This site has moved! See this page at numitron clock.html.

2013-08-06-18-30-48_deco.jpgThis page is the main page for the project Alan Numitron Clock.
Since it's at the junction of other projects and prototypes, here's the reference of other legacy projects. The first prototype derives from the WordClock that takes care of the timekeeping job and uses the ardReveil v5 Tubed boards for tubes support.

Chronology: WordClock speedup clock making ⇒ ardReveil v5 Tubed 2 tubes chainable display ⇒ Alan Numitron Clock this project

clock48.pngSee my other clocks projects : with voltmeter, with RGB dot matrix, with VFD tubes, ...

Project summary

I found those beautiful vintage IV9 & IV16 tubes and I had to use them, clock being the perfect candidate. I made already mutliple others based on what was supposed to be a WordClock (hence the project name) only, but became more diversified. I did also a first test with a chainable 5cm x 5cm tube board, this is a 5cm x 10cm dual board improved version.

When I made this project and designed it the idea I had was of course the design (very important) but also reusability and pragmaticallity regarding the components used. What I mean by the latest is that you never really know what component you'll have at hand, depends on your provider, the component availability, it's price, or even the package DIP or SMD. Hence the board can work with 3 different type of RTC clocks: just use your favorite or the one in your shelf stock. Personally I love the Maxims DS3231 and DS3234 which are temperature compensated (to a fantastic extend for the DS3234), and both are accessed through different protocols: SPI for the DS3234 and TWI for DS3231. There's also the EPSON RTC4543 for those living in Japan like me. So again depending of what else you need to wire, choose your poison: all the pins of the MCU are accessible and there's even a small zone for some DIP components.
The top board uses 74HC595 for maintaining the displayed digits: they come very cheap but I didn't want to be stuck to the DIP or SMD model (having both in stock), so the board can use any of the two. Same goes with the current limiter resistors: SMD, through hole or even resistor array, your pick. And of course there's a SMD or DIP led footprint under each tube for the blingbling! (single color, not RGB led)

Hall of fame:



Bottom board (top view) holding the mcu, real time clocks, battery, buttons... On the under side is another potential USB connector and DS3231 footprint
Top board (bottom view) holding the tubes, their current limiter resistors and 4x 74HC595 8bits shift registers. Designed to be populated with through holes or SMD components, depending what you get at hand.


  • Top board with tubes on Google SVN.
    • It's the "extended" version a 100x50mm board
    • Works with tubes Tiny Numitron IV-16 and IV-9
    • SMD LED under the tubes for nice bling-bling
    • Resistors and 74hc595 can be SMD or through-hole
  • Bottom board with Atmegaxx8, RTC (3 flavors), battery, voltage regulator on Google SVN.
    • It's the "extended" version a 100x50mm board
    • Micro controller is ATmel atmega328 (or any atmegaxx8 in DIP package)
    • RTC can be Maxim DS3231 or DS3234, EPSON RTC 4543 SA/SB
    • Battery, USB plug, 90degrees buttons, small area for through-hole extra components

Self-criticism about the board

For a possible v1.1 of that board:
  • [HIGH] Was I wasted the day I put a USB connector on the front side of the board? Move that to the back side next to buttons...
  • [Medium] Change the pin assignments of buttons, now 2 only are usable under some conditions (if use TWI)
  • [low] Align the top board pinout with a similar one on the bottom board so they could become stackable (Arduino style)
  • [low] Make the bottom board pullups resistors, diode and caps double-traced DIP/SMD to make a lower profile board
  • [low] Replace the DIP ATmegaxx8 by a SMD version?


(Google SVN)
Code is Arduino v1.0 based for now (planning a ATmel Studio version one of these days Edit: see below). Edit the main .ino files and enable the #define directives you need :
  • #define USE_DISPLAY_NUMITRON to enable the correct display logic
  • Choose the RTC chip you use in the list RTC_DS3231, RTC_DS3234, RTC_4543SA
  • There's some buttons also on the main board to be used (A and B are used to set time by default, you can use C & D for otherthing if you are not using Numitron tubes)
You'll need a programmer to upload the code to the main board using the ISP programmer.
Update 20141125: long time I wanted to do it, now it's a reality: I rewrote the code in a real IDE, ATmel Studio 6. Bye bye ugly Arduino IDE! I have to rewrite/adapt some libraries, so it's done step by step, but now I already ported a big part of the code. I used the occasion to fix a few things I didn't like in the original Arduino version, more logical architecture, cleaner. Have a look!

Top board and bottom main board (top views)
The first prototype, and the final product

The graphic on the top board (the gears) was done by me using the Obsidian Dawn "Gears brushes", thanks to them.

Self-criticism about the code

Not too ugly, I could do better but quality is ok now. However since I'm currently rewriting it for ATmel Studio:
  • Main loop: throw in some interrupts for the display refresh? Frequency must be parametrizable, since this board is part of the Wordclock project and not only displays with tubes. A define with some watchdog-as-interrupt would do the trick?
  • General rewriting, currently it's messy (though I don't want to write it in C++ with classes, C++ gives me the hives)


Serial #3 : Epson RTC, white leds, all IV-9 and no cover (SOLD)

Edit: the RTC was changed to be a DS3231 because I wanted to be sure of the results I announced on selling and I need to re-test the Epson chip to be sure of its drit. Just changed the main bottom board, a couple hours of work and done.

Serial #4 : Maxim DS3234, orange leds, IV-9 for hours and IV-16 for minutes and wood cover red on black (SOLD)


Serial #5 : Maxim DS3231, white leds, IV-9 only and metal box (on my desk, not for sell :P)




Top board

  • 74HC595 (DIP or SMD) x4
  • SMD 1206 100ohm x28
  • SMD 1206 470ohm x4
  • Numitron IV9 x4
  • LED SMD or DIP x4
  • 1.5uF cap DIP x1

Main board

  • ATmega 328 DIP x1
  • 1.5 uF cap next to mCU x1
  • Power couplig cap ~10 uF x1
  • Crystal 16MHz x1
  • 22pF cap x2
  • 6pin ISP connector x1
  • Buttons 90degrees x2
  • RTC:
    • DS3231
      • RTC DS3231 SMD x1
      • Resistor 10k x2
    • DS3234
      • ...
    • Epson
      • ...
  • CR2032 battery holder



Extended: 0xFF, High: 0xD9, Low: 0xF7


There's an image for DS3231 here should work out of the box, just burn it on the mCU.