Homebrew Oscillator Is In A Glass By Itself

September 7, 2019 by Kristina Panos 8 Comments

Great things happen when we challenge ourselves. But when someone else says ‘I bet you can’t’ and you manage to pull it off, the reward is even greater. After [WilkoL] successfully made a tuning fork oscillator, his brother challenged him to make one out of a wine glass. We’ll drink to that!

First, [WilkoL] needed to find a way to make the wine glass vibrate continuously without having to stand there running a moistened finger around the edge. A piezo speaker mounted close by did the trick. Then he had to detect the sound waves, amplify them, and feed them back in.

After toying with the idea of making a laser microphone, and tossing aside the idea of a regular microphone (because squealing feedback), he settled on using light. LEDs didn’t work, probably because the light is too divergent. But he found out that by aiming a laser just right, the curve of the wine glass modulates the light, and the waves can be detected with a phototransistor. Then it was just a matter of amplifying the the sound and feeding it back to the piezo.

In the demo video after the break, you can see the vibrations in the glass manifest once he pours in some water. As anyone who’s ever played the water glasses can tell you, this also changes the frequency. [Editor’s note: I expected a much larger change in pitch. Not sure what’s going on here.]

Speaking of, here’s a steampunky glass armonica that uses an old turntable motor to rotate the wine glass, and a pneumatic cylinder to raise and lower the water level.

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Capture A Star In A Jar With Sonoluminescence

September 6, 2019 by Dan Maloney 19 Comments

If nothing else, [Justin Atkin] is persistent. How else do you explain a five-year quest to create sonoluminescence with simple tools?

So what exactly is sonoluminescence? The short answer is as the name suggests: a release of light caused by sound. In [Justin]’s case, he used an ultrasonic transducer to set up a standing wave at the resonant frequency of a flask of water. A drop of water is used to entrain a small air bubble, which is held in a stable position in the flask in much the same way as styrofoam beads are in an acoustic levitator. Turn off the lights and you’ll see that the bubble glows with a ghostly blue light.

What causes the glow? Good question. According to [Justin], we just don’t know for sure what causes it, although the leading theory is that cavitation of the bubble causes the trapped gas to compress and heat violently, turning into a brief bit of plasma. But there are problems with that theory, which is one of the reasons he wanted to show just how easy the process can be – now that he’s shaken out the bugs with five years of effort. It wasn’t easy getting the transducers attached and the driver circuit properly tuned, but with little more than a signal generator, an audio amp, and a spool of magnet wire, you too can make your own “star in a jar.”

We applaud [Justin]’s determination to bring this project to a successful conclusion. It’s not unlike his dogged effort to make a cold plasma torch, or even his desktop radio telescope.

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3D-Printed Film Scanner Brings Family Memories Back To Life

September 4, 2019 by Dan Maloney 14 Comments

There is a treasure trove of history locked away in closets and attics, where old shoeboxes hold reels of movie film shot by amateur cinematographers. They captured children’s first steps, family vacations, and parties where [Uncle Bill] was getting up to his usual antics. Little of what was captured on thousands of miles of 8-mm and Super 8 film is consequential, but giving a family the means to see long lost loved ones again can be a powerful thing indeed.

That was the goal of [Anton Gutscher]’s automated 8-mm film scanner. Yes, commercial services exist that will digitize movies, slides, and snapshots, but where’s the challenge in that? And a challenge is what it ended up being. Aside from designing and printing something like 27 custom parts, [Anton] also had a custom PCB fabricated for the control electronics. Film handling is done with a stepper motor that moves one frame into the scanner at a time for scanning and cropping. An LCD display allows the archivist to move the cropping window around manually, and individual images are strung together with ffmpeg running on the embedded Raspberry Pi. There’s a brief clip of film from a 1976 trip to Singapore in the video below; we find the quality of the digitized film remarkably good.

Hats off to [Anton] for stepping up as the family historian with this build. We’ve seen ad hoc 8-mm digitizers before, but few this polished looking. We’ve also featured other archival attempts before, like this high-speed slide scanner.

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Race RC Cars From Anywhere On Earth

August 31, 2019 by Lewin Day 9 Comments

Racing games have come a long way over the years. From basic 2D sprite-based titles, they’ve evolved to incorporate advanced engines with highly realistic simulated physics that can even be used to help develop real-world automobiles. For [Surrogate.tv], that still wasn’t quite good enough, so they decided to create something more rooted in reality.

The game is played in a web browser. Players are assigned a car and view the action from a top-down camera.

Their project resulted in a racing game based on controlling real RC cars over the internet, in live races against other human opponents. Starting with a series of Siku 1:43 scale RC cars, the team had to overcome a series of engineering challenges to make this a reality. For one, the original electronics had to be gutted as the team had issues when running many cars at the same time.

Instead, the cars were fitted with ESP8266s running custom firmware. An overhead GoPro is used with special low-latency streaming software to allow players to guide their car to victory. A computer vision system is used for lap timing, and there’s even automatic charging stations to help keep the cars juiced up for hours of play.

The game is free to play online, with the races currently operating on a regular schedule. We look forward to trying our hand at a race or three, and will be interested to see how the latency holds up from various parts of the world.

We’ve seen other remote RC builds before; usually featuring the power of the Raspberry Pi. We’ve also covered useful techniques for low latency video for real-time applications. Video after the break.

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Experiments In 3D Graphics Via Excel

August 29, 2019 by Lewin Day 10 Comments

3D graphics were once the domain of university research groups and large, specialized computing systems. Eventually, they were tamed and became mainstream. Your phone, tablet, and home computer are all perfectly capable of generating moving 3D graphics. Incidentally, so is Microsoft Excel.

This is the work of of [s0lly], who has been experimenting wtih Excel in this way for quite some time. Starting with pseudo-3D graphics, the project then progressed to the development of a real 3D engine. Naturally, things couldn’t stop there. The next logical step was to advance to raytracing, which was pulled off with aplomb. Shiny spheres on featureless planes are par for the course here.

The graphics are necessarily basic, with resolutions on the order of 256×144. Output is by changing the individual color of the various cells of the spreadsheet. The relevant files are available on Github, for those eager to tinker with experiments of their own. We’ve seen others attempt similar work before, with [C Bel] writing a full game engine for the platform. Video after the break.

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How The Power Gets To The Outlet

August 28, 2019 by Al Williams 10 Comments

[Practical Engineering] is ready to explain how power substations get electricity to you in his latest video, which you can see below. One of the things we always notice when talking to people either in our community or outside it is that most people have no idea how most of the modern world works.

Ask your non-technical friend to explain how a cell phone works or how a hard drive stores data and you aren’t likely to get a very good answer. However, even most of us are only focused on some particular aspect of electronics. There are a lot of people who hack on robots or radios. The AC power grid,though isn’t something a lot of people work with as a hobby. Do you know exactly what goes on in that substation you pass every day on your commute? If you don’t, you’ll learn something in the video.

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Finely Machined Valve Controls Miniature RC Hydraulics

August 28, 2019 by Dan Maloney 4 Comments

Hydraulic components are the industrial power transmission version of LEGO. Pumps, cylinders, valves – pretty much everything is standardized, and fitting out a working system is a matter of picking the right parts and just plumbing everything together. That’s fine if you want to build an excavator or a dump truck, but what if you want to scale things down?

Miniature hydraulic systems need miniature components, of which this homebrew hydraulic valve made by [TinC33] is a great example. (Video embedded below.) If you’re curious about why anyone would need these, check out the tiny hydraulic cylinders he built a while back, wherein you’ll learn that miniature RC snowplows are a thing. The video below starts with a brief but clear explanation about how hydraulic circuits work, as well as an explanation of the rotary dual-action proportional valve he designed. All the parts are machined by hand in the lathe from aluminum and brass stock. The machining operations are worth watching, but if you’re not into such things, skip to final assembly and testing at 13:44. The valve works well, providing very fine control of the cylinder and excellent load holding, and there’s not a leak to be seen. Impressive.

[TinC33] finishes the video with a tease of a design for multiple valves in a single body. That one looks like it might be an interesting machining challenge, and one we’d love to see.