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| Home Brew Analog Computer System |
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| zapta:
--- Quote from: GK on November 28, 2012, 10:05:12 am ---..... I've been working like a man possessed to design and build my own solid state hybrid digital/analog computer to modestly put virtually all of those extinct commercial offerings to shame (complexity, size, precision, etc). --- End quote --- I wonder why there are still commercial analog computers these days that digitals computers are so cheap and powerful. Can you give a few examples where they have an advantage over digital? Years ago I used to maintain an analog computer. It was a Philips unit with a CRT that used to display underwater sound wave propagation based on the vertical thermal profile of the water. I had billion of potentiometers on the front and zillions trim pots inside. Calibrating it was a nightmare and it needed 24h to stabilize before being used (it was 100% solid state). |
| Dave Turner:
As a relative newcomer to the EEVblog forum I've only just come across this thread; much of the day has been lost reading it. It has brought back many of my memories, particularly as earlier this year I was forced due to circumstances to skip, almost overnight, ALL of my magazine collections of Practical Wireless, Practical Electronics etc. etc. dating from the early sixties through to the early nineties. Including those editions about the Analogue Computer mentioned at the start of this thread. (Several thousand magazines). In 1966 I joined the newly formed computer club at school and wrote my first "Hello World" equivalent in Algol via coding sheets and punched cards to be run on the mainframe at Keele University. Wonderful a 2 week development cycle. To the point of this thread a book book given to me then was a source of inspiration some of which is relevant. Have a look at http://books.google.co.uk/books?id=aQ84AAAAIAAJ&printsec=frontcover&dq=cambridge+university+press+we+built+our+own+computers&hl=en&sa=X&ei=YvOUUvvPBuSV7AbwsoCIDw&ved=0CD0Q6AEwAA#v=onepage&q=cambridge%20university%20press%20we%20built%20our%20own%20computers&f=false I may be missing something but why would you need to use the ABS() function when using integer arithmetic? I don't know whether the compiler is clever enough to recognize this or not; but if not you could save computational time. Please keep this project going with as many updates as are reasonably possible. Under many circumstances, once set up, an Analogue computer will solve a problem faster in real time than a Digital computer. With the preponderance of digital circuitry now, this is often forgotten. (Occam's Razor) |
| GK:
--- Quote from: zapta on November 26, 2013, 09:21:28 pm --- --- Quote from: GK on November 28, 2012, 10:05:12 am ---..... I've been working like a man possessed to design and build my own solid state hybrid digital/analog computer to modestly put virtually all of those extinct commercial offerings to shame (complexity, size, precision, etc). --- End quote --- I wonder why there are still commercial analog computers these days that digitals computers are so cheap and powerful. Can you give a few examples where they have an advantage over digital? --- End quote --- I'm not aware of any analog computer model still being commercially made. An analog computer could still be useful in the electronics lab for the study of control theory fundamentals, and that is where their application lingered on the longest. |
| GK:
--- Quote from: Dave Turner on November 26, 2013, 10:05:55 pm ---As a relative newcomer to the EEVblog forum I've only just come across this thread; much of the day has been lost reading it. It has brought back many of my memories, particularly as earlier this year I was forced due to circumstances to skip, almost overnight, ALL of my magazine collections of Practical Wireless, Practical Electronics etc. etc. dating from the early sixties through to the early nineties. Including those editions about the Analogue Computer mentioned at the start of this thread. (Several thousand magazines). --- End quote --- Hi, Thanks for the interest. Pitty you had to turf all those old magazines! Although it doesn't contain much at the moment, I have a website ( http://www.glensstuff.com ) that will eventually have a full write up and all technical details of the project. I've made a lot of progress with the construction so far, but no one section/chassis is fully complete at this time, which is why the presentation hasn't much happened yet. |
| GK:
--- Quote from: GK on November 26, 2013, 08:10:44 am ---The article gives an explanation of the graphical method (Figure 1) for manually drawing out the character on Cartesian coordinates and then working out and plotting the X and Y waveforms required for reproduce the character. This is quite simple and straight forward enough, but the article does not then go on to explain or detail the "purely graphical" method for manually computing the Fourier components of the produced X and Y waveforms - though a reference is given: T.C. Blow, Graphical Fourier Analysis, Electronics, p194, Dec. 1947. Anyone have a stash of old copies of Electronics magazine?? I need to further compute the Fourier components for the numbers 8 and 9 and the letter A through F. Any other reference provided or insight into the technique would be appreciated! --- End quote --- Soooo, there isn't anyone here skilled in the art of graphical Fourier analysis then?? Our state library doesn't have copies of the periodical Electronics dating as far back as 1947. However I am working my way around the issue and here is how far I got this evening. I now have an Excel spread sheet that will plot the waveform from the entered Fourier coefficient values (5 harmonics, sine and cosine terms). The idea is that I will draw out my characters on graph paper, as described in that article and pictured Fig.1, to work out the coordinate values for the X and Y waveforms require to reproduce the alpha or numeric character on the CRT display. I will then enter the coordinate values for each waveform in a special reserved column in my spread sheet, which will then plot them up onto the same chart as the waveform generated by the Fourier coefficients. I will then manually alter the Fourier coefficients by trial and error until the Fourier coefficient generated waveform is a best fit to the desired waveform. At that point I will have my required Fourier coefficient values. |
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