I want to design a simple circuit to detect when a push button is pressed but this push button is pulled up to 5v or 12v and the circuit can work with both voltages. Also a debouncing circuit is a need.
Do you have a specific question? Try and work out the design for yourself & if you are unsure, post back here. You can find reference design on google if you need it. Search for debouncing circuits for a start.