I had published an ATX lab supply conversion about 10 years ago. It inspired a lot of folks to take their first steps in hobby electronics through that instructable.
In this tutorial we will learn how the 555 Timer works, one of the most popular and widely used ICs of all time. It is a highly stable integrated circuit that can produce accurate time delays and oscillations. The 555 Timer has three operating modes, bistable, monostable and astable mode.