[HN Gopher] Controlling RGB LEDs with only powerlines: Anatomy o...
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Controlling RGB LEDs with only powerlines: Anatomy of a Christmas
light string
Author : cpldcpu
Score : 138 points
Date : 2022-01-29 17:37 UTC (1 days ago)
(HTM) web link (cpldcpu.wordpress.com)
(TXT) w3m dump (cpldcpu.wordpress.com)
| HPsquared wrote:
| This is modern electronic design in a nutshell.
|
| The large-scale physical design is as simple as possible (just
| regular wiring), the individual components are all "smart"
| (Christmas lights each with their own integrated IC, doesn't get
| more embedded than that) and addressable via a communication
| protocol.
|
| Imagine how difficult the wiring would be to have 100 addressable
| lights that didn't use this arrangement!
| IgorPartola wrote:
| You don't need individual data lines to address each LED. A
| serial bus and a microcontroller would be enough. The only
| difference is that here there is no dedicated data line/lines.
|
| 1-wire is a similarly clever protocol.
| HPsquared wrote:
| I was getting at, if you didn't have embedded electronics in
| each light - there could be some arrangement of wiring to
| control 100 LEDs individually (e.g. a 10x10 grid).
| anamexis wrote:
| 300 LEDs, even, because they're RGB.
| wccrawford wrote:
| Most addressable LED strings have 3 or 4 wires, with 1 or 2
| being data.
|
| The ones in the article have only 2 wires, positive and
| negative.
| kurthr wrote:
| What is interesting is that one could in fact do this with a
| single wire. You might eventually see something like this for
| micro-LED display solutions.
|
| The key is to drive a current and control the voltage at both
| ends of a string such that each LED detects modulation and
| bypasses (itself) or consumes power (in-line). That might be
| relevant where the strength of a single (e.g. steel) wire was
| used to support a long string. By driving relatively low (max
| RGB) current at higher voltages and time (e.g. PWM) sequencing
| the light modulation.
|
| In a simple case, imaging there are 100 RGB lights, half of
| them excited on each polarity and bypassed with a 0.2V Schottky
| stacking to +/-10V minimum (for digital data) at <100mA. You
| might synchronize and send data to the smart lights each "zero
| crossing" and get away +/-50Vpp for the string by only having
| 10 (12.5%) stacked (inline) on at any one time (a controller
| for the LED FETs can stay awake on a capacitor). As long as you
| run at a few kHz you won't have noticeable flicker, capacitive
| and you can update with a few bits per light each cycle.
|
| More complex designs could use FETs to improve data link
| efficiency of the minimum voltage and higher current (lower PWM
| times) could substantially reduce peak voltage to +/-5V or so.
| wyager wrote:
| In 10 years every one of these LEDs will be running an IPv6
| stack, and they'll still be using the same wire-and-glue
| construction.
| Freak_NL wrote:
| All of them on wifi... Imagine the utter hell of living in an
| apartment building surrounded by neighbours blasting every
| Hertz of the wifi-spectrum with hundreds of cheap devices.
| eulers_secret wrote:
| This is now, haha. I can see over 200 APs from my bed
| (1/2ish are xfinity wifi).
|
| Fortunately my place is so small a 100' cat-5 cable reaches
| any point in it, so I just use wired. Wifi barely works.
|
| Considering wifi-6, but I can't figure out if it helps with
| this type of congestion or not...
| 323 wrote:
| In 20 years each LED will be a pod in a Kubernetes cluster,
| running Node.JS and the output color will be controlled
| through React interacting with blockchain smart contracts.
| rini17 wrote:
| And they will still flicker annoyingly.
| kingcharles wrote:
| Each LED will have its own NFT.
| jhanschoo wrote:
| There's one part about the article that I'd like confirmation
| about: does this mean that the LEDs come out of the factory
| already configured as belonging to one of the 6 zones? This would
| be as opposed to, say, WS2812 LED packages where they are
| identical.
| 323 wrote:
| That's my interpretation, that they are randomly assigned:
|
| > _The control groups are randomly distributed across the
| curtain._
| jhanschoo wrote:
| Thanks, I missed that line!
| mrintellectual wrote:
| I love electronics and electrical engineering in general. But
| this article explains perfectly why it is less accessible than
| software engineering - the former requires a individual
| components, soldering iron(s), a digital oscilloscope, etc. while
| all you need is access to a computer with internet for the
| latter.
| kken wrote:
| I think it has never been easier to enter electronics
| (especially embedded stuff) than it is now. You can get a
| starter set including RPI/Arduino/Breakboard/Components for
| less than $100. Also, with a breadboard no soldering iron is
| needed.
|
| Try chemistry, mining, process engineering or even mechanical
| engineering in comparison?
| spookthesunset wrote:
| Totally agree. Electronics has never been easier thanks to
| low-cost microcontrollers like the ESP32. Most of the
| "electronics" you'll be doing is simply plumbing--connecting
| the GPIO outputs of your microcontroller to whatever
| peripherals you want to support. It's a good gateway into the
| wider world of electronics.
| jcun4128 wrote:
| I am curious what the next thing up is that is more
| "legit". At this time I've used Arduino/ESP/Teensy. I
| bought an STM32 and Beaglebone but wondering what does
| something like a Boston Dynamics dog use? Probably a full
| on processor like i7.
|
| Edit: oh it uses i5 with Ubuntu ha, plus separate graphics
| for the AI part
| gus_massa wrote:
| We bought one of this kit for our daughter when she was ~10
| year old. It has a the explanation of a few projects and the
| components to put in the breakboard. She liked it, and we
| bought some additional components, like a 7 segment display
| and leds of additional colors.
| solarkraft wrote:
| It's wonderfully easy to enter advanced electronics nowadays,
| but has accessibility really kept up with the rate of
| advancement (electronics getting smaller and more
| complicated)?
| buescher wrote:
| Chemistry takes some initiative these days, but the dark age
| after the golden age of chemistry sets is pretty much over.
|
| Mining, I dunno, buy a shovel? Hobby prospecting - sluicing
| and panning for gold, mostly - was still a thing in the rural
| west when I was a kid. I'd bet you could find a forum or
| something if you searched.
|
| Process engineering, I don't know what you'd want to do as a
| hobbyist.
|
| Mechanical engineering - 3d printers and chinese machine
| tools are affordable. It's never been easier to buy small
| parts and fasteners. The free finite element simulation
| packages are getting pretty good.
| jcun4128 wrote:
| Made me think of Cody's lab guy's sweeping some dirt from a
| highway and pulling palladium out.
| 123pie123 wrote:
| you can always play around with the simulators
|
| https://falstad.com/circuit/
| wyager wrote:
| As someone who tried to use falstad, spice, etc to learn as a
| kid, simulators never really worked for me pedagogically. I
| was only able to learn by using physical devices. Nothing
| really beats a breadboard for immediate feedback (whether
| reward or punishment).
| xxs wrote:
| >why it is less accessible than software engineering
|
| Having experience in both, and started at rather young age
| (pre-teens both) - the hurdle is the "magic smoke" (that all
| electronics devices work with). Mistakes are very punishable
| with components and power supplies blowing up, while software
| mistake are extremely forgiving... unless you work on an 8bit
| 6502 that doesn't have properly implemented RST signal and cold
| restarts the entire machine instead, wiping off its memory, on
| top of lacking any permanent storage.
|
| Mistake and learning electronics costs resources and time each
| time, and it's a lot more frustrating. Also bread boards
| (nowadays) don't really need a soldering iron.
| halpert wrote:
| The video of the manufacturing process is quite interesting. A
| lot of human labor is involved.
| HALtheWise wrote:
| I'm really excited for the inevitable improved version of this
| that supports binary addresses and setting approximate PWM
| brightness levels.
|
| Given the manufacturing process[0] linked, it could be a _little_
| tricky to actually assign a known ID to each light in the strand,
| but either using the placement order when the strand is made or
| using a stochastic process to randomize the IDs and subsequently
| calibrate the strand should be viable, and result in a low cost
| strand with WS2812-like capabilities.
|
| [0]: https://youtu.be/wCKlCUBsaT4
| Freak_NL wrote:
| One downside to this type of Christmas lights is that these
| design parameters -- i.e., make it possible to manufacture
| feature-rich novelties with a minimum of wiring and changes to
| the assembly line -- result in a product that has no user-
| serviceable parts: when a few LEDs die, the whole product should
| be thrown out.
|
| I say 'should' not because I think so, but because this is
| literally what is written on the labels affixed to many such
| products. We went from lights featuring incandescent light bulbs
| which came with a few spares in the box (anyone could replace
| those), to LED lights with a few spares (finicky to replace, but
| doable), to almost exclusively fixed-in-place LED lights without
| replacements and labels attached that tell the user to throw the
| chain out when lights break. And now more and more complexity
| with integrated ICs.
|
| Only those of us with a soldering iron can salvage some of them,
| and this new category seems like it might not be repairable at
| all (excepting the really clever EE folk like the author).
| Environmentally speaking, the increased complexity and focus on
| ease of manufacturing of such products seems to reduce their
| lifespan as well, with repairability already at a minimum.
| IIAOPSW wrote:
| This is all true, but people voted for it with their wallets.
| At all levels, people understood that when their electronics
| break they would be paying for it again, making the ownership
| of the product more like renting with recurring payments.
| People understood the term "planned obsolescence". But they saw
| the cheap shinny blinky lights and decided they wanted it. The
| consumer is far more guilty than the company that gave them
| what they wanted.
| carapace wrote:
| If we must assign guilt, one the one hand I do kinda blame
| people for being thoughtless consumers, on the other we've
| been subject to a relentless and ubiquitous system of
| commercial propaganda (advertising) promoting that lifestyle.
|
| What's the way forward?
| WaxedChewbacca wrote:
| I don't think people understand the trades they're making.
| They see that one offering seems to do approximately the same
| stuff as another one, but it only costs half as much, and
| don't understand that the cheaper offering is one one
| millionth as fixable as the more expensive one. By the time
| it fails, they forgot the circumstances under which they
| bought it, so they may never connect cause and effect.
| reader_x wrote:
| As a consumer, I find string light packaging almost useless
| to estimate (1) lifespan until it breaks, or (2)
| possibility I can repair it when it does --therefore I
| hesitate to spend more than I have to on the theory that at
| _any_ price I'm lucky if string lasts more than 2-3
| seasons.
| JaimeThompson wrote:
| Given the lack of wage increases in many parts of the world
| perhaps the consumers, as a whole, aren't buying the better
| stuff because this is all they can afford.
| convolvatron wrote:
| if I have a choice between a $10 X and a $20 Y, is it
| necessarily the case that Y will be a better product than X,
| last longer than X, and/or result in more wages being paid to
| the workers that made Y?
| Freak_NL wrote:
| Aside from the points noted by other commenters about this
| being a choice most consumers cannot reasonably be expected
| to make, the notion that there is choice at all is simply
| false. Almost all Christmas lights sold in shops last year
| were of the current generation of fixed LED light strings
| sold in a plastic tub. The year before these were sold mostly
| in cardboard packages. For the basis indoor Christmas tree
| light product, this accounts for 95% of the product
| available, and almost all of the offering in physical
| stores1.
|
| There's no reasonable chance of voting with your wallet
| against those numbers. Sure, I might be able to get some
| fancy hand-crafted Swedish Christmas lights with a ten year
| replacement part availability guarantee on some website, and
| who knows, perhaps a very effective word-of-mouth campaign
| will make them quite successful! -- and still not make a dent
| in the global market. Realistically, it won't have any
| measurable impact in the greater scheme of things. This
| product is driven by sellers and manufacturers going for the
| absolute bottom in price because it is technologically
| feasible, externalities (like the environmental impact) are
| not part of the cost, and most consumers have plenty of other
| worries and simply crave a bit of Christmas cheer.
|
| 1: Here in the Netherlands, although likely globally
| applicable.
| chrisseaton wrote:
| > result in a product that has no user-serviceable parts
|
| You seem to think this is a step backward?
|
| If you remember old lights you had bulbs that regularly blew,
| and the bulbs had to be thrown away and replaced. If you
| couldn't find compatible new bublbs you had to throw the whole
| thing away. The LEDs are not replaceable... but they hardly
| ever break either.
|
| The LED lights product lasts longer, and doesn't consume bulbs.
| Strictly better, isn't it?
| jhoechtl wrote:
| > The LED lights product lasts longer
|
| Not my experience. My living room lighting already blew up
| two times and no, it wasn't the transformer which would be
| easy to replace.
|
| > and doesn't consume bulbs.
|
| Instead I have to throw away the whole thing with all its
| coper inside.
|
| > Strictly better, isn't it?
|
| Not in my books
| gambiting wrote:
| Is there something wrong with the power in your house?
| Maybe slightly over/below the nominal voltage? I've been
| buying only LED lamps and bulbs for the past 10+ years and
| literally never had a single one break for me. Not even the
| stupid GU10 ones which get stupidly hot - they just work
| and work.
|
| And yes, I'm sure many of us remember pulling out an old
| string of christmas lights, only to discover it doesn't
| work and then spending two hours looking at every single
| bulb close up to figure out which one is blown, and pray
| any of the replacements work. The LED strings just work
| forever.
| auxym wrote:
| I bought christmas mini LED string lights last year from
| home depot, specifically labeled for outdoor use. Took them
| out this holiday season, and over half of the strings
| didn't work anymore.
|
| They have replaceable "bulbs", but HD doesn't sell them,
| "because they are never supposed to break".
|
| Found replacements that sort of work (different shade of
| white) a another store for some of the strings, but not for
| others, and had to throw them away. Very sour with the
| experience.
| 01100011 wrote:
| I had that happen but all of the issues were related to
| the individual led bulb connectors getting loose and were
| easily fixed by reseating them. Dunno if you had a
| similar issue but wanted to mention it.
| chrisseaton wrote:
| The old product was _designed_ to use consumables even if
| it was functioning correctly!
| sbcd wrote:
| This is just anecdote versus anecdote, but I've never had
| to replace a LED because of them blowing out. Just
| recently, I replaced a LED that has been turned on for 24
| hours a day every day for a whole 5 years, and it was still
| working. You may ask, why replace it then? well, high
| quality LED bulbs might not blow up, but they lose
| brightness over time. Still, I'd say 5 years of mileage for
| a light has is never turned off is a solid return on
| investment, particularly when considering how little energy
| they consume compared to previous light bulb technologies.
|
| The same thing also happens with the LED strips within
| monitors, monitors get replaced when they become too dark.
|
| I would be suspicious about the quality of the electricity
| in the place you live or work at when you see this stuff
| break at too high of a frequency. Not directly related to
| LEDs, but somehow I had electronics like computers or just
| plain old regular incandescent light bulbs break far more
| often in a house I used to live in, and I used to blame bad
| luck with the devices I bought, until I moved into another
| apartment and things actually started to have acceptable
| life expectancy.
| xxs wrote:
| >My living room lighting already blew up two times and no
|
| The reason is not the LEDs themselves but... money. The
| LEDs are overdriven to show higher lumen numbers (and
| wattage) on the box. That results in overheating both of
| the LEDs and the driving circuits - one of them fails. In
| short it's the good old - planned obsolescence.
|
| It's absolutely possible to have LEDs that last for 50k
| hours (while losing 20% of their brightness) but don't
| fail. Sometimes even adjusting a resistor value (to reduce
| the current through the LEDs) would do the trick.
| HPsquared wrote:
| That could be an interesting hack to the power supply,
| turning down the power a bit.
|
| Not the kind of thing that gets people motivated though,
| "let's make this product less powerful" isn't a common
| modding activity.
| stordoff wrote:
| Big Clive does this sort of thing on his YouTube channel
| fairly often. A few examples:
|
| * Adjusting a current regulator to drop a 10W lamp to ~2W
| - https://www.youtube.com/watch?v=YeWnHnZ-ojw
|
| * Adjusting a capacitive dropper-based lamp from 5W to
| 0.5W - https://www.youtube.com/watch?v=RKRz7EplgDE
|
| * Making a "Dooby" (inspired by the Philips Dubai
| lamps[1]) lamp - using a series capacitor to make various
| lamps run at 0.1-2W -
| https://www.youtube.com/watch?v=ISTB0ThzhOY
|
| [1] They're designed to have a higher energy efficiency
| and a longer operational life -
| https://www.youtube.com/watch?v=klaJqofCsu4
| xxs wrote:
| >let's make this product less powerful" isn't a common
| modding activity.
|
| Actually it is for 'consumer' LEDs products, like a top
| 1. Undervolting GPUs and laptop CPUs is rather common
| too.
| [deleted]
| [deleted]
| spookthesunset wrote:
| Don't forget those old incandescent strings could draw up to
| 100 watts each!
|
| > And now more and more complexity with integrated ICs.
|
| I dunno. Which is more likely to fail? The older
| electromechanical "blinkers" they used or a solid state IC?
|
| I do get it though. Society is addicted to disposable things.
| But I'm not sure the problem is these things being non-user-
| servicable. When these things go, they go... Usually the
| cabling gets fucked on them long before the LED's.
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