Introduction & VFD Tube Calculator

[Senk Ju]

Hello!

I'm new to this group and wanted to take the opportunity to introduce myself quickly.

My interest in Nixie tubes started in 2016 when I saw this video by Techmoan. I bought a ready-made Nixie clock shortly after, but never considered building my own projects with them, as I knew they required fairly high voltages and I didn't have any experience in electrical engineering.

Last year, however, I was sitting around bored and remembered that I had always wanted to build something using a microcontroller. I'm usually more of a software guy, but I've always found the prospect of writing software that actually does something "in reality" intriguing. I didn't feel comfortable working with high voltages, so I did some research into alternative display technologies with a similar charm to Nixies, and stumbled upon VFD tubes.

Without any real plan in mind, I ordered some from an Ukrainian seller on eBay. I initially considered using IV-11 tubes, but decided to use IV-12 instead, as I preferred them to have real pins that could be used with a socket.

It took me almost 10 months to complete my project, mostly because I was learning along the way and didn't own any equipment when I started. I am, howver, very pleased with the outcome. I have created a GitHub repository with more details for those who are interested.

https://github.com/oskar2517/vfd-tube-calculator

I now feel relatively comfortable working with Nixie tubes (mostly because I now own a power supply that lets me lower the current to a non-lethal value) and am currently in the midst of building my first Nixie clock using ZM1020 tubes for the digits and a ZM1070 tube for the seconds' indicator.

I'm not only interested in Nixie tubes, but most of the display technology from around that period. Besides Nixies and VFD tubes, I have played around with Numitrons, Dekatrons and Pixie tubes and have recently acquired an E1T tube which I am looking forward to figuring out how to drive.

Senk Ju

[Paolo Cravero]

Well done and well documented Senk Ju (except there are no comments in your very clean code)!

As far as the division operation goes, you may use a software trick to display the decimal part: the integer part is shown as the result, but press-and-hold the equal (rocket) button will display the decimal part. Or let the equal button switch between integer and decimal, but that become confusing. This trick, using a dedicated key, was used on some 1970's calculator that had too few digits to display a full result that was supported by the computing logic, instead.

Reading your code I noticed you used the standard Arduino digitalRead/digitalWrite library functions. They hide lots of sanity checks and they are pretty slow (56 cycles people say). digitalReadFast/digitalWriteFast or direct access would provide a faster I/O (down to 2 cycles) at the expense of loosing readability of your code. You probably don't need this kind of optimisation with 5 digits but I am sure your journey will not stop here :)

I think that early LED displays are equally fascinating, have a very peculiar deep red color (660 nm) and are easier to drive. They do draw "high" current as their efficiency was low, resulting in heat generation which leads to self-destruction: just run them at the lower acceptable supply voltage.

Paolo

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[Senk Ju]

Thank you! 

Good idea about the division. I will definitely implement it like this.

I didn't know about digitalReadFast/digitalWriteFast. They will certainly come in handy at some point. As you expected, with the five tubes of my calculator, regular I/O operations seem to be fast enough. At least I don't see any flicker in the multiplexing.

I agree with old LED displays being fascinating. I have only seen them in pictures and videos by people telling me how nice they look so far. I will have to take a closer look at them.

As for comments, yeah, I'm a bit lazy about that. I saw someone forked the project and, from the looks of it, had an AI document the code for them. I will try to better myself :)

Senk Ju

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