Reactive Load For Amplifiers Teaches Lessons About Inductors

August 24, 2022 by Bryan Cockfield 26 Comments

The sound produced by any given electric guitar is shaped not just by the instrument itself but by the amplifiers chosen to make that sound audible. Plenty of musicians swear by the warm sound of amplifiers with vacuum tube circuits, but they do have some limitations. [Collin] wanted to build a reactive load for using tube amps without generating a huge quantity of sound, and it resulted in an interesting project that also taught him a lot about inductors.

The reactive load is essentially a dummy load for the amplifier that replaces a speaker with something that won’t produce sound. Passive loads typically use resistor banks but since this one is active, it needs a very large inductor to handle the amount of current being produced by the amplifier. [Colin] has also built a headphone output into this load which allows it to output a much smaller quantity of sound to a headset while retaining the sound and feel of the amplifier tubes, and it additionally includes a widely-used tone control circuit as well.

There’s a lot going on in the design of the circuitry for this amplifier load, including a lot of research into low-frequency inductors that can handle a significant amount of current. [Collin] eventually ended up winding his own, but the path he took to it was long and winding. There’s a lot of other circuit theory discussed as well especially with regards to the Baxandall EQ that he built into it as well. And, if you’d like to learn more about tube amplifiers in general, take a look at this piece which notes one of the best stereo amps ever produced.

Sputtering Daguerreotypes, Batman!

August 15, 2022 by Elliot Williams 14 Comments

The Daguerreotype was among the earliest photographic processes, long before glass plates or film, that relied on sensitizing a thin layer of silver on top of a copper plate. The earliest Daguerreotype plates were made physically, by rolling a copper-silver plate thinner and thinner until the silver layer was just right. Good luck finding a source of Daguerreotype plates made this way in 2022. (There are electroplating methods, but they all end up with chemically contaminated silver.)

On the other hand, magnetron sputtering is a process of depositing pure metal in thin layers using plasma, high voltages, and serious magnets, and [Koji Tokura] is making his own sputtered Daguerreotype plates this way, giving him the best of both worlds: the surreal almost-holographic quality of the Daguerreotype with the most difficult film preparation procedure imaginable.

The star of the show is [Koji]’s sputtering rig, which consists of a Tupperware glass sandwich box as a vacuum chamber and a microwave oven transformer as the high voltage source. In use, he pumps the chamber down, introduces a small amount of argon, and then lights up the plasma. The high voltage accelerates the plasma ions into a sheet of silver, and the silver particles that get knocked free coat the copper plate. A strong magnet creates a local plasma, which accelerates the coating procedure, but since [Koji] only had a relatively small magnet, he scans the plate with the magnet, using a scavenged 2D pen plotter mechanism.

Check out his video on the Hackaday.io page, and his Daguerreotype gallery as well. (We don’t think that they were all made with this procedure.)

The result is a chemically pure Daguerreotype plate produced in a seriously modern way, and we’d love to see the images in person. In these days of disposable images made by the AIs in your cell phone, it’s nice to see some people taking photography in strange directions. For instance, maybe you’d like to make your own ultra-large collodion plates. Or something else? If you do, show us!

Jigsaw Puzzles Are Defeated

August 4, 2022 by Brian McEvoy 30 Comments

To some folx, puzzles are the ultimate single-player game, but to others, they are like getting a single Tootsie Roll on Halloween. [Shane] of Stuff Made Here must fall into the latter category because he spent the equivalent of 18 work-weeks to make a robot that solves them automatically. Shots have been fired in the war on puzzles.

The goal of this robot is to beat a hybrid idea of two devilish puzzles. The first is all-white which could be solved by taking a piece at random and then checking its compatibility with every unsolved piece. The second is a 5000-piece monster painted white. There is a Moby Dick theme here. Picking up pieces like a human with fingers is out of the question, but pick-and-place machines solved this long ago, and we learn a cool lesson about how shop-air can create negative pressure. Suction. We wonder if anyone ever repurposed canned air to create a vacuum cleaner.

The meat of this video is overcoming hurdles, like a rhomboidal gantry table, helping machine vision see puzzle pieces accurately, and solving a small puzzle. [Shane] explains the solutions with the ear of someone with a technical background but at a high enough level that anyone can learn something. All the moving parts are in place, but the processing power to decode the puzzle is orders of magnitude higher than consumer machines, so that will wait for part two.

Continue reading “Jigsaw Puzzles Are Defeated” →

LEGO-Sorting Vacuum Defeats The Problem

March 24, 2022 by Kristina Panos 17 Comments

What’s the worst thing about LEGO? Most would agree that it’s the fact that those bright and colorful pieces of ABS are somehow the most evil thing that can come between your bare feet and solid ground. [Unnecessary Inventions] have done a one-eighty from their handle and made a quite useful invention — a LEGO-sorting vacuum cleaner called Suck It.

Well, technically, it’s a shop vac attachment, but it does the job beautifully. [Unnecessary Inventions] started with a never-used machine and a clear plastic cylinder cut into fourths. Then he designed some 3D printable brackets that have two jobs: they hold the cylinder together again, and they do so in stages that collect and sort LEGO by size.

The sorting brackets have no top and bottom layers to them — they are all sorting holes and infill to allow maximum suction. But wait, it gets even better, because the brackets click together satisfyingly with embedded magnets. The only thing that would make this build better is some kind of head attachment that could gather more than a narrow swath at a time. Be sure to check out the build and demo video after the break.

Of course, with this method, you still have to open up the sections and put your LEGO away. You could just vacuum them straight into the box.

Continue reading “LEGO-Sorting Vacuum Defeats The Problem” →

Pressure Gauge Built In A Vacuum

February 23, 2022 by Bryan Cockfield 6 Comments

Necessity might be the mother of all invention, but we often find that inventions around here are just as often driven by expensive off-the-shelf parts and a lack of willingness to spend top dollar for them. More often than not, we find people building their own tools or parts as if these high prices are a challenge instead of simply shrugging and ordering them from a supplier. The latest in those accepting the challenge of building their own parts is [Advanced Tinkering] who needed a specialty pressure gauge for a vacuum chamber.

In this specific case, the sensor itself is not too highly priced but the controller for it was the deal-breaker, so with a trusty Arduino in hand a custom gauge was fashioned once the sensor was acquired. This one uses an external analog-to-digital converter to interface with the sensor with 16-bit resolution, along with some circuitry to bring the ~8 V output of the sensor down to the 5 V required by the microcontroller. [Advanced Tinkering] wanted a custom live readout as well, so a 3D printed enclosure was built that includes both an LCD readout of the pressure and a screen with a graph of the pressure over time.

For anyone else making sensitive pressure measurements in a vacuum chamber, [Advanced Tinkering] made the project code available on a GitHub page. It’s a great solution to an otherwise overpriced part provided you have the time to build something custom. If you’re looking for something a little less delicate, though, take a look at this no-battery pressure sensor meant to ride along on a bicycle wheel.

Continue reading “Pressure Gauge Built In A Vacuum” →

Rapid-Reload Vacuum Cannon Totally Demolishes Those Veggies

January 14, 2022 by Dave Rowntree 9 Comments

[NightHawkInLight] has been developing his design for a vacuum canon for a while now, so it seems fitting to drop in check out the progress. The idea is pretty straightforward, take a long rigid tube, insert a close fitting piston, magnetically attached to a projectile, and stopper the open end with something easily destroyed. The piston needs to be pulled into the tube with some force, to pull a vacuum against the stopper. The interesting bit happens next, when the piston exits the other end of the tube, with the vacuum at its maximum, there is a sudden inrush of air. Apparently this inrush of supersonic velocity, and the momentum of the mass of air is sufficient to eject the projectile at considerable velocity, smashing through the plug and demolishing the target. So long as the target is of the soft and squishy variety anyway.

It’s an interesting idea, and certainly gives plenty of bang for not many bucks. That big lump of acrylic tubing (presumably used for ease of explanation in the video) looks fairly expensive to buy off the shelf, but we reckon any old pipe would probably work out fine.

We’ve definitely covered our share of DIY projectile weapons, like this air cannon made from PVC pipe parts, and of course there’s this crazy big one, that you should definitely not try at home.

Continue reading “Rapid-Reload Vacuum Cannon Totally Demolishes Those Veggies” →

Quantum Atomic Interferometer For Precision Motion Sensing

December 28, 2021 by Dave Rowntree 16 Comments

The current state of the art of embedded motion sensing is based around micro-electromechanical systems (MEMS) devices. These miracles of microfabrication use tiny silicon structures, configured to detect acceleration and rotational velocity in three dimensions. Accumulate these accelerations and rotations, and you’ve got a device that can find its orientation and track movement without any external waypoints. This is the basis of the technique of dead reckoning.

Why do we care about dead reckoning anyway? Surely GPS and related positioning systems are good enough? Above ground GPS is usually good enough, but underwater and underground this simply won’t work. Even heading indoors has a dramatic effect on the GPS signal strength, so yes, we need another way for some applications.

Right now, the current state of the art in portable sensors are MEMS devices, and you can get them for the cost of a hamburger. But if you want the ultimate in accuracy, you’ll want a quantum atomic interferometer. What that is, and how it will be possible to make one small enough to be useful, is half of the story. But first, let’s talk MEMS.

Continue reading “Quantum Atomic Interferometer For Precision Motion Sensing” →