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Subject: 
Re: The latest rage in pneumatic computing
Newsgroups: 
lugnet.robotics
Date: 
Sun, 22 Jun 2003 17:30:39 GMT
Original-From: 
Andy Gombos <gombos_2000@earthlink.NOSPAMnet>
Viewed: 
933 times
  
Using the paper tape idea - the input consists of a row of holes and spaces.
The spaces are large enough for a piston end to get through, and change some
part of the meachine on the other side (to store state).

Output could be a piston with a sharp object, that simply punches a hole in
the paper.  Unless you had a very big punch, output could not be easily fed
back into the input.

Reading/Writing the direct state of the RAM is probably going to be a much
easier solution, and use a good deal less parts.

----- Original Message -----
From: "Mark Tarrabain" <markt@lynx.SPAMBLOCK.net>
To: <lego-robotics@crynwr.com>
Sent: Sunday, June 22, 2003 1:18 PM
Subject: Re: The latest rage in pneumatic computing


Steve Baker wrote:
I wonder if there are savings to be made by building the adder from • scratch
rather than out of standard XOR/AND/OR gates.

I thought so too, so I designed one.  See elsewhere in this thread.

The big remaining issue is storage - both RAM and ROM.

Yeah, I thought so too.

Whilst you can theoretically build this out of flip-flops - and
flip-flops out
of standard 2 input logic gates - I can't help feeling that having more
than
a few dozen bits of storage would consume Lego's entire production of
pneumatics!

If you want to build something that can actually run moderately • interesting
programs, you'll need a LOT of ROM and at least a couple of bytes of • RAM.

If each bit could be something like an axle pushed through a hole in a • beam
with a '1' and a '0' being encoded by the amount of rod sticking out of
the hole,
then it would be perfectly feasible to build many hundreds of bytes of
storage
using only the Lego that most AFOL's have in their collections.

ROM could be built identically to RAM but with fixed pegs instead of
movable axles

The question is how to address it, read it and write it.

Since we can presumably build a pneumatic 'stepper motor' that would
move a long
stack of beams up or down one row for each change to it's input, we
could step
through a list of instructions stored in 'push rod' memory quite easily.

This is almost exactly what I was envisioning!!!   Cool.  Glad to know
I'm not the only one psychotic enough to come up with a cockamamy idea. :)

With a counter built from a multi-stage pneumatic adder, one could
contemplate
building a 'jump' instruction.  You're also going to need some kind of
pneumatic 'shift-register' to hold the results of additions carried out
with
your one-bit adder circuit.  (Either that or a LOT of those adder
circuits!)

Reading memory would require something like a bank of switches that are
flipped
by the push-rods or pegs that are protruding far enough.

Writing RAM memory could be done by pistons forming the output of gates
simply
pushing against the movable axles from one side or the other of the • memory
cell.

Actually, I was thinking that what you could do is make LEGO-ish (maybe
one dimensional) "punch cards".  And any program's output would be
"printed" onto another "punch card" for output.  The problem with this
is that I don't see any simple way to implement this without using a
light sensor.   Pneumatics can certainly push the axles out of the
holes, but I'm not sure how you'd use them to read without possibly
punching more holes in the "punch card", and losing any chance of
reading what was there in the first place.

The question becomes one of how 'pure' you'd like to build your • pneumatic
computer and whether you consider the use of geartrains and even • possibly
electrical motors to be 'cheating'.

I'd say it's not cheating as long as you're not using the RCX or some
other microcontroller to do the work.  Motors and gears are okay as long
as they are controlled by pneumatic and mechanical logic.

Mark




Message has 1 Reply:
  Re: The latest rage in pneumatic computing
 
(...) Yeah, but that would be the whole idea. Otherwise it would be easy.. just knock out axles where you want a 1 and leave 'em in where you want a zero and let a human being read it. But I was thinking of a situation where the output could be fed (...) (21 years ago, 22-Jun-03, to lugnet.robotics)

Message is in Reply To:
  Re: The latest rage in pneumatic computing
 
(...) I thought so too, so I designed one. See elsewhere in this thread. (...) Yeah, I thought so too. (...) This is almost exactly what I was envisioning!!! Cool. Glad to know I'm not the only one psychotic enough to come up with a cockamamy idea. (...) (21 years ago, 22-Jun-03, to lugnet.robotics)

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