I was using the first of a batch of LEDs i recycled from a "icicle" light set when I ran across some interesting ones. The box said that it flickers, but I didn't see that until later and only plugged it in long enough to see that it lit.
Among the LEDS were a number that looked different inside than the usual cathode/anode configuration you can see. The two poles of these looked equal and something like a harp together or an open book. I gave them power to test them and found that these little devils actually flash -- or at least some of them do.
There were about 8 or 9 of 'em in a string of 70. There were two groups that flashed at different rates, fast and slow. Then there were a few that were some kind of latching relay or ? These would come on briefly when power was applied, then turn off. I suppose these provided the "icicle" flicker.
I think these would work great for a simple flasher circuit, like the lights seen on water towers and other tall structures. If they come in red, there you go, although the clear could be colored to suit you needs. The size was 3mm and they had the cone reflector, so could easily work for the old-style emergency lighting "bubble gum" lights. I also wonder about availability of different flash rates.
Anyone know more about these LEDs? I wasn't aware of them, but I'm not electronic guru, either.
Mike Lehman
Urbana, IL
Flashing LEDs typically have the equivalent of an LM3909 LED flasher chip built in, but the flashing would be regular, not random. Haven't seen any random flicker ones, that's kind of strange.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Randy,
There were some other components associated with these lights. There were about a dozen small components that looked like they might be resistors placed in series inside the sockets. They didn't have tubular bodies like a resistor, sort of more and I could not get a resistance reading on them with my multimeter, so I suspect they're not. Maybe a small capacitor?
There were also two tubular items encased in plastic in series. I have seen these before on other LED strings, so thought these might be resistor packs. I couldn't get any resistance readings from them either.
I didn't even try to decipher the circuit path as I was destroying these icicle lights, so can't offer more there.
I think it's some kind of cascade circuit that relies on differences in the flash rates provided by these special LEDs to provide the flicker effect. Each one individually flashes at a steady rate, it's when they're in circuit together that things get complicated, rendering the effect.
I got the last one on the shelf, otherwise I'd get another one and try to analyze a bit more. I suspect your guess as to what's inside each one (LM3909) is correct or very close to correct. It would be good to know what these are called or spec-ed as, as they could have interesting uses, either individually or linked together in a circuit similar to the flicker one in these strings.
Mike,
Those are most likely 'fuses' for the lighting strings. Most 'flicker' or 'flash' LED's have the circuitry built into the LED. Places like these have these LED's for model railroad uses:
http://www.moreleds.com/
http://www.modeltrainsoftware.com/ledlights1.html
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
Jim,
No, the fuses in these were still the small glass ones in the plug like most of them these days. I kind of muffed the sentence discussing that above, but if they were capacitors and the circuit was set right, then the combination of the flashing LEDs and the small capacitance might cause the intended flicker effect.
Hey, I think I found at least a partial explanation at a couple of the pages you linked to. The lower 2 of the 3 LEDs on this page are flashing ones, although only in yellow and red, nothing in whote like the ones I got from this string of Xmas icicles.
http://www.moreleds.com/special.htm
Page down on this one to where shows how linking flashing LEDs in a cascade circuit with resistors does work to make flicker, so I suspect the circuit I have here is some variant on that. Not sure
http://www.moreleds.com/3mmyellowflashing.htm
My doubts are due to the fact that I can't get a resistance readings out these little devils and the fact that they were placed across the anode and cathode, rather than being in series with one of the leads like we usually do with resistors. That was why I was thinking they might be caps, although there were no shocking developments with 'em.
This guy does have some neat stuff (and loves animals, too, which ain't bad). For locos and rolling stock, I do tend to use RR oriented LED vendors to get the right look for headlights. I'm not all that picky for structure lighting, as the warm white ones work well to my eyes in simulating incandescent lighting, so It's still hard to beat picking apart a Xmas string for decent LEDs at less than a quarter apiece for this app.
Hmm, gotta look again, but on the page withe the railroad oriented stuff, warm-white 3mm and 5mm LEDs are 10 for $9.95, in the big giant page listing all LED types, warm white 3mm and 5mm are 50 cents each, or 45 cents each in 10 unit quantities. Hmmm.
I found that he does offer flashing white 3mm LEDs on this page elsewhere another of his internal sites, along with the various color ones:
http://www.quickar.com/leds.php?session=