Creating an NFC door lock with the Qduino Mini

Have you ever wanted to unlock your front door with just your bus pass, a tag or an old hotel room key? Now you can.

In today’s world, convenience is a huge factor. From mass transit to hotels, more and more devices are becoming enabled with contactless technology to expedite our days. Wouldn’t it be great to do the same at home? After all, having to search through your bag to find your keys can often times be a daunting task, and time-consuming nevertheless. Just imagine how easy it could be to unlock your front door using nothing but that bus pass, that old hotel room key, or any other item embedded with an NFC tag. Thanks to Maker Quin Etnyre, now you can. Even better, the entire project costs less than $100!

As its name would imply, the NFC Door Lock is a compact, Qduino Mini-powered door lock that senses when there is an NFC tag present, unlocks your door using a servo motor and multiple 3D-printed parts, and makes absolutely no modifications to your current door accessory. In other words, you can take it apart if needed in just a few minutes.

“This is super useful and I hope to put it on all doors of my house — it’s a relatively easy build in a few hours for an advanced user or a great weekend project for beginners,” the 14-year-old Maker explains.

Fresh on the heels of a super successful Kickstarter campaign, the Qduino Mini is ideally suited for this project. For those unfamiliar with it, the Arduino-compatible board is equipped with a built-in battery charger and fuel gauge that can notify a user whenever a LiPo needs a little extra juice. However, since the Qduino Minis won’t be readily available until this summer, Etynre suggests using a SparkFun Pro Micro (ATmega32U4), a LiPo battery charger, and a LiPo battery fuel gauge.

Using his ATmega2560 based Bukito 3D printer, the Maker went on to create a couple of parts for the lock, including its round mounting plate, servo head, servo mounting blocks, as well as the housing for its electronics. All of these components can be completed in a matter of two-three hours.

Etnyre then acquired hookup wire, an Adafruit NFC Shield, the Qduino Mini and some right angle male headers, before splitting off three pins from the block of male headers, and soldering them to one edge of the proto space on the NFC Shield. Throw in some cutting between the IRQ and D2 on the NFC Shield, along with a little coding using the Adafruit PN532 NFC library, and you’re well on your way to finishing the smart lock.

Next, the Maker removed the inside face of his deadbolt and mounted the servo head onto the door. He placed the entire assembly of the Qduino Mini and NFC Shield inside the 3D-printed box, attached the servo cable to its connector and ran the cable through the designated hole in the lower lefthand corner of the housing. From there, the lock is affixed to the door.

Want to add an NFC Door Lock to your home? Head over to Etnyre’s entire project page here. Meanwhile, don’t forget to check out the Qduino Mini here.