analog computers

That Lego-looking thing on the first page is the one I used in school. I put a better picture of it on abse.

Bob

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Fun, Since reading "Chaos" by Gleik I've wanted to build an analog computer and have it draw pretty pictures on a CRT screen. (It would seem wrong to look at the images with a digital 'scope.)

George H.

Digital:

ftp://jjlarkin.lmi.net/Spiral.jpg

Analog:

ftp://jjlarkin.lmi.net/Hills.JPG

John

Sacrilege, in fact. ;)

Of course there were two competing schools even inside the analogue computing world. The first was to do everything once, at very low speed and high accuracy, with pen plotters to capture the output. That's great if you have one system that you want to solve. The other, pioneered by George Philbrick, was do do it repetitively at lower accuracy and look at the results on a CRT--much better if you're trying to tweak the DQs to give you the results you want.

I have a book on analogue computers in aeronautics. I bought it because it was written by one Clarence L. Johnson, who (I'm pretty sure) turns out _not_ to be the Clarence L. (Kelly) Johnson of Skunk Works fame. (That was a bit disappointing, but what can you do.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net

Made with an all-analogue arb, I bet. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net

OK if you move down on this page you can see our "death spiral".

Not a very good picture I'm afraid. One axis is angular velocity and the other angualr position.

I'd like to make some of the period doubling Lorenz butterfly type things.

George H.

The sad news is that the ol' Tektronix 503 (saved from destruction when I was at Vanderbilt) was dead when I turned it on last time.

I don't have another working CRT 'scope, so this project is on indefinite hold.

George H.

d e

Both were generated by a VME arb. The spiral is a test pattern that turned out to be about six lines of 68K assembly code, basically two

32-bit integrators eating one another's tails, with some right-shifts in there to add a little damping.

Some guys at LLNL did an analog arb. It was a pc board, FR4 with copper on both sides. They machined a pattern that made a transmission line whose reflection was the waveform they wanted. Weird patterns.

John

Fun! I've used coax stubs to invert the sign of the leading edge of a TDR pulse, but that's as far as I've gone in that direction.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net

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use

"Chaos" was great. The program back then was "FracTools" and it is impossible to find any more. It calculated every pixel of the posistion (zoom) chosen. It was a real nice engine, but it ran under a weird defunct OS called "Gem".

Nowadays, they calculate a much "rougher" "overview" where they then recalculate values within those. The problem is that the final resolution image is grainy and has blocky artifacts. I liked the exact, per pixel calculation that FracTools used, but cannot find render engines that work that way any more.

What I did find is "The Best Little Screen Saver In The World"...

It is for your music player (WinAmp, Media Player, Flac, Etc) It also has a screen saver mode, but what it does is construct and render fractal imagery of various types on top of pallete shifted images of your photo gallery behind it. That IS cool.

It makes for the best screen saver Windows ever had, and is very much worth it, since it is fully cusomizable and script driven.

It is called " G-Force" and comes from Sound Spectrum

I worked on an English Electric LACE analogue computer (designed in

1954) when I was a student at the Kidsgrove plant around 1963.

Gem was not an OS.

Try fractint.

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