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Flickering LED's

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Electric Rain

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I need to make something that will make some white LEDs (Maybe 10 or so.) flicker. I’m going to make the LEDs look like stars, so I only need them to flicker a very small amount. A VERY small amount, barely noticeable. (Flicker meaning dim in and out a little.) I also don’t want it to run on more then 9 volts, maybe 12. And I don’t want any controls. Like pots or switches. If it’s powered, it works. No flicker control pot, on/off switch or anything. Can someone provide me with schematics? I am doing this for a family business that we own. And so I need to figure this thing out within, about 1 1/2 months or so. I don’t mean to rush, but we are going to a craft show on the November 27th, and I need to figure it out quite a bit in advance before that. (But we’ll be able to figure it out before that anyway.) If you need more details on what I need, please don’t hesitate to ask.
 
First think that comes in my mind:

Use a 555 as an oscillator, but taking the capacitor voltage as your output (a saw tooth wave form). Here you can find a good reference:


You'll need to use a voltage follower to light the LEDs.

Hope that helps
 
i think that a triunghiular oscilator wich can vary the voltage from 100% to about 50% would do better than a square osc. i think that the effect will be better. i think that the frequency should be like 5-15Hz.
 
The LM3909 might have been good for this situation because it was cheap and so easy to use. You might still be able to find some at low cost. I did a quick search and found that several have developed their own discrete component equivalent because of the obsolesence of the 3909. Search on LM3909 and you will find lots of stuff.
 
bogdanfirst said:
i think that a triunghiular oscilator wich can vary the voltage from 100% to about 50% would do better than a square osc. i think that the effect will be better. i think that the frequency should be like 5-15Hz.
I am suggestin a sawtooth waveform, not a square one. The charge/discharge of the capacitor in a 555 oscilator will do the trick, and it's really cheap and easy to set up.

Cheers
 
Go with a 4017/555 combo with slightly different resistance for each output. Only problem is it isn't random and anyone watching closely would probably soon see the pattern.
 
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