Using NFC Tags for Home Automation

Using NFC Tags for Home Automation

nfc stickers and reader

I’ve found that screens are not my favorite way to manage my home automation. It’s too annoying to unlock a phone/computer/kiosk, start an app, and find the right menu option.

Even my magic spellbooks, while convenient, can be clunky for simple tasks that I (or guests) want to perform often. They can do just about anything, but as a result, they can be both overkill and daunting to use.

Something also gets lost with home automation. A friend once mentioned to me how he prefers physical on/off light switches, but dislikes how his home automation cannot change the switch position when the light is toggled remotely. His off-hand complaint has had me thinking about how to make automations which are more tactile and embedded in the real world.

Why NFC?

  • They simply provide a way to detect when two things are next to each other.
  • NFC stickers are cheap: packs of NFC stickers work out to $0.37 USD each.
  • They’re also small: thin, waterproof, and easy to hide.

These things, together, make them a potentially good solution for creating the sort of tactile interactions I mentioned above.

Mobile Phone NFC -> Home Automation

Android and iOS phones both have built-in NFC support these days. One approach is to encode a specific action each time you tap your phone to a tag.

To specifically create automations:

  • iOS: the native Shortcuts app on iOS can be triggered by NFC and directly call the official Home Assistant app (see below).
  • Android: the HASS NFC app makes the process much easier.
iOS Shortcuts calling Home Assistant
Triggering a Home Assistant action with iOS Shortcuts

The main disadvantage to this approach to NFC is that automations are tied to a mobile phone. This means guests have the automations installed on their phone.

It would theoretically be possible to write the NFC tag such that it contained the necessary credentials to trigger a webhook, but this exposes a security vulnerability in the NFC data and still requires some minimal setup on the part of a guest.

Custom Hardware

It’s surprisingly cheap and easy to build a simple NFC reader.

arduino nano and RFID RFC reader

Right now, I’m playing with Arduino Nano boards and cheap NFC scanners. A single device setup, like outline above, runs about $7.25 USD.

Screen Shot 2020 02 11 at 9.01.30 AM
The Arduino package MFRC522 works out-of-the-box and includes pin wiring information.

One obvious use of this hardware is as a door lock, common in any office. The device could be placed in front of a door that has a smart lock. Guests could carry NFC tags (or badges) which are scanned to open the door. At home, the same principle could serve as a way to get in the house without bringing (traditional) keys.

I’m interested in exploring embedding such cheap reader devices in physical objects around the house. Such readers can take the place of a mobile phone, with all the configuration pre-loaded. For example, you might change the music in the room or the lighting scene by moving the device atop a different tag. I think that if the objects themselves are interesting and intuitive, it could provide a very interesting way to interact with the environment.

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Written by
(zane) / Technically Wizardry
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