A Primer On Optical Storage Data Preservation

Picking a storage medium for data preservation can be a conflicting time. Sure, they say optical storage tends to last, but it can’t be as straightforward as just burning everything onto Blu-Rays, right? Here’s a paper from Canadian Conservation Institute, teaching you the basics of using compact disks for data storage, it appears, without missing a single detail, and taking about ten minutes to read.

Here, you will learn about the different kinds of disks available and how their manufacturing-inherent qualities affect their preservation capabilities. Are dual-layer DVDs better than single-layer ones, or is it the opposite? How do CDs compare? And what about Blu-Ray disks? Wonder no more, here you will get answers to questions you didn’t known to ask. Data preservation is a game of numbers to preserve numbers, and this paper also outlines how to properly record, store, and test your disks to raise your chances.

Whether you’re only looking to delve into data preservation, or trying to improve your own policies, this looks like is a perfect document for you. After all, if you’re not aware of the best practices, you might end up having to digitize old floppies or even LaserDisks – not that those aren’t fun journeys to read about, of course, and we recommend it. Data preservation isn’t just about optical disks, of course – it’s a practice with a rich history.

Thrift Store CD Rack Turns Into Small Parts Storage Playground

What in the world could an accessory for an obsolete audio medium possibly have to do with keeping all your unruly bits and pieces in order? First of all, we’re not sure the CD is quite dead yet; we’ve got about a thousand of them packed away somewhere, and we’re pretty sure they’ll be back in style again one of these days. Until then, though, the lowly CD rack might be just what you need to get your shop under control.

As [Chris Borge] relates the story, he stumbled over this CD rack at a thrift sale and quickly realized its potential. All it took was some quick design work and a bit of 3D printing. Okay, a lot of 3D printing, including some large, flat expanses for the drawer bottoms, which can be a problem to print reliably. His solution was simple but clever: pause the print and insert a piece of stiff card stock to act as the drawer bottom before continuing to print the sides. This worked well but presented an adhesion problem later when he tried to print some drawer dividers, so those were printed as a separate job and inserted later.

Sadly, [Chris] notes that the CD format is not quite Gridfinity compatible, but that’s not a deal breaker. He also doesn’t provide any build files, but none are really necessary. Once you’ve got the basic footprint, what you do with your drawers is largely dependent on what you’ve got to store. The video below has a lot of ideas for what’s possible, but honestly, we’re looking at all those little parts assortment kits from Bojack and Hilitchi piled up in a drawer and just dreaming about the possibilities here. Add a voice-activated, LED inventory locator, and you’d really have something. Off to the thrift store!

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Old Clock Transformed Into Mesmerizing Light Display

It’s easy to find a cheap clock at any dollar store that will manage to tell the time, but chances are that the plastic-fantastic construction won’t do you any aesthetic favors. Fear not, though, for [ROBO HUB]’s upcycled design turns a humble clock into a mesmerizing horological display of beauty.

The build starts by scavenging the movement out of a cheap plastic clock. A CD is then glued to the front of the movement to serve as a reflective backing plate. For numerals, the clock uses F3, F6, F9, and F12 keys nabbed from a keyboard.

The real party trick, though, is in the lighting. This build is elevated beyond hackneyed 90s desk clocks by the inclusion of a ring of LED strip lighting. When switched on, the LED light reflects and refracts on the surface of the CD, creating a mesmerizing shifting pattern featuring all the colors of the rainbow.

CDs are actually quite magical from an optical perspective and have all kinds of nifty uses.

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Decoding Compact Disc Audio From Scratch

In the rare case we listen to an audio CD these days, we typically rely on off-the-shelf hardware to decode the 1s and 0s into the dulcet tones of Weird Al Yankovic for our listening pleasure. [Lukas], however, was recently inspired to try decoding the pits and lands of a CD into audio for himself.

A fair bit goes into decoding Red Book digital audio.

[Lukas] did the smart thing, and headed straight to the official Red Book Audio CD standard documents freely available on archive.org. That’s a heck of a lot cheaper than the €345 some publishers want to charge. Not wanting to use a microscope to read the individual pits and lands of the disc, [Lukas] used a DVD player. The electrical signals from the optical pickup were captured with an oscilloscope. 4 megasamples of the output were taken at a rate of 20 megasamples per second. This data was then ported over to a PC for further analysis in Python.

[Lukas] steps us through the methodology of turning this raw data of pits and lands into real audio. It’s a lot of work, and there are some confusing missteps thanks to the DVD player’s quirks. However, [Lukas] gets there in the end and shows that he truly understands how Red Book audio really works.

It’s always interesting to see older media explored at the bare level with logic analyzers and oscilloscopes. If you’ve been doing similar investigative work, don’t hesitate to drop us a line! 

Reading Data From A CD, With A Microscope

There was a time when electronic engineering students studied the audio CD, for all its real-world examples of error correction and control systems. There’s something to be found in the system still for young and old though, and thus we were intrigued when we saw [Peter Monta] reading the data from a CD using a microscope.

CDs encode data as so-called pits and lands in a spiral track across a metalised surface, with a transition from pit to land signifying a logic 1 and a missing transition signifying a 0. Reading a section of the raw data is achieved in the first part of his write-up, but in the next installment he goes further into retrieving more data through stitching together microscope pictures and writing some code to retrieve data frames. He’s not quite at the audio playback stage, but he’s planning in the future to spiral-track a full image to rip an entire disc.

There are plenty of CD drives around to read audio the conventional way, but the techniques here still find a use where less ubiquitous media has to be read. In the last decade for example there was an effort to read the BBC Domesday Project from the 1980s, as it became clear that few of the original readers survived in working order.

Scavenging CDs For Flexible Parts

CDs are becoming largely obsolete now, thanks to the speed of the internet and the reliability and low costs of other storage media. To help keep all of this plastic out of the landfills, many have been attempting to find uses for these old discs. One of the more intriguing methods of reprurposing CDs was recently published in Nature, which details a process to harvest and produce flexible biosensors from them.

The process involves exposing the CD to acetone for 90 seconds to loosen the material, then transferring the reflective layer to a plastic tape. From there, various cutting tools can be used to create the correct pattern for the substrate of the biosensor. This has been shown to be a much more cost-effective method to produce this type of material when compared to modern production methods, and can also be performed with readily available parts and supplies as well.

The only downside to this method is that it was only tested out on CDs which used gold as the conducting layer. The much more common aluminum discs were not tested, but it could be possible with some additional research. So, if you have a bunch of CD-Rs laying around, you’re going to need to find something else to do with those instead.

Thanks to [shinwachi] for the tip!

Retrotechtacular: 1990s CD Mastering Fit For A King

Before it was transformed into an ephemeral stream of ones and zeroes, music used to have a physical form of some kind. From wax cylinders to vinyl discs to tapes of various sizes in different housings and eventually to compact discs, each new medium was marketed as a technological leap over the previous formats, each of which justified incrementally more money to acquire.

But that’s the thing — each purchase resulted in you obtaining a physical item, which had an extensive manufacturing and distribution process behind it. And few artists demanded more manufacturing effort than Michael Jackson in his heyday, as revealed by this in-depth look at the CD manufacturing process for The King of Pop’s release of the HIStory double-disc set in 1995.

The video was produced as sort of a love letter to Michael from the staff and management of the Sony Music disc manufacturing plant in Pittman, New Jersey. The process is shown starting with the arrival of masters to the plant, strangely in the form of U-matic videocassettes; the 3/4″ continuous loop tape was normally used for analog video, but could also be used for recording digital audio. The digital audio is then sent for glass mastering, which is where the actual pits are created on a large glass disc under cleanroom conditions. In fact, much of the production process bears a strong similarity to semiconductor manufacturing, from the need for cleanrooms — although under less stringent conditions than in a fab — to the use of plasma etching, vapor deposition, and metal plating operations.

Once the master stampers are made, things really ramp up in replication. There the stamper discs go into injection molding machines, where hot polycarbonate is forced against the surface under pressure. The copies are aluminized, spin-coated with UV-cure lacquer, and sent on down the line to testing, screen printing, and packaging. Sony hired 40 extra full-time workers, who appear to have handled all the tedious manual tasks like assembling the jewel cases, to handle the extra load of this release.

As cheesy as this thank-you video may be, it was likely produced with good reason. This was a time when a Michael Jackson release was essentially a guarantee of full employment for a large team of workers. The team was able to produce something like 50,000 copies a day, and given that HIStory sold over 20 million copies, that’s a lot of workdays for the good folks at Pittman.

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