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How Do I Make LED's Fade with an already build flashing circuit? Answered

Hello everyone!
In my spare time I've built a simple circuit which makes an LED flash.
The flashing is controllable through a Potentiometer.
I have attached a circuit diagram (made really fast, so i know it's bad) and the picture of the breadboard.

Now, my question is:
How can I make the LED fade on and off instead of flashing?
I've tried to hook up a transistor but i've not succeeded.
If everyone could help, I'd appreciate it.

Here is the stuff I think could be useful that I have avilewable:

Some BC 144 Transistors (I suppose they're PNP)
Some PN 2222a Transistors
220uF Cap, 100uF Cap and a 10uF Capacitor.
A lot of resistors.

I do have more components but I don't think they could be used for this project.

And excuse me for any mistakes, English is not my Language, Thank you!


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Best Answer 3 years ago

Your English is fine :-)

To make the LEd fade in and out you need a very fast flash rate.

The fading is caused by altering the on to off ratio - so the longer it is off then the dimmer it seems to be. and the longer it is on the brighter it seems to be.

This is generally called Pulse Width Modulation (PWM)


You will certainly need to alter whatever circuit you have to make it produce PWM at a frequency above 25 Hz.


shows lots of circuits using the 555 timer that can do this.


Answer 3 years ago

Thank you very much! I'll try as soon as I have time!