Plight Of The Lowly Numitron Tube

In the 60’s and 70’s there were many ways to display numeric data. Nixie tubes, Vacuum Florescent Displays (VFD), micro projection systems, you name it. All of them had advantages and drawbacks. One of the simplest ways to display data was the RCA Numitron. [Alec] at Technology Connections has a bit of a love/hate relationship with these displays.

The Numitron is simply a seven-segment display built from light bulb filaments. The filaments run at 5 V, and by their nature are current limited.  Seven elements versus the usual ten seen in Nixie tubes reduced the number of switching elements (transistors, relays, or tubes) needed to drive them, and the single low-voltage supply was also much simpler than Nixie or even VFD systems.

Sounds perfect, right? Well, [Alec] has a bone to pick with this technology. The displays were quite dim, poorly assembled, and not very pleasing to look at. RCA didn’t bother tilting the “8” to fit the decimal point in! Even the display background was gray, causing the numbers to wash out in ambient light. Black would have been much better. In [Alec]’s words, the best way to describe the display would be “Janky,” yet he still enjoys them. In fact, he built a fancy retro-industrial-themed clock with them.

The Numitron was not a failure, though — we know variants of this display ended up in everything from gas pumps to aircraft cockpit gauges. You can even build an LED-based replica clock — no glowing filaments necessary.

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A Numitron clock showing "30 degrees C"

Simple But Stylish Numitron Clock Can Display Time, Date And Temperature

While it seems like Nixie tubes get all the attention when it comes to making retro-style displays, there are plenty of other display technologies that can make a good-looking retro design. Take the Numitron tube: introduced by RCA in the early 1970s, these display tubes might look superficially similar to Nixies but work in a completely different way. The Numitron uses incandescent elements that make up seven-segment displays.

The main advantage Numitrons have over Nixes is that they don’t require a high-voltage supply, which makes them much easier to hook up to modern low-voltage electronics. [mircemk] used this to his advantage when he built a simple clock using four numitrons that can display the time, the date, and the ambient temperature.

The brains of the device are formed by an Arduino Nano coupled with a DS3231 battery-backed real-time clock module. For now, the time has to be synchronized by connecting the Arduino to a PC and reprogramming it, but [mircemk] has plans to update the design with pushbuttons to allow the user to set the time manually.

Four shift registers are all that’s needed to interface the microcontroller to the display tubes, thanks to their low-voltage operation. They do need quite a lot of current, so [mircemk] used the high-power TPIC6C595 instead of a  regular 74HC595 chip. We wonder if the tubes’ high power consumption could be the reason why the temperature in his lab seems to hover around 30 °C.

A simple but stylish plastic enclosure completes the design. Since Numitron tubes are relatively low-cost and no other specialized components are needed, this could be one of the cheapest and easiest ways to make a retro display tube clock. Although we’ve seen a couple of Numitron clocks and even watches before, today’s build is a great example of how simple such a design can actually be. Continue reading “Simple But Stylish Numitron Clock Can Display Time, Date And Temperature”

Numitron Clock Is A Tidy ’70s Throwback

As far as hacker clock builds go, the more obscure the parts involved, the better. By this yardstick, [sjm4306] has a great piece on his hands with this Numitron-based build.

The Numitron was a type of display popular in the 1970s, and often used in aircraft avionics and other high-end hardware. The display is a 7-segment type, but using filaments instead of LEDs. [sjm4306] was able to lay his hands on four of these devices, along with some bulbs to act as the digit seperator and AM/PM indicator. Due to being incandescent in nature, multiplexing wasn’t a practical option, with lower duty cycles drastically dimming the display. Instead, a 32-bit cascaded shift register was used to enable all the segments to be driven at the same time.

It’s a great build that uses some genuine original display hardware to create a clock with a compelling vintage aesthetic. This would make a great gift to a pilot from the era, or any hacker that likes the unusual display technologies of yesteryear. You can even build a Numitron watch, if you’re so inclined. Video after the break.

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A Surprisingly Practical Numitron Watch

Regular Hackaday readers are surely familiar with Nixie tubes: the fantastically retro cold cathode display devices that hackers have worked into all manner of devices (especially timepieces) to give them an infusion of glowing faux nostalgia. But unfortunately, Nixie displays are fairly fragile and can be tricky to drive due to their high voltage requirements. For those who might want to work with something more forgiving, a possible alternative is the Numitron that uses incandescent filaments for each segment.

There hasn’t been a lot of prior-art that utilizes Numitrons, but that might be changing, given how fantastic this wristwatch created by [Dycus] looks. With a multi-day battery life, daylight readability, and relatively straightforward construction, the Filawatch is likely to end up being something of a reference design for future Numitron watches.

[Dycus] has gone through three revisions of the Filawatch so far, with probably at least one more on the way. The current version is powered by a ATmega328 microcontroller with dual 16-bit LED drivers to control the filaments in the KW-104S Numitron display modules. He’s also included an accelerometer to determine when the wearer is looking at the display, and even a light sensor to control the brightness of the display depending on the ambient light level.

If there’s a downside to Numitron displays, it’s their monstrous energy consumption. Just like in the incandescent light bulbs most of us have been ditching for LED, it takes a lot of juice to get that filament glowing. [Dycus] reports the display draws as much as 350 mA while on, but by lighting it up for only five seconds at a time it can be checked around 150 times before the watch needs to be recharged.

Its been a few years since we’ve seen a Numitron watch, and it’s interesting to see how the state of the art has advanced.

[via /r/electronics]

Counting Without Transistors

The Hackaday Prize is all about Building Hope. We want to see hardware creators change the world with microcontrollers and breadboards. That’s a noble goal, but it also doesn’t mean you can’t have fun. That’s exactly what [Yann] is doing with a pile of surplus Soviet components, a bunch of bodge wire, and exactly zero transistors. He’s building a hexadecimal display module using only relays and diodes. It’s absurd, but still very very cool.

The inspiration for this build comes from homebrew computing. With this, there’s a recurring problem of displaying the status of a bus. Sure, a bank of LEDs will work, but then you have to count to F. The better solution to this is a hexadecimal display. The best solution to this problem is using Numitrons — seven segment Nixies, basically — and doing it all with relays and diode steering.

This module accepts four bits as an input and uses a clever arrangement of diodes to turn those four signals into the digits 0-F. Yes, it’s hexadecimal, but that’s just what you do when you’re building your own computer.

Right now, [Yann] has one module on a slim-profile protoboard that should stack easily enough for an 8 or even a 16-bit wide bus. That’s four tubes and hundreds of diodes for the 16-bit version, but the good news is all of these modules are identical, vastly simplifying the construction of the display panel of a homebrew computer.

Smell That? It’s Time.

Steampunk is beautiful. There is something about the exposed metal and primitive looking artifacts that visually appeal to the brain of a maker and engineer alike. Makers have been busy the last decade building clocks with this theme because hey, everyone needs a clock. [Fuselage] has put together a Steam Punk Clock that releases actual steam(actually steam oil smoke) for its hourly chime. How cool is that?

The clock is designed around the Conrad C-Control Unit (translated) which has the Motorola 68HC08 and [Fuselage] uses BASIC to write the routines for the system. Unlike a lot of steampunk clocks that use Nixie Tubes, this one uses 4 Numitron displays for the hours and minutes display. An analog dial panel display is employed for the seconds’ and is driven by a PWM signal. The absence of the RTC module was not obvious until we saw that the BOM includes a DCF77 receiver. For the uninitiated, DCF77 is a longwave time signal and standard-frequency radio station in Mainflingen, Germany. If you are anywhere within a 2000 km range of that location, you can pick up a 24-hr time signal for free which is excellent if you plan to make say… a radio clock.

The steam/smoke generator is a subproject of sorts. The custom machine is designed to have a separate oil reservoir and pump in addition to the actual generator so that the system does not run out of fuel as quickly. Clearly [Fuselage] did his homework which is explained in brief in his project logs. The final design has a brass tube as the main heating and also serves as the outlet chamber. The oil is pumped from under the heating filament in the brass tube, and excess fluid drains off back into the reservoir. A piece of nichrome wire serves as the filament that vaporizes the liquid to gaseous form. Sensors make sure of the oil levels in the reservoir as well as the steam tube. Servo motors and fans add the effect of the opening the exhaust rain cap, and a small LED helps illuminate the exhaust to complete the impression of real steam.

The project is a great example of a simple but effective implementation and for those who are wondering about Numitron Tubes, check out this tutorial on the subject. Of course, there is the Giant Electro-mechanical Clock for those looking at more sizable works of art.

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Celebrate Display Diversity For A Circuit Circus Clock

There’s a lot to be said for nice, tidy projects where everything lines up and looks pretty. Seeing straight lines and pleasing proportions speaks to our obsessive-compulsive tendencies, and tends to soothe the mind and calm the spirit. But disorder is not without its charm, and mixing it up a little from time to time, such as with this mixed-media digital clock, can be a good idea.

Now, we know what you’re thinking — yet another Nixie clock. True, but that’s only half the story — or more accurately, one-sixth. There’s but a single Nixie in [Fuselage]’s circus-punk themed clock, used for the least significant digit in the hours part of the display. The other digits are displayed with four seven-segment devices — a Numitron, a vacuum fluorescent display, and an LED dot display — plus a real oddball, an old electromechanical display with individual slides for each character and a rear-screen projector. The RTC part of the project is standard Arduino fare, but as you can imagine the power supply needed for such a diversity of displays is pretty complex and has to provide everything from +5 to -270 volts. Each display needs its own driver, too, making this more of a zoo than a circus. The mixed up look just works with the circus theme, too. We’d really like more information on the projector display, though.

Looking for a real statement for your next clock build? Check out the rare as hens’ teeth NIMO tube.

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