Plug the RFID module into the breadboard with enough space around it. Connect the VCC pin to the Arduino's 3.3V (not 5V), and ...

This Arduino Uno setup can be powered by a 6F22 9V battery or other suitable ... input pins while the GND pin is the common ground (0V) connection. The VCC and JD-VCC pins are the power supply input ...

The Uno also has a limited number of pins, making it difficult to work with when the project requires plenty of input and output components. However, these two areas are where the Arduino Mega shines.

Conversely, the Uno's pins are female. Both the Arduino Nano and Uno can be powered via their integrated USB connectors. This automatically supplies regulated 5V power to the board, allowing you ...

and no I/O pin. It only applies to certain microcontrollers, but he provides example Arduino code showing how handy this can be for battery-powered projects. The usual way to measure VCC is simple ...