On 5/11/2010 4:33 PM, Orchid XP v8 wrote:

> Looking at this cavernous, echoing building stuffed *litterally* to the
> roof with densly-packed racks of switches... Christ, it must have been
> like hell on Earth! Deafening would be an understatement!!

You have a different meaning for hail than we do in the States, but it 
was described as sounding like hail on a tin roof. (In U.S. vernacular 
hail is large ice balls from about 5mm all the way to 20cm or more.) So, 
yeah. a little loud.


> Think about how a transistor works: You have one circuit that controls
> another. So how hard would it be to rig up a valve where pressure from
> one pipe moves the valve allowing (or blocking) water from flowing
> through a seperate circuit? In principle it ought to be pretty trivial.
> (Of course, making a valve that actually works well in practise probably
> requires far more equipment than I personally have...)

Right OK, just like all of the analogies. The gates would be controlled 
by current, then. I suppose you could control them by voltage (pressure) 
as well, but the valve would need to be easily actuated by pressure. 
Hmm, the analogy holds well.

> The problem is going to be that once you have more than a few of these
> linked together, effects like gravity and insertia become significant.
> These don't affect electronics, for some reason...

Well, water molecules are several orders of magnitude larger and more 
massive than electrons... so it makes sense. Though, I suppose it could 
be said a coil imparts a certain inertia to the motion of electrons.

I realize I'm stretching the analogy with that, but you'll see the point.


>
> Maybe that's what I did wrong... I was expecting an open TTL input to
> float low. Anyway, I don't think I shall go down the FPGA route. (!)
>

Yep. That got me when I fist started playing with TTL gates.

Here's and FPGA with 3000 cells for around US$18 ... Expensive in terms 
of a single IC, but not too terribly bad.

However they can also run as high as US$6,485.79 (!!) Oh, and good luck 
soldering that one to a board at home (Though, I've heard you can 
actually attach a BGA to a circuit board using a toaster oven, but very 
hard to verify that no pins are bridged or poorly connected.

>
> Another thing I thought about was a lego-style kit where you have lumps
> of plastic in the shape of logic gates, with nice connectors for the
> inputs and outputs, and LEDs in each input and output to indicate which
> logic state it's at. The trick, of course, is power routing. ;-)
>

Meh, that should be too hard to do. Either you have a substrate that you 
drop the blocks on, or the power routes through additional pins. I've 
seen a lot of electronics kits for kids that use lego-like blocks to 
connect components together, rather than the old spring terminals that 
my kit had when I was a kid.

-- 
~Mike

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