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From: phd@SPEECH1.CS.CMU.EDU (Paul Dietz)
Newsgroups: sci.electronics
Subject: Re: Electronic Time Capsule
Message-ID: <980@PT.CS.CMU.EDU>
Date: 27 Feb 88 16:40:30 GMT
References: <3a7af473.44e6@apollo.uucp> <2041@psivax.UUCP>
Sender: netnews@PT.CS.CMU.EDU
Organization: Carnegie-Mellon University, CS/RI
Lines: 33
Keywords: Timing, and power...

Just a short summary:

Power sources:
Batteries	Get serious...
Solar		How do you make sure that the cells remain exposed?
Nuclear		Not feasible for the the basement project...
mechanical	(i.e. tides, wind, etc.) subject to failure.
thermal		Very good reliability, low power output.

Timing sources:
crystal		mechanical reliability problems.
rc		reliable, accuracy ~1% fairly easy to achieve
mechanical	won't last if built in a basement...
chemical	(clock reactions, or how about an Hg filled
		speaker cable, with a copper plug that gets dissolved
		away, and allows the mercury to close a circuit?)
		Reliable, but timing accuracy is poor.
daylight	Same problems as solar power...
thermals	Could be a possibility since unit would not have to be
		exposed, and earth/water (depending where you put it)
		give a nice slow time constant. (these effects are both
		daily, and yearly...)

As for putting it underwater, I'm sure it is possible to find materials
which would be extremely resistant to things like barnical growth.
(How about teflon, aluminum, or maybe lead?)

Paul H. Dietz                                        ____          ____
Dept. of Electrical and Computer Engineering        / oo \        <_<\\\
Carnegie Mellon University                        /|  \/  |\        \\ \\
--------------------------------------------     | | (  ) | |       | ||\\
"If God had meant for penguins to fly,             -->--<--        / / |\\\  /
he would have given them wings."            _________^__^_________/ / / \\\\-