A High Resolution ADC From Scratch

October 4, 2025 by Bryan Cockfield 6 Comments

It’s a well-known conundrum that while most computers these days are digital in nature, almost nothing in nature is. Most things we encounter in the real world, whether it’s temperature, time, sound, pressure, or any other measurable phenomenon comes to us in analog form. To convert these signals to something understandable by a digital converter we need an analog-to-digital converter or ADC, and [Igor] has built a unique one from scratch called a delta sigma converter.

What separates delta sigma converters apart is their high sampling rate combined with a clever way of averaging the measurements to get a very precise final value. In [Igor]’s version this average is provided by an op-amp that integrates the input signal and a feedback signal, allowing for an extremely precise digital value to be outputted at the end of the conversion process. [Igor] has built this one from scratch as well, and is using it to interface a magnetic rotary encoder to control digital audio playback.

Although he has this set up with specific hardware, he has enough detail in his video (including timing diagrams and explanations of all of the theory behind these circuits) for anyone else to build one of these for other means, and it should be easily adaptable for plenty of uses. There are plenty of different ADC topologies too, and we saw many different ones a few years ago during our op-amp challenge.

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A Treasure Trove Of Random Vintage Tech Resources

October 3, 2025 by Lewin Day 7 Comments

Finding, collecting, and restoring vintage tech is the rewarding pastime of many a Hackaday reader. Working with old-school gear can be tough, though, when documentation or supporting resources are hard to find. If you’re in need of an old manual or a little scrap of software, you might find the Vintage Technology Digital Archive (VTDA) a useful destination.

The VTDA is a simple website. There is no search function, or fancy graphical way to browse the resources on offer. Instead, it’s merely a collection of files in a well-ordered directory tree. Click through /pics/DiskSleeves/VTDA/ and you’ll find a collection of high-resolution scans of various old diskettes and their packaging. /docs/computing/Centronics/ will give you all kinds of useful documentation, from press releases to datasheets for printers long forgotten. You can even find Heathkit schematics and old Windows bootdisk images if you dive into the depths.

While it doesn’t have everything, by any means, the VTDA has lots of interesting little bits and pieces that you might not find anywhere else. It’s a great counterpart to other archival efforts out on the web, particularly if you’re a member of the retrocomputing massive.

Thanks to [Itay] for the tip!

On 3D Scanners And Giving Kinects A New Purpose In Life

October 2, 2025 by Maya Posch 32 Comments

The concept of a 3D scanner can seem rather simple in theory: simply point a camera at the physical object you wish to scan in, rotate around the object to capture all angles and stitch it together into a 3D model along with textures created from the same photos. This photogrammetry application is definitely viable, but also limited in the sense that you’re relying on inferring three-dimensional parameters from a set of 2D images and rely on suitable lighting.

To get more detailed depth information from a scene you’d need to perform direct measurements, which can be done physically or through e.g. time-of-flight (ToF) measurements. Since contact-free ways of measurements tend to be often preferred, ToF makes a lot of sense, but comes with the disadvantage of measuring of only a single spot at a time. When the target is actively moving, you can fall back on photogrammetry or use an approach called structured-light (SL) scanning.

SL is what consumer electronics like the Microsoft Kinect popularized, using the combination of a visible and near-infrared (NIR) camera to record a pattern projected onto the subject, which is similar to how e.g. face-based login systems like Apple’s Face ID work. Considering how often Kinects have been used for generic purpose 3D scanners, this raises many questions regarding today’s crop of consumer 3D scanners, such as whether they’re all just basically Kinect-clones.

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How A Failed Video Format Spawned A New Kind Of Microscope

September 23, 2025 by Lewin Day 11 Comments

The video cassette tape was really the first successful home video format; discs just couldn’t compete back in the early days. That’s not to say nobody tried, however, with RCA’s VideoDisc a valiant effort that ultimately fell flat on its face. However, the forgotten format did have one benefit, in that it led to the development of an entirely new kind of microscope, as explained by IEEE Spectrum.

The full story is well worth the read; the short version is that it all comes down to capacitance. RCA’s VideoDisc format was unique in that it didn’t use reflective surfaces or magnetic states to represent data. Instead, the data was effectively stored as capacitance changes. As a conductive stylus rode through an undulating groove in a carbon-impregnated PVC disc, the capacitance between the stylus and the disc changed. This capacitance was effectively placed into a resonant circuit, where it would alter the frequency over time, delivering an FM signal that could be decoded into video and audio by the VideoDisc player.

The VideoDisc had a capacitance sensor that could detect such fine changes in capacitance, that it led to the development of the Scanning Capacitance Microscope (SCM). The same techniques used to read and inspect VideoDiscs for quality control could be put to good use in the field of semiconductors. The sensors were able to be used to detect tiny changes in capacitance from dopants in a semiconductor sample, and the SCM soon became an important tool in the industry.

It’s perhaps a more inspiring discovery than when cheeky troublemakers figured out you could use BluRay diodes to pop balloons. Still fun, though. An advertisement for the RCA VideoDisc is your video after the break.

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Play Capacitor Cupid With The Matchmaker

September 23, 2025 by Donald Papp 5 Comments

Occasionally a design requires capacitors that are much closer to being identical in value to one another than the usual tolerance ranges afford. Precision matching of components from parts on hand might sound like a needle-in-a-haystack problem, but not with [Stephen Woodward]’s Capacitor Matchmaker design.

The larger the output voltage, the greater the mismatch between capacitors A and B.

The Matchmaker is a small circuit intended to be attached to a DVM, with the output voltage indicating whether two capacitors (A and B) are precisely matched in value. If they are not equal, the voltage output indicates the degree of the mismatch as well as which is the larger of the two.

The core of the design is complementary excitation of the two capacitors (the CD4013B dual flip-flop achieves this) which results in a measurable signal if the two capacitors are different; nominally 50 mV per % of mismatch. Output polarity indicates which of the capacitors is the larger one. In the case of the two capacitors being equal, the charges cancel out.

Can’t precision-matched capacitors be purchased? Absolutely, but doing so is not always an option. As [Stephen] points out, selection of such components is limited and they come at an added cost. If one’s design requires extra-tight tolerances, requires capacitor values or types not easily available as precision pairs, or one’s budget simply doesn’t allow for the added cost, then the DIY approach makes a lot more sense.

If you’re going to go down this road, [Stephen] shares an extra time-saving tip: use insulated gloves to handle the capacitors being tested. Heating up a capacitor before testing it — even just from one’s fingers — can have a measurable effect.

[Stephen]’s got a knack for insightful electronic applications. Check out his PWMPot, a simple DIY circuit that can be an awfully good stand-in for a digital potentiometer.

Oil-Based Sprengel Pump Really Sucks

September 17, 2025 by Tyler August 21 Comments

Have you heard of the Sprengel pump? It’s how they drew hard vacuum back before mechanical pumps were perfected — the first light bulbs had their vacuums drawn with Sprengel pumps, for example. It worked by using droplets of a particular liquid to catch air particles, and push them out a narrow tube, thereby slowly evacuating a chamber. The catch is that that liquid used to be mercury, which isn’t something many of us have on hand in kilogram quantities anymore. [Gabriel Wolffe] had the brainwave that one might substitute modern vacuum pump oil for mercury, and built a pump to test that idea.

Even better, unlike the last (mercury-based) Sprengel pump we saw, [Gabriel] set up his build so that no glassblowing is required. Yes, yes, scientific glassblowing used to be an essential skill taught in every technical college in the world. Nowadays, we’re glad to have a design that lets us solder brass fittings together. Technically you still have to cut an eyedropper, but that’s as complex as the glasswork gets. Being able to circulate oil with a plastic tube and peristaltic pump is great, too.

If you try it, you need to spring for vacuum pump oil. This type of pump is limited in the vacuum it can draw by the vapor pressure of the fluid in use, and just any oil won’t do. Most have vapor pressures far in excess of anything useful. In the old days, only mercury would cut it, but modern chemistry has come up with very stable oils that will do nearly as well.

How well? [Gabriel] isn’t sure; he bottomed out his gauge at 30 inches of Mercury (102 kPa). It may not be any lower than that, but it’s fair to say the pump draws a healthy vacuum without any unhealthy liquid metals. Enough to brew up some tubes, perhaps.

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Raytracing makes the design easier, but the building is still as tricky as ever.

A 10″ Telescope, Because You Only Live Once

September 16, 2025 by Tyler August 21 Comments

Why build a telescope? YOLO, as the kids say. Having decided that, one must decide what type of far-seer one will construct. For his 10″ reflector, [Carl Anderson] once again said “Yolo”— this time not as a slogan, but in reference to a little-known type of reflecting telescope.

Telescope or sci-fi laser gun? YOLO, just try it.

The Yolo-pattern telescope was proposed by [Art Leonard] back in the 1960s, and was apparently named for a county in California. It differs from the standard Newtonian reflector in that it uses two concave spherical mirrors of very long radius to produce a light path with no obstructions. (This differs from the similar Schiefspiegler that uses a convex secondary.) The Yolo never caught on, in part because of the need to stretch the primary mirror in a warping rig to correct for coma and astigmatism.

[Carl] doesn’t bother with that, instead using modern techniques to precisely calculate and grind the required toric profile into the mirror. Grinding and polishing was done on motorized jigs [Carl] built, save for the very final polishing. (A quick demo video of the polishing machine is embedded below.)

The body of the telescope is a wooden truss, sheathed in plywood. Three-point mirror mounts alowed for the final adjustment. [Carl] seems to prefer observing by eye to astrophotography, as there are no photos through the telescope. Of course, an astrophotographer probably would not have built an F/15 (yes, fifteen) telescope to begin with. The view through the eyepiece on the rear end must be astounding.

If you’re inspired to spend your one life scratch-building a telescope, but want something more conventional, check out this comprehensive guide. You can go bit more modern with 3D printed parts, but you probably don’t want to try spin-casting resin mirrors. Or maybe you do: YOLO!

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