Flickering LED's

[Electric Rain]

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.

 

[sbayeta]

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

 

[bogdanfirst]

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.

 

[stevez]

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.

 

[sbayeta]

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

 

[Manihigh]

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.