The 555 adjustable timer circuit starts timing when switched on. The green LED lights to show that timing is in progress. When the time period is over the green LED turns OFF, the red LED turns ON and ...

Finding that his recently purchased LED Christmas lights defaulted to an annoying blinking pattern that ... alternating 500 Hz square waves with a 555 timer and a 74HC74D dual flip-flop.

Here is a 1Hz pulse/frequency generator using the popular timer IC 555 which is wired as an Astable Multivibrator. The output pulses can be indicated visually by the LED. An Astable Multivibrator, ...