Conventional wisdom defying christmas tree? - Page 1
Forum section: electronics / beginners

author: FreedNightHawk
author_rank: Newbie
timestamp: December 17, 2020, 02:26:32 am
content: So, my mother in law has a christmas tree, pre-lit with RGB LEDs. One of these LEDs was stuck blue, so I pulled it out to see if it was just a mucked up connection. What I found makes no sense to me at all.I've seen these LEDs cycle from blue, green, red, amber and white, as well as dimming effects.So when I pulled the lamp out and it had only 2 leads... Yeah. I can't wrap my head around how this works. A single lamp is able to do everything you expect an RGB LED to do, using only 2 leads. Looking at the lamp carefully it looks like every other 3 and 5mm LED I've ever played with, no sign of any sort of chip embedded within the plastic or anything.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: December 17, 2020, 02:40:21 am
content: It's quite common tho have chips embedded in LED's. It started long ago with blinking LED's, there are also the flickering LED's that emulate candle light.Christmas lightning is made by the billions, which means that high level of optimizations for mass produced products and sub cent optimizations for batches of bigger then millions of units come within the possibilities.What's really into them may be hard to distinguish.These day's I would not be surprised if the LED's were made on one side of the wafer, and some electronics for blinking it on the back side of the same wafer.There is something with back-lit CMOS sensors in camera's. Maybe some of that technology leaked over to LED's.

author: FreedNightHawk
author_rank: Newbie
timestamp: December 17, 2020, 03:14:59 am
content: I can understand that, but even addressable RGB LEDs have a 3rd leg. One power, one ground, and one data. I don't how they're getting ARGB functions on only 2 pins.

author: Mr.B
author_rank: Unknown
timestamp: December 17, 2020, 03:24:18 am
content: Are all the fade/blink/color cycles synchronized on the tree?Is the power supply DC?Have you put a scope on the DC supply?Very remote possibility there is color fade command data on the supply line and a very small MCU in each LED...I have seen this method used in other applications, but not LED xmas tree lighting... yet...

author: FreedNightHawk
author_rank: Newbie
timestamp: December 17, 2020, 03:36:36 am
content: No, the colors can fade and blink individual amongst the lamps, One can be red while another is blue and a third is green, and then they can all switch. They behave EXACTLY as addressable RGB lights. Any given LED can be assigned any given color and any given brightness.I have not stuck a scope on them because the only thing I had remotely resembling a scope, a Snap-On MODIS, blew a couple of power regulators that I haven't been able to replace yet.

author: Mr.B
author_rank: Unknown
timestamp: December 17, 2020, 03:47:38 am
content: Sorry, what I meant by *synchronized* was that they appear to be responding to some sort of controller, rather than all randomly doing their own thing.The *command data* over the supply line trick is quite common in real world applications.My home gas hot water has a two wire controller in the kitchen that lets you set the delivery temperature and see the filter/pressure status of the califont for example.As I said above, I have not yet seen this technology utilized in addressable LEDS, but it would not surprise me if it were available.Mass market addressable LEDs cost cutting - slightly smarter MCU in the LED, one less wire to factor into the cost of the LED string.

author: sleemanj
author_rank: Super Contributor
timestamp: December 17, 2020, 04:40:20 am
content: Slow (cross fading) and fast (flashing) RGB leds with embedded chips are common as muck decorative items. Just apply power and they will do their thing.If you put a bunch of them in parallel they will start out in sync and drift over time. They are doing each their own thing on their own schedule, just happens that they follow the same sequence and their individual oscillator frequencies are relatively close. If drifting was an issue then just reset (power cycle for a millisecond) the entire string every [average sequence time].Alternatively if addressing is necessary then comms could be done simply over the power line. but for xmas tree decorations that seems like an unnecessary expense to have addressable chains.

author: Mr.B
author_rank: Unknown
timestamp: December 17, 2020, 07:14:29 am
content: Quote from: sleemanj on December 17, 2020, 04:40:20 amAgreed.But, if the China manufacturers think there is a marketing advantage in having fancy synchronized LEDs on a two wire system, then why not.It would not surprise me in the slightest.

author: Gary350z
author_rank: Regular Contributor
timestamp: December 17, 2020, 07:26:36 am
content: I have seen somewhere recently that there are now addressable RGB LEDs that only have two pins, where the data comes down the power line, and they were in a string. I think it was in a BigCliveLive video.

author: Mr.B
author_rank: Unknown
timestamp: December 17, 2020, 07:37:22 am
content: Quote from: Gary350z on December 17, 2020, 07:26:36 amI would be interested to see a link.Only for interests sake... Curious if this *simple* technology has migrated into mainstream China manufactured xmas tree lighting.

author: Gary350z
author_rank: Regular Contributor
timestamp: December 17, 2020, 03:03:04 pm
content: Quote from: Mr.B on December 17, 2020, 07:37:22 amI don't remember which video it's in, and BigCliveLive videos are about 3 hours long, so it would be very time consuming to search for it, and it was only a brief mention. I think he said it would be in an upcoming video on bigclivedotcom. He gets most all his stuff from China on ebay, so you could look there if your really interested. That's all I know.