Maker Bob Alexander has dug deep for his newest laptop construct, and in doing so eschewed the trendy fad for binary gadgets incapable of counting past two with out duplication — by constructing a “decimal laptop” first proven on the quilt of Electronics Illustrated in 1966.
“Regardless of the journal’s hype of it being a pc,” Alexander admits, “it is actually simply an including machine. However I favored its retro look and the best way numbers are entered with a phone dial. The ‘laptop’ used ring buffers for counting. Neon lamps activate at larger voltages than they flip off at. This permits the lamps to behave as switches and reminiscence places. It’s attainable to construct a circuit, with none transistors, the place a neon lamp is lit, and a pulse from the phone dial causes it to show off, and the subsequent lamp to activate.”
The one downside: the directions, printed as the quilt function in Electronics Illustrated‘s November 1966 situation, require elements which can be a little bit arduous to seek out today — like NE-2 neon lamps, lengthy out of manufacturing, to be put in in a Bud Industries C-1588 enclosure. Worse nonetheless, even new-old inventory could not work: “not solely are the lamps all totally different from one another,” Alexander explains, “however their conduct modifications as they age.”
Alexander’s resolution was to leap right into a time machine to the Nineteen Seventies, selecting up some expertise that might make the design extra dependable and strong whereas nonetheless preserving the aesthetic of the unique — including solid-state 74HC192 decade counters and 74141 binary-coded decimal (BCD) decoder chips to drive the neon lamps, quite than counting on the lamps’ unpredictable conduct instantly.
The construct makes use of Nineteen Seventies-era 74-series ICs to counteract the unreliability of the lamps themselves. (📷: Bob Alexander)
“How does the article justify its declare you can subtract, multiply, and divide with this including machine,” Alexander asks. “Properly, subtraction is completed utilizing 9’s complement. For the others, you continue to want to recollect your multiplication tables, and the including machine simply assists you with the including and subtracting.”
The construct is documented within the video above, and on Alexander’s web site; a PDF scan of the journal from which the design was taken is obtainable from the World Radio Historical past website.