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62 IEEE Spectrum | October 2004 | NA

PARDON ME, GOT THE TIME?BY MICHAEL JAY GEIER

If you’re an engineer, your re-ply just might be, “Sure. Youwant that in binary?” Let’sface it, we tech types loveclocks: LED, LCD, nixie, ana-log, GPS, radio synchronized,even atomic. So IEEE Spectrumpicked out a few gems foryour mantelpiece.

Take the Powers of 2clock from Realnerds (http://www.realnerds.com). Thisclock will confound your non-techie friends while bringing asmile of recognition to everyprogrammer you know. Nonumbers here, just sixcolumns of LEDs, one columnfor each digit marking thehours, minutes, and seconds,in blue (US $22.98) [see pho-to, “Bit by Bit”] or red ($19).

As the seconds tick off, theresulting pattern is enigmatic to anyone notfamiliar with the code, which is binary-cod-ed decimal. Read upward from the bottom ofa column, each LED represents 1, 2, 4, or 8.Time is read by adding (quickly) the valuesof the lighted bits in each column. For ex-ample, the time on the clock in the photo is02:26:52. (The columns representing the tensof minutes and hours need only reach 5, so3 bits are sufficient. Likewise, the first col-umn needs 2 bits to represent 0, 1, or 2.)

It sounds baffling but really isn’t; mynontechie brother, who didn’t even real-ize the thing was a clock when he firstsaw it, got the hang of reading it in about2 minutes and fell in love with it. Theconstantly changing pattern is mesmeriz-ing, though it can be distracting becauseof the high brightness of the LEDs. It’s anice effect on a bookshelf in the den, butyou probably won’t want to put this clockover your TV or anywhere in your bed-room. Still, it’s a cool clock.

If you’re over 40, you probably remem-ber nixie tubes, the pre-LED vacuum-tubereadout in wide use through the 1960s [see“New Life for Nixies,” Spectrum, June2002]. With their neon-orange glow androunded, fully formed digits, nixies havean elegant look. Though the tubes are nolonger being made, surplus stocks permitthe manufacture of small quantities ofnixie products.

Jeff Thomas at Resonant InstrumentsLLC, in Mesa, Ariz., blends modern tech-nology with the nixie tube, with hisNixiChron clock ($499; http://www.amug.org/~jthomas/clockpage.html) [seephoto, “Back to the Future”]. Its anodizedmetal base and bare tubes are geek-chic,and the tiny Global Positioning Systemreceiver that plugs into the back keeps itaccurate anywhere in the world. An in-cluded extension cable lets you put theGPS module on your windowsill or evenoutside, but I had no trouble picking upthe satellite signals at my desk.

The clock’s menu offers all kinds ofoptions, including a scrolling display oftemperature from a built-in thermome-ter and latitude/longitude coordinates.It’s a truly classy timepiece and my fa-vorite of the bunch.

Another, but very different, nixie clockis the GeekKlok from Zetalink Tech-nology (http://www.zetalink.biz) [seephoto, “Segments of Orange”]. The nix-ies used in this kit are segmented in 16straight lines, so various fonts and sim-ple animations can be presented. The ef-fect can be bizarre, with some fonts (in-cluding Klingon from “Star Trek”!)unreadable to anything but the trainedeye. An internal crystal oscillator providesthe time base, with correction once a dayfrom the ac power line’s frequency.

TIME SCOPE: Looking like a prop from a 1950s’ sci-fi movie, the

Scope Clock is available in a clear plastic or wood case and comes

either preassembled or in kit form.

TOOLS & TOYS

October 2004 | IEEE Spectrum | NA 63

BIT BY BIT: [Above] The Powers

of 2 clock’s LEDs tick off the

time in binary-coded decimal.

SEGMENTS OF ORANGE: [Top

right] The GeekKlok can display

a number of fonts. BACK TO

THE FUTURE: [Bottom right]

A marriage of today’s tech and

retro-chic, the NixiChron gets its

time from satellites.

The clock also accepts a 1-pulse-per-second signal from an external timinggenerator, for time accuracy as good asthat of the source. At $99, the kit is a bar-gain, though the nixie tubes are extra andcome from a different supplier, to whichZetalink refers you.

Still in the retro-look department,the Scope Clock from David Forbes atthe Cathode Corner Web site (http://www.cathodecorner.com) presents thetime on the face of an oscilloscope tube.Each number is drawn as a series of arcson the 7.6-centimeter-diameter screen[see photo, “Time Scope”]. Dependingon the type of external case you select—it comes in plastic or hardwood—pricesfor assembled versions range from $350to $495, with kits available for $50 less.

My review unit’s clear plastic case isvery sci-fi and makes me wish I had aspark generator to put next to it, for thefull 1950s “movie mad scientist” look.Timing comes from an internal crystal,but an optional input connector allowsfor an external 1-pps timing source.

Using a 1-pps time source is standardin the world of atomic and GPS-derivedclock systems. You don’t have your own

atomic clock? Well, they’re not com-pletely out of reach. You can get atomicclocks with serious accuracy at surpris-ingly reasonable prices.

Stanford Research Systems, inSunnyvale, Calif., sells its FS725 RubidiumFrequency Standard for $2495. With notime display, this isn’t a clock by itself,but its 1-pps output can drive any com-patible display. With estimated 20-yearaging of less than 5 parts per billion, thisbaby should keep you on time!

A rubidium frequency standard may bedarned good, but the best standards usecesium. Agilent Technologies Inc., PaloAlto, Calif., sells its 5071A PrimaryFrequency Standard for $50 390, withlong-term stability, the company claims,exceeding 0.01 parts per trillion. Short ofexotic clocks such as the AtomicFountains used to establish official time,that’s about as good as it gets, and Agilentthrows in a built-in clock display, too.

Don’t have quite that much to spend ontimekeeping? You can find bargains some-times on eBay. Rubidium standard clocks,some brand new, have gone for around$500 to $1500, and used cesium standardclocks for $1000 to $2000. The surpluscesiums, though, generally have worn-outcesium tubes that won’t stay frequencylocked for long periods, so they aren’t use-ful where ultimate accuracy is required.

Oops, I’m out of time! �

RESOURCES

MICHAEL JAY GEIER has been writing for the

technology press for 25 years. Living in Mar Vista,

Calif., he contributes regularly to EE times, 73Amateur Radio Today, and Envisioneering.