Something About the Hitchhikers Guide and "middles"

A project log for Low Voltage Vacuum Tube Logic Gates

Creating four basic logic gates (AND, OR, NAND, NOR) from common vacuum tubes, powered at low voltages

Lord of ResostersLord of Resosters 12/26/2019 at 23:350 Comments

Ok Ok, so I am almost certain that the introduction was the most bland and disinteresting method of introducing a project *ever*, so hopefully I can rectify that.

The Middle

As the title may suggest, the project is happily at the middle of development. At the moment, the main electronics of the project have been completed, and a simple arduino sketch that cycles through 00, 01, 10, and 11 as well as monitoring the analog inputs to make sure all of the logic gates are behaving themselves. (trust me, at these voltages they do like to... not work as intended). The actual software still needing to be written. Theres a reason I'm a terrible electronics engineer, not a terrible software developer. 

The current set up of the project is effectively a prototype - knocked together with tubes and resistors that I had on hand. I can at least say that I aim to produce a PCB version of this project (which still needs a catchy title) using only a single (CHEAP) tube that could be thrown onto tindie. Thats still in the future at least. 

So what are the tubes, and the purpose of them?

CV491 - effectively a military 12AT7 (?), basically a dual triode, that is being used as an OR gate

EF183 - pentode, arranged as a NAND gate.. that has had its inputs shorted to a NOT gate, which inverts the output from the OR gate, so the output is a NOR gate (I did mention this was thrown together).

6D2 - dual diode, somehow SOMEHOW creates an AND gate, which is surprisingly effective.

12AT7 - another dual triode, only one of the triodes is used to create a NOT gate, inverting the AND output to produce a NAND gate. (the other triode in the tube didn't work as a NOT gate for some reason)

The vacuum tubes are soldered point to point (OK I am really struggling with the correct grammar there)

The resistors used for the anodes and the inputs are located on a separate piece of veroboard - makes connecting the arduino easier.