VFD Tube Calculator Shows Off Wide Array Of Skills

With all the tools and services available to us these days, it’s hard to narrow down a set of skills that the modern hacker or maker should have. Sure, soldering is a pretty safe bet, and most projects now require at least a little bit of code. But the ability to design 3D printable parts has also become increasingly important, and you could argue that knowledge of PCB design and production is getting up there as well. With home laser cutters on the rise, a little 2D CAD wouldn’t hurt either. So on, and so on.

If you ever wanted an example of the multitude of skills that can go into a modern hardware project, take a look at this gorgeous Vacuum Fluorescent Display (VFD) tube calculator built by [oskar2517]. As fantastic as the final product is, we were particularly impressed with everything it took to get this one over the finish line.

A .7 mm walnut veneer covers the pieced together plywood frame.

It’s got it all: 3D printed parts, a laser cut wooden frame, a custom PCB, and even a bit of old school woodworking. To top it all off, the whole thing has been meticulously documented.

But what’s perhaps most impressive here is that [oskar2517] was approaching most of these techniques for the first time. They had never before worked with IV-12 tubes, designed an enclosure in 3D, had parts laser cut, applied wood veneer, or designed a custom PCB. They did have solid experience writing code in C at least, which did make developing the Arduino firmware a bit easier.

Although they might look outwardly similar, VFD tubes like the IV-12 are easier to work with than Nixie tubes thanks to their lower operating voltage. That said, a look through our archives shows that projects using Nixies outnumber VFD tubes by nearly four to one, so there’s no shortage of folks willing to take on the extra effort for that sweet warm glow.

A Human-Sized Strowger Telephone Exchange

A large hacker camp such as EMF 2024 always brings unexpected delights, and one of those could be found in the Null Sector cyberpunk zone: a fully functional Strowger mechanical telephone exchange. Better still, this wasn’t the huge array of racks we’ve come to expect from a mechanical exchange, but a single human-sized unit, maybe on a similar scale to a large refrigerator. [LBPK]’s PAX, or Private Automatic Exchange, is a private telephone network, 1950s style.

It stood at the back of the container, with a row of four telephones in front of it. We particularly liked the angular “Trimphone”, the height of 1960s and 70s chic. You could dial the other phones in the network with a two digit number, and watch the exchange clicking in the background as you did so. Some of the sounds weren’t quite the same as the full-sized equivalents, with the various tones being replaced by vibrating reeds.

This exchange has an interesting history, being built in 1956 by “Automatic Telephone & Electric” for the Midlands Electricity Board, power generator for much of central England, where it served its commercial life. On decommissioning it went to the Ffestiniog narrow gauge railway, in Wales. He was lucky enough to learn of its existence when the Ffestiniog had no further use for it, and snapped it up.

We have to admit, we want one of these, however he makes clear that it’s an unwieldy machine that requires quite some attention so a Hackaday mechanical exchange will have to remain a dream for now.

Why Your Old Phone Sounded The Way It Did

The mobile phone may be sweeping away the traditional wired phone, but that doesn’t change the fascinating history and technology of the older device. At [This Museum Is Not Obsolete] they have a fully functional mechanical telephone exchange as one of their exhibits, and they’ve published a video examining the various sounds it’s capable of making.

When a voice synthesiser was the stuff of science fiction, exchange status couldn’t be communicated by anything but a set of different tones. If you’ve ever encountered a mechanical exchange you’ll recognise the harsh-sounding low-frequency dial tone, and the various sets of beeps denoting different call status. These were produced with a set of oscillators being switched in and out by shaped cams, and the bank of these on their exchange is most of the subject of this video. The common ones such as the engaged tone and the dial tone are explained, but also some we’d never heard such as the one signifying the exchange as out of capacity.

We may never own a mechanical exchange of our own, but we’re glad that someone does and is sharing it with us. You can see the video below the break.

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The end result of the build, a supersized ultrasonic sensor, held in a person's hands

A Super-Size Functional Tribute To An Ultrasonic Sensor

Sometimes, it’s time to shut down the oscilloscope, and break out the cardboard and paints. If you’re wondering what for, well, here’s a reminder of an Instructable from [CrazyScience], that brings us back to cardboard crafts days. They rebuild one of the most iconic components for an electronics tinkering beginner — an ultrasonic distance sensor, and what’s fun is, it stays fully functional after the rebuild!

This project is as straightforward as it gets, describing all the steps in great detail, and you can complete it with just a hot glue gun and soldering iron. With materials being simple cardboard, aluminum foil, popsicle sticks, some mesh, and a single ultrasonic sensor for harvesting the transmitter and receiver out of, this is the kind of project you could easily complete with your kids on a rainy day.

Now, the venerable ultrasonic sensor joins the gallery of classics given a size change treatment, like the 555 timer we’ve seen two different takes on, or perhaps that one Arduino Uno. Unlike these three, this project’s cardboard skeleton means it’s all that simpler to build your own, what’s with all the shipping boxes we accumulate.

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Tiny Orrery Is A Watchmaker’s Tour De Force

Six tiny gears, a few fancy pins, and some clever casting are what it takes to build this tiny orrery. And patience — a lot of patience, too.

As model solar systems go, this one is exceptionally small. Its maker, [Mike] from Chronova Engineering, says it measures about 20 mm across and qualifies as the smallest orrery around. We can’t officiate that claim, but we’re not going to argue with it either. It’s limited to the Sun-Earth-Moon system, and while not as complete as some other models we’ve seen, it’s still exquisitely detailed. The gears that keep the Moon rotating 12.4 times around the Earth for each rotation of our home planet around the Sun are tiny, and take an abundance of watchmaking skill to pull off.

The video below shows the whole process, which is absolutely entrancing to watch. There are some neat tricks on display, from milling out the arms of the main wheel using a powered tailstock spindle to casting the Sun from resin in a silicone mold. The final model, with the model Earth and Moon spinning around the Sun on delicate brass wheels, is a visual treat.

We’ve seen some interesting stuff from Chronova Engineering lately, including this bimetallic tea timer.

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A person holds a glass jar in their left hand and a spark plug in their right atop a white cylindrical canister. The jar and canister are sitting on top of a green cutting mat.

Spark Plug Becomes Glass Cutter

Sometimes a hack doesn’t need to be rocket science to be useful. Take for instance [MofigoDIY] using an old spark plug to build a glass cutter.

Sure, going to grab a glass cutter at the hardware store might be easy, but there’s something satisfying about going the DIY route. [MofigoDIY]’s version of this classic hack is a bit more refined than the quick and dirty route of smashing the spark plug alumina and hot gluing it into a tube.

After using a rotary tool to cut off the threads and expose the narrow part of the ceramic, [MofigoDIY] grinds it down to a fine point. This lets the spark plug itself become the handle, so you don’t need any additional parts to make the cutter. Toward the end of the video, a heated wire is used to break a glass jar apart after it was scored which might be of interest even if you already have a glass cutter. Once you’re finished making your glass cutter, make sure you dispose of any chips left over, since ceramic spark plug fragments are considered burglary tools in some areas.

Would you rather just build the glass up additively? How about using a laser cutter to sinter glass or 3D printing fused silica using a polymerized composite precursor?

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Rotary Phone Lives On As Arduino Kitchen Timer

It’s safe to say that few people still use rotary phones on a daily basis. Hell, most of us don’t even use landline telephones anymore. But just because these classic phones are no longer being used for their original purpose doesn’t necessarily mean they’re doomed to become e-waste.

[Scott-28] recently sent in a particularly well-documented project that turned an antique rotary phone into a digital kitchen timer using an internal Arduino. While we’re not sure practical is a word most folks would use to describe the resulting device, it’s certainly a conversation starter, and the details on how it was all implemented make for an interesting read.

As explained in the README, [Scott-28] first used an oscilloscope to figure out the pulses generated by the phone’s dial. From there, it was relatively easy to connect the dial to one of the pins on an Arduino Uno to determine which numbers the user had entered. The trickier part was getting the original bells to work — in North America, it takes up to 90 VAC to get a phone’s ringer going, which is quite a bit more than the lowly Arduino can handle.

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