Let's blink some leds again. Well, fading could be more accurate term. Meaning of this article is to show you an easy circuit that lets you light up your case with slowly alternating colors or just to make your power led come alive. Color changing FireWheel could be also cool, what do you think? This is by no means a step by step how to but I think that it will be enough anyway.

So, here it is. It actually looks a lot complicated drawn as it does in real life.

How does it work?

30 microfarad condensator and the resistor marked with blue 100k control the speed of the fading. You can replace the 100 kilo ohm resistor with 100k linear potentiometer so you can adjust the speed any time.

You can make the circuit even simplier by leaving out other of the transistors and those leds that are connected to it. Good for power led pulsing etc.

In LM324 there are 4 operation amplifiers. We used only two of them so you have an option to build another similar circuit around the IC. This way you can use second potentiometer to control the another circuit and it's fading speed etc.

In this picture you can see the circuit with only one transistor and one led. Transistor is BC547 and the led is ultra bright red with 220 ohm resistor in series.

Circuit in action:

270 KB DIVX video.

133 KB GIF animation.

Similar basic structure as the last one but with one added transistor on few more leds. Other controls two blue and one green led and other controls two red leds.

Circuit in action:

170 KB DIVX video.

198 KB GIF animation.

Wow, it fades. Thanks goes to Bill Bowden who made the initial schematic. From that link you can find detailed explanation why/how this thing works.


Questions, comments?
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27.02.2002 - Japala