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In lugnet.technic, Mark Tarrabain wrote:
> Brian H. Nielsen wrote:
> > While working with Mark's full adder design, the XOR gate in particular, I
> > found something which may be useful in some pneumatic constructions.
>
> Egad! Another madman joins the fray! ;)
I've alway found low level circuit design interesting. Using pneumatics and
LEGO pieces to create them seems like a good challenge. I have some ideas that
might turn into workable designs.
> > In Mark's fulladder http://www.members.shaw.ca/markt1964/fulladder3.jpg
> > consider just the XOR gate (the 3 switches on the piston on the right). There
> > are actually 3 outputs from the XOR gate. The bottom switch outputs AND, the
> > middle switch outputs XOR, and the top switch would output NOR if it weren't
> > plugged up. These 3 functions are mutually exclusive and one and only 1 will
> > always be true. This can be used to retract pistons attached to the outputs
> > whose values are false.
> >
> > Setup just the XOR gate and connect each output to the expansion port of a
> > piston. Now, with the 3 pistons in compressed mode connect the 3 compression
> > ports all to the same T, forming a closed system on the compression ports. Now
> > when the XOR gate is pressurized one piston will be forced to expand and create
> > positive pressure in the other pistons compression ports causing them to
> > retract.
>
> Am I misunderstanding you or are you suggesting that the pressure
> created by the expansion of one piston would actually be sufficient to
> compress *TWO* others? Unless the pistons had no loads at all, I'm not
> sure if that would really work.
I've tested it, and it does work. I don't know how many switches the
compressing piston can switch, but the force exerted seems capable enough.
One of the reasons for interconnecting the compression ports while the pistons are all in the compressed state is that it maximizes the volume of air trapped in the compression chambers and sets a bias for all the pistons to want to retract. When one of the pistons expands it increases the air pressure even more in the other piston(s) compression ports. Since one and only only one piston is ever expanded at a time there will only be one piston that ever needs to be compressed at a time.
The more pistons that are interconneted in this fashion, and the longer the
tubing, the lower the compression force will be on the piston being compressed.
Minimizing both is therefore desirable. My test setup for the XOR gate outputs
used 3 large pistons and about 9" total tubing to interconnect the compression
ports.
Brian
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Message has 1 Reply:
 | | Re: A better full adder!
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| (...) I wasn't trying to imply that you hadn't actually tried it... I was only suggesting that I didn't think that pistons being driven solely by the compression of air created by the expanding of other pistons would be strong enough to compress (...) (21 years ago, 1-Jul-03, to lugnet.technic, lugnet.robotics)
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Message is in Reply To:
| | Re: A better full adder!
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| (...) Egad! Another madman joins the fray! ;) (...) Am I misunderstanding you or are you suggesting that the pressure created by the expansion of one piston would actually be sufficient to compress *TWO* others? Unless the pistons had no loads at (...) (21 years ago, 1-Jul-03, to lugnet.technic, lugnet.robotics)
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