Neon logic

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Fri Feb 28 18:19:01 2003

> I came across reference to a file, LAMP.ZIP, you posted briefly for the
> Classic Computer list back in '99. Would it be possible for me to get this
> file? I'm fascinated by the idea of making counters, logic gates, and
> memory elements using neon lamps, but repeated google searches reveal very,
> very little hard information (other than there were such circuits).

There's a reasonable book on this subject called 'Cold Cathode Tube
Circuit Design'. It covers things like gas-filled voltage stabilisers,
trigger tubes (the cold cathode thyratrons you mention), dekatrons, etc.

I certainly remember there being circuits for counters, shift registers,
etc in that book.

No idea where you'd find a copy now, but it might be a startign point

Incidentally, HP made a decade counter/display board where the counter
FFs were made from pairs of transistors in the conventional way (8
transistors on the board). These were controlled with diodes to count in
1242 (not 1248) BCD code.

The outputs of these counters drove 8 neon bulbs, and by varying the bias
applied, the state of the counter could be latched in the bulbs (that's
why this is relevant here). These bulbs were mounted inside a plastic
block on the PCB, and shone onto a think-flim circuit of CdS
photoresistors. These were connected to form a binary to decimal decoder
to drive a nixie tube.

These days it seems amazing that you could make a BCD counter, latch and
display driver using only 8 transistors :-)

-tony
Received on Fri Feb 28 2003 - 18:19:01 GMT