You should have seen LEDs glowing and fading in a LED Strip lights, used for decoration in festivals and functions. They look beautiful, and give a different look. This fading LEDs circuit can be created using numerous methods like using microcontroller, ICs etc. But how can we forget our Evergreen IC, 555 Timer IC, yes we can create a fading LED using 555 timer.
555 Timer IC
Capacitor – 10uF
Resistors – 100k, 470 ohm
Battery – 9v
Circuit Diagram and Explanation
The slow fade led circuit is very simple, 555 has been used in Astable mode and a transistor is used to amplify the current. In Astable mode 555 IC oscillate at a particular frequency (depending on RC components), means output at PIN 3 goes HIGH and LOW periodically. So in our circuit whenever the output at PIN 3 goes HIGH, the transistor starts working as an amplifier, and amplifies the current. This current goes into the capacitor and charge the capacitor to the 2/3 Vcc (555 IC principal), at the same time LED glows. After this, output at PIN 3 becomes low, transistor becomes OFF and capacitor start discharges through the collector-emitter junction. Capacitor discharges into the LED, which gives the LED fading effect. As the capacitor discharges, LED illumination fades. Then again, PIN 3 goes high and capacitor charges and LED illuminates.
The led fading time is dependent on the resistors and capacitors value, if we increase the value of capacitor the LED would fade slowly. Like I have demonstrated in video, when I attached another capacitor of 10uf, fading effect becomes slow.