Broadcast TV Simulator Keeps The Nostalgia Flowing

September 26, 2024 by Dan Maloney 40 Comments

Watch out, Gen X-ers — there’s a nostalgia overload heading your way, courtesy of this over-the-air TV simulator. And it has us feeling a little Saturday morning cartoon-ish, or maybe even a bit Afterschool Special.

[Shane C Mason]’s “FieldStation42” build centers around a period-correct color TV, and rightly so — a modern TV would be jarring here, and replacing the CRT in this irreplaceable TV would be unthinkable. Programming comes via painstakingly collected sitcoms, dramas, news broadcasts, and specials, all digitized and stored on disk and organized by the original networks the programs came from. Python running on a Raspberry Pi does the heavy lifting here, developing a schedule of programs for the week that makes sense for the time of day — morning news and talk, afternoon soaps, the usual family hour and prime time offerings, and finally [Carson] rounding out the day, because that’s all we had for late night.

As for switching between stations, rather than risk damaging the old TV, [Shane] really upped his nostalgia game and found an old antenna rotator control box. These were used to steer the directional antenna toward different transmitters back in the day, especially in fringe areas like the one he grew up in. He added a set of contacts to the knob and a Pi Pico, which talks to the main Pi and controls which “channel” is being viewed. He also added an effect of fading and noise in the video and audio between channels, simulating the antenna moving. The video below shows it in action.

For those who missed the Golden Age of TV, relax; as [Shane] correctly surmises after going through this whole project, Golden Ages only exist in your mind. Things were certainly different with 70s mass media, a fact which this build captures neatly, but that doesn’t mean they were better. Other than Saturday mornings, of course — those were objectively better in every way.

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DOOM On A Volumetric Display

September 9, 2024 by Dave Rowntree 15 Comments

There’s something magical about volumetric displays. They really need to be perceived in person, and no amount of static or video photography will ever do them justice. [AncientJames] has built a few, and we’re reporting on his progress, mostly because he got it to run a playable port of DOOM.

Base view of an earlier version showing the motor drive and PSU

As we’ve seen before, DOOM is very much a 3D game viewed on a 2D display using all manner of clever tricks and optimizations. The background visual gives a 3D effect, but the game’s sprites are definitely very solidly in 2D land. As we’ll see, that wasn’t good enough for [James].

The basic concept relies on a pair of 128 x 64 LED display matrix modules sitting atop a rotating platform. The 3D printed platform holds the displays vertically, with the LEDs lined up with the diameter, meaning the electronics hang off the back, creating some imbalance.

Lead, in the form of the type used for traditional window leading, was used as a counterbalance. A Raspberry Pi 4 with a modified version of this LED driver HAT is rotating with the displays. The Pi and both displays are fed power from individual Mini560 buck modules, taking their input from a 12 V 100 W Mean-Well power supply via a car alternator slip ring setup. (Part numbers ABH6004S and ASL9009 for those interested.) Finally, to synchronise the setup, a simple IR photo interrupter signals the Pi via an interrupt.

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A Digital Replacement For Your Magic Eye

September 2, 2024 by Lewin Day 20 Comments

Magic Eye tubes were popular as tuning guides on old-school radio gear. However, the tubes, the 6U5 model in particular, have become rare and remarkably hard to come by of late. When the supply dried up, [Bjørner Sandom] decided to build a digital alternative instead.

The build relies on a small round IPS display, measuring an inch in diameter and with a resolution of 128×115 pixels. One can only presume it’s round but not perfectly so. It was then fitted with a 25mm glass lens in order to give it a richer, deeper look more akin to a real Magic Eye tube. In any case, a STM32F103CBT was selected to drive the display, with the 32-bit ARM processor running at a lovely 72 MHz for fast and smooth updates of the screen.

The screen, controller, and supporting circuitry are all built onto a pair of PCBs and installed in a 3D-printed housing that lives atop a tube base. The idea is that the build is a direct replacement for a real 6U5 tube. The STM32 controller receives the automatic gain control voltage from the radio set it’s installed in, and then drives the screen to behave as a real 6U5 tube would under those conditions.

By virtue of the smart design, smooth updates, and that nifty glass lens, the final product is quite a thing to behold. It really does look quite similar to the genuine article. If you’ve got a beloved old set with a beleagured magic eye, you might find this a project worth replicating. Video after the break.

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Film, As You Have Never Had It Explained Before

September 1, 2024 by Jenny List 17 Comments

For all the advances in digital photography, there remains a mystique for photographers and filmmakers about chemical film. Using it presents an artistic and technical challenge, and it lends an aesthetic to your work which is difficult to find in other ways. But particularly when it comes to moving pictures, how many of us have ever ventured beyond the Super 8 cartridge? If you’re not lucky enough to have a Spielberg budget, [Stand-Up Maths] is here with a video taking the viewer through the various movie film formats. He claims it’s the first video shot for YouTube in 35mm, and given that his first point is about the costs involved, we can see why.

In particular it serves as an introduction to the various film terms and aspect ratios. We all know what full frame and IMAX are, but do many of us know what they really mean in camera terms. A particularly neat demonstration comes when he has two cameras side by side with the same stock as a split screen, one 35mm and the other 16mm. The cheaper smaller framed format is good quality, but using a profession resolution chart you can see some of the differences clearly. The full film is below the break, and we’d suggest you watch it in the full 4K resolution if you are able to.

Meanwhile, some of us have been known to dabble in 8mm film, and even sometimes shoot footage with it.

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The Trashiest Of Mains Inverters

August 31, 2024 by Jenny List 21 Comments

Switch-mode technology has made inverters which take a low DC voltage and turn it into a usable mains voltage within the reach of everybody. But still, there might be moments when a mains supply is needed and you’re not lucky enough to have AliExpress at your fingertips, and for that, here’s [Rulof] with a mains inverter that is simultaneously awful and awesome. He’s made a rotary converter, from trash and off the shelf parts.

While a switch-mode converter operates using PWM at many times the output frequency for efficiency, we’re guessing that most readers will be familiar enough with how AC works to see how a low frequency converter turns DC into AC. A set of switches repeatedly flip the polarity, and the resulting square wave is fed into a transformer to step up to the final voltage. The switches can be mechanical as with old-style converters that used vibrating reeds or rotary armatures, or they can be electronic using power transistors. In this case they are a set of microswitches actuated by a set of cams on a shaft driven by a small motor, and the transformer comes from a surplus UPS.

We’re guessing that the frequency will be only a few Hz and the microswitches will suffer from switching such an inductive load, but as you can see in the video below the break it does light a mains bulb, and we’re guessing it would be enough to activate most wall-wart switching power supplies. We’re not so sure though about his use of the IEC sockets from the UPS to carry 12 volts, as the current may be a little much for them.

Meanwhile if you thirst for more of this kind of thing, we have you covered.

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A milling machine with an attached pantograph following the various intricate patterns of a spirograph on the bench next to it. The spirograph is a series of acrylic gears and brass connecting bars mounted on a wooden base.

Taking A Spirograph Mill For A Spin

August 31, 2024 by Navarre Bartz 3 Comments

Spirographs can make some pretty groovy designs on paper, but what if you want to take it a step further? [Uri Tuchman] has used the pantograph on his milling machine to duplicate the effect in harder materials.

[Tuchman] starts with a quick proof-of-concept using an actual plastic Spirograph toy to make sure it isn’t a totally unworkable idea. Unsurprisingly, the plastic is too flexible to give a highly detailed result on the MDF test piece, so he laser cut an acrylic version as the next prototype. This provided much better stiffness, but he needed to adjust gear ratios and ergonomics to make the device more usable.

The final iteration uses a combination of laser cut acrylic and machined brass components to increase rigidity where needed. A hand-turned knob for the crank adds a classy touch, as does the “Spiromatic 2000” brass plate affixed to the wooden base of the mechanism.

This isn’t the first spirograph-related project we’ve seen. How about one made of LEGO Mindstorms, another using Arduino, or one that makes these patterns on your oscilloscope?

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Make Your Own Point Contact Transistor

August 31, 2024 by Jenny List 22 Comments

Beyond the power variant, it sometimes seems as though we rarely encounter a discrete transistor these days, such has been the advance of integrated electronics. But they have a rich history, going back through the silicon era to germanium junction transistors, and thence to the original devices. if you’ve ever looked at the symbol for a transistor and wondered what it represents, it’s a picture of those earliest transistors, which were point contact devices. A piece of germanium as the base had two metal electrodes touching it as the emitter or collector, and as [Marcin Marciniak] shows us, you can make one yourself (Polish language, Google Translate link).

These home made transistors sacrifice a point contact diode to get the small chip of germanium, and form the other two electrodes with metal foil glued to paper. Given that germanium point contact diodes are themselves a rarity these days we’re guessing that some of you will be wincing at that. The video below is in Polish so you’ll have to enable YouTube’s translation if you’re an Anglophone — but we understand that the contact has to be made by passing a current through it, and is then secured with a drop of beeswax.

A slight surprise comes in how point contact transistors are used, unlike today’s devices their gain in common emitter mode was so poor that they took instead a common base configuration. There’s a picture of a project using three of them, a very period radio receiver with bulky transformers between all stages.

If you’re interested in more tales of home made early transistors, read our feature on Rufus Turner.

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