Protect your electronics from cold-start with this simple-and-cheap 555 based on-delay timer
Have you noticed those sparks when you plug in your charger or adapter to the mains? This phenomena is due to the discharged power supply input capacitors; in this state they behave as short circuit. This short circuit can spread to your electronic circuits, reducing their useful life or other circuits that could be connected to them. In my laboratory I have a power supply and an oscilloscope that when I connect them to electrical power they wait a certain time before going into active mode. Both are quite expensive and delicate devices and for the same reason their designers have taken care of the phenomenon of cold start (that is, when the capacitors of their power supply are discharged). The power supply waits two seconds before turning on voltage to my circuits after I pressed the power button, and the oscilloscope does the same by waiting around that same time to start working. Have you heard those "clicks" inside devices like the ones I mentioned?