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Numitron tube tutorial

Nixies and VFDs are great displays, but when using them you’ve got to deal with some fairly high voltages, at least for the micro projects we see on Hack a Day. Luckily, there’s another ancient technology that can be driven at tiny voltages. [Kenneth] put up a great tutorial on Numitron tubes┬áto show the Internet how to get these guys working.

Numitron tubes are like Nixies, but instead of the ten number-shaped filaments in each Nixie, Numitrons are old-school seven-segment displays. [Kenneth] picked up a few on ebay and the seller was kind enough to include a Russian data sheet. Each filament in his IV-9 Numitrons required about 20mA to light up, perfect for the constant current LED drivers [Kenneth] picked up

The test circuit consisted of an ATtiny2313 and an A6278 LED driver. The code on the ATtiny cycles the digits 0 through 9. This is sent through the LED driver and lights up the tiny filaments inside the tube. Check out the video after the break to see the Numitron in action

Comments

  1. Sean says:

    I’ve been using these tubes in a clock kit I’m working on. The A6278 is a discontinued driver, so good luck finding what remains. But, the TLC5916 is a nice, cheap drop-in replacement.

  2. This is all well and good, but the A6278 LED driver is obsolete and can’t be found anywhere (DigiKey, Mouser, Newark, anything from findchips.com, or eBay)

    Please suggest a replacement for your readers ;-)

  3. DanJ says:

    Why the need to current limit? It’s been many years since I played with numitrons but I seem to remember that they were designed to work directly from +5 volts without any current limiting. Just hook them up to a driver like the 7447 and go. Add a single silicon diode to the power rail to increase their life dramatically by running them at a slightly lower voltage.

    • Bill says:

      The filament will draw a big current surge as it’s heating if it’s directly connected to 5V. Current limiting should increase the life of the tube and prevent overloading the driver chip.

  4. Sean says:

    I believe they’re actually designed to run at 4.2V, so yes, a diode on the power rail is a good idea. If you don’t limit current you’ll blow out the filament (word on the street – I haven’t tried sacrificing a tube yet).

  5. Matt says:

    https://github.com/openfly/arduino/blob/master/demos/arduino-numitrons_sn74hc595_demo.c

    That’s some demo code for using an arduino with an 74hc595 shift reg to drive numitrons.

    You can drive segments of GPIO of the avr chips… just no more than 2 at a time.

    Fun little tubes I have a few on my flick feed.

  6. Matt says:

    FYI I’ve heard thermal shock can kill filaments from an EE who used to build drivers for them. The idea is to keep current on the filament as much as possible to keep it warm.

  7. DanJ says:

    Thanks for the info guys. I’ll definitely do some research before building something with the six tubes I have in a box somewhere.

    I wonder if their operating voltage changed over the years. They were often used in gas pumps prior to LCDs (1970s) because they were visible in sunlight. I remember finding a display board at a junk shop. It was nothing but a TTL driver and the display.

  8. Matt says:

    FYI you can within a limited range get some PWM out of the numitrons.

    However like any filament bulb… upping the voltage means you burn off more of the filament and the filament will then meet its gory end faster.

    But… PWM on a numitron. Consider the possibilities. Especially if like me you have several hundred of them.

  9. Buzbee says:

    +1 on the use of 7447s and a silicon diode to increase tube life. That’s use I used for my Numitron clock. Because they were intended to be used behind colored filters, you can run them dimmer and still see the well indoors.

  10. mmmmm, tubes.

  11. JB says:

    Nice tubes. Definitely and alternative for “retro” looking projects.

  12. Taylor says:

    Im struggling to find a chassis mount for the IV-9 tube, are there any out there what are suitable? or is it just a case of soldering it directly to the PCB?

  13. Couple questions on setup:

    I am using an Arduino, Numitron IV-9 and 7H4C595 Shift registers.

    The Diode: does this go on every leg of the Numitron or just on leg #1 (common)?

    7H4C595 to Numitron: What’s the connection scheme from the shift register to the IV-9?
    The 595 has outs for Qa – Qh.
    The IV-9 has legs for each segment where:
    1 = common (Vcc)
    2 = decimal point
    3 = B
    4 = C
    5 = A
    6 = F
    7 = G
    8 = D
    9 = E

    So I am hooking up like this:

    Shift : Numitron leg
    Qa 15 : 3
    Qb 1 : 4
    Qc 2 : 5
    Qd 3 : 6
    Qe 4 : 7
    Qf 5 : 8
    Qg 6 : 9
    Qh 7 : –

    I am using the code from Matt above, but it is not working correctly. I am getting filaments lighting up, but they are not spelling numbers. Any help on the hookup?

  14. th says:

    I just wanted to point out a small error in what you said about Nixie tubes. A quote:

    “Numitron tubes are like Nixies, but instead of the ten number-shaped filaments in each Nixie, Numitrons are old-school seven-segment displays.”

    Nixies don’t have filaments. They work on a completely different principle. They are actually neon lamps with multiple cathodes shaped like numbers.

    http://en.wikipedia.org/wiki/Nixie_tube

    There exists some other display devices with individual filaments shaped like numbers but they are not called nixies.

    th

  15. Farkanoid says:

    Hooray some love for PIC microcontrollers!

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