Author Topic: Mysterious LED  (Read 765 times)

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Offline Lucky-Luka

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Mysterious LED
« on: April 16, 2021, 02:25:12 pm »
Hi all
I'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/opU5CsuhHgA
Thanks
Memento audere semper.
 

Offline exe

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Re: Mysterious LED
« Reply #1 on: April 16, 2021, 02:38:50 pm »
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. Like https://www.eevblog.com/forum/projects/lm723-die-pictures/
 
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Offline Zero999

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Re: Mysterious LED
« Reply #2 on: April 16, 2021, 06:43:45 pm »
Noopy's thread on optoelectronics is interesting.

https://www.eevblog.com/forum/projects/optoelectronics-die-pictures/
 

Offline floobydust

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Re: Mysterious LED
« Reply #3 on: April 16, 2021, 06:48:42 pm »
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.
 

Offline Gyro

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Re: Mysterious LED
« Reply #4 on: April 16, 2021, 06:56:38 pm »
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.

After 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.
Chris

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Offline Lucky-Luka

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Re: Mysterious LED
« Reply #5 on: April 16, 2021, 07:34:55 pm »
Quote
After 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.
Can you explain better what you have done?
It's amazing (for me) the technology hidden in these cheap LEDs!
Memento audere semper.
 

Offline edavid

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Re: Mysterious LED
« Reply #6 on: April 16, 2021, 07:37:54 pm »
« Last Edit: April 16, 2021, 07:41:18 pm by edavid »
 

Offline DrG

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Re: Mysterious LED
« Reply #7 on: April 16, 2021, 09:12:47 pm »
We had a thread earlier that wandered into those little electronic candles - your pic was similar to mine https://www.eevblog.com/forum/chat/a-burning-candle-in-epoxy-resin/msg3106588/#msg3106588

Those little things do a poor job of simulating a candle flicker. If you are interested, check out this guys attempt https://cpldcpu.wordpress.com/2016/01/05/reverse-engineering-a-real-candle/ very well thought out and analyzed in my view.
- Invest in science - it pays big dividends. -
 
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Online amyk

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Re: Mysterious LED
« Reply #8 on: April 17, 2021, 04:10:14 am »
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. ::)
 

Offline Gyro

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Re: Mysterious LED
« Reply #9 on: April 17, 2021, 08:56:30 am »
Oh yes, that famous little oriental tune: https://en.wikipedia.org/wiki/F%C3%BCr_Elise

https://www.instructables.com/Listen-to-a-led-tea-light/

Interesting, 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.
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Offline Lucky-Luka

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Re: Mysterious LED
« Reply #10 on: April 17, 2021, 09:46:34 am »
I've tried with my LEDs but their tune doesn't mean anything :(
Memento audere semper.
 

Offline Twoflower

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Re: Mysterious LED
« Reply #11 on: April 17, 2021, 10:35:27 am »
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:
 

Offline Gyro

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Re: Mysterious LED
« Reply #12 on: April 17, 2021, 11:15:33 am »
Yes, I'm sure the dies integrated into LEDs are optimised for minimum size and best function, rather than re-purposing existing ones.
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Offline RoGeorge

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Re: Mysterious LED
« Reply #13 on: April 17, 2021, 11:24:54 pm »
After 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.

At some point I thought it's some 1st April joke.   ;D
Mine were from LIDL, with a single CR2032 batt from around year 2015.
They don't sing, only buzz in single tone pulses.   :-\

Offline james_s

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Re: Mysterious LED
« Reply #14 on: April 18, 2021, 03:07:23 am »
We had a thread earlier that wandered into those little electronic candles - your pic was similar to mine https://www.eevblog.com/forum/chat/a-burning-candle-in-epoxy-resin/msg3106588/#msg3106588

Those little things do a poor job of simulating a candle flicker. If you are interested, check out this guys attempt https://cpldcpu.wordpress.com/2016/01/05/reverse-engineering-a-real-candle/ very well thought out and analyzed in my view.

The same guy analyzed one of these flicker flame LEDs.

https://cpldcpu.wordpress.com/2013/12/08/hacking-a-candleflicker-led/
 
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Offline Gyro

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Re: Mysterious LED
« Reply #15 on: April 18, 2021, 09:18:45 am »
Mine were from LIDL, with a single CR2032 batt from around year 2015.
They don't sing, only buzz in single tone pulses.   :-\

The Germans have no sense of humour!  ;D


(Sorry, that was very politically incorrect!)
« Last Edit: April 18, 2021, 09:33:28 am by Gyro »
Chris

"Victor Meldrew, the Crimson Avenger!"
 


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