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The video above is a quick demo of the process. You can do this with your NFC-enabled smartphone instead of another tag as well. The trick here is that instead of using NFC to just turn the power on or off to your computer, you can actually program the shield to enter your password so all you have to do is press enter when you swipe your tag. You’ll need a few things to make the setup work, including an Arduino Leonardo and Adafruit’s NFC Shield, along with some extra tags and a soldering iron.
It’s not hard to type in a password, but this can help you get back to work quickly if you have an auto-locking PC or you lock your system every time you get up. Plus, it’s a fun way to use your phone or a card as an authentication device, and it’s a good way to get started with electronics projects. Hit the link below for the full walkthrough.
NFC Computer Unlocker [Instructables]