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In lugnet.technic, Mark Tarrabain wrote:
> Okay, Kevin... you talked me into trying this inverted logic thingamy.
>
> (I'm just too competitive for my own good...)
>
> How's this?
Very impressive! Two pistons!
>
> http://www.members.shaw.ca/markt1964/fulladder3.jpg
Well, I'm not competative. Hah! I'm ahead on not being competative! LOL!
>
> Takes A and NOT A, B and NOT B, and Carry in as inputs and produces
> A+B+C, NOT A+B+C, and Carry Out as outputs. I saw no need to produce a
> carry complement output since the adder does not require a carry
> complement input. The general idea being that one would chain instances
> of these together to make a full adder as many bits wide as desired.
Well, I can eliminate one switch on the Cin/A/NOT A piston. You don't need to
throw the switches the full range do you? You can get the release from A/NOT A,
and have to have it come from the local switches, right? So you can replace
three switches with one of my 2 switch muxes. Looking more carefully, the left
piston's switches never release, so I guess this is not true.
I was tracing through your circuit and I think I understand, but I'm either
messed up or I found a flaw.
http://www.brickshelf.com/gallery/kclague/Computing/adder.bmp
It seems to me that the bottom input of the COut switch needs to be A AND CIn,
not A AND NOT CIn, right?
I was able to make sense of the switch that has NOT B going into it as:
1. NOT B AND NOT (A AND CIn OR NOT A AND NOT CIn) ---- top port
2. NOT B AND (A AND CIn OR NOT A AND NOT CIn) ---- bottom port.
And the B Switch
3. B AND NOT (A AND CIn OR NOT A AND NOT CIn) ---- top port
4. B AND (A AND CIn OR NOT A AND NOT CIn) ---- bottom port.
But it seems to me that you combine them together wrong, unless I've screwed up
my truth tables.
You combine 1 and 4 for A+B+C, when I think you need to combine 1 and 3.
Am I whacked?
>
> Oh yeah... it also requires rubber bands on the pistons to retract them
> when there's no pressure, but since rubber bands are likc less than a
> penny for half a dozen, I'm thinkin' that's probably not a serious problem.
Nope they are an accepted part of the process.
>
> 8 switches and 2 pistons. 5 switches ganged on one piston and 3
> switches ganged on the other.
>
> My brain hurts... I need sleep. :)
>
> > > Mark
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Message has 2 Replies:
 | | Re: A better full adder!
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| (...) Thanks. Here's how it works: Consider only the right piston for a moment. The output of this subsystem (which will be driving the left piston) is simply (A&~C)|(~A&C), which is an XOR operator, or a half-adder. So what drives the left piston (...) (21 years ago, 28-Jun-03, to lugnet.technic, lugnet.robotics)
| | | Re: A better full adder!
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| (...) While working with Mark's full adder design, the XOR gate in particular, I found something which may be useful in some pneumatic constructions. In Mark's fulladder (URL) just the XOR gate (the 3 switches on the piston on the right). There are (...) (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!
|
| Okay, Kevin... you talked me into trying this inverted logic thingamy. (I'm just too competitive for my own good...) How's this? (URL) A and NOT A, B and NOT B, and Carry in as inputs and produces A+B+C, NOT A+B+C, and Carry Out as outputs. I saw no (...) (21 years ago, 28-Jun-03, to lugnet.technic, lugnet.robotics)
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