In this short tutorial I'd like to explain how to make simple USB device which allows you to very quickly unlock your computer without keyboard. You will need only the Pro Micro microcontroler with ATmega32U4 (or Arduino Leonardo with this chip), RFID reader together with card and breadboard.
For RC522 reader USE ONLY 3.3V version of Pro Micro. VCC is the voltage supplied to the on-board ATmega32U4. This voltage will depend on whether you’re using a 3.3V/8MHz Pro Micro or a 5V/16MHz version, it’ll be either 3.3V or 5V respectively (but for this project you need 3.3V version!) This voltage is regulated by the voltage applied to the RAW pin. If the board is powered through the ‘RAW’ pin (or USB), this pin can be used as an output to supply other devices.