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| Home Brew Analog Computer System |
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| SeanB:
Bingo, I have one Phasor printer still intact, and in perfect working order, you just need wax ink at $200 per pack of 3 blocks, which it will happily consume in a month even if you do not print a single page. If you turn it on it does a clean cycle, which uses a half block of each of the Cyan, Magenta, yellow and Black ( black is free BTW) wax blocks. I used to print a lot of jobs to that printer with a black background and white text, just because it was so good at making a very good dense black print, and of course it actually does not cost any more, it will have dumped that black wax in the maintenance tray in any case. There was one DTP graphics shop with a dozen of these printers, and a salon next door, which used the black wax blocks to darken the regular pale wax to do hair removal, sort of as a differentiator. Beeswax is not hygroscopic, and is traditionally used as a protective coat in RF circuits, you will have come across it in older transistor radios as a coating applied to the FM RF and AM RF sections to keep them all from vibrating or moving if dropped. Melts in boiling water or a double boiler for you to pour into a mould, and is soft enough and flexible enough to enable rework without taking it all off. |
| GK:
OK, I'll send you a PM. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- I am currently finalizing the electrical design of a companion for my log amplifier module - the antilog module. The log module detailed already has the transfer characteristic: eout = k (ln * ein) where ein is a unipolar intput ranging 10mV to 100V (4 decades). k is a fixed scaling factor of 20 and eout clips at a +/-105V. A table of ein/eout looks like this: --- Code: ---ein eout 10mV -92.1V 100mV -46.05V 1V 0V 10V 46.05V 100V 92.1V --- End code --- The antilog amplifier the direct inverse transfer characteristic: --- Code: ---ein eout -92.1V 10mV -46.05V 100mV 0V 1V 46.05V 10V 92.1V 100V --- End code --- The equation is simply eout = exp(ein/k) where k again is a fixed scaling factor of 20. So if you wire a log module in series with an antilog module (either way around) you end up with a linear transfer characteristic (disregarding errors). My, perhaps stupid question is this: what is the most commonly accepted way of expressing a natural antilogarithmic equation? exp (exponential function) as above, or: eout = antiloge(ein/k) that's e indicating base 2.71 or: eout = e(ein/k) ? Here is the basic schematic: |
| T3sl4co1l:
I don't know that there's any significance between "antilog" and "exponent". I would go with "exponent". Whereas there's a difference between antiderivative and integral (the integral is with the "...plus a constant" part, depending if it's definite or indefinite). Of course, your integrator module is implicitly definite, so that's taken care of. There are different types of logs, but this is an analytical rather than computational luxury (the complex logarithm has an infinite number of corkscrew layers to choose from; the Ln(z) function denotes the simplest "main branch" choice around zero). Tim |
| GK:
Antilogarithm appears to be an antiquated term for the exponential function. The Wikipedia "Exponential function" page cites a text dated 1911 for usage of the term. Funny that before I stumbled upon the Wikipedia page I couldn't find this explicitly and unambiguously stated anywhere. So long as the superscript is practical I think I'll prefer ex. That is more descriptive of the function (Euler's number raised to the power of x) than exp(x). |
| recjohnson:
Very interesting thread! I have just started reading and have a long way to go.. The sine function generator you posted in the first post reminded me of a function generator chip ICL8038 that has a similar topology inside. While I go through rest of the thread, I just want to say, this is a damn impressive project! Thanks for posting in such detail. |
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