Project Kickoff: The Cold War Clock
Michael Mechmann
Michael Mechmann


Let’s get this party started!

So I finally got a halfway-decent work bench for the garage, and a new soldering iron to replace the twenty-year-old RadioShack special I’ve been working with for way too long. I’m not sure I trust that thing to be plugged in anymore without bursting into flames.

The important thing, though, is now I have a space where the cats A) don’t notice that I’m gone; and B) can’t interfere if I’m running a 400° soldering iron. I’m sure A won’t last too long but for now at least it’s somewhere I can escape the desperate screaming Nemo does every time someone closes a door.

So What Is This Project?

The “Cold War Clock” is basically Yet Another Nixie Tube Clock project. I know, it’s overplayed, but dangit if I don’t like the look of them neon tubes. Don’t worry, I won’t be putting blue LEDs in this one — it’s all neon, all the way.

What does the Cold War have to do with it? Nothing but the aesthetics (oh, sorry, I mean the AESTHETICS). In addition to the clock, I intend to include a Bluetooth receiver or perhaps a full-fledged Raspberry Pi so that I can use it as an internet radio receiver as well, basically making it a retro-futuristic clock radio. If I go the Pi route I’ll want to have a small screen that at least looks like a CRT display, and whatever the audio source I have some analog VU meters that should round the whole look out.

What’s The Status?

The project has officially moved from “design” phase to “build” phase, and — as you can see in the image above — I’ve tested the Nixie tubes and their high-voltage power supply.

I’ve also tested some of the antique Russian Nixie driver chips that I got, and the VU meters, just to make sure that they work. I do have a bunch of new TI bit shift registers that I’ll be using as inputs for the Nixie drivers that I haven’t tested yet, but I feel more confident that they’ll work.

The last design-phase piece is really just deciding if I want to put a whole dang Raspberry Pi in this thing. I may start off with a Bluetooth audio module just to get things going, but the challenge is that the Nixie driver chips expect parallel binary input (meaning they have four separate pins for input that must be set simultaneously). There are other high-voltage switching chips out there, but they are all disastrously small, and would require a custom PCB, and I’m 90% sure I can’t solder anything that size at my current skill level. So the question becomes: if I don’t want to put a Pi in there, where is the binary clock signal coming from?

I’ve looked around at some binary clock circuits, and right away I found one big problem: most of them do the smart thing and don’t separate out the individual digits, but rather have a single binary number to represent each time component (hours, minutes, and seconds). For the Nixie clock, I would need a separate binary nibble for each tube, each digit. I did find at least one clock circuit that separates the digits into their own binary displays, but it relies on a specific RadioShack part for both power and 60Hz signal. This brings me to the second big problem: lots of these projects instruct you to cannibalize a wall clock to get its crystal oscillator, and many of these pages say this as though it’s the most natural thing in the world. Now maybe it’s just me, but I wouldn’t recognize a clock oscillator if it slapped me in the nuts. And I’m not sure I really want to buy a new clock just to brutalize it so I can then build what is a somewhat complex circuit. The Pi (or something similar) can be used along with those bit shift register chips I mentioned before, which turn serial binary into parallel, eliminating a significant amount of build time — though it does add some amount of programming time as a result.

Ultimately, I suspect that the potential benefit of not having to manually set the time will pull me toward using a Pi or other mini-computer as the brains behind this thing. But we shall see! There’s a lot to do before that.

What’s Next?

Next I’ll be testing all of the Nixie driver chips on all digit channels to make sure they all work, and then testing them in series with the bit shift registers to ensure I can convert arbitrary 6-digit numbers into sensible outputs. So ideally the next update will have lots of lovely pictures of tubes all lit up and such.

How Often Will You Update?

Good question! I don’t know, but more often than “never.” I guess you’ll have to follow my blog to find out — updates are posted as regular blog entries that get grouped up into the project page.

Where Can I See Project Updates?

You can see all the project updates as well as some general project info at the project page. I don’t have a separate project feed set up but if your RSS reader supports it, you can filter my posts by the category cold-war-clock to get just updates about this project.