Decatron Clock Project

  
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Instead of simply incrementing the time every new second, it would be great to have a display of forward- and backward-spinning digits, slowly rolling-out to the new time, a little bit like the reels of a slot machine. Having never encountered them, decatrons are completely new to me. How do they work, how to interface them to a processor Instead of
Decatron Clock Project - schematic

working on it for a few months or so and then writing a new web-page on it, I decided to present this page in the form of a web-log. The idea is that this page is expanded every time the project has advanced a bit. Like the E1T "scaling tube" the decatron preceded the nixie tube, perhaps not by invention, but certainly by application. The most likely reason is that, besides a being a display device, both the Scaling Tube and the Decatron perform the counting function themselves, whereas Nixie tubes require quite a bit of electronics to make them work. They are both small wonders of ingenuity. The Decatron was first announced in a paper in Electronic Engineering of May 1950 entitled: "The Decatron, A New Cold Cathode Counting Tube" by R. C. Bacon and J. R. Pollard from Ericsson Telephones Research Laboratories, Nottingham, England [4]. The paper discusses the general operation, the performance, and the circuit requirements. The working of the Decatron is best explained in the words of the inventors: A cathode glow on one of a set of inter-connected cathodes, arranged around a central common anode, is caused to transfer from one position to the next by application of controlling voltages to intermediate electrodes or "guides". This arrangement will become clear by considering Figs. 2 and 3. Fig. 2 shows, around the central anode disk A, a number of equi-spaced rods or wires (on a pitch circle of 20mm. diameter in the case of...



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