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LED flicker circuit?

B

BellaCroix

[H]ard|Gawd
Joined
Mar 25, 2004
Messages
1,054
Hello all, been a while since I've been around but starting a new build and needed help trying to figure out how to do something and this was the first place I thought to come look for help.

I need to find a way to make 3 LEDs flicker like a candle flame. I thought about trying to gut a couple of those jack-o-lantern LED safety candles but they all run on 3 volt watch batteries and I'd rather hardwire them to the 5v rail (also I'd rather not have to use 3 seperate boards in the small space I have to work with).

I've searched on-line trying to find a schematic to do this but am coming up short.

So my questions:

1) Since I'm using 3 LEDs would it be okay to just use the guts from one LED candle?
2) If I'm stuck using three seperate boards from those candles what kind of resistor would I need to use to keep from blowing something up? I gutted one to see what was in there and how it worked and it already had a 47 ohm resistor inside it.
3) Anyone have a schematic to build my own instead of gutting one (or three) of these things?

Thanks for your help!
 
Without knowing exactly how the circuit is laid out, it's hard to answer your questions. I don't know how the LED candles are driving the LEDs, or what the supply voltage to the LEDs is, or even what color the LEDs are.

That being said, this page appears to have plenty of info on building your own circuit.
 
Typically red, orange, yellow, and green LEDs draw around 20mA at 2V. While white and blue LEDs require 4 or 5V.

Judging by the size of that IC and the fact that only a very small resistor is used in series to limit the current it probably puts out just enough current to power a single LED. Therefore I would not recommend driving several LEDs with just the one chip.

In this kind of situation I personally would get a 500 ohm pot and put it in series with LED you want to drive with the chip. Then lower the resistance until it looks bright enough, grab a similar valued resistor and away you go.

Well more likely I would hook it up to the scope and look at the voltage across the resistor then figure out roughly how much current it was drawing... but the other idea should work fine.

EDIT: That circuit looks like some fun... but unless you're comfortable doing PCB design then I wouldn't bother.
 
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