This one was kind of weird. I decided "Okay if I put light colors where I see light colors and dark colors where I see dark colors it should turn out like red velvet right". And it didn't and I figured "okay, fuck you, fill in everything with red" which ended up making the light parts even darker than the rest and by putting exactly the tones I didn't want everywhere I got it to look like I wanted. Go figure.
I finally built something I wanted to do for quite a while: Chua's circuit.
It's a chaotic oscillator, which, instead of producing something incredibly boring like a sawtooth wave or whatever, creates a monkeyfighting, honest-to-god strange attractor. In fact, it's pretty much the opposite of a boring, well-behaved wave: it never repeats. It never does the same thing twice, which is pretty crazy if you think about it.
After doing a compact one on stripboard which turned out to be a pain in the ass as I was looking for shorts and everything, I did it again on perfboard with lots of space and laid out like the circuit diagram:
I immediately got the double scroll after turning the knob, which was a nice surprise:
About half the parts are from old junk like broken TV sets.
The sound file below is what it sounds like hooked up to a guitar amp, the high-pitched beeps at the beginning and the end are produced when the circuit is not chaotic, at the start there is period doubling which happens when the sound becomes more complex and then it turns chaotic as I turn the potentiometer knob:
How the hell did I miss this that's the coolest thing I've seen all year.
It's going to get better. I'm making an amplifier stage to drive the deflection coils of a CRT monitor, that cheap digital scope responds too slowly to appreciate the effect and it's quite small and doesn't do rainbow colours. I tried some audio amplifier ICs but they can't really drive the low impedance of the horizontal coil and they filter out DC so the pattern wobbles around its center of gravity.
The circuit is very sensitive to components and conditions. Built with a TL082 op-amp and 15 millihenry inductor, it works great! Swap in a TL072 and it's quite lop-sided: (Ignore the crawling claws, who were only visiting)
It was probably an old TL072, back when they were "reject" TL082's with higher offsets. But they were still quite good as op-amps go.
So I stole your idea and used a great big common-mode choke coil, crosswired. That gets 40 millihenries, far more than it needs, at something like 5 ohms. Even less wonky now and pretty easy to find the unstable point.
I also noticed by scope has an "A-B" setting for channel A, which make a nice isometric view:
Lastly, the "center tap" of the inductor makes a great place to plug in a crystal earphone and hear the sweet song of chaos without mucking with the hypersensitive op-amp section.
I used only one side of the choke and peeled the wire off until it measured around 21 mH. The plan was to start there and take more wire off until I'd find out that it didn't work at all and then start winding my own. But then it worked on the first try so I left it that way.
Today I got some nice high current adjustable voltage regulators in the mail (LD1084V) that I want to use for the amplifier. So, with a bit of luck, the big chaos screen will be up and running very soon.
I used only one side of the choke and peeled the wire off until it measured around 21 mH.
Ah. My choke only measures 10mH on one side, which isn't enough. I tried wiring both sides in parallel - causing it to cancel out to 0mH, just like a common-mode choke is supposed to. I had to electrically flip one of the coils, wiring kitty-corner in series - which caused the inductance to quadruple to a whopping 40mH, which worked just fine. I used a 10K pot, not a 2.5K one, which might be important or might not.
Quote:
The plan was to start there and take more wire off until I'd find out that it didn't work at all and then start winding my own. But then it worked on the first try so I left it that way.
With an entire side of the choke unused, you've got a nice opportunity. They are magnetically coupled, so it will act as an isolation transformer. Hook one end to ground (external ground, not necessarily your own ground) and the last lead can be your 'audio out'.
Quote:
Today I got some nice high current adjustable voltage regulators in the mail (LD1084V) that I want to use for the amplifier. So, with a bit of luck, the big chaos screen will be up and running very soon.
Careful with those, low-dropout regulators are noisy and evil. It'll need to be very nicely decoupled everywhere or you'll build a 5-amp power oscillator. Annoying enough here, but quite a surprise when building audio circuits!
Today I got some nice high current adjustable voltage regulators in the mail (LD1084V) that I want to use for the amplifier. So, with a bit of luck, the big chaos screen will be up and running very soon.
Careful with those, low-dropout regulators are noisy and evil. It'll need to be very nicely decoupled everywhere or you'll build a 5-amp power oscillator. Annoying enough here, but quite a surprise when building audio circuits!
I already did that with those audio amplifier ICs, I forgot to add. They were still a bit naked because I'm lazy and they were oscillating wildly at around 1 MHz. So what the heck, I took a battery powered radio and tuned it to a channel in a language I don't know in that range and put it on the other side of the room and found out I could do very clear morse code by tapping my finger on the heatsink. It was quite interesting.
I've been playing around, trying to create a wallpaper image for my desktop, something that would take about 15 seconds to create in gimp or pretty much any other graphics app. But that would be boring so I'm doing it by hand in c, using loops and maths and such to set the color value of each pixel.
My mistakes make for way more interesting pictures than what I'm going for.
Believe it or not, this one is the closest I have gotten so far to what I'm trying to do:
You probably already have some kind of x2+y2 thing going on. If the bright artefacts along the axes aren't what you want, you probably need some small delta applied to the x and y to fix the rounding issues near zero.
This is a wallpaper I made with a raytracer I wrote for a computer graphics course. It's a spherical dome with a fractal in the complex plane on the outside, a floor made out of fuzzy mirror and a Sierpinski tetrahedron made out of diamond.