HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Comments
View Comments: Newest First|Oldest First|Threaded View
Page 1/6  >  >>
lgrant
User Rank
Bronze
Re: Synchronous clocks
lgrant   7/22/2013 4:09:06 PM
NO RATINGS
@Eric Tucker - In addition to salesmen giving clocks to power stations, there was a more formal version: the Warren Telechron Master Clock: A very accurate clock movement driving one hand on a clock dial, while a synchronous motor drove an additional hand, so they just had to adjust the generator frequency to keep the one hand on top of the other.

http://www.my-time-machines.net/warren_master_clock.htm

Best regards,

Lynn

Rob Spiegel
User Rank
Blogger
Re: The grid affecting time
Rob Spiegel   6/10/2013 10:47:34 AM
NO RATINGS
Good story, robatnorcross,

I have a friend like that as well. One evewning a mutual friend said, "Do you ever call him on this?" I replied, "I used to, but he's always right, so I quit calling him on it."

robatnorcross
User Rank
Gold
Re: The grid affecting time
robatnorcross   5/24/2013 1:25:04 PM
NO RATINGS
Hi Rob. Actually the "machine" is a telephone. The Naval Observatory (USNO) in Washington at the time had 27 atomic clocks of various types that were located around in closets, rooms, etc (to account for room temp variations). The time from each clock was averaged and fed to a rack mounted thing called a Nano Clock (I forget who made those) the output of the Nano Clock went to an announcing machine (of which I designed part of) that stored phrases like the words "one", "two", "u. s. naval observatory time is", etc. When you call the USNO telephone number a Weatherchron announcer seizes the line and on the next cycle that starts every five seconds (I think) assembles the words into a complete phrase that sounds resonably natural.

The "voice announcer" number is on the USNO website and anyone can call it (including jewelers). The machine has been in service for several decades pretty much non-stop.

The machine was designed way back when UV erasable EPROMs were common and the voice was stored in a bank of Eproms in 8 bit telephone CODEC format.

The man who owned the company died a couple of years ago and was one of the smartest people I've ever known, and one of the best friends I ever had. He knew (as far as I could tell) just about everything about everything. The DAY AFTER the space shuttle disaster, he told me that the problem was the O-ring seals on the engine. He studied and read just about everything technical he could get his hands.

He would some times look at something I had designed and ask "If this was an airplane would you fly on it?" at which point I would usually make some changes.

I miss him everyday and quote him all the time.

rkinner
User Rank
Iron
Re: The grid affecting time
rkinner   5/17/2013 5:24:12 PM
NO RATINGS
The station I worked for had Western Union clocks in the studios.  They reset to the correct time once an hour and you could see the second hand either speeding up or holding at the same spot for 2-3 seconds each hour, around 10 minutes before the hour.  The sync signal was sent via a dedicated phone line if I understand correctly.  We joined the ABC Entertainment Network on the half hour and the clock was always within 1/2 second.  (BTW, it was WCWA-AM/FM when I started after high school, the call on FM changed to WIOT and format went to progressive rock from elevator music before I graduated)

Since the network sent a tone 10 seconds prior to the start and went silent for the time before the news started, you could simply open the switch to the mixer board once the tone stopped and the news started (whether you were ready or not).  We did also need an ID in that time period as well.  I hit the net fairly well while I worked the board but sometimes...  the post brings back memories.

Tonkabot
User Rank
Iron
Home digital clocks are usually synced to 60 Hz
Tonkabot   5/17/2013 3:43:00 PM
NO RATINGS
 

Rob said: Jim, I guess that makes digital clocks intrinsically more accurate than analog clocks, since they are not subject to variations in the power source.

Actually in a lot of home digital alarm clocks there is a simple zero-crossing detect circuit, and that 60 hz signal is divided down into seconds and minutes.

This way the time is 'always right', barring the power company playing with the frequency which strikes me as highly unlikely as every generator attached to the grid is syncronized.

A simple zero-crossing detector is going to be cheaper than a crystal

Rob Spiegel
User Rank
Blogger
Re: The grid affecting time
Rob Spiegel   5/14/2013 7:41:01 PM
NO RATINGS
That's great, Robatnorcross! Can you expand on it a tad (explaining the machine the store uses, perhaps) and submit it to Made by Monkeys?

Please do. Send it to: rob.spiegel@ubm.com

Thanks.

robatnorcross
User Rank
Gold
Re: The grid affecting time
robatnorcross   5/13/2013 4:05:23 PM
NO RATINGS
A friend of mine got a Rolex for his birthday from his wife one year. After wearing itfor a few days he noticed it was running a few second slow. He returned it to the store to complain and the gentleman explained that he must have been mistaken and that every Rolex they sold was checked against the time standards at the U.S. Naval Observatory in Washington. My friend then explained to the man behind the counter that he BUILT the machine that the store was using to test the watches.

Rob Spiegel
User Rank
Blogger
Re: The grid affecting time
Rob Spiegel   5/13/2013 1:19:34 PM
NO RATINGS
Interesting the variances in Hz in power grids. So a clock maker need to know what Hz the clock is likely to be used. I can see there must have been great relief in the development of digital clocks.

Rob Spiegel
User Rank
Blogger
Re: The grid affecting time
Rob Spiegel   5/13/2013 10:00:31 AM
NO RATINGS
Jim, I guess that makes digital clocks intrinsically more accurate than analog clocks, since they are not subject to variations in the power source.

kenish
User Rank
Platinum
Re: The grid affecting time
kenish   5/10/2013 5:54:01 PM
NO RATINGS
The areas of Japan generally southwest of Kyoto are 60Hz, while the rest of the country is 50Hz.  http://en.wikipedia.org/wiki/File:Power_Grid_of_Japan.svg  It was the result of the US and England helping rebuild the power grid after WW2.  Pretty incredible for a modern industrial nation to have 2 line frequencies!  Back-to-back AC/DC/AC converters create the intertie between the two (dotted lines on the map in the link).

The US has 3 major, separate grids with a DC intertie in West Texas between them.  But the isolation is not due to frequency differences.  I believe the grids are kept in pretty close phase sychronization.

Since AC clocks in Japan had to have motors and gearing compatible with the line frequency, they perfected the ubiqitous AA battery-powered wall clock movement.

My dad grew up in the LA area, which was 50Hz until the late 1940's.  I remember him talking about the power company taking clocks and converting or trading them for 60Hz operation.

Page 1/6  >  >>


Partner Zone
Latest Analysis
Factory floor engineers may soon be able to operate machinery and monitor equipment status simply by tapping their eyeglasses.
GE Aviation not only plans to use 3D printing to mass-produce metal parts for its LEAP jet engine, but it's also developing a separate technology for 3D-printing metal parts used in its other engines.
In this TED presentation, Wayne Cotter, a computer engineer turned standup comic, explains why engineers are natural comedians.
IBM's new SyNAPSE chip makes it possible for computers to both memorize and compute simultaneously.
The “Space Kid,” 11, will be one of the first civilians to have his design manufactured in space by NASA, thanks to the City X Project, which inspires kids to think about new 3D-printed inventions that could be useful for humans living in space.
More:Blogs|News
Design News Webinar Series
9/10/2014 11:00 a.m. California / 2:00 p.m. New York
7/23/2014 11:00 a.m. California / 2:00 p.m. New York
7/17/2014 11:00 a.m. California / 2:00 p.m. New York
6/25/2014 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Sep 22 - 26, MCU Software Development – A Step-by-Step Guide (Using a Real Eval Board)
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Next Class: September 30 - October 2
Sponsored by Altera
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service