scott wrote:
>> Well, I don't know. Watching somebody staring at a piece of paper and 
>> thinking really hard doesn't sound entertaining to me, but then again 
>> I haven't tried it with somebody who's really awesome at thinking...
> 
> The awesome bit is when they finish thinking and write something down.

Typically when they write it down, they write it in a way that makes 
absolutely no sense to you or I.

The awesome bit, for me, is when they explain what it means, and why it 
works, and you look at it and go "ah... neat!"

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> Well yes, this is the other possibility: Instead of flowing liquid (or 
> gas), use rotating beams. If the beam is being driven to rotate, that's 1. 
> If it's being held still, that's 0.
>
> Only problem is... what sort of clutch do you use to enguage a gear if a 
> beam is rotating above a certain speed? ._.

There are several options to choose from.  First one that comes into my mind 
is to have some weights (small ball bearings) that move outwards from the 
rotation axis as speed increases due to the centripetal force.  This linear 
motion outwards can be used to engage a clutch between two other shafts. 
Similar concept is used to govern the speed on some engines:

http://en.wikipedia.org/wiki/Centrifugal_governor

Another option (simpler but not as long lasting) could be to have a simple 
frictional contact with another shaft that is constrained to rotate by a 
torsional spring.  As the input shaft speeds up the 2nd shaft will reach 
some static equilibrium position, again this could be used to move another 
clutch that connects two different shafts.

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>> The awesome bit is when they finish thinking and write something down.
>
> Typically when they write it down, they write it in a way that makes 
> absolutely no sense to you or I.

It depends on whether you were following along with what they were doing 
before.  Obviously if you turn up to see the one-liner written down it's not 
going to be awesome at all if you don't understand it.

Seems similar to if you've never watched a sport before and switch on the TV 
to see the best "goal" ever - it's not going to be awesome for you.

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>> Only problem is... what sort of clutch do you use to enguage a gear if 
>> a beam is rotating above a certain speed? ._.
> 
> There are several options to choose from.  First one that comes into my 
> mind is to have some weights (small ball bearings) that move outwards 
> from the rotation axis as speed increases due to the centripetal force.  
> This linear motion outwards can be used to engage a clutch between two 
> other shafts. Similar concept is used to govern the speed on some engines:
> 
> http://en.wikipedia.org/wiki/Centrifugal_governor
> 
> Another option (simpler but not as long lasting) could be to have a 
> simple frictional contact with another shaft that is constrained to 
> rotate by a torsional spring.  As the input shaft speeds up the 2nd 
> shaft will reach some static equilibrium position, again this could be 
> used to move another clutch that connects two different shafts.

Yeah, this sounds like the two options I came up with.

I was wondering if something like the "Bendix drive" used in a starter 
motor might work, but looking at how it operates, it seems unsuitable.

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On 12/05/2010 9:01 AM, Invisible wrote:
>
>> Did you know that using pneumatics you can make amplifiers,
>> integrators, switches etc.?
>
> I don't see why not... although I would imagine achieving good linearity
> might be tricky.



-- 

Best Regards,
	Stephen

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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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On 5/11/2010 4:37 PM, Orchid XP v8 wrote:

>
> The nice thing about relays is that they're (usually) double-throw. That
> means you need fewer relays than you would, say, transistors.
>

Yep. Surprisingly easy to construct AND, OR and even XOR gates with 
relays. ;)

-- 
~Mike

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On 5/12/2010 3:02 AM, Invisible wrote:
> Stephen wrote:
>
>> Good luck and photos are required. :-)
>
> Pictures or it didn't happen. ;-)

Haha... Ohh boy. Maybe now I'll have something to post to my blog. Yeah, 
I'll share pictures when I get to building it.

I'm still in the design phase. Maybe this evening I'll print up some 
screen captures of the layout in the sim.

-- 
~Mike

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On 5/12/2010 12:24 AM, Stephen wrote:

>
> Yes, the GPO.
>

pardon my ignorance, but what is a GPO?

-- 
~Mike

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>> 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 analogy is pretty perfect. Electrical current = water current. 
(Litres per second rather than Columbs per second.) Electrical potential 
(i.e., voltage) = water pressure. Resistance = ...well, resistence.

Wikipedia even has a name for it:

http://en.wikipedia.org/wiki/Hydraulic_analogy

An electric circuit is just like a water circuit, but pushing water 
around instead of electrons. All the same things like flow-rate, 
density, pressure, etc all make sense.

I envisiged pressure-actuated valves. (I.e., pressure on the input 
channel slides a valve, revealing an outlet. A spring slides the valve 
back again when the input pressure drops. The slilding of the valve 
opens or closes a channel for another water circuit.) If you wanted 
current-actuated, you'd need a turbine or something to measure flow-rate 
rather than pressure.

>> 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.

Even so, you would have thought starting and stopping the motion of 
several hundred trillion electrons would take more energy than just 
keeping them flowing.

>> 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.

Hmm, interesting.

> 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.

I was looking at the price of a "kit", which contains not only the FPGA 
chip itself, but also the [expensive] gizmo for programming it. The chip 
also comes ready-mounted on a board with a USB interface and there's 
driver software so you can control the thing from your PC. But yes, the 
cost is far, far more than the piffling price of one little chip. (And 
then there's the version of the simulator software which can actually 
*program* the physical chip, not just simulate what it would do...)

>> 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.

Yeah, the substrate is probably the way to go. It draws attention from 
the ubiquitous power lines and focuses it on the routine of the signal 
lines.

> 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.

Hell, I've still *got* the spring-terminal kit. ;-)

Yes, today you could make some cool stuff. Trouble is, kids today don't 
have the patience for it, it seems. Why spend hours wiring up a circuit 
so that a few LEDs twinkle when you can sit in front of a PS3?

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