills will live on here, the business will not. Take a look at the list of crafts, do any of you have them? Or do you know of any craftspeople who have any of the skills listed, that the HCA might not know about? Let us know in the comments.

Treadle lathe image: Patrick-Emil Zörner (Paddy) [CC BY-SA 2.0].