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In lugnet.technic, Mark Bellis wrote:
> In lugnet.technic, Kevin L. Clague wrote:
> > In lugnet.technic, Mark Bellis wrote:
> >
> > [SNIP]
> >
> > >
> > > Here are the pneumatic gate circuits I promised you:
> > > AND / OR / NAND / NOR gate:
> > > http://www.brickshelf.com/cgi-bin/gallery.cgi?i=1346510
> > >
> > > XOR / XNOR gate:
> > > http://www.brickshelf.com/cgi-bin/gallery.cgi?i=1346511
> >
> >
> > I can't wait until they are viewable to compare AND gates. SSC1 ended up using
> > my design of that. If mine differs, I'll post it too.
>
> (SNIP)
>
> Oops! I forgot to post the jpg links rather than the item links, since it's a
> while since I posted stuff! That's what comes of doing too many exhibitions!
>
> The AND etc... gates are dual no-leak bidirectional gates that perform the
> function of a full electronic logic gate. They're not designed to be for gating
> four leg positions, for which I'd use 1 switch per leg, daisy-chained.
> >
> > Would you like to work together on pneumatic documentation styles for Brick
> > Journal? I will be writing for Brick Journal both on CAD and MOCs.
> >
> > Kevin
Mark,
I did a lot of thinking about pneumatics in my long drive home over the last
few days, and am going to try to share them here (yah, Steve, there I go giving
away my competitive edge ;^).
I started thinking about a piston and its ports. Each port can have pressure,
or release. Since each piston has two ports, we can list all possible states at
the port.
Expand Contract
Port Port
release release - piston state remains unchanged, unless some outside
force acts upon it.
pressure release - piston expands, unless it was already expanded
release pressure - piston contracts, unless it is already contracted
pressure pressure - Dave Schilling's parlor trick, the piston expands
slowly
In the simplest of pneumatic circuits, a piston is always in either expand
state (pressure/release), or contract state (release/pressure). This means that
a piston is always under pressure on one port, but not pressure on both.
The kinds of gates you have designed, in general provide either an expand
state, or a contract state. These outputs are rather like a differential pair.
You have AND, NAND, OR and NOR gates that are six switch implementation of said
gates. You call your implementation "no-leak". I studied your design and
realized it would work very well for hydraulic LEGO.
I'm not sure I understand why you feel "no-leak" is needed in pneumatic
circuits.
Lets start with the simplest gates. These gates have a single pressure
output, unlike the differentiual gates you have describe. These are the gates I
use to synchronize leg up and down movement. Here is a picture of the sinplest
AND gate I know. Mark Tarrabain is the one who taught me this.
http://www.brickshelf.com/gallery/kclague/pneumatics-tutorial/and_1.jpg
It is a single piston and a single switch combined to give us pressure at the
single output if both inputs have pressure. The pressure comes out the left
port of the switch.
After Mark taught me that about the single switch, I decided to create a
single pressure output OR gate:
http://www.brickshelf.com/gallery/kclague/pneumatics-tutorial/or_1.jpg
The single pressure output comes from the center switch and is named Q. The
input A controls the piston, and input B goes into the rightmost switch.
I also designed an XOR gate with single pressure output:
http://www.brickshelf.com/gallery/kclague/pneumatics-tutorial/xor_1.jpg
Input A controls the piston and also goes to the leftmost switch. Input B
goes to the rightmost switch. The output Q comes out the center switch. Notice
that OR and XOR are physically identical, except for inputs to the leftmost
switch.
My pneumatic inchworm, pedmatic, quadrapeds, and hexapods are built
exclusively using single pressure (single switch) AND gates.
On my pneumatic adding machines, the gate technology I used (oh, so outdated
;^) provided two pressure outputs, a differential pair output.
I provide my four switch version of a dual pressure output AND gate here:
http://www.brickshelf.com/gallery/kclague/pneumatics-tutorial/and_2.jpg
The picture contains the original single pressure output and_1 type gate, with
three switches added to create the NOT Q output. Switch S1 releases pressure to
the outside world, when S1's handle is to the left. S2, S3 and S4 are hooked up
tight as a drum, and depend on the inputs B and NOT B, to release pressure to
the outside world. I used this dual output pressure AND gate in SSC1 for the
central timing circuit. It worked flawlessly at BrickFest. Does my AND gate
above qualify for by your definition of "no-leak", if not, why not?
I'm trying to guess what "no-leak" means, so I tried a third AND gate design,
just in case.
http://www.brickshelf.com/gallery/kclague/pneumatics-tutorial/and2nl.jpg
I have two pressure output OR gate as well:
http://www.brickshelf.com/gallery/kclague/pneumatics-tutorial/or_2.jpg
Notice this OR gate only adds one switch to the single pressure OR gate.
I have a two pressure XOR gate:
http://www.brickshelf.com/gallery/kclague/pneumatics-tutorial/xor_2.jpg
This is just like a single pressure XOR gate, but with one more switch.
http://www.brickshelf.com/gallery/kclague/pneumatics-tutorial/xor_2.jpg
Can you explain what you mean by "no-leak", and why it is important in
pneumatic design?
Thanks,
Kevin
1. Differential output (for lack of a better term) - The gate has two inputs,
each with a differential pair. In each pair, one
>
> Sounds good. I've applied standard electronic circuit diagram techniques to my
> pneumatic drawings, such as avoiding too many crossovers. I hope my use of flex
> tubing also helps, especially where tubes cross. Having said that, the gate
> circuits have a lot of overlaps because they are complex circuits with multiple
> parallel paths. Have fun tracing the air paths in 1-0 or 0-1 settings!
>
> Do you have Visio at all? If so I could send you a template of the parts. It
> makes it nice and quick to draw complex circuits, without having to worry about
> objects snapping to studs etc... I can just draw a new part if I need one. I
> drew the hand pump today for basic circuits that I'll post soon, not being used
> to using one for my MOCs!
>
> Perhaps you could add your walkers to this BrickWiki page:
> http://brickwiki.zapto.org/index.php/Pneumatics
>
> Mark
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