Nixie Tube RPN Calculator Project

If you like Nixie tubes and/or DIY calculators, checkout this interesting talk from the HP Handheld Conference in Orlando last month by [Eric Smith] from Brouhaha and [John Doran] from Time Fracture. For 20-some years, [Eric] and the late [Richard Ottosen] have been incrementally developing various DIY calculators — this paper from the 2005 HHC conference is an excellent overview of the early project. [John] got one of those early DIY calculators and set about modifying it to use Nixie tubes. However, he got distracted by other things and set it aside — until reviving it earlier this year and enlisting [Eric]’s aid.

This presentation goes over the hardware aspects of the design. Unlike the earlier PIC-based DIY calculators, they decided to use a WCH RISC-V processor this time around. The calculator’s architecture is intentionally modular, with the display and keyboard housed in completely separate enclosures communicating by a serial interface. If the bulkiness alone doesn’t exclude it from being pocket-sized, the 170 VDC power supply and 1/2 W per digit power consumption certainly does. This modularity does lend itself to DIYers replacing the display, or the keyboard, with something different. [Eric] wants to build a mechanical flip-digit display for his unit. As for the software, [Eric] reviews the firmware approach and some future upgrades, such as making it programmable and emulating other flavors of HP calculators.

If you’re embarking on a similar project yourself, check out this talk and take notes — there are a lot of interesting tidbits on using Nixie tubes in the 21st century. If [Eric]’s name sounds familiar, you may know him from the Nonpareil calculator software used on many emulators and DIY calculator projects, one of which we covered some years ago. [John] is also a long-time tinkerer, and we wrote about his gorgeous D16/M HCMOS computer system back in 2012. Thanks to [Stephen Walters] for sending in the tip.

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Four large nixie tubes showing the number 2

[Dalibor Farný]’s Enormous Nixies Light Up Contemporary Art Museum

Nixie tubes come in many shapes and sizes, but in only one color: the warm orange glow that makes them so desirable. They don’t usually come in large numbers, either: a typical clock has four or six; a frequency counter perhaps eight or nine. But some projects go bigger – a lot bigger in [Dalibor Farný]’s case. He built an art installation featuring more than a hundred jumbo-sized nixie tubes that make an entire wall glow orange.

This project is the brainchild of renowned installation artist [Alfredo Jaar], who was invited to create an exhibition at the Hiroshima Museum of Contemporary Art. Its title, Umashimenkana, means “we shall bring forth new life” and refers to a poem describing the birth of a child amid the suffering and despair following the atomic bombing of Hiroshima. Visitors to the exhibit experience a dark room where they see a wall of orange numbers count down to zero and erupt into a waterfall of falling zeroes.

Nixie tube expert [Dalibor] was the go-to person to implement such an installation – after all, he’s one of very few people making his own tubes. But even he had to invest a lot of time and effort into scaling them up to the required 150 mm diameter, with 135 mm tall characters. We covered his efforts towards what was then known as the H-tube project two years ago, and we’re happy to report that all of the problems that plagued his efforts at the time have since been solved.

The cathodes of a large nixie tube being assembledOne of the major issues was keeping the front of the tubes intact during manufacture. Often, [Dalibor] and his colleagues would finish sealing up a tube, only for the front to pop out due to stress build-up in the glass. A thorough heating of the entire surface followed by a slow cooling down turned out to be the trick to evening out the stress. All this heat then caused oxidation of the cathodes, necessitating a continuous flow of inert gas into the tube during manufacture. Those cathodes already had to be made stronger than usual to stop them from flexing, and the backplate light enough to keep everything shock resistant. The list goes on.

After ironing out these quirks, as well as countless others, [Dalibor] was finally able to set up a small-scale production line in a new workshop to get the required 121 tubes, plus spares, ready for shipment to Japan. The team then assembled the project on-site, together with museum staff and the artist himself. The end result looks stunning, as you can see in the excellent video embedded below. We imagine it looks even better in real life – if you want to experience that, you have until October 15th.

You might remember [Dalibor] from his excellent video on nixie clock fault analysis – which we hope won’t be necessary for Umashimenkana. He might be able to make your favorite shape into a nixie tube, too. Thanks for the tip, [Jaac]!

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Turning Soviet Electronics Into A Nixie Tube Clock

Sometimes you find something that looks really cool but doesn’t work, but that’s an opportunity to give it a new life. That was the case when [Davis DeWitt] got his hands on a weird Soviet-era box with four original Nixie tubes inside. He tears the unit down, shows off the engineering that went into it and explains what it took to give the unit a new life as a clock.

Each digit is housed inside a pluggable unit. If a digit failed, a technician could simply swap it out.

A lot can happen over decades of neglect. That was clear when [Davis] discovered every single bolt had seized in place and had to be carefully drilled out. But Nixie tubes don’t really go bad, so he was hopeful that the process would pay off.

The unit is a modular display of some kind, clearly meant to plug into a larger assembly. Inside the unit, each digit is housed in its own modular plug with a single Nixie tube at the front, a small neon bulb for a decimal point, and a bunch of internal electronics. Bringing up the rear is a card edge connector.

Continues after the break…

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These Fake Nixie Tubes Have A Bootup Screen

[IMSAI Guy] bought a fake Nixie clock, and luckily for all of us has filmed a very close look and demonstration. Using OLED displays as the fake Nixie elements might seem like cheating to some, the effect is really very well done.

Clock digits with bootup screens is something we didn’t know we liked until we saw it.

When it comes to Nixie elements, it’s hard to say which gets more attention and project time from hardware folks: original Nixie tube technology, or fake Nixie elements. Either way, their appeal is certainly undeniable.

Original Nixie tubes have shown up in modern remakes of alarm clocks, and modern semiconductors make satisfying a Nixie tube’s power requirements much easier with clever and compact Nixie drivers costing under $3 USD. This is also a good time to remind people that Nixie tubes don’t have to be digits. This audio spectrum visualizer, for example, uses IN-13 tubes which serve as elements of a bar graph.

Authentic Nixie elements require high voltages and are labor-intensive to manufacture to say the least, and as far as fake Nixie elements go, this one looks pretty good once it lights up. You can see it in action in the video, embedded below.

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Dual Channel POV Display Also Has Nixie Tubes

What’s a tachyscope? According to [Daniel Ross], it is an animated display from an alternate timeline circa 1880. The real ones, of course, didn’t have LEDs and microcontrollers. The control unit looks like an old-timey radio, complete with Nixie tubes. The spinning part has blue and white LEDs, each accepting data from one of two serial ports. You can select to see data from one port, the other, or both. You can see the amazing contraption in the video below.

The LEDs are surface mounted and placed inside a glass test tube. Each display has its own processor. The project appears to have a PCB, but it is just a piece of fiberglass with a color print on top of it and holes drilled with a rotary tool. The board has no actual conductors — everything is point-to-point wiring. The base of the unit is old cookware. The slip ring is pretty interesting, too. It uses an old video tape head, D-cell batteries cut up, and contacts from a relay.

You might remember [Daniel] from his steampunk Victorian computer project, including a punk teletype and a magic eye tube. If you want some theory on these kinds of displays, we can help. If you just want a simple display, it doesn’t have to cost much.

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An IN-12B Nixie tube on a compact driver PCB

Modern Components Enable Cheap And Compact Nixie Driver Circuit

Nixie tubes can add some retro flair to any project, but they can also complicate your electronics quite a bit: after all, you need to generate a voltage high enough to ignite the tube and then switch that between ten separate display segments. Traditionalists may want to stick with chunky mains transformers and those unobtainium 74141 segment drivers, but modern components allow you to make things much more compact, not to mention way cheaper. [CNLohr] took this to an extreme, and used clever design tricks and his sharp online shopping skills to make an exceptionally compact Nixie driver circuit that costs less than $2.50.

That price doesn’t include the tubes themselves, but [CNLohr] nevertheless bought the cheapest Nixies he could find: a pair of IN-12B tubes that set him back just $20. He decided to generate the necessary 180 volts through a forward converter built around a $0.30 transformer and a three-cent MOSFET, controlled by software running on a CH32V003. This is one of those ultra-cheap microcontrollers that manage to squeeze a 48 MHz RISC-V core plus a bunch of peripherals into a tiny QFN package costing just 12 cents.

The existing toolchain to program these micros left a lot to be desired, so [CNLohr] wrote his own, called
ch32v003fun. He used this to implement all the control loops for the forward converter as well as PWM control of the display segments – a feature that adds a beautifully smooth turn-on and turn-off effect to the Nixie tubes. There’s still plenty of CPU capacity left to implement other features, although [CNLohr] isn’t sure what to put there yet. Turning the tubes into a clock would be an obvious choice, but the basic system is flexible enough to implement almost anything requiring a numeric display.

The compactness of this circuit is impressive, especially if you compare it to earlier solutions. There’s plenty of fun to be had with cheap-yet-powerful micros like the ch32v003, provided you can find them.

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The Nixie Clock From Outer Space

Nixie clocks are nothing new. But [CuriousMarc] has one with a unique pedigree: the Apollo Program. While restoring the Apollo’s Central Timing Equipment box, [Marc] decided to throw together a nixie-based clock. The avionics unit in question sent timing pulses and a mission elapsed time signal to the rest of the spacecraft. Oddly enough, while it had an internal oscillator, it was only used during failures. It normally synched to the guidance computer’s onboard clock.

There is a detailed explanation of the unit, along with some of the ancillary equipment and panels. Much of what the output from the unit is driving counters to display timers, although some of the clocks drive other pieces of equipment, like the telemetry commutator, which time stamps each telemetry frame.

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