This DIY gas leakage detector is designed for educational and basic monitoring purposes. For critical safety applications, ...

Not exactly schematics, but [Duckman] has some Arduino pinout diagrams he made using ASCII-art. These could be useful when pasted into source code as comments, documenting the pinouts for your ...

The resistor values (R1&R2) in the circuit diagram provide some over-voltage protection then measuring low voltages. Keep it in mind that any input voltage higher than about 55V could fry the Arduino.

The Arduino Wire library is a core aspect of Arduino's integrated development environment, or IDE, and is a must-have if you're using sensors or extra microcontrollers in your project.

As a industrial controls engineer that has worked globally, keep the arduino in hobby zone where it belongs. There are machines running with 20, or 30 year old control systems that are PLC controlled.