About this now I have a mo.
Have you checked out GK's pong game project ?
https://www.eevblog.com/forum/projects/oscilloscope-pong-for-1-or-2-players/
Wouldn't be hard to drop the paddle control so it just bounces around the CRT.
I hadn't seen that actually
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
... damn that's hardcore! I purposely avoided any references or googling for this one to exercise the brain. I read something about 30 years ago about how some of the earlier analogue type games worked and have been meaning to do something for years.
Good news here on that front though. I got it working. The original quadrature oscillator I found in an old opamp book was a piece of shit and kept stalling so I binned it and stuck my head in TAOE for a bit. Turned out there's a very very nice quadrature oscillator in there all along. Neat little pair of phase shifters and then an inverting amp bringing 360 degrees phase. Some value tweaking and Berkhausen was satisfied!
The whole thing is a neat little con.
The X axis is the integral of a square wave summed to a low portion of a sine wave with a phase of zero degrees. Basically a sine wibble on top of a triangle wave.
The Y axis is the integral of a slightly slower square wave summed to a low portion of a sine wave with a phase of 90 degrees. Basically a cosine wibble on top of a triangle wave.
The integrated square waves produce the horizontal and vertical movements. The sine and cosine functions result in a circle via the X-Y modulation.
The TDS210 does a fair representation of it as well believe it or not. I was quite impressed with the X-Y mode.
Anyway enough crap, quick video:
And the final breadboard (done on a solderless board just to annoy tggzzz
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
).
![](https://i.imgur.com/hYQE0Af.jpg)
Opamp count: 2 square wave generators + 2 integrators + 2 summing amps + 3 phase shifters = 9 opamps. All cheap ass LM358. Can probably be made single rail with LMC6482 or something and use the left over opamp as a rail splitter. Whole thing uses less than 8mA with the LM358
I'll draw up the schematic tomorrow if anyone else wants to build one.
I might add a feeper so it goes "feep" every time it hits an edge as well. Can do that easily enough by getting the edges to ring a gyrator/capacitor network in parallel (similar to an LC circuit) and amplifying it.
And on that note I'm going to bloody bed as my brain is fried
![Indifferent :=\](https://www.eevblog.com/forum/Smileys/default/indifferent0023.gif)