[time-nuts] Hands on digital clock

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Wed Feb 17 00:49:28 UTC 2010

> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Hal Murray
> Sent: Tuesday, February 16, 2010 4:25 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Hands on digital clock
> > It seems to me there is a way to make the segments folding so they
> > could be  changed without removing and inserting boards.  Kind of like
> > a folding  ruler.  I'll have to do some experiments with scraps of
> > wood in my shop.  On  a smaller scale of course.
> Several years ago, I walked by one of the solar powered radar sets that shows
> you your speed on a pair of big 7 segment displays.  It was clicking as the
> displayed speed changed so I stopped to look at it.
> The segments rotate about the long axis.
> So think of flipping the ruler segments over rather than folding them.

Those are very nifty displays.  I can't recall when I first saw them, but it has to have been back in the 80s or perhaps 70s.

The display element is magnetized, and they have a coil behind it that gets either a positive or negative pulse to flip it. I seem to recall some sort of capacitor and SCR circuit was used.  They're nice because they don't consume any power when not changing, and can be artificially illuminated as bright as you like.  The "signaling" is pretty robust, so you can put the display at the end of a long wire, too.

They aren't very fast, though.  You couldn't display motion video.

But for a time nut?  Sure.  You could carefully balance them for aerodynamics, and actuate them with floats and falling weights from your clepsydra, for instance.  Some sort of fluidic water level to 7 segment decoder would be needed, but that could be very fun to design with buckets and counterweights (e.g. you make a 3 input AND gate with a bucket that holds 3 liters of water, counterweighted with a 2.5 kg weight)

Hmm, you sort of inherently get a thermometer code from a clepsydra, so you need a thermometer to 7 segment decoder.  I envision a giant jacquard loom or piano roll scheme, with holes to fill or drain the weights that turn the segments.  Air pressure is also legal, I suppose.

It kind of depends on whether you need it to be totally gravity driven, or whether a pump/compressor is ok.

(If you've ever seen the Villa d'Este in Tivoli, near Rome, you'd be amazed at what can be done with air and water pressure, ALL gravity fed)
http://en.wikipedia.org/wiki/Villa_d%27Este  (which is actually a pretty lame description)  google for "villa d'este organ fountain" and you'll turn up some youtube video.
http://www.youtube.com/watch?v=gGJumf6m44M is one of them

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