Pendulum Clock with Atomic Precision

u19925 writes "Now you can get atomic clock precision out of your grandma pendulum clocks. Here is how it works: There is a camcorder fitted inside the clock which monitors the pendulum swing. It has an atomic clock signal receiver. It compares the pendulum swings with the atomic signal hearbeat. The camcorder also has an arm. If the pendulum clock drifts, then it uses its arm to push or pull the pendulum to make correction." It's not an April Fool's joke, but it is rather impractical.

Comments

Why not magnets?

[FyRE666]

Why not just control the swing with a couple of magnets mounted at the ends of the pendulum's arc? It would surely be cheaper and easier to maintain than a camera and mechanical arm ;-)

Re:Why not magnets?

[Zeinfeld]

Why not just control the swing with a couple of magnets mounted at the ends of the pendulum's arc? It would surely be cheaper and easier to maintain than a camera and mechanical arm

These are not grandfather clocks, they are large public clocks and the movements are very old. The objective is to avoid human contact since people tend to break them advancing or retarding them for summertime.

So this is not a Rube Goldberg device, it is a piece of conservation technology :-)

The Westminster Tower Clock, with its famous bell 'Big Ben' is kept accurate by a warden who runs (ok shuffles, most jobs of that type go to aged war veterans) up a flight of stairs and adds or removes pre-decimal pennies from the pendulum bob. Ah you cry, but the time taken by a pendulum does not depend on the weight, well yes but the pennies slightly raise the center of gravity of the bob you see...

The camera bit sounds a little over the top, surely an led and a receiver???

Re:Why not magnets?

[hlee]

Richard Feynman once observed a flying spinning/wobbling paper plate with a motif on its side, and doodled a surprisingly complex mathematical equation describing its behaviour. When questioned later - WHY??? Hell, because it was fun! Of course, this did lead to his seminal work on quantum mechanics, and a nobel prize.

Sure this pendulum thing seems kind of silly, but may be the feedback mechanism could inspire some new neural network neuron - a precursor to true AI!

You could be just trolling asking a question like that - I'm just glad people don't always experiment with stuff that's always "useful".

Re:Why not magnets?

[unitron]

"The camera bit sounds a little over the top, surely an led and a receiver???"

I'm guessing that you mean an opto-isolator type circuit. Other possibilities, a magnet embedded in the pendulum and a hall-effect device near each end of the path of the swing or a coil attached to a circuit which will detect the inductance change caused by the pendulum's proximity, or just let the pendulum brush across a contact pair and complete a circuit.

I was going to do this

[Zeinfeld]

Actually this was a project I had in mind, but it can be done with much less kludge.

My plan was to put a magnet on the pendulum and then put the regulation mechanism on the reverse. This would measure each swing of the pendulum from the emf induced in a coil on the back of the clock. This would also be used to advance or retard the pendulum if necessary.

Re:I was going to do this

[Bob Munck]

Scientific American did that in their Amateur Scientist section about 45 years ago. The WWV receiver used tubes, but they had two fingertip-sized transistors driving the electromagnet. I considered building one for my junior-high science fair, but built a four flip-flop "computer" instead. Eight transistors, cost me about 5 bucks each. That was about a day's worth of my father's income.

This was in Scientific American

[TerryAtWork]

About 20 years ago - only they used the mechanism from a quartz clock.

Re:Latency?

[AndroidCat]

The most accurate clock I have is an ancient "digital" flip-leaf that depends on the powerline 60 Hz for its time base. It's not very precise because the line freq does drift from time to time. However, once it drifts too far, the the power company applies a correction to bring it back into range. Accurate, but not precise.

My computers and other appliances use crystal clocks which are very precise. But they slowly drift, and no correction is applied (except when I net sync my computer) so they drift and keep on drifting. Precise, but not accurate.

The net connection/camera/lever arrangement may not be as precise as an atomic clock, but it will be very accurate. See how it works? ;^)

Re:Latency?

[cant_get_a_good_nick]

I seem to recall an article recently that some clocks in Brazil were off becuase the line wasn't up to snuff. I think the power was off so much that some cycles weren't being counted, so the clocks ran way slow.

Then there's the story about the engineering students that noticed their professor never wore a watch, so they rigged something up to the power line to alter its frequency. They ran the clock fast he kept talking faster and faster to keep pace with the clock. I forgot how far they got before he noticed, but from what I remember, they had him compressing the class pretty much.

Ultra-accurate mechanical clocks

[Wesley Felter]

Danny Hillis designed the Clock of the Long Now to keep time accurate to the second for 10,000 years, and it's completely mechanical.

Re:Latency?

[YouAreNotTheBest]

Don't you people read the article???? huh..

From the article:

"If the antique clock loses time, a small piston speeds it up with a gentle nudge on the pendulum; if it runs fast, the piston slows it down. Each day, the clock is kept accurate to a tenth of a second. "

duh... don't think that the precision is atomic..

what a crappy title?? "Pendulum clock with atomic precision"
also crappy description about camcorders and stuff that are never described..

the idea of this system is to prevent antique clocks from damages that could be caused by frequent manual time corrections.. corrections are needed due to the minor drifts carried over a period of time (and also the daylight saving time changes)

quoting from the article:
"There is a growing shortage of people who are familiar with the workings of the large mechanical clocks on churches and public buildings, as routine maintenance tasks such as winding the clocks become automated. Yet they still need to be put forward an hour in spring and moved back again in the autumn without damaging their fragile mechanisms, some of which are 250 years old."

Let's make it more difficult...

[Anonymous Coward]

Feed the camera into a PC (running Linux if you prefer). Have a vision system (lots of software) analyze the motion and compare it to the results from the USNO / NIST atomic clock. Control the timing of the clock dynamically by placing a small stepper motor on the pendulum that moves the weight up or down...

Why do you need a camcorder?

[shylock0]

The camcorder seems a little extravagant. Why not just use an induction loop (a la EZ-Pass or bicycle spedometers) to sync the pendulum with the atomic clock?