Cable plano Cable cinta

1. Ribbon cable...makes it look almost digital!

2. To quote Wikipedia: Depending on the programming environment, zero divide may generate positive or negative infinity by the IEEE 754 floating point standard, generate an exception, generate an error message, cause the program to terminate, or result in a special not-a-number value. Or light up an LED...this is correct in this instance, since nothing is connected to the four quadrant divider's denominator jacks (violet).

(The OVR MASK switch allows the user to ignore the zero divide (and other) error conditions connected with the divider.)

First Calculation

Integrator rack front panel in progress. Multiplier board wired up to banana sockets. And 2 x 3 = 6 apparently - or, rather, (2 x 3) / 10 = 0.6 .

Cool huh?

Fire in the Disco

...this tantalum bead (apparently a cross between a passive two-terminal electrical component used to store energy electrostatically in an electric field, and a firework) just exploded for no apparent reason. There were real flames! Looked like a coffee bean - but smelt much worse! Shorted out as is the fashion for these things and annoyingly took with it the output transistor on the negative rail of the main power supply. All fixed now. And both capacitors replaced with electrolytics.

Glow with all the Colors of the Rainbow

Panel for the integrator rack drilled...now the mildly tedious task of adding all the front panel furniture...the photo shows the rear of the panel with the 4 mm banana jacks...these are made by Emerson Network Power - chosen because they are available in all the usual colors plus orange and violet: in analog computing the more colors, the merrier.

It's Summertime...

Each board has two separate summers (x1, x2, x5 and x10 gains); inverted and non-inverted outputs. Switching is same idea as for the integrators - in SBY (Stand by) mode the input jacks are grounded and disconnected from the op amp inverting input. The latter is connected to a potential divider (10k to ground (Ra in Jackson [1]) and 100 k to op amp output (Rb in Jackson)). The op amp can be nulled in this configuration. I've tried many different op amps; the TL081 (despite being obsolete) seems the best (and just 30 pence each!). The summers work fine up to 20 kHz - not too bad for the stripboard layout. And to quote Richard Hamming: The purpose of computing is insight, not numbers - by which I mean I am more interested in the insight the computer may give rather than how fast it might work.

Reference

[1] 'Analog Computation', A. S. Jackson, McGraw Hill Book Co. New York 1960, Figures 7-3 and 7-4.

Well, I think that completes the electronics for the second rack...next task is to drill the 212 holes for the front panel :(