> 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.
That is awesome. And I am so sad an individual that my first thought was of a software plug-in that would use this frequency to generate realistic candle-flicker effects.
To continue this tangent, legend has it that some of those battery powered tea candle lights actually reuse the chip from cheap music playing trinkets. If you replace the yellow LED with a speaker, you might hear beepy christmas music or happy birthday.
I've never found one myself (most of them have a better candle simulation chip than that), but they are apparently out there.
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!
Chaotic circuits are neat, but they are actually not random (their output distribution is not uniform or gaussian). And candles are not random either :)
> "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.
Nice, I was not aware of that! Quite interesting. Thank you for the source.
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.
Related to this, I once read that the reason nearly every car alarm in the 1990-2010 approx era had the same pattern of awful sound patterns was that they all simply used the same off the shelf sound IC which was produced in such quantities as to make any custom option untenable.
The “car alarm sequence” of 10s patterns was just the self-test demo program for the sound chip.
I believe they were the HK628 and UM3561 chips which were launched in the 1980s for toys. You can actually hear that alarm sound on some toys from that decade. They were simple chips that stored 8-16 preprogrammed sounds and the urban legend is that the car companies just kept the alarm demo sound (I think there were two different ones). The chips ended up everywhere: toys, care, appliances, industrial machinery, etc.
Very neat! I've also seen that some will use Linear Feedback Shift Registers [0] for the candle effect, or maybe that's the same thing you're talking about.
Edit: I see the article in a sibling comment makes note of this too.
> Now, it’s a curious thing that we try to emulate the imperfections of candles. After all, candle makers have worked for centuries (and millennia) on optimizing candles NOT to flicker?
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.
While visiting a friend in Russia I was perplexed by the candle in his flat - it had zero flicker, was stable and unmoving. Eventually I learned how they heated the flat, with water flowing through pipes and heat radiation - so little to no air movement.
No, central heating + radiators are somewhat region specific. For example Australia runs almost entirely on split system reverse aircons and electric heaters.
I have recently become quite fascinated with how much of what we use daily relies on the laws of physics always working the exact same way. This is a wonderful example of that.
The self-trimming wick is the trick. Before that was invented, people had to use special scissors to trim the wick and avoid uncontrollable large (and flickering) candle flames.
Not just flickering; smoking badly as the underheated, unburnt parts roasted outside the flame.
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.
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...
seems like a very complicated simulation problem. i'd be surprised if you could derive from first principles.
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.
From the article:
> 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/Dolbear%27s_law
Very interesting article from the same guy where he reverse engineers the randomness of a flicker LED.
https://cpldcpu.com/2013/12/08/hacking-a-candleflicker-led/
I was today years old when I learned that the frequency of a flicker candle flame is ~9.9Hz :-)
That is awesome. And I am so sad an individual that my first thought was of a software plug-in that would use this frequency to generate realistic candle-flicker effects.
To continue this tangent, legend has it that some of those battery powered tea candle lights actually reuse the chip from cheap music playing trinkets. If you replace the yellow LED with a speaker, you might hear beepy christmas music or happy birthday.
I've never found one myself (most of them have a better candle simulation chip than that), but they are apparently out there.
This was 10-15 years ago.
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...
What a testament to the might of the global electronic supply chain that entire computers are cheap enough to be in disposable candles.
Single use Vape-pens too. Some of those have displays and Bluetooth.
Insane.
Just to offer an alternate perspective.
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!
https://en.wikipedia.org/wiki/Chua%27s_circuit
Chaotic circuits are neat, but they are actually not random (their output distribution is not uniform or gaussian). And candles are not random either :)
btw, slightley related: https://cpldcpu.com/2020/06/15/building-a-chaotic-oscillator...
> their output distribution is not uniform or gaussian
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.
Nice, I was not aware of that! Quite interesting. Thank you for the source.
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.
Wow, I'm clearly behind on my flickering candle LED technology knowledge. Thanks!
Related to this, I once read that the reason nearly every car alarm in the 1990-2010 approx era had the same pattern of awful sound patterns was that they all simply used the same off the shelf sound IC which was produced in such quantities as to make any custom option untenable.
The “car alarm sequence” of 10s patterns was just the self-test demo program for the sound chip.
I believe they were the HK628 and UM3561 chips which were launched in the 1980s for toys. You can actually hear that alarm sound on some toys from that decade. They were simple chips that stored 8-16 preprogrammed sounds and the urban legend is that the car companies just kept the alarm demo sound (I think there were two different ones). The chips ended up everywhere: toys, care, appliances, industrial machinery, etc.
Very neat! I've also seen that some will use Linear Feedback Shift Registers [0] for the candle effect, or maybe that's the same thing you're talking about.
Edit: I see the article in a sibling comment makes note of this too.
[0] https://en.wikipedia.org/wiki/Linear-feedback_shift_register
I never thought it would be as regular as that graph and thought it was random. The world around us is so fascinating.
and is it slower or faster on the moon? oh wait...
> Now, it’s a curious thing that we try to emulate the imperfections of candles. After all, candle makers have worked for centuries (and millennia) on optimizing candles NOT to flicker?
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.
The beginning of an alternative-universe candle computer that could've been used in the past.
While visiting a friend in Russia I was perplexed by the candle in his flat - it had zero flicker, was stable and unmoving. Eventually I learned how they heated the flat, with water flowing through pipes and heat radiation - so little to no air movement.
Isn’t it like this mostly everywhere ?
No, central heating + radiators are somewhat region specific. For example Australia runs almost entirely on split system reverse aircons and electric heaters.
> as it mainly depends on gravity and diameter of the flame
So cannot be used on a ship. Bummer.
Our sea-faring ancestors wouldn't be happy with this clock.
> cannot be used on a ship.
TIL there’s no gravity on ships. That’s why they float.
https://en.wikipedia.org/wiki/Marine_chronometer
Space-ship, maybe? :P :)
There's lots of gravity in space too.
I have recently become quite fascinated with how much of what we use daily relies on the laws of physics always working the exact same way. This is a wonderful example of that.
> Todays candles have been optimized for millenia not to flicker.
Where can I learn more about that? My google fu is failing me.
The self-trimming wick is the trick. Before that was invented, people had to use special scissors to trim the wick and avoid uncontrollable large (and flickering) candle flames.
https://en.wikipedia.org/wiki/History_of_candle_making#Indus...
Not just flickering; smoking badly as the underheated, unburnt parts roasted outside the flame.
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.
Very cool. I've always wondered what the shape of a flame is and how one could use physics to derive it. anyone have any leads for this?
Look up some YouTube videos of candles or lighters used in zero-gravity. It’s a sphere.
The candle shape on earth is caused by the weight of the air.
The third reference from the article provides some pointers (see also references there).
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...
Thank you! And appreciate the TLDR.
seems like a very complicated simulation problem. i'd be surprised if you could derive from first principles.
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.
Or take a candle onto the ISS. Which they did.
My mind is blown candles flicker at a fixed rate
Are we absolutely sure we're not in "the matrix" ?
I believe it's depending on the 3 candles used in the example and their proximity to each other, etc
+ room air currents.
Next somebody tells us that lava lamps have a regular component to them.