Dekatron, a counting vacuum tube!

A project log for Vacuum tube game in 21st century

Playing vacuum tube is not so difficult as expected. Let's play great heritage of human being by modern technology!

kodera2tkodera2t 07/18/2019 at 09:138 Comments

Indeed I've already got this unique tube before but till now I did not touch this tube. The neck was its special pinout. Indeed I don't have 13-pin vacuum tube socket, so this time I made it by 3D printing.

The circuit inside enclosure is quite simple, purely consisting of C, R, and diode. The plate voltage is generated by triple voltage rectifying and from AC 100V. (leading around 400V DC). For its light rotating, the tube requires two phase clock, same as rotary encoder. The current circuit generating 50 Hz two phase clock by just R-C phase shifter. This dekatron supports bi-directional rotation, so I added SPDT switch for phase capacitor for forward and reverse (CW, and CCW) rotation.

But maybe DEKATRON is the only one DIGITAL vacuum tube in the history. It is not just display like Nixie and VFD, but works as digital counter and memory and display.

Actual opration can be found in the following movie.... 

As you can watch the spinning color in the video, the color of A102 is not orange but blue-violet, meaning filling gas is not neon but argon or something else neon.


Muhomor wrote 07/22/2019 at 18:49 point

Wow! Can you tell me, what kind of pins you use for your socket?

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kodera2t wrote 07/24/2019 at 13:42 point

They are, actually pins for 5V-12V-GND connector of storage (3.5 inch IDE, SCSI...)

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Dave's Dev Lab wrote 07/19/2019 at 15:40 point

Nice looking build!

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kodera2t wrote 07/21/2019 at 07:24 point

Thank you!

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Dave's Dev Lab wrote 07/21/2019 at 19:51 point

i went with a more steam-punk look with the one i built a few years ago -

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Ken Yap wrote 07/19/2019 at 14:05 point

Hahaha, cool! Brings back memories. I first encountered them in a lab digital counters. The front of the instrument had several dekatrons in a row and a carry signal from a lower digit would increment the higher digit. At the end of the counting period you would read off the count from the tubes.

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kodera2t wrote 07/21/2019 at 07:25 point

Actually this is the first time for me to see working dekatron, and also first possession! It is really direct counting but I can understand why no one use this today ;-)

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Ken Yap wrote 07/21/2019 at 07:27 point

Yeah, I wonder too. 😉

In those days digital displays (filament, nixie, LEDs) were expensive, and counter ICs were also expensive. So to have counter and display in one tube was an acceptable trade-off. They weren't that fast though, I seem to remember hundreds of kilocounts per second was the max.

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