Another Tesla Coil Starts

Everyone interested in electronics should build at least one Tesla coil. But be careful. Sure, the high voltage can be dangerous, but the urge to build lots of coils is even worse. [Learnelectronics] shows how to build a slayer exciter using a 3D-printed core, and lots of wire of course. You can see the coil, an explanation of the design, and a comparison to a cheap kit in the video below.

Of course, you hear about Tesla coils, but it is really more of a Tesla transformer. The 3D-printed core holds the many turns of the secondary coil. The larger Tesla coil, amusingly, upset the camera which made it hard to get close-up shots.

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A Picture Frame For Your Eyes Only

We can think of all kinds of reasons you’d want to display a picture that only you and the family can see, and we don’t even have to work blue to do it. Whether as a joke, or as a serious way to hide a special image, this magical picture frame by [Placitech] is just the thing.

You might recognize this as using PDLC switchable “smart” film. Whenever power is applied, the panel goes from frosty opacity to near-crystal clarity in an instant. The trick here is to to image recognition and only allow certain faces to unlock the picture.

The brains of this operation is an ESP32-CAM module, which does all the heavy lifting of getting the image in the first place, handling it, and deciding via code who is eligible to flick the switch. Everything is housed in a nice 3D printed frame that [Placitech] designed.

Be sure to check out the build video after the break, and files are available via [Placitech]’s Discord if you’d like to build this yourself.

There’s a lot you can do with PDLC panels, as evidenced by this amazing dress.

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Putting The C In C64

Older CPUs and some fairly modern microcontrollers are not made to readily support C compilers. Among those are the 1802, some 8-bit PICs, and the 6502 at the heart of the Commodore 64. That’s not to say you can’t make a C compiler for any of them, but the tricks required to handle the odd word sizes, lack of stack manipulation, or whatever other reason C isn’t a good fit tends to make compiled code bloated and possibly slower. [Dr. Mortal Wombat] took a different approach. The oscar64 compiler takes C source code and compiles it to a virtual machine code or native machine code for cases where performance might be important.

Turns out, the penalty for using native code isn’t as much as predicted, at least in some cases, The performance penalty for using the interpreter, however, can be significant in many common cases. The 6502 has a small stack that is hard to address, and indexing into a user-maintained stack is slow. The word size problem also produces lots of code as you have to break 16-bit operations into multiple 8-bit ones. The compiler aims to be C99-compliant, including floating point, recursion, multiple dimensions for arrays, and pointers to structures.

There are a few things left to hammer out. The linker doesn’t support external libraries, and the floating point code doesn’t understand NaN. On the other hand, many C++ features are available, like namespaces, reference types, templates, and more. The compiler can target several Commodore machines from the C128 to the PET. It also works with some Nintendo and Atari systems and can create various cartridge formats.

If you are writing code for any kind of 6502, it is probably worth checking out. Compiling C for the 6502 is no small feat, but then, so it is targeting PowerPoint. Don’t have a C64? Build one.

Image: [MOS6502], CC-BY-SA 3.0

Darkroom Robot Automates Away The Tedium Of Film Developing

Anyone who has ever processed real analog film in a darkroom probably remembers two things: the awkward fumbling in absolute darkness while trying to get the film loaded into the developing reel, and the tedium of getting the timing for each solution just right. This automatic film-developing machine can’t help much with the former, but it more than makes up for that by taking care of the latter.

For those who haven’t experienced the pleasures of the darkroom — and we mean that sincerely; watching images appear before your eyes is straight magic — film processing is divided into two phases: developing the exposed film from the camera, and making prints from the film. [kauzerei]’s machine automates development and centers around a modified developing tank and a set of vessels for the various solutions needed for different film processes. Pumps and solenoid valves control the flow of solutions in and out of the developing tank, while a servo mounted on the tank’s cover gently rotates the reel to keep the film exposed to fresh solutions; proper agitation is the secret sauce of film developing.

The developing machine has a lot of other nice features that really should help with getting consistent results. The developing tank sits on a strain gauge, to ensure the proper amount of each solution is added. To avoid splotches that can come from using plain tap water, rinse water is filtered using a household drinking water pitcher. The entire rig can be submerged in a heated water bath for a consistent temperature during processing. And, with four solution reservoirs, the machine is adaptable to multiple processes. [kauzerei] lists black and white and C41 color negative processes, but we’d imagine it would be easy to support a color slide process like E6 too.

This looks like a great build, and while it’s not the first darkroom bot we’ve seen — we even featured one made from Lego Technics once upon a time — this one has us itching to get back into the darkroom again.

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There Are Stradi-various Ways To Make A Violin, And This Is One

We’ve always said that if we had enough money, we’d have a large room that housed every musical instrument we’ve ever been even mildly interested in. While that dream may never come to pass, it would be far more likely to happen if many of the instruments could be 3D-printed, like this electric violin.

We really like this compact design, which mimics a headless guitar with the tuning pegs down by the bridge. [Carmensr] started with a model on Thingiverse, which uses violin strings wound around electric guitar tuners instead of wooden friction pegs. To further the guitar comparison, the three-piece neck contains a truss rod of sorts.

So how does it work, though? The magic is in the special bridge, which contains a piezo element. The bridge picks up the strings’ vibrations and sends them to a little pre-amplifier, which creates a signal that can then be used by a program like Audacity or connected directly to a speaker. Be sure to give it a listen in the video after the break.

Of course, there’s no reason not to design and print acoustic violins. It would be fun to experiment with different filaments for different sounds.

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Make Your Own Play Station (The Space Is Important)

The early history of the Sony Playstation lies in a stillborn collaboration between Nintendo and Sony to produce an SNES with a CD-ROM drive. So the story goes, Nintendo’s Philips deal angered Sony, who decided to make their own console line, and the rest is history. A very small number of prototypes were made, badged as “Play Station,” and should you find one that escaped today, you’re sitting on a fortune. [James] doesn’t have one, but he did have half a Playstation and an SNES shell, so he could make an ungodly child of the two consoles that you can see in the video below the break.

Those Playstation CD-ROM drives were notorious for melting back in the day, so it’s no surprise they’re still for sale today. Thus, he was able to bring the Sony back to life. What follows is an episode of console cutting worthy of a slasher horror movie, as instead of a bit of fine Dremmeling, he brings out an angle grinder and slices away with abandon. We don’t like the Nintendo switch carrying mains voltage, but we’re fine with the PlayStation expansion connector going away. The Nintendo eject button needs a hack to operate the Playstation door open button when pressed. It’s cool to see the board has a mod chip. We used to fit those as a sideline in a previous life. Continue reading “Make Your Own Play Station (The Space Is Important)”

Liquid Tin Could Be The Key To Cheap, Plentiful Grid Storage

Once expensive and difficult to implement, renewable energy solutions like wind and solar are now often the cheapest options available for generating electricity for the grid. However, there are still some issues around the non-continuous supply from these sources, with grid storage becoming a key technology to keep the lights on around the clock.

In the quest for cost-effective grid storage, a new player has entered the arena with a bold claim: a thermal battery technology that’s not only more than 10 times cheaper than lithium-ion batteries, but also a standout in efficiency compared to traditional thermal battery designs. Fourth Power is making waves with its “sun in a box” energy storage technology, and aims to prove its capabilities with an ambitious 1-MWh prototype.

Hot Stuff

Simple heating elements turn electricity into heat, putting it into liquid tin that then heats large graphite blocks. Credit: Fourth Power, Vimeo screenshot

The principle behind Fourth Power’s technology is deceptively simple: when there’s excess renewable energy available, use it to heat something up. The electrical energy is thus converted and stored as heat, with the idea being to convert it back to electricity when needed, such as at night time or when the wind isn’t blowing. This concept isn’t entirely new; other companies have explored doing this with everything from bricks to molten salt. Fourth Power’s approach involves heating large blocks of graphite to extremely high temperatures — as high as 2,500 °C (4,530 °F). Naturally, the hotter you go, the more energy you can store. Where the company’s concept gets interesting is how it plans to recover the heat energy and turn it back into electricity.

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