SparkFun Forums

[filmo]

Hi,

I'm thinking of building a retro-vacuum tube display clock. Thought it would be nice to have some sort of automatic time acquisition capabilities so I never have to set the clock.

Seems like some sort of GPS would do the trick. Basically acquire the time signal from a satellite and then adjust for timezone. Am I on the right track or is there a simpler way to acquire time data?? GPS might be overkill.

If GPS is the way to go, can I go cheap or do I need to go higher end to get a time signal.

Any thoughts appreciated. Thanks.

[Shifted]

You could pull it in from an internet source, or have a battery backed real time clock, you can get the batteries to last a looong time.

I think there is some sort of radio signal too, broadcast over FM, some clocks automatically set the time that way if I remember right.

[filmo]

Thanks for the suggestions.

At this point I'm most interested in broadcast methodology. I do not want to build a clock the requires internet access and the battery solution still requires that the time be set initially.

I would be interesting in how to suck a time signal off the FM broadcasts if anybody knows about this. Sparkfun obviously has a lot of GPS modules that can acquire signal but this seems overkill. Perhaps it's not.

[Shifted]

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

Take a look at that article, it offers some chips that have the RDS protocol built in.

[filmo]

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

Take a look at that article, it offers some chips that have the RDS protocol built in.

That's a great tip. Thanks.

[filmo]

RDS chip integration seems like it might be more difficult than just using a GPS (given that sparkfun already has several breakout boards for this type thing.)

[bigglez]

I'm thinking of building a retro-vacuum tube display clock.

Nixie tubes? Or, some of the lesser known tube
technology from the cold war era?

Thought it would be nice to have some sort of automatic time acquisition capabilities so I never have to set the clock.

You have several choices depending upon your timing needs.
If your clock is only four digits (HH:MM) you won't notice
multiple seconds errors over twenty-four hours. Unless of
course these are accumulative and give more than sixty
seconds of error in one month.

If you new time piece has six digits (HH:MM:SS) then a
one second error is noticeable, and almost certainly
would require "above average" timekeeping. Typical
"average" timekeeping is a crystal controlled oscillator
without temp compensation. (XO, not TCXO).

A six digit clock will run very well on just AC mains
frequency timing. The US power grid is held to about
50ppm over twenty-four hours. (Even though this data
is hard to confirm with the utility companies, who don't
publish specs).

Every clock requires initial setting or sync to a known
standard. A cell phone is a great way to sync, as is a
PC viewing www.time.gov, for example.

To get sub-one second measurement you'd need more
than a human operator, but unless you are an astronomer
or time-obsessed the extra effort is not worth it.

Seems like some sort of GPS would do the trick. Basically acquire the time signal from a satellite and then adjust for timezone. Am I on the right track or is there a simpler way to acquire time data?? GPS might be overkill.

Any interpretive system (i.e. decoding GPS NMEA data,
or broadcasted radio signals) will require some programing
skills - are you up for the task?

In EU the FM radio system has encoded data, but this is
not widely accepted in the USA and CN. I happen to have
a BBC designed and built RDS receiver (model RC3SP/23/152)
for this service but haven't bothered to get it working.

Another radio source is WWV which is readily receiveable
in North America, and the basis for the "atomic" wall
clocks seen in magazine ads. It's tricky to do without
the 60kHz receiver IC and correct ferrite antenna.
Also, if your retro clock has a SMPS to power the tubes
the radio siginal will be swamped by RFI (been there and
tried that).

[filmo]

I'm thinking of building a retro-vacuum tube display clock.

Nixie tubes? Or, some of the lesser known tube
technology from the cold war era?

Seems like some sort of GPS would do the trick. Basically acquire the time signal from a satellite and then adjust for timezone. Am I on the right track or is there a simpler way to acquire time data?? GPS might be overkill.

Any interpretive system (i.e. decoding GPS NMEA data,
or broadcasted radio signals) will require some programing
skills - are you up for the task?

Yep, some nixie tubes.

I'm probably more up for the programming than the electronics...

[filmo]

PS. Thanks for the great info and explanation of the options...

[bigglez]

Yep, some nixie tubes.

An example 4-digit Nixie tube clock and a 6-digit Minitron tube clock:

[filmo]

Cool, very similar to what I was thinking about. Is the hours:minutes separator in the first one 2 LEDs or a special vacuum tube of a "colon"

I like how you used the 'dot' on the HH:MM:SS one to indicate DST/PM. I think I'll have to steal (I mean borrow...) that idea from your...

Are you selling these as kits or did you just make them as one-offs? I noticed your logo on the case.

[bigglez]

Cool, very similar to what I was thinking about. Is the hours:minutes separator in the first one 2 LEDs or a special vacuum tube of a "colon"

The colon is two glass neon vacuum tubes, held in
clear heat shrink tubing. The tubes are readily
available as part number NE-2.

Further, the colons operate from 180V 1ms pulses
to illuminate both electrodes steadily. Neons that
run from DC would only have one electrode glowing.

The colon alternately blinks up and down for 500ms
each, as the clock's heart beat, but appear on together
in the long exposure PIX.

One version is for biQuinary Nixie tubes (ZM1032),
another for one-of-ten Nixie tubes (CD66, etc.)

I have other projects under way for larger top view
Nixies (B6091), and Burroughs 15 segment Nixies
(B7971) that were salvaged from a New York
Stock Exchange project (1970s vintage computers).

Are you selling these as kits or did you just make them as one-offs? I noticed your logo on the case.

Nope. Done for fun only. The side view Nixie designs
use a single custom PCB. The top view Nixies and
the Minitron clock use two PCBs interconnected
90degrees to support the displays. Everything else
is PCB mounted. The only wire in the whole project
is the AC power cord.

Those PCBs were fabbed by the BatchPCB service,
thank you SFE!

[Shifted]

The RDS might be difficult, but with the clock mostly being an indoor thing, I don't think you are going to guarantee any kind of signal acquisition. That means when the power fails, you'll have to bring the clock near a window or outside to acquire the time. And unless it's battery backed, you're going to need a long extension cord permanently hooked to it.