Clock Question

The easiest thing to do is plunk down $15 and buy a commercial digital clock with a wwvb receiver built in. Mine are all marketed by Oregon Scientific, but I'm bettin' they're available at Radio Shack.

Assuming by "wall clock" you mean something that you look at and don't really need anything closer than a second...

The next easiest thing to do is plunk down a buck for a garage sale pc and set it's clock to the master clock on your main pc. Just resync it periodically so it stays in sync within the resolution of your display. My PC is hooked into the stereo to play MP3s and has a BIG clock display. Here's the batch file: rem this runs on music at startup to sync things up. rem This sets local time to main system time. net time \\main /SET /YES

Or you can just broadcast the time over your network. I use the mailbox protocol, just because that was all that worked with the OS I had at the time. I'd probably try to use named pipes if I did it again. Have a process running at the destination to catch the time and display it.

Or you can write a basic program to stuff the time out any of the ports. The time is easy. Depending on your OS, accessing the ports may be a hassle. You still need a display.

Having said all that, I find that I never need to know the time more accurately than what my watch says. I keep a stock of "chill pills" for use when I think I might need more resolution. The impulse soon passes ;-) mike

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build a uP clock controller with an Ethernet port on it, plug it into your DSL hub, and get the time from one of the timeservers.

Why count on your computer, unless you've logged onto NTP when you installed Linux. ;-)

Cheers! Rich

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Rich Grise

I got mine at Walgreen's. :-)

Cheers! Rich

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Rich Grise

And you didn't read my response. I live in a small, very rocky canyon (actually part of the mouth of an extinct volcano :-), so the WWVB signal level is too low.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Jim Thompson

Maybe you pick up the signal when it reflects off the planes going overhead. ;-)

Best regards, Spehro Pefhany

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If they're reflecting WWVB they must be blocking out the sun for quite a
while as they fly by!
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John Fields

Sno-o-o-o-ort ;-) (That's an inside joke that only long-term lurkers will recall :)

For some reason WWVB doesn't do well even in parts of the valley that you'd think would be OK... for instance the flat farm fields south of Chandler have a pitiful signal.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Jim Thompson

Think outside the box!

You can access the WWVB atomic clock online, so build a 60 KHz transmitter and use the NIST modulation system to let you use standard "Atomic wall clocks" anywhere you want around your house, or property. It would be easier to build the transmitter than the custom clocks. Then you can have as many displays as you need, with very little extra cost. You can buy a cheap 60 KHz crystal for the transmitter, or use a higher frequency crystal and divide it down.

Modulation is simple: a 10 dB reduction in level, at a one bit ber second data rate.

If you want to be more creative, build a 60 KHz repeater. ;-)

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Michael A. Terrell
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Michael A. Terrell

As usual, Michael, you're not paying attention.

I have NIST on my machine, checked every 60 minutes.

WWVB signal is too weak in my rock pile location.

For WWVB signals, see my website, I designed a custom chip *many* years ago.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Jim Thompson

You either didn't read, or understand my post.

I noted that in my message.

Also noted

You have said this, many times.

You also ignored the part about building a transmitter to drive the standard radio controlled clocks, and driving it with the time data from your PC that is updated from the atomic clock in Bolder. Co. the transmitter woulkd be very simple. A crystal, a analog switch to shunt the signal across a resistor to control signal level, and a single gain stage to drive a loopstick anteanna.

Digikey has a 60 KHz crystal for the transmitter. As you know, he time code is a simple one bit per second format. The 10 dB signal level reduction used to modulate the carrier is quite simple, as well. That leaves a microprocessor of your choice to receive the data from the PC on any port of your choice. Then it reformats the time code and modulates the 60 KHz carrier. Personally, I would use something like the Rabbit Semiconductor development board with a ethernet interface. Then it can be placed anywhere on your home network that is convenient to transmit to all the radio controlled clocks.

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Digikey part number: SE3320-ND, Epson Electronics America, Inc. part number: C-2 60.0000K-P crystal, price $1.23000 each, 4439 in stock

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Michael A. Terrell
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Michael A. Terrell

The real trick is outputting on the serial port in a timely ;-) fashion.

The link is the least of the issues.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Jim Thompson

Imagine the fun you could have by setting up your own competition to WWVB in your neighborhood! Almost certainly illegal, but the FCC is pretty toothless these days anyway.

Actually not a bad idea, but make sure your signal can't be detected at your property line!

Another consideration. If there is any "leakage" of the REAL WWVB signal into your area, you might have a tough time differentiating between 10db, 1Hz "AM" and beat artifacts between you and the real thing.

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Richard Crowley

They only react to complaints, and spend the rest of their time making their required visits to commercial radio and TV stations.

Jim said he was down in a hole with no signal at all so he should have that problem. If anyone else picked up his signal, they wouldn't know the difference. I don't need a transmitter here in Ocala. The WWVB signal comes in well, and shows full strength on my clock's signal level indicator. I'm about as far as you can get from the transmitter, without moving to Miami.

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Michael A. Terrell
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Michael A. Terrell

That is why I would use the Ethernet port and set the transmitter's processor at night, during lunch, or any time your network won't be busy enough to delay the data packets. Then you can measure the number of seconds it takes to transmit the full data, (it should be one minute) then add that to the microprocessor's software. You should be able to set the clocks to a fraction of a second, with a little bit tweaking.

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