Flickering LEDs

[july1962]

Not sure if this is the fight forum, so my apologies if it's not.

I have an idea for a Christmas light project that I want to try this year. I want to incorporate several hundred "flickering" LEDs....the kind they use in those little tea light units.

I wasn't sure if there was a chip of some kind inside that made them flicker or if it was the bulb itself, so I pulled one apart. I tested the bulb directly to the battery and it indeed flickered.

However, what I want is a pure white (instead of yellow-ish) and brighter, than what they use in the tea lights. I've scoured the internet for days and contacted a couple of suppliers but cannot find these bulbs. I don't think suppliers like dealing with home users. I also contacted the tea light manufacturer by email, but there was no reply.

I've also seen instructions online to make LEDs flicker, but it doesn't seem as practical for what I want to do on a large scale.

Does anyone know where I could get flickering LEDs as described above?

[budude]

Yeah - this is the fight forum - put 'em up :p

How about these: http://cgi.ebay.com/100-Flash-Flashing-Blink-Water-Clear-White-3mm-LED-WWF3-/290473183770?pt=LH_DefaultDomain_0&hash=item43a18d0a1a

[P. Short]

The link says that those LEDs are flashing...is that the same thing as flickering?

[july1962]

Yeah - this is the fight forum - put 'em up :p

How about these: http://cgi.ebay.com/100-Flash-Flashing-Blink-Water-Clear-White-3mm-LED-WWF3-/290473183770?pt=LH_DefaultDomain_0&hash=item43a18d0a1a

Yeah, it's funny....someone else sent me that ebay link as well. But I think those "flash" as opposed to "flicker." I wrote to the seller to see, but it says 1 second flashing.

The ones I want pretty much stay on...they just flicker a bit like a candle flame.

[BuzzKill]

You can build a flickering LED with a ATtiny 13. There are also ways to simply combine LED's that flash at different rates to get the same effect like the 3rd link listed below. I used the 3rd link to build mini-campfires for center pieces for an event. The effect worked really well.

http://www.instructables.com/id/Flameless-candle-from-an-attiny13/
http://hackaday.com/2008/10/30/flickering-led-circuit/
http://www.modeltrainsoftware.com/fire-led.html

Or you could just get a bunch of cheap LED tea lights, gut them, and repurpose for your needs.

[dmcole]

I wasn't sure if there was a chip of some kind inside that made them flicker or if it was the bulb itself, so I pulled one apart. I tested the bulb directly to the battery and it indeed flickered.


Early incarnations of flickering tea lights -- circa 2004-2006 -- did indeed use an application-specific integrated circuit (ASIC) on a tiny printed circuit board, which had a couple of resistors and a switch. You can still buy them that way -- the ones sold by Walgreens as recently as July were of that design.

But most tea lights sold in the last 12-18 months use an LED that flickers on its own. I've examined those LEDs and have to assume that they do their flickering via some chemical property, because I can't see anything inside the LED that would indicate that a chip has been integrated.

I haven't seen any of those LEDs made available for general sale, though I must admit I don't cruise the eBay sites as much as I probably should. I would doubt that even if you could find them they would be of any color other than orange-yellow, as that's what the market demands.

If you want to move forward on this, you're probably going to have to find someone who is familar with the Chinese LED market and figure out which of the fabs makes these. Short of that, if you're willing to compromise on cost and color, you could buy a skid of tea lights wholesale and take them apart.

If I were ever able to get the Sawyer array working, I'm pretty sure a version of the firmware could be written to flicker the LEDs rather than blink them.

HTH.

\dmc

[ErnieHorning]

Maybe it’s just the video but to me, they don’t look much like flickering. I think that for a decent simulation, it needs to look more analog. Quasi random PWM ought to look pretty realistic.

I’m sure there’s a way to do it with a 555 but if you need a couple hundred, I would use a PIC10. It would be cheaper and simpler to assemble. You should be able to get the current down pretty low too.

[dmcole]

Oh, and a PS to my ASIC posting -- I have read (but not proven) that many of the ASICs for tea lights were in fact those chips that play songs in greeting cards. The LEDs were driven through a transistor but the signal was the sound of the greeting card.

I also read somewhere of a guy who used small transistor radios tuned in to all-talk radio stations, and the audio signal drove small LEDs or incan lamps for model railroad campfires.

Speaking of which, looks like the guy at ModelTrainSoftware.com has figured out where to buy the flickering LEDs in bulk (but at $6 for three, he could buy three 50-cent tea lights, rip them apart and still make a decent profit).

\dmc

[BuzzKill]

The LED's at the Model Train place do not flicker. They blink. They just pair them up so they blink at different rates. The effect is actually pretty coo when implemented properly. ie like in the bottom of a barrel, or in the bottom of a camp fire. I placed mine low and flat, and used a small amount of prismatic cellophane over the top of the LEDs to break up and disperse the light a little more.

[dmcole]

The LED's at the Model Train place do not flicker. They blink.

Ah, sorry. Misunderstood.

\dmc