Interesting analogue calculator on that other site


Interesting analogue calculator


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Unfortunately I spotted it close to the end, but thought it would make an interesting "look at" before it's removed.



The link still works, though!

I would like to see the electronic circuit. I thought about many current and voltage dividers, series and parallel arrangements and current and voltage sources, but I wonder how did the designers put these all together and made it work with the few components seen in the last picture. One question: could not identify what are those components in the bottom of the equipment (left side of the last picture): valve tubes? Electrolytic capacitors? Anything else?

"Fascinating!" (no quoting this time...)


Luiz (Brazil)


Seems to me (with very little electronics knowledge) that addition/subtraction are achieved by simply adding and subtracting resistances. Not sure how multiplication/division work, but something similar.

This simple construct would cause negative results to peg the needle to the left; hence the negative number switch, which would switch polarities.

The scale factor switch likewise has an obvious function, but the implied range of results is so limited, that one wonders why so much trouble for math problems that can be worked out on paper or mentally pretty easily.



But I took it into a different perspective.

Human neural network deals with numbers in such a relatively easy way. At least for most of us -humans in general- this is true. Building machines that implement such capability is another story. Since Babbage proposed the differential machine and others came with electromechanical and electronic implementations, we now deal computers in such a relatively easy way as well.

But only a few of humans actually know how to implement such capabilities in these machines.

I myself can follow some internal electronic structures from digital arithmetic IC´s, but I cannot build a complete electronic adding machine in my brain... not yet, at least. I know much of the pieces, I know how to connect some of them, but I need to go further prior to 'see' it all working as a whole. I am an Electrical Engineer, electronic knowledge has been a personal achievement.

I think that knowing how these small analogue calculators work may give some perspective...


Luiz (Brazil)

Edited: 23 May 2010, 11:01 p.m.


Look like the batteries (or maybe electrolytic caps)


...One question: could not identify what are those components in the bottom of the equipment (left side of the last picture): valve tubes? Electrolytic capacitors? Anything else?...

I'd vote for capacitors. They are wired in series with a red wire coming off the top and a green wire on the bottom. I was going to say some kind of odd-ball battery, but then I noticed the four 9v batteries directly to their right, so I wouldn't think there would be two kinds of batteries in it.

I'm guessing it was a student project of some kind (science fair, electronics class, etc.) based on the hand-made dial scale and some of the, err, "expedient" construction (e.g. soldering directly to the 9v batteries).

I remember using old analog computers in school to perform simulations that needed multiplication, division, integration and differentiation. Not sure why they were still in use; perhaps they were supposed to give us a better feel for the problems we were simulating on them (usually mechanical problems like the famous "damped mass on a spring" headache) than the digital simulations.




I captured the picture with [PrintScreen] and turned it 'upside up' so I could see the actual boxes of the 9V batteries (shame on me... the top connectors looked like valve tubes' 'heads' to me...) and the other blue boxes with two connectors in their top. Somehow (the picture does not help that much...) they seem to be a 'complementary' set of four batteries, as if the power supply is +/- 36Vcc with a common (neutral) terminal. One of the poles would come from the set of small 9Vcc batteries while the other pole is provided by the four blue batteries. Chances are that the active circuitry (voltage/current sources?) are fed through the blue set.

I really would like to see the schematics...


Luiz (Brazil)


I have been fascinated by those "analogue computers" for so long. But didn't dare to buy one due to the "another item piling up"-fear.
I think I spotted at least three TO-cans (transistors). So by the components I would place it around mid to late 60s, when transistors became affordable. Earlier DIY-experiments would have used way cheaper valves.


Hi, Frank;

have you also noticed the PCB´s layout? It´s been used a 'proto' type PCB, with pre-drilled holes in parallel cooper tracks, so I considered it could be an earlier experiment. Also, along with the TO-type transistors, it seems that some SOT-type units have been used (or else they are just small elect-caps). I also noticed some CR25 resistors in some of the rotating switches.

There we go, acting as A. C. Doyle´s restless character...


Luiz (Brazil)



This must have been a project of an electronics magazine of the early seventies (maybe ETI (Electronics Today International), Elektuur/Elektor or Funkschau which were popular in Europe then?). I remember it from a classmate, whose father was a physicist by profession who loved to tinker with electronics in his free time. One day my classmate brought this "computer" to school, much to the amazement of our teacher! (By coincidence we will have our 30-year class reunion next weekend, but this "boy" is not on the list of attendees, so I can't ask...)

I think it uses opamps (you can see them in metal casings on the small curcuit boards) for multiplication and division, at least one set of batteries are needed for their symmetrical supply voltage of +/-15V.

Regards, Max

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