Ok, here is an example :
When i press AC switch i have +12 volt output signal.Then i connect this signal to one of MCU GPIOs and use it for IDLE control adjustustment. So i want to be able to use any input of the MCU and not be aware all the time if the input signal will be above 5 volts. The maximum posible voltage that may be use it will be 15volt.
Do you have basic knowledge about Ohm's law, Zener diodes, resistors and how to use them in a practical design?
Can you find a "Proto Area" on your bord?
The answers would make your question easier to understand.