In a electronic system there are some inputs that controlled by the end user, these inputs are read by electronics and acted as an output. The inputs can come from a source, switches, buttons, sensors, relays, and communication device, etc. In certain environments and situations, these input signals can pose a threat to the electronics reading, especially if those electronics are designed without protections. for example electronics in the world of industrial.
An important example for this environment is interfacing a sensitive electronics with input coming from condition of a factory floor. Usually electronic inputs are read by some of intelligent processor such as a microcontroller, FPGA, or a state machine. In situation like these, it is imperative to protect the processor from the inputs, while still providing a usable signal for the processor to read.
Below are the basic Input Output Protection Diagram to protect you Microcontroller IO(Input-Output)
1x 5v1 Zener Diode
1x 220 Ohms