Mysterious LED - Page 1
Forum section: electronics / beginners

author: Lucky-Luka
author_rank: Unknown
timestamp: April 16, 2021, 02:25:12 pm
content: Hi allI've analyzed an LED taken from a votive candle.Why is it flickering (they do that to remeber the fire of wax candles)? What's inside of it?https://youtu.be/opU5CsuhHgAThanks

author: exe
author_rank: Unknown
timestamp: April 16, 2021, 02:38:50 pm
content: There is an IC driver doing that. I didn't find a die shot of what you have, so I propose to look at ws2812 die shot:http://mirekk36.blogspot.com/2013/09/co-to-jest-czyzby-powrot-do.html.If you are curious about die shot, check this website:https://richis-lab.de/Bipolar20.htm. Or check posts from Noopy on this forum. Likehttps://www.eevblog.com/forum/projects/lm723-die-pictures/

author: Zero999
author_rank: Super Contributor
timestamp: April 16, 2021, 06:43:45 pm
content: Noopy's thread on optoelectronics is interesting.https://www.eevblog.com/forum/projects/optoelectronics-die-pictures/

author: floobydust
author_rank: Super Contributor
timestamp: April 16, 2021, 06:48:42 pm
content: I saw Ikea LED candles all flickering exactly the same. I shut them off and then turned them on at the same time, and they were all synchronized.They seem to be reading a pattern in ROM and just cycling through it. That should be part of the IC in OP's LED.

author: Gyro
author_rank: Super Contributor
timestamp: April 16, 2021, 06:56:38 pm
content: Quote from: floobydust on April 16, 2021, 06:48:42 pmAfter seeing some rumours on the web, I tried hooking a piezo sounder across the leds on a bunch of old LED candles (COB rather than embedded in the LED). A few types did indeed play nice little oriental tunes - clearly dual use greeting card ICs. Others just produced nasty random noise, so at least some have (had) ROM lookup.

author: Lucky-Luka
author_rank: Unknown
timestamp: April 16, 2021, 07:34:55 pm
content: QuoteCan you explain better what you have done?It's amazing (for me) the technology hidden in these cheap LEDs!

author: edavid
author_rank: Super Contributor
timestamp: April 16, 2021, 07:37:54 pm
content: Oh yes, that famous little oriental tune:https://en.wikipedia.org/wiki/F%C3%BCr_Elisehttps://www.instructables.com/Listen-to-a-led-tea-light/

author: DrG
author_rank: Super Contributor
timestamp: April 16, 2021, 09:12:47 pm
content: We had a thread earlier that wandered into those little electronic candles - your pic was similar to minehttps://www.eevblog.com/forum/chat/a-burning-candle-in-epoxy-resin/msg3106588/#msg3106588Those little things do a poor job of simulating a candle flicker. If you are interested, check out this guys attempthttps://cpldcpu.wordpress.com/2016/01/05/reverse-engineering-a-real-candle/very well thought out and analyzed in my view.

author: amyk
author_rank: Super Contributor
timestamp: April 17, 2021, 04:10:14 am
content: I once saw some extremely cheap "flickering candle" lights that had a curiously short and repetitive pattern: three short blips, then three slightly longer blips.

author: Gyro
author_rank: Super Contributor
timestamp: April 17, 2021, 08:56:30 am
content: Quote from: edavid on April 16, 2021, 07:37:54 pmInteresting, I would certainly have recognised that one! The tune from mine was definitely oriental in nature, quite delicate. I wonder how many variations there are out there. Presumably only on the older candles.

author: Lucky-Luka
author_rank: Unknown
timestamp: April 17, 2021, 09:46:34 am
content: I've tried with my LEDs but their tune doesn't mean anything

author: Twoflower
author_rank: Frequent Contributor
timestamp: April 17, 2021, 10:35:27 am
content: My understanding is that flicker LED candles with external chips might play a tune as they re-use sound-chips. LEDs with an integrated flicker chip use specific PRBS chips. Probably the sound chips are too big to fit in a LED housing.By the way. Here is one candle LED that is a bit more realistic:

author: Gyro
author_rank: Super Contributor
timestamp: April 17, 2021, 11:15:33 am
content: Yes, I'm sure the dies integrated into LEDs are optimised for minimum size and best function, rather than re-purposing existing ones.

author: RoGeorge
author_rank: Super Contributor
timestamp: April 17, 2021, 11:24:54 pm
content: Quote from: Gyro on April 16, 2021, 06:56:38 pmAt some point I thought it's some 1st April joke.Mine were from LIDL, with a single CR2032 batt from around year 2015.They don't sing, only buzz in single tone pulses.

author: james_s
author_rank: Super Contributor
timestamp: April 18, 2021, 03:07:23 am
content: Quote from: DrG on April 16, 2021, 09:12:47 pmThe same guy analyzed one of these flicker flame LEDs.https://cpldcpu.wordpress.com/2013/12/08/hacking-a-candleflicker-led/

author: Gyro
author_rank: Super Contributor
timestamp: April 18, 2021, 09:18:45 am
content: Quote from: RoGeorge on April 17, 2021, 11:24:54 pmThe Germans havenosense of humour!(Sorry, that was very politically incorrect!)