water analogy- a simple calculator

It's not exactly simple

There is no analogy between electronics and water. The only analogy i know is teh analogy between water and electricity.

Pressure is voltage. Flow is current.

You can have pressure without flow. You can have voltage without current.

Small pipes have higher risistance.

You can calculate with water. Put 4 liter in a bucket. add 3 liter to the same bucket. The result is 7 liter. take out 2 liter and jou have 5 liter left in the bucket.

With electronics you have only buckets (bits) that are full or emty.

A basic building bloc in electronics has 2 inputs and 1 output. The function of such a bloc is described by the truthtable. There are three basic functions. The and, the or, and the xor (exclusive or). There is also the invertor.

The truth table for the and is

I don't know how to build this with water. As far as i know they have sulutions in pneumatics.

tuinkabouter:

A rubber diaphragm that obstructs the pipe is a capacitor. A lead rod inside the pipe is a coil. A check valve is a diode. A rubber baloon inside the pipe is a FET A nozzle directed to the output pipe with a control nozzle mounted normal to it is a BJT.

That's digital electronics.

And therefore with water & pipes.

I'd say very probably yes - they do it with transmission fluid in an automatic tranny; you'd just have to figure out how to do the switching elements, which could be spool valves and schtuff, but beyond that you're kinda on your own.

Good Luck! Rich

Evidently you've never heard of analog, or linear, circuitry.

But thanks for playing! Rich

And don't forget, a hydraulic jack is a transformer.

Bret Cahill

(The baloon mouth (gate) feed from up stream through some flow impedance)

(I don't quite get this one... but then I always found FET's easier to understand (at least in principle))

That was nice, Thanks.

George H.

al

Oh, I call them hydraulic rams. It's not quite a transformer, that's a lot more efficient than a ram. (At least that's my understanding of a ram.)

George H.

I am a bit biased the last 25 years, but i know how to calculate a transistor amplifier... But not anymore i think. And i forgot the tubes.

And automatic transmissions have hydraulic computers:

Cheers! Rich

I'd think "transducer" would be more accurate, unless you've got one ram driving another one of a different size.

Cheers! Rich

George Herold:

Me too. ;-)

The example is about a nozzle that "shoots" water in the output pipe. If the water jet is disturbed by another, smaller, jet coming from the "base nozzle" it will partially or totally miss the output pipe.

Actually the operation should be reversed, in the sense that the "collector pipe" should not be aligned with the "emitter nozzle", so that the main jet can enter it only if deflected by the "base jet".

It's a weak analogy, because the equations don't match. You can't apply Ohms-law type reasoning to fluid flow because pressure drop is nonlinear on fluid flow.

John

Except that most people don't understand the fluid situation to start, and lots of people don't do these sorts of physical analogies very well. I find it easier to just explain the electricity.

As I said, it's a weak analogy. You have to misunderstand fluid flow for it to even sort of work. I've never liked using plumbing to explain electronics.

John

John Larkin:

Right. That's why this analogy is precious.

Everybody that has played with a garden hose as a kid has wondered why, if you obstruct its end with the thumb, the water jet goes farther.

The solution to this apparent absurdity not only explains them Ohms law, but also entices their curiosity by satisfying a long-standing question.

Probably that's the reason why most of the ITIS (vocational high school) graduates I interviewed don't know Ohm's law. We should make the teaching of the water analogy compulsory in schools.

OK, what's the electrical equivalent of the finger-on-the-hose thing? Schematic, please.

There is no equivalent of Ohm's Law in fluid flow. There's not much point in teaching electronics qualitatively.

John

John Larkin:

Sorry, but, for some reason, my newsreader uses, as fixed font, a proportional one. Apart from that, I'm used to publish schematics on NGs with FidoCad and, "spoiled" by it, I can't stand anymore using "ASCII art".

But I can describe it very easily: a voltage source connected to a resistor and a variable resistor.

The more the finger obstructs the hose, the higher the value of the variable resistor, the less circulating current and the higher voltage in the node between the two resistors and the pressure in the hose.

Very useful also to explain the difference between a real generator and a voltage source. The generator's internal resistance is another of those unbelievably "mysterious" topics.

During one of those interviews I used some time to explain to the "candidate" (a friend's son) the hose thing. His smile, after years doing exercises he could not figure out what they meant, was priceless.