Finishing function generator for analog computer (THAT)

THE ANALOG THING (THAT) ANALOG COMPUTER IS ANOTHER TOY OF MINE

Anabrid has produced a relatively low cost modern analog computer which they call The Analog Thing or THAT for short. I own one although I won't spend much time with it until I have the current restorations completed. 

https://the-analog-thing.org/ 

The computer uses voltages from -10V to +10V to represent the analog of some variable. Its output is displayed on an oscilloscope or plotter. 

DESIGN POSTED FOR A FUNCTION GENERATOR WHICH I WHIPPED UP

An analog computing enthusiast designed a simple function generator which expands the range of problems that can be accomplished on a THAT. The functions it provides are:

  • x^y
  • x^2
  • x^3
  • sqrt(x)
  • x^(1/3)
  • sign(x)
  • x/(10y)
  • sqrt(x^2 + y^2)
  • x^(5y)
  • e^(x-1)
  • e^(2x-2)
  • 1+ln(x)
  • 1+0.5ln(x)
  • (atan2(y/x))/pi
  • sin(x*pi)
  • cos(x*pi)


I don't have the labels on the box yet. The left side has the X input on top, Y input on the bottom and ground in the middle. The knob selects one of 16 functions to produce. The right side has the output jack at top and a ground connection in the middle. The bottom switch will choose between unipolar (0 to +10V) or bipolar (-10V to +10V) output.  

TESTING, DISCOVERED SWAP OF ICS

I did some testing using a variable voltage source and a multimeter to read the output. The puzzling output led me to discover that I had swapped the two op-amp integrated circuits, which means that at least the lower voltage one is fried and possibly the other as well given the mismatch of pins to circuit connections. 

As soon as I get the replacement chips I will install them and complete testing. 

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