What makes flickering LED's flicker?

Thread Starter

tracecom

Joined Apr 16, 2010
3,944
I disassembled one of the LED tealights and found an LED, a switch, and a battery. I expected to see an R/C network or transistor(s) or something, but I didn't find the source of the flicker. There was no current limiting resistor either.

Is the flicker circuit built into the silicon? or what?
 

iONic

Joined Nov 16, 2007
1,650
It also might be ralated to the heat generated by the LED causing an open, cooling and then closing the circuit...etc. not really sure.
 

Wendy

Joined Mar 24, 2008
22,243
I have take one of them apart. What! You guys want to say something!

It has two LEDs, both 3mm, both blinking at different rates. In binary this works out to 4 states.
 

iONic

Joined Nov 16, 2007
1,650
Yeas, that's cool! Somewhere I saw a circuit where they used a single christmas tree blinker to make multiple non-blinking LED's blink. This dual blinking LED could make a string of flickering candles. Perhaps you couls add some sort of delay to make them non-synchronized!
 

thatoneguy

Joined Feb 19, 2009
6,359
If it is a "Water Clear" case on the LED, you will see a TINY black dot near anode or cathode inside LED. It is the controller circuit for the LED to provide the random PWM "flicker effect".

Self-color changing RGB LEDs have them inside as well, though they are a touch larger, being seen as the size of a black gnat inside, instead of a black speck.

Anyways, inside that tiny, lead-less looking package is the 'brain'.
 

marshallf3

Joined Jul 26, 2010
2,358
I have take one of them apart. What! You guys want to say something!

It has two LEDs, both 3mm, both blinking at different rates. In binary this works out to 4 states.
Very cool, I often wondered how those worked. I was eventually going to try to look it up but here you've gone and answered the question for me - thanks!

I remember when those random tri-colors first came out, they were putting them into ink pens and all sorts of things (and still are) but it's mainly children's toys now. Wasn't hard to deduce how they worked but the flickering candle one was really escaping me.
 

Thread Starter

tracecom

Joined Apr 16, 2010
3,944
look CLOSELY at the LED. See if there is additional circuitry inside.
Yes. Looking through a jeweler's loupe, I can see what looks like a small smd. Amazing that you can buy these tealights including an LED with an enclosed SMD circuit, a switch, a battery, battery contacts, a lens, three pieces of injection molded plastic, one screw, packaging, labor, freight from China, profit for the manufacturer, a rep fee, and profit for the retailer all for 50 cents. :rolleyes:

I wish it was made in the USA, but there's no telling how much it would cost.
 

Wendy

Joined Mar 24, 2008
22,243
A buddy of mine has bought some electric candles that obviously have PICs or somesuch in them. The pattern repeats, about about 256 counts. I made note of one distinctive flicker pattern and timed it.

Yet a third way I've covered in my revamped LEDs, 555s, Flashers, and Light Chasers in chapter 12. Basically you use an audio source (such as radio or MP3) to make a LED flicker.
 

#12

Joined Nov 30, 2010
18,217
Too cool! For my next invention that I want somebody else to make, a flashlight that narrows its beam when I aim at something and hold still for half a second. It would only require a 3 axis accelerometer and a microprocessor in each of the LEDs and sell for $10.
 

retched

Joined Dec 5, 2009
5,208
A nice little motor to turn move the lens from "wide" to "narrow".

Good idea. Be sure to have a manual mode to. Some folks are too shaky and it would never narrow.

Like the old military flashlights that have a button on the slide switch.

A 3 position switch, with momentary button.

On-auto
On-manual
OFF

In manual, it defaults to wide. Push and hold the button and it narrows. Release to go back to wide.

Actually, you might be on to something. ;)
 

Rane

Joined Mar 5, 2011
3
I sought a green flickering LED but found that tea light LEDs have almost no green in their spectrum - and such flickering LEDs seem unavailable from electronics suppliers. However I put an ordinary green LED in series with the tea light LED, doubled the voltage (from 3 to 6v) and got a green LED flickering in sync.
 
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