OT-ish... what to do with > 400 relays...

From: David V. Corbin <dvcorbin_at_optonline.net>
Date: Thu Feb 19 22:37:40 2004

I will have to look for them, they are deep in storage will other items from
my teenage years.

A little bit of the history though....

My father was a wireman/engineering prototype builder. This is back in the
days when most systems had significant harnesses thay were hand made (with
lacing cord, no such thing a tie wraps). The harnesses were build (typically
my placing a full size blueprint on a piece of plywood, placing "nails" at
all of the junction points and curves, and springs at the end of each leg.
The wires would them be cut to length, stripped, tinned (coated with solder)
and placed onto the board. Lacing cord would then be usig to tie the wires
together (I can still do a half decent running stitch, but can not find any
waxed lacing cord....).

While my father had quite a reputation in the New York area, and was sought
after for may projects by companies such as Grumman, he really did not have
much of a background in how the devices actually worked. On the other hand,
I was growing up around this stuff (burned my hand on a soldering iron for
the first time at the age of 2), and was always curious.

A number of the companies my father did business with had computers (often a
teletype with an acoustic coupler tied into a timeshare service). The
engineers there would often sign me in, and let me play one of the available
games. This started my interest in computers. These same companiew would
regularly scrap various prototype and test fixtures. I would take them home
(more often my father actually brought them to me), and scavange the parts.
One of the most common items (froma company named Beukers Labs if memory
serves...) were SPDT 6V relays (about one cubic inch in size). I had a few
hundred of them.

I had learned about digital logic gates, but had no ready access to any
integrated circuits. My skills were not good enough to make transistors work
reliably (my fault not theirs). So many of my project wer based on relays. I
figured out how to make inverters, or gates, and gates and latches. I
started to combine these into larger circuits. At about the same time my
father brought home a 1967 Digital Logic Handbook. I was completely
fascinated by M series modules (flip chips) and the fact they could build a
real computer (ok they used transistors, but what the heck). The "project
was born.

I started figuring out how to implement a simple instruction set (CLR, ADD,
STORE, TEST, JUMP, READ (Switches), DISPLAY (LAMPS), NOP). The number of
relays was quickly astronomical (try to build an adder with carry....).
Since 3 bits was enough to define an instruction, it became the word size.

Since 3x6 was a standard size for the harness boards (and we had lots of
them!), I used one of them for the layout. After spending quite some time, I
came up with most of the "schematic" and proceeded to start building a
harness. Once the harnes was build, I screwed the relays directly to the
board, and soldered the wires to them.

Of course it did NOT work...But after much troubleshooting (including
wripping most of the harness apart, flywiring between various points. I got
the beast to do what it was designed to do (which really turned out to be
nothing usefull at all... 8 data locations, 1 accumulator, one input port (3
bits), one output ports (3 bits), and 16 instruction locations (which as a
result ment you could only jump to "even" instruction bytes...

Amazing I was so proud of it. That fall I got the opportunity to be on the
school districts "new" PDP-8, and the rest of my life was set in motion....
Received on Thu Feb 19 2004 - 22:37:40 GMT

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