Thoughts Grenade

Fifty Years On

Origin

One must be thought-about fortunate if, throughout their life, they
encounter a “wild expertise”. These are individuals who spin
off unique concepts quicker than others can write them down, undertake
challenges few others would think about, no much less try, and make you
really feel exhausted but exhilirated simply making an attempt to maintain up. The primary
such particular person I met in my life was Harry S. Pyle, who was a classmate
of mine in engineering faculty. On the time I met him, as a college
freshman, Harry was already an electronics wizard, having obtained the
highest stage of beginner radio license (Beginner Further),
been awarded a lifetime membership within the American Radio Relay
League based mostly upon his proficiency in Morse code, and was amongst
the small variety of radio amateurs utilizing radioteletype (RTTY)
gear. Legend had it that Harry might select his name signal
by ear when transmitted in frequency-shift-keying encoding
on the beginner radio bands. I by no means noticed him do that, however I
by no means doubted he might.

In later years Harry would go on to develop into, with Victor Poor,
co-designer of the instruction set of the
Intel 8008 microprocessor,
which was the ancestor of the Intel x86 structure
utilized by a majority of general-purpose computer systems right this moment. He was
a principal designer of
ARCnet, the primary industrial native
space pc community, and later labored within the space of pc
imaginative and prescient and communications. Here’s a
list of patents
granted to Harry Pyle. Harry Pyle
died in 2013.

In 1969, Harry amazed all people with a bit digital gadget
he’d constructed which, utilizing the primitive digital built-in circuits
of the time, generated random music, performed it via a speaker,
and flashed lights on its entrance panel. It was exactly what
individuals anticipated computer systems to do, based mostly upon portrayals within the motion pictures
and on tv, and but it may very well be held in your hand and was,
internally, quite simple. He defined the way it labored, and I
instantly knew I needed to have one. Digital electronics
was in an important state of flux on the time, with every producer
launching their very own line of built-in circuits, most incompatible
with each other, so there was no level in slavishly reproducing
Harry’s design. Ranging from the idea, I designed my very own
gadget from scratch, utilizing Signetics Utilogic diode-transistor
small scale integration built-in circuits which have been fashionable
on the time however shortly thereafter made out of date by 7400 collection
transistor-transistor logic (TTL). The structure was similar
to Harry’s system, however I opted for extra with-it and fewer power-hungry
light-emitting diodes (LEDs) for the show as an alternative of the
incandescent bulbs he used. I constructed the electronics meeting on
a sheet of perforated board utilizing wire-wrap fabrication (some
individuals look down their noses at wire-wrap right this moment, nevertheless it was good
sufficient for the Apollo Steerage Laptop and virtually each mainframe
backplane of the Sixties, and my wire-wrapped electronics works
completely fifty years later.)

{Hardware}

Right here is the Thoughts Grenade I constructed. Transfer the mouse over the picture
to indicate legends on the controls. The knob at left controls the
pitch of the music, whereas the knob at proper units its tempo
(pace). The 4 switches on the backside choose one in every of 16
tunes, every 511 notes lengthy, which the system can play. The
show panel exhibits the state of the 9 bits of the
linear-feedback shift register used to generate the pseudorandom
sequence of notes.

With the duvet eliminated, we see the entrance panel with
the tempo and pitch controls, the show panel and,
beneath it (largely obscured by the rat’s nest of wires)
the tune choose switches, and the circuit board. Beneath
the circuit board is the bottom-mounted speaker and the
AC energy provide I added later to the unique
battery-powered design.

Here’s a detailed view of the circuit board; transfer the mouse
over the picture to indicate useful models. The built-in circuits
have been mounted in wire-wrap sockets, whereas discrete parts had
their leads pushed via the board and unfold to carry them in
place. Off-board parts, such because the tempo and pitch
potentiometers, tune choose switches, and light-emitting diodes
(LEDs) have been linked through three IC sockets into which dummy IC
“headers” have been plugged with wires resulting in the
parts. The 9 220 ohm resistors on the backside left are
collection current-limiting resistors for driving the LEDs from
logic stage indicators.

The entire wiring of the digital parts was performed by
wire wrapping. Discrete parts comparable to resistors,
capacitors, and transistors had their leads pushed
via the perf board, bent outward a bit to carry
them in place, then soldered to at least one finish of a wire to
both wire wrap or solder to the vacation spot.

In 1969, few individuals had seen light-emitting diodes (LEDs). The
entrance panel of the Thoughts Grenade had a block of pink plastic into
which I drilled 9 holes that didn’t penetrate the entrance
floor. In every gap I positioned a tiny pink LED (the one color
out there on the time) in a transparent package deal, with its leads bent
again to protrude from the outlet. The damaging leads have been all
linked collectively and grounded, whereas the constructive leads have been
soldered to wires which ran to connectors that plugged into the
circuit board. After testing, I mounted the LEDs in place by
squirting clear silicone sealing compound into the holes. The
accomplished show panel was mounted with black silicone sealer
to the again of the sq. gap I might punched for it within the entrance
of the cupboard.

The unique Thoughts Grenade was powered by a 6 volt “lantern
battery”. Within the mid-Nineteen Seventies, I retrofitted a built-in AC
energy provide utilizing a 6.3 volt filament transformer, a bridge
rectifier, smoothing capacitor, and a TO-3 5 volt regulator.
The regulator generates comparatively little warmth, so merely
mounting it to the grounded field and leaving the package deal to
dissipate warmth by convection is ample. The facility provide
was considerably inelegant in that while you plugged within the system
the sound would “burble” for a short interval till
the smoothing capacitor charged up, however then stabilised.
As a result of the transformer is designed for 60 Hz AC energy, and the
chance the electrolytic smoothing capacitor is shot after
virtually half a century, to run the Thoughts Grenade for the video in
this web page I disconnected the ability provide and ran the circuitry
from a 5 volt DC bench energy provide.

How It Works

The Thoughts Grenade is predicated upon a 9-bit
linear-feedback shift register
which acts as a pseudorandom sequence generator with a interval of
511. The shift register is constructed from Signetics SP322B
flip-flops, with the bit shifted out from the low-order being
exclusive-ored with fifth bit within the register and shifted in as
the brand new high-order bit, producing the utmost sequence size of 511
for a 9-bit register. A Signetics N8242A Unique Or gate
is used to compute the bit shifted into the register on every step.

The shift register is clocked (shifted) by an analogue pulse
generator whose fee is managed by the “Tempo”
(proper) knob on the entrance panel, which adjusts the speed at
which the register shifts between round twice a second to extra
than ten instances a second. Every time the register shifts, it can
tackle a brand new worth between 1 and 511, and the sample is not going to
repeat till all 511 values have been generated. This produces
the pseudorandom sequence which generates the “music”
performed by the Thoughts Grenade.

To show this quantity right into a musical tone, we look at the worth of
the least vital 4 bits of the 9 bit shift register,
which may have a worth from 0 to fifteen. We then have a 4 bit
counter, additionally constructed from the identical sort of flip-flops because the
shift register, which counts up ranging from 0. The worth in
the counter is in comparison with that within the low 4 bits of the
shift register with logic constructed from Signetics SP337A and SP387
NAND gates and, when equality is detected, the counter is reset
to zero and a sign emitted which inverts a flip-flop devoted
to producing the tone. The output of this flip-flop is
amplified by an influence transistor and used to drive the speaker.
The counter is incremented by a separate analogue pulse
generator whose pace is managed by the “Pitch”
(left) knob on the entrance panel: this units the frequency vary
for the 16 tones generated based mostly on the low 4 bits of the
shift register. When the low 4 bits of the shift register
are all zero, the counter might be reset so quick that the
generated tone might be above the vary of human listening to (and the
capacity of the speaker to breed), and can produce a pause,
or relaxation notice, within the output.

The 4 switches on the entrance panel management whether or not the worth
of every of the 4 low bits of the shift register is shipped
on to the comparator or inverted earlier than the comparability.
This permits deciding on 16 completely different sequences of the notes
performed by the system. These are referred to as the “Tune Choose”
switches. They solely have an effect on the mapping of the shift register
state to audible tones and could also be modified at any time.

See Also

Designing a Programming Language to Speedrun Creation of Code

In Motion

Here’s a quick video of the unique Thoughts Grenade in motion.
To keep away from utilizing the built-in energy provide, which was designed
for 120 volt 60 Hz AC energy, I disconnected it and powered the
electronics from a 5 volt DC bench energy provide. The piercing
timbre is because of the sq. wave output of the tone generator.
This video was made with the duvet eliminated, which permits ambient
gentle to shine via the pink plastic block holding the LEDs;
with the duvet in place, you do not see the distraction of the
wires and non-illuminated LEDs.

The Software program Simulator

Little did I think about, when designing and constructing the Thoughts
Grenade {hardware} in 1969, that fifty years later I might be
emulating it on a pc which ran greater than a thousand instances
quicker than the one I utilized in my day job on the time and,
moreover, was sitting by myself desk. However right here we’re.

Because of HTML5 and JavaScript, it’s now attainable to emulate
the {hardware} Thoughts Grenade fully in software program that runs inside
any fashionable Net browser. Beneath is an abstracted model of the
Thoughts Grenade entrance panel. Press the ability button on the backside
to get issues going. The slider on the left controls the pitch
and the slider on the proper units the speed at which the notes
play. The test bins beneath the lights choose any of the 16
attainable tunes that may be performed.

The Univac 1108 Morse Code Exec

This is not the primary software program simulation of the Thoughts Grenade! In
October 1971, I wrote the Morse Code Exec, a fully-general
Univac 1108
collection working system which may very well be booted into any reminiscence
module by any processor or IOC of a Univac 1108 single- or
multiprocessor system and would, if the “Audio”
button was pressed on the CPU upkeep panel, run the Thoughts
Grenade music algorithm on a Moon Race-era multi-megabuck
supercomputer and, ahem, as well, ship Morse code for
keys you typed on the console. Hey, for those who had a
multiprocessor, you can have multi-channel audio! Do not
consider it? This is
source code!

Thoughts Grenade in Second Life

In December 2019, the Thoughts Grenade got here to life as soon as extra, this time
within the Second Life
digital world. Constructed as an object which could be instantiated
on the planet, and programmed in Second Life‘s Linden
Scripting Language,
Fourmilab Mind Grenade is
out there at no cost from the Second Life Market, delivered
with “full permissions”, permitting customers to look at and modify it
as they want, together with the supply code of the script that drives
it. Full supply code and help recordsdata could also be
downloaded from GitHub.

The Second Life Thoughts Grenade is an prolonged model of
the unique design, very similar to the “Swinging Sixties” Net
implementation on this web page, offering a 31 bit shift register which,
operating at 4 notes per second, repeats solely as soon as each 17 years,
and color show based mostly upon the three most up-to-date states of every
bit displayed. Here’s a video demonstration of the Thoughts Grenade
operating in Second Life.

Just Show the Simulator

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