Subject:
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Re: Classic timing circuits and XOR gates (long)
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Newsgroups:
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lugnet.technic
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Date:
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Tue, 9 Aug 2005 20:10:32 GMT
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(details)
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In lugnet.technic, Kevin L. Clague wrote:
(SNIP)
> Actually, the old and new circuits are about even, except the new one works
> faster.
>
> My first attempt at SSClagorpion actually uses a four step sequence:
> 1. Lift leg, sweept it forward, sweep down leg backwards.
> 2. Drop leg.
> 3. Lift leg, sweep it forward, sweep down leg backwards
> 4. Drop leg.
>
> It uses a two piston central timing circuit (feedback loop as Mark B. calls it)
> with ANDs instead of XORs.
> _
> / \_ Timing piston A
> _
> _/ \ Timing piston B
>
> /\__ A and NOT B - lift/drop leg group 1
>
> __/\ B and NOT A - lift/drop leg group 2
>
> But when I add leg up/down synchronization is stretches some:
> __
> / \__/ Timing Piston A (Ax <= Bx AND LEG GROUP 1 down)
> Ac <= Bc AND LEG GROUP 2 down)
> __
> __/ \_ Timing Piston B (Bx <= Ax AND LEG GROUP 1 up)
> (Bc <= Ac and LEG GROUP 2 up)
> _
> / \____ A AND NOT B
> _
> _/ \___ leg group 1 lift/drop
> _
> ___/ \_ B AND NOT A
> _
> ____/ \ leg group 2 lift/drop
>
> 012345786 Time
>
> 012345012 State
Here is a picture of SSC1
http://www.brickshelf.com/gallery/kclague/SSClagorpion1/p8040144.jpg
SSClagorpion 1 has eight legs broken into two groups of four.
The circuit is based on a two piston, negative feedback loop. This feedback
loop can be described as:
Piston B mimics what Piston A is doing.
Piston A does the opposite of what Piston B is doing.
This leads to this timing diagram:
._
/ \_ Piston A expanding and contracting
_
_/ \ Piston B expanding and contracting.
Time->
Piston A drives leg lift. Piston B drives leg drop.
Piston A also makes the legs move forward and backwards.
Here is a schematic.
http://www.brickshelf.com/gallery/kclague/SSClagorpion1/walk_cycle.jpg
On the left, the raw pressure from the compressor comes in, and is noted as P.
Next are the two rectangles labeled A and B. Those are the central timing
pistons A and B (eeach rectangle represents two pistons). I have not named each
part or numbered their ports......
Piston A controls five switches. The leftmost switch is the one normally
provided in a standard feedback timing loop. It forces piston B to mimic piston
A. The right four switches comprise a dual pressure AND gate. The pressure
driving pistons A act as one dual pressure input to the AND gate. The pressure
into the four rightmost switches comprise the other input to the dual pressure
AND gate (in this case NOT B and B are driven into this (these?) input).
Below piston A's switches is a row of four switches hooked together serially.
These create a four input, single pressure AND gate. This AND gate makes sure
that all the legs in leg group one are down, before we lift the second leg
group. There is one switch for each leg in group two.
The next row of four switches form a second four input, single pressure AND
gate. They make sure that the second leg group's four legs are down, before we
can lift the first leg group.
Pistons' B and their five switches function just like Pistons' A and their five
switches.
The two rows of switches below Pistons B and switches synchronize leg lif for
leg group two and leg group one respecively.
After Brickfest I will redraw this ciruit with all the notations needed to make
a verbal expanation easier.
>
> So synchronizing the leg up/down stretches the timing from 4 to 6 states.
>
> I did not add synchronization for leg sweep.
>
> > >
(SNIP)
Kevin
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Message has 2 Replies:
 | | SSC: Re: Classic timing circuits and XOR gates (long)
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| (...) I don't care what Eric says. This is pretty just like it is. :) (sorry to stray from pneumatics) It looks like a totally studless design. (some of the beams used are studded, but could be replaced with studless) Is that correct? I don't see (...) (19 years ago, 9-Aug-05, to lugnet.technic)
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Message is in Reply To:
| | Re: Classic timing circuits and XOR gates (long)
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| (...) Yes, the XOR gates are not load bearing, but somewhere in the body. I tried to make the legs "just follow allong", but this did not guarantee that the legs were all weight bearing when needed, and it fell. I added a switch to each leg hooked (...) (19 years ago, 9-Aug-05, to lugnet.technic)
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