Subject:
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Re: Brickfest Pneumatic Master and new Pneumatic Gate Circuits
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Newsgroups:
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lugnet.technic
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Date:
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Mon, 22 Aug 2005 17:07:31 GMT
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Viewed:
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4200 times
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In lugnet.technic, Mark Bellis wrote:
> In lugnet.technic, Kevin L. Clague wrote:
[MUCH SNIPPAGE]
Mark,
I did this simple repost to remove the remainder of this conversation from
events.brickfest.
I'll go home and study your feedback, build models and test them, and provide
a writeup.
Kev
>
> Kevin,
>
> I think "differential output" is what I really meant, though I called it "no
> leak" because the supply never leaks, one output or the other is always
> pressurised and there is never a state where both outputs leak. There is also
> only one place where the leaking output leaks on the XOR and XNOR gates, from
> the single switch - subsequent parity stages have no leaks at all. The idea
> behind it was to have full control of both outputs in all possible states, since
> that is also the goal of a finite state machine. It suits me being a control
> freak :-)
>
> I use differential output gates because the output is suitable for driving the
> input of the next gate, so these circuits are building blocks. To invert the
> output, swap the output hoses. To invert the input, swap the input hoses.
>
> My differential gates are suitable for driving load-bearing cylinders because
> there will be minimal pressure loss in the gate when the inputs change to
> another state that has the same output. That was another requirement of the
> design, which is helped by using as much flex tube as possible. The
> load-bearing functionality was the main reason for having no leaks.
>
> Another thing was to avoid any gate being transparent. This means, similarly to
> electronic flip-flops, that the input can't go through to the output without a
> proper change of state. In a transparent electronic D-type flip-flop, if the D
> input changed, the Q and !Q outputs would change with it. In a non-transparent
> flip-flop the change of Q and !Q has to wait for the data at D to be clocked
> into the flip-flop, such that it changes state. This avoids logic races in
> electronic flip-flops and it was also something I wanted to avoid in pneumatics,
> in order to be sure of the next state of the system at all times and prevent
> movement into an undesirable or lock-up state.
>
> Another feature of my designs is that the input need not necesarily be a
> pneumatic function. All that is required is something that moves a set of valve
> switches, so it could be a motor or hand input. I've not yet tried adding
> machines but I could make one on the same basis as a binary full adder from an
> electronics book, using and AND gate and an XOR gate for each of two half adders
> and and OR gate for the summation.
>
> Don't blame me, I'm just an electronics engineer :-)
>
> I do use single switch ANDing on enable lines, where I need only one pressure
> and not a differential output. I use enable lines to interupt the air supply to
> a set of cylinders, so the enable is a gated air supply to the middle port of a
> switch, such that a cylinder can't move either way if it is not enabled. I
> haven't yet applied an enable line to only one port of a cylinder because the
> system might end up with either pressure on both ports or a leak on both ports,
> both of which I want to avoid. For enable lines I apply the supply to the
> middle switch port and take the output from one side with a stopper on the other
> side. The supply must never leak.
>
>
> On the first of your gates, are you feeding pressure A into the cylinder and
> also through a B switch to the AB port?
>
> Also, you seem to be addressing hose pressures as the objects that have a state.
> I have always used valve positions as the objects that have "0" and "1" states.
> This means that, assuming the centre port is pressurised, in state "0" the right
> port is pressurised whilst the left port leaks, and vice versa.
>
> I looked at your 4-switch dual pressure AND gate, assuming that the "B" input is
> from another valve switch, but it appeared to cause both outputs to leak in 0-1
> or 1-0 states, due to the mismatch between the two hoses from the B switch (into
> B and !B ports) and he states of A and B. What parts are used that don't appear
> in the diagram?
>
> Solving the 0-1 and 1-0 mismatch was what pleased me most about my AND gate
> design.
>
> Mark
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