> A fascinating fact is that the oscillation frequency is rather stable at ~9.9Hz as it mainly depends on gravity and diameter of the flame.
This reminds me of when I first heard about Dolbear's law by which you can get an approximate measurement of the air temperature using the number of chirps per minute from a cricket.
https://en.wikipedia.org/wiki/Cooley%E2%80%93Tukey_FFT_algor...
In the Quake source code, they have strings to represent the intensity over time of a flickering light source:
https://github.com/id-Software/Quake/blob/bf4ac424ce754894ac...
// 3 CANDLE (first variety)
lightstyle(3, "mmmmmaaaaammmmmaaaaaabcdefgabcdefg");
I've never found one myself (most of them have a better candle simulation chip than that), but they are apparently out there.
In between they used dedicated ASICS: https://cpldcpu.com/2013/12/08/hacking-a-candleflicker-led/
And more recently simply microcontrollers: https://cpldcpu.com/2024/01/14/revisiting-candle-flicker-led...
Single use Vape-pens too. Some of those have displays and Bluetooth.
Insane.
While technically a PIC12 is a computer since it has I/O, tiny storage, a PC and an ALU - it’s hard to even think of it in the same category as what most think of as a computer. IMHO the takeaway is more what the bare minimum it takes to be a computer, which isn’t much. (In other terms, a PIC does not meet the DOOM threshold).
PICs are so old and rudimentary that they started out as peripheral controllers for “real” computers in the 70s. It turns out you can do some useful embedded stuff with a basic chip, but even the newest of these are on 30 year old semiconductor tech at this point.
That may sound jaded, on the other hand I do find mass production of modern level integration and speeds to still be marvelous.
And as an EE, the “white” LED in the candle is more interesting than the uC!
Still awesome this is small and cheap enough to put into individual lights of course.
btw, slightley related: https://cpldcpu.com/2020/06/15/building-a-chaotic-oscillator...
https://www.worldscientific.com/worldscibooks/10.1142/7200#t...
> "More in details, Ando and Graziani demonstrated that the Chua's circuit can be used to generate either a gaussian or a uniform white noise. To do this, they investigate the statistical and spectral characteristics of the signals generated by a Chua's circuit with respect to different values of the parameters α and β. They then applied the x^2 method to determine which set of parameters leads to a signal having the statistical and spectral characteristics more similar to those of either a Gaussian or uniform noise. By using this method, a signal with a Gaussian-like distribution is obtained with a confidence of 95% for this set of parameters: ..."
They've got charts of the probability density functions for each that seem reasonable to me.
It seems to be a corner case. As I learned to know them, chaotic circuits have unpredictable cyclic behavior. Chua's circuit typically follows an oscillatory behavior with a double attractor.
If true randomness is the goal, it is much easier to use other sources of randomness like avalanche transistors, jitter of ring-oscillators in the analog domain or LFSRs if you are in the digital domain.
(1) a process can be random without being uniform or gaussian
(2) a deterministic process can generate a uniform or gaussian output
(3) chaotic systems are traditionally deterministic by definition. they're deterministic and are sensitive to initial conditions.
I think the main confusion for analog implementations of chaotic circuits is that they often have an inherent source of noise (e.g. johnson or flicker noise of resistors, transistors) which will be amplified into large changes by the sensitivity of the system to initial (and also intermediate) conditions.
So the actual implementation has an unpredictable behavior, but this is because the randomness of the components is amplified.
I don't know what the most obvious distinction between a chaotic analog circuit and a TRNG is. For me it was always obvious that any kind of visible structure in the trajectory (the attractors) contradicts randomness. But whenever people see Chua's circuit brought up, there are lots of commends regarding random number generators. It turned into a bit of a pet peeve of mine.
I don't know much (or really anything) about circuits and circuit noise.
There is a long history of deterministic pseudo RNGs, which you may already know about. https://en.wikipedia.org/wiki/Pseudorandom_number_generator. These are sometimes chaotic. In this line of thinking, a thing that generates unpredictable noise and adds chaos would make probably a good hardware PRNG.
But the chaotic part is not actually random (although it's hard for attackers to predict). And whether the noise is random depends on a bunch of physics.
But if this has gotten to the point of a pet peeve to you, you might be interested in Randomness Extractors (https://en.wikipedia.org/wiki/Randomness_extractor) which are a way of thinking about questions like "we have an unpredictable source of bits, but it's not as random as it seems... how can we extract actual randomness from it?"
For example, extractors can take low quality somewhat random non-uniform (or non-gaussian) output and use it to create high quality uniform (or gaussian output).
The “car alarm sequence” of 10s patterns was just the self-test demo program for the sound chip.
Edit: I see the article in a sibling comment makes note of this too.
[0] https://en.wikipedia.org/wiki/Linear-feedback_shift_register
> the dimensions of the fuel source are defined by the size (diameter) of the candles and possibly their proximity
Candles vary in size, so other candles may have different frequencies.
This reminds me of teenage me circa 1990 exploring electric guitar distortion and having an interesting conversation w/ my dad, who'd done a pretty serious paper on eliminating audio distortion as part of his CSEE degree from MIT.
Where can I learn more about that? My google fu is failing me.
https://en.wikipedia.org/wiki/History_of_candle_making#Indus...
Weirdly, the trick wasn't in changing the wick material to burn better, but changing their shape so they curled over (and remained marginally in the flame until burnt) instead of just sticking straight out: rectangular instead of circular braided string.
It's funny how different houses are around the world. Even in similar latitudes/climate.
Eventually found this page [1] which includes a basic description:
A baseboard heater is a convection heater. In such heaters, cold air coming in from a window enters the heater through a vent and hot air is dispersed through metal fins that are heated through electricity.
But it's still confusing because if it's cold outside (=you need heating) why would you have your window open to let in the cold air? That would also make your already-heated air escape ... duh.
Agreed, it's amazing how something that "feels" like it would get the same solution everywhere it's needed still does not, due to cultural differences, history, and stuff.
[1]: https://www.cadet.glendimplexamericas.com/en-us/articles/ele...
But I suspect the Russian example was radiant heating in the floor slabs, which will cause less air convection than hot water pipe radiators.
So cannot be used on a ship. Bummer.
Our sea-faring ancestors wouldn't be happy with this clock.
TIL there’s no gravity on ships. That’s why they float.
The candle shape on earth is caused by the weight of the air.
https://arxiv.org/pdf/1803.10400
But its not trivial at all, its a complex fluid dynamics problem. I stumbled upon all the "coupled candle oscillators" literature when I was looking for a shortcut to a semi-physical candle model. But there is no easy way out...
you need to model the atmosphere as environment, heat flow, wicking action, chemical reactions, fluid dynamics under gravity. Then model human perception to turn the spectral radiance into a perceived shape.
Are we absolutely sure we're not in "the matrix" ?
Noob question: How were the diagrams created?