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Build A Nixie Tube Clock
J Aldridge writes: "People are still using Nixie tubes. Their warm glow seems to be the digital equivalent of the warm sound of vacuum amplifiers. One person has constructed a tube wristwatch."
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Although web archive's archives of the Repair FAQ only go back to 15 Feb 2K1, if I remember correctly the removed link went to the page Slashdot is linking too. Word from the wise: I'm not saying Nixies are inheirently dangerous, but many schmatics involving Nixie tubes do not isolate from the power line. And don't forget the big red warning on the page:
What do you think of MusicCity now?
The coolest looking nixie tube based clocks I've seen on the web are these over at World Power Systems.
(Be sure to check out the Story Teller if you go to that site - extremely cool!)
Wow, those nixie clocks bring back some fond memories. I always wanted to build a nixie project, but as a novice hardware hacker, couldn't even read the hookup schematic. Now, a little older, wiser, and with the help of these kits maybe I'll finally build one.
However, while browsing some of the associated links, I came across this clock, which I find even cooler:
http://www.cathodecorner.com/
It uses an oscilloscope tube to draw the time in green phosphor arcs - no pixels. Way cool! And a kit is available with a guts-on-display plexiglass case. Awesome...
--Jim
I seem to remember: 190 volts minimum at 3 to 5 milliamps. Discouraging if you want to use batteries.
Big whoop. It's not hard to make a switching power supply that will give you whatever voltage you want from a battery supply. Lots of sample circuits are out there.
You can also buy inexpensive inverter modules that make 100VAC from a battery supply - typically used for powering LCD electroluminescent backlights. Seach on digikey for "backlight inverter".
While I agree with you about the need for a transformer for safety reasons, the mains frequency is useful for a clock. I built a Heathkit digital clock, back when digital clocks were rare items, that used the mains frequency as the input to the logic circuits. It never drifted more than a few seconds from the time signals broadcast by WWV. The power grid operators would adjust the frequency of the grid to keep the long term average frequency at exactly 60 Hz. If the frequency dropped during the day, due to high load, they would run it a bit fast at night to compensate.
Mea navis aericumbens anguillis abundat
The idea dates from around 1915--there were several patents for similar
cold-cathode gas display devices before WWII.
National Union made such numeric displays around 1940,
the GI series tubes used bent wires to form numerals and
had large 9-pin bases.
The Haydu Brothers Co. developed what we call Nixies today
circa 1947/48--
Burroughs bought the Haydus out in 1952, making all their
display tubes (and their complex "Trochotron" counter tubes)
into Burroughs products. After Burroughs
was absorbed by Unisys, tube manufacture ceased--however,
companies such as Richardson/National and Philips were making
Nixies well into the 1980s. Richardson still has the special
tooling to make them, and could make more if demand
appears. Prices for NOS Nixies are rising, because so many people
are building clocks and fooling with old test equipment....
--Eric Barbour
VACUUM TUBE VALLEY magazine
(www.vacuumtube.com)
Actually, all modern power supplies ARE isolated from the power line - that's the core of a switching power supply.
.1 amp, never work alone, one hand in your back pocket)) I design these things for a living.
First, the incoming AC is rectified to DC and filtered. This gives you 300VDC on about 10 to 1000 microfarads of capacitance - enough to kill you dead if it goes through your chest. That part of the circuit is directly connected to the power line.
Then the DC is chopped by a transistor and fed into a transformer (this is the "switching" part of the power supply). This chopping is done at between 60 kHz and 1 MHz (depending upon the power supply). The other side of the transformer (the secondary) is completely isolated from the power line. This voltage is then rectified, filtered, and supplied to the rest of the device. The voltage is measured, and fed back to the switching controller, which drives the switching transistor through either an optocoupler or pulse transformer, closing the feedback loop and regulating the voltage.
If you look at a modern switcher, you will usually see the "hot" side is completely isolated - even unto having sections of the PCB cut to prevent arc-over.
So, the bulk of the power supply, and the rest of the chassis, are NOT electrically connected to the power line. In fact, less of the system is connected to the power line than in an old style line frequency tranformer design. (Now, there were some old designs that rectified the power line and used that directly. THOSE designs were "hot" chassis designs, and were widowmakers...)
That said, you shouldn't go poking around inside a monitor or TV unless you know what you are doing. The anode voltage on the CRT is between 12kV and 25kV (although the source impedance is high enough that it won't kill you). However, the deflection circuits that sweep the electron beam across the CRT are at about 400V and have enough energy to knock you on your ass.
I've worked on TVs, monitors, radio transmitters (including tube based 250 watt repeaters (3kV at
www.eFax.com are spammers
Yes, technologically, Nixies & related are a pain to interface to +5V CMOS logic, but that's not the point. LCDs are clearly superior in sooo many ways, but they are... well, boring.
... fun.
Pretty much all instrumentation these days looks the same, membrane switch, LCDs, a few LEDs, a pile of nifty software, an order-of-magnitude more accurate than the previous model, runs on a AA cell for 2 years until you throw it out.
However, our lovely bodies are physical, and they like being enticed with 'interface' (sic) that connects with more than just yore brane. You can *touch* nixies, the glass is nice to touch, and so are heavy bakelite knobs, switches you can *feel* change state.... Nixie digits jump around. The orange color works well with your eyes. There's no blinky multiplex updates to dazzle.
In general, pre-photomicrolithography electronic stuff was more fun to touch and use (though largely sucked when it came to power consumption, reliability, size, heat output, portability, ad nauseum) as is quite obvious.
A Tektronix scope is an excellent example of technology and interface design and of paradigms lost -- they use first-principle physics (the cathode ray tube is more than just a display, it's an integral measurement component), a mixture of solid-state and state-of-the-art electron tubes, analog computing components (verniers), big clicky knobs, coded by color, size, shape and placement, nice colors and shape, a manual that contains data and meta-data (operating, maintenance, design! and curious gratuitous cartoon graphic characters walking along signal paths...) Like other targetd instrumentation, it embodied and defined a culture of use that was far more
But performance-wise, my TDS-220 software'n'LCD 100MHz BW gigasample scope, the size of an old table radio, is incomparable. It's a pretty amazing contrast for only 30 years of development.
But now we get the best of both worlds (sic), teensy micros under the nice part of the old stuff. I think it's a pretty normal development, culturally, this re-use of the "outsides" of old equipment to achieve a revisionist view.
Interface is always where the interesting stuff is.
The best nixie and 'scope clock technology out there today, is hands-down, David's (http://www.cathodecorner.com), surface mount, AC power line isolation, small, low-power, software driven, switcher HV supply, reasonable price (no I get no kickback frmo his sales).
I wrote a brief history of nixie and decimal tube history here: http://wps.com/texts/decimal-tubes/index.html, nothing exhaustive, but a good start.
For home-brew, a transformer/diode bridge/series regulator with zener is somewhat crude, but easy to make, reliable, and reasonably low power. For a transformer I use a Thordarson-Meissner # 26R60 transformer from Allied Electronics (web order) around $19 each (provides 6.3V and 150V outputs). This is no where near as elegant as David's but for one-off it's fine.
I too make clocks (http://wps.com/products) but I'm not in the clock business per se, mine are simply art (more accurately craft) objects, though I'll make more. My emphasis is more on a functional, tactile artifact, a Nice Thing to hold and use. I've only made a half dozen so far, I've got another half-dozen in the works. After I use up my stock of PCBs I'll end up buying guts from David, it's a much better design.