Subject:
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Re: Crazy idea - analog computer
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 2 Nov 2004 00:48:36 GMT
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Original-From:
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Steve Baker <sjbaker1@&AvoidSpam&airmail.net>
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Viewed:
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1061 times
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There is a lot of confusion here. There are three things to decide upon:
1) Analog or Digital.
2) Mechanical or Electronic (or Pnuematic or Hydraulic or...whatever).
3) Programmable or Fixed Function.
The Meccano machine referred to earlier is most certainly an analog,
mechanical, fixed function computer.
Babbages difference engine was a digital, mechanical, fixed function
computer - it calculated difference equations - but that's all it could do.
Babbages analytical engine would have been a digital, mechanical, programmable
computer...but he never finished it.
Analog computers tend to be either hard or impossible to 'program' - so they
are generally 'fixed function' - they do one thing and one thing only and in
these modern times, they are rather un-interesting and tend to be relegated
to museums.
We have an old pneumatic analog computer at work as a part of our original
1940's Link flight simulator. To 'reprogram' it to be something other than a
flight simulator - you'd have to essentially rebuild it by reconnecting all
of the components. I saw an electronic analog machine at NASA that had a
large wire plugboard (think of an old-fashioned telephone exchange with the
operator manually patching through calls). That machine was *relatively*
programmable - someone showed me how it could be reprogrammed to simulate
a ball bouncing along the ground by plugging several dozen wires into the
right sockets in the plug board.
However, you are really only setting up some equations and having the
machine solve them. You can't tell an analog computer "do this, then do
that, then if this happens do something else"...It takes a truly programmable,
digital computer to do that.
Digital computers (whether mechanical or electronic or something else) may or
may not be easy to reprogram...Babbages difference engine wasn't programmable.
His Analytical engine would have been had he ever finished it.
There was also a brief flurry of 'Hybrid' computers where a simple digital
computer could electronically 'rewire the plugboard' of the analog part of
the machine.
I think it would be very interesting to build a mechanical/digital computer
out of Lego...even more so if it were programmable...but that's a LOT to
ask!
A mechanical/fixed function/analog computer is something you build every time
you connect two gear wheels together. An analog computer that has the fixed
function to calculate the result of the equation:
Y = X * 5
...is just a crank with a 16t gear driving a 40t gear. If you turn the crank
X times, the output shaft turns Y times. That's a simple analog computer
and it's really NOT very interesting.
I suppose you could build Lego Analog computers to calculate more difficult
things - perhaps up to the complexity of the Meccano Differential Analyser...
but the real, serious, interesting and impressive challenge would be to build
a programmable digital computer from Lego mechanical parts.
---------------------------- Steve Baker -------------------------
HomeEmail: <sjbaker1@airmail.net> WorkEmail: <sjbaker@link.com>
HomePage : http://www.sjbaker.org
Projects : http://plib.sf.net http://tuxaqfh.sf.net
http://tuxkart.sf.net http://prettypoly.sf.net
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Message is in Reply To:
 | | Re: Crazy idea - analog computer
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| (...) No, it isn't a crazy idea. It's been wonderfully done with Meccano: (URL) it would be a great challenge indeed to come up with one using all LEGO! C S Soh (20 years ago, 1-Nov-04, to lugnet.robotics)
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