
Oscilloscope pong for 1 or 2 players - lnolte
http://www.eevblog.com/forum/projects/oscilloscope-pong-for-1-or-2-players/
======
std_throwaway
Title doesn't do any justice, it's an all-discrete circuit made from diodes,
transistors and such. They are soldered not on a PCB but mostly free hanging
in air above a copper ground plate. One wrong move and "bazoing" _sparkles_.
The guy didn't draw a schematic beforehand either. He mostly made it up as he
went. Amazing.

[http://www.eevblog.com/forum/projects/oscilloscope-pong-
for-...](http://www.eevblog.com/forum/projects/oscilloscope-pong-
for-1-or-2-players/?action=dlattach;attach=298785;image)

~~~
VLM
"mostly free hanging in air above a copper ground plate"

It is impressive work, both for people inside and outside the industry.

I've built a lot of RF stuff that way, his technique is "normal". What
impresses me about the quality of his work is there's no solder or flux
splashes on the board and none of the wires have been burned by the iron and
the board isn't tarnished like an old copper penny from all the handling. Also
there's no visible reworking.

A lot of people buy non-inductive carbon comp many meg value resistors for use
as standoffs which I didn't see in the pixs I saw. Most relatively low
impedance ckts laugh at being shorted to ground by 8.2 megs yet it can be
physically useful to anchor connections. Another option I've done and seen
others do is take a piece of PCB and chop it into squares and stick the
squares on the groundplane with glue or solder. I've had unfortunate incidents
with the "hacksaw a grid of isolated squares" where the hacksaw didn't isolate
the squares so I haven't done that since the 80s, but others have better luck.
I've had extremely mixed results making microstripline using a shear and
soldering the strips into place. You can buy pre-etched boards to support
ground plane construction, including little boards when you need some SMD.
I've done the "flip the chip over, super glue, and solder wire wrap wires to
the leads" but its not fun.

I made a complete 80M ham radio receiver back in the 80s using the ARRL
Hayward "radio amateur solid state design" or something like that, the title
was all generic words you can't google for, using that construction technique.
The brown book with the 70s era power RF transistor on the front cover (back
in the bad old days when like 100 watt device cost like half a car payment and
blew up if you looked at it wrong and was made of beryllium oxide heat sink
and came with a toxic waste shipment bag for when you disposed of it). Anyway
it looked like a war relic by the time I was done. I think I built at least
two VFOs and three mixers by the time I was done (different designs,
troubleshooting to get lower drift, etc) and things gradually got trashed as I
modified endlessly. I'm not sure every stage was simultaneously 100% perfect
at any time, but at one time or another every stage at least momentarily
worked.

The truly skilled make things look easy that are actually pretty well
impossible, which makes the article very impressive.

~~~
blacksmythe

      >>  I've done the "flip the chip over, super glue, and solder wire wrap wires to the leads" but its not fun.
    

Depends on your idea of fun, but this is a pretty standard way of
breadboarding analog/RF circuits. (not used much as PC board fab has gotten so
fast and cheap)

I have done it many times, and I think it is fun :)

~~~
VLM
Its a top of the board troubleshooter vs bottom of the board troubleshooter
thing. I can look at a chip and poke a scope probe on pin 7 almost by reflex
from the top but from the bottom (aka flipped chip) I guarantee I'll solder at
least one chip "flipped".

I'm enough of an old timer that I'm still used to thru-hole enough that
flipping a chip doesn't totally mess me up. I would imagine "kids these days"
who never worked a thru hole PCB will likely be rather confused about where
pin 1 appears when a chip (or board) is flipped....

Of course your fine tip sharpie pen is handy for numbering pins and preventing
OCD cycles (Is that flipped over chip an opamp or a microcontroller? You can't
see after its glued down, ya know). And lack of scribble on the groundplane is
yet another example of this being project being fine workmanship. He doesn't
even have stuff like +12V or LSB/MSB marked which is impressive.

------
partycoder
There's also Quake on an oscilloscope

[https://www.youtube.com/watch?v=aMli33ornEU](https://www.youtube.com/watch?v=aMli33ornEU)

[https://www.youtube.com/watch?v=GIdiHh6mW58](https://www.youtube.com/watch?v=GIdiHh6mW58)

~~~
Simpliplant
Wow, this looks even more amazing!

------
israrkhan
This is amazing, never thought you can make a pong game without writing a
single line of code, without using any CPU.

Moving the bars with knobs, and drawing lines is fine, but doing bounce ball
effects with sound.. miracle

~~~
cr0sh
If you can "read" a schematic, you'll see that it's actually fairly simple; in
fact, you should be able to notice the repetition of many areas - it's a very
modular design.

Just a bunch of simple and repeated circuits arranged in a certain manner;
it's essentially a very special-purpose "computer" where the "code" is fixed
in the hardware (literally "hard coded"). Much of it borrows or is identical
to analog computing circuits (most especially the way the "ball" is drawn -
sine/cosine waves generated and scaled, then combined on the x/y axis, which
are also updated by oscillators for the ball movement).

Don't get me wrong, it's an amazing achievement, especially done "blind" and
"dead-bug" style.

Also, note the various places where it looks like two diodes are in parallel,
hooking up one line to ground. I'm not sure exactly what it is doing here in
this circuit, but I know that in single-element ultrasonic distance sensor
circuits, such a similar construct is used to protect the input of the
receiver portion of the circuit from the high-voltage (due to amplification)
of the transmitter when the "ping" is generated; in other words, it acts like
a "voltage clamp" or filter to attenuate the signal. That is probably what is
going on here, too - to prevent high-voltage spikes from being transmitted
further down the line, and routing them to ground. Something like that...

------
acomjean
Thats really cool. Especially completely analog.

Like the original "tenis of two" circa 1960
[https://en.wikipedia.org/wiki/Tennis_for_Two](https://en.wikipedia.org/wiki/Tennis_for_Two)

In a older thread about asteroids, I learned some older arcade games there
were these things called XY monitors which were used by early video games
(Asteroids, battle zone, starters, tempest..), which drew on the screen by
moving a beam around the screen and turning on and off. Moving slower means
things are brighter. Similar to an oscilloscope.

[https://news.ycombinator.com/item?id=13981733](https://news.ycombinator.com/item?id=13981733)

There is a youtube video where someone takes a modern laser projector and
recreates asteroids similar to the beam moving on the oscilloscope (Though
programmed using c).
[https://www.youtube.com/watch?v=FkHjG759ABY&t=774s](https://www.youtube.com/watch?v=FkHjG759ABY&t=774s)

There were some interesting links in response to my comments: including an xy
monitor manual.

[1] [http://www.arcade-museum.com/manuals-
monitors/Atari%20Monito...](http://www.arcade-museum.com/manuals-
monitors/Atari%20Monitor%20TM-146%20Issue%201%20Electrohome%20G05-801%20Monochrome%20XY.pdf)

~~~
semi-extrinsic
> drew on the screen by moving a beam around the screen and turning on and off

Actually all CRT displays (box TVs/monitors) did this, only they move the beam
in a predefined pattern (line by line downwards) and all you can do to control
image is to turn the beam gradually on or off. Color uses an RGB shadow mask
and three phospohors with different colors stuck together to make a pixel.

But on vector displays like you mention, which were much less common, the
software actually defined the beam path and you could have super-precise
vector graphics. Some displays were of the storage tube type, which would glow
for several minutes, so once drawn you could add more stuff to an image, but
to erase you had to reset the whole screen - very similar to a Kindle display.
Others had ~30fps refresh rate.

Vector displays were great back when memory was so limited a 640 _480_ 8 bits
image was out of the question. Storing only vertices of polygons is much
cheaper. But due to the poor text rendering and shading capabilities of vector
displays, bitmapped CRTs took over once memory had been riding Moore's law for
a while.

~~~
problems
Wouldn't you expect vector text to look better? Sharper. Like going from text
at 100 DPI to 300 DPI. Is it a precision issue with controlling the beam?

~~~
VLM
Linearity of the scope amplifiers was a big issue. Back when this was a thing
there was a big difference in image quality between a Tektronix or HP oscope
vs some no name scope. For probably 40 years people have been hooking up 8 bit
microprocessors and DACs to a scope and trying to display a clock or something
and getting a perfectly round clock dial with a cheap scope is not easy.

------
ksml
If someone could explain how this works to someone who only understands basic
circuits, that would be much appreciated. How does it maintain state and draw
shapes on the oscilloscope and trigger sounds with such basic components?
Amazing!

~~~
exDM69
I'll try my best to explain with my electronics hobby background...

It's full of analog circuitry like integrators, comparators, op amps etc
(note: it's made from discrete transistors, so you won't find an opamp chip in
there). The "state" as you mentioned is maintained as a a voltage.

The velocity of the ball is stored as a voltage, and the position is produced
by integrating that with an integrator. Collisions are found with a
comparator, and connected to the circuitry that maintains the velocity.

The output to the oscilloscope is two voltages that control the position of
the beam.

Analog electronics is one of those dying art forms where the number of people
capable of doing things like this is quickly dwindling. It's no longer a
viable way of building actual products except for a few special applications.

I find it a sad state of affairs that we, the mankind, have learned and
developed skills and knowledge that we'll be collectively forgetting less than
a century later.

~~~
ue_
I find it hard to believe that analogue electronics is disappearing. I'm an
undergrad ECE student and the largest part of my course is analogue, with work
in labs too. Granted, it's not an immensely popular hobby, but many art forms
and jobs are necessary but aren't hobbies.

~~~
cr0sh
If it's RF, or chip-surface level - there's analog in there somewhere. While
digital logic is somewhat forgiving, for production level work you do need to
have some understanding of analog to make a successful design and stable
implementation. Plus there's always the power-supply stuff, and a bunch of
other things that will always be analog as well. So I agree that it won't
completely die off (especially in the commercial realm) - but it certainly
isn't as common in the hobbyist world as it once was.

/saying this as someone who considers analog a black though beautiful art

------
jccalhoun
I wonder if the person who made it knew about Tennis for Two?
[https://en.wikipedia.org/wiki/Tennis_for_Two](https://en.wikipedia.org/wiki/Tennis_for_Two)

~~~
sixothree
Almost certainly. His youtube channel spends a large amount of time tearing
down oscilloscopes and other electronic test equipment.

------
peter303
I remember doing similar in MIT digital lab in 1975. My team built Conways
Game of Life out of TTL gates. I did the display on the oscilloscope. The grid
was 32 by 32, limited by memory sizes at the time. Memory was the most
expensive chips at the time, so the lab rationed them. We had double buffer
design. One chip held the current generation for display and input to the game
engine. The other chip held the next generation.

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femto
Next step: build his analog pong computer into his home built CRO? Just like
having "snake" inside your phone, but it's pong inside your CRO.

[https://www.eevblog.com/forum/projects/designed-a-cro-in-
spi...](https://www.eevblog.com/forum/projects/designed-a-cro-in-spice/)

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JoeDaDude
Lol, this reminds me of the time many moons ago when a highly experienced tech
showed me how to receive and display (good ol' NTSC) TV on a scope

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madengr
Wow! That's some serious analog talent.

