I have a couple of things automated in my room (fan, lights etc) using a server running on Rapsberry Pi 2 and relays.

Now I would like to implement a system to automatically detect when I am in the range of the Raspberry Pi, namely about 4-5 meters. Using a portable device such as a bracelet or a small thing attached to my clothes is what I would like and then the reader would somehow detect when I am around.

Long range RFID tags seem to be an interesting option, but I couldn't find a good solution that is compatible with RPi... and also I am not sure if it is safe to use such an antenna in my room.

I am not sure about bluetooth devices that would somehow automatically connect when I am around the RPi either, but I think that the device that will be attached to me won't be passive anymore.

Also, using my phone which automatically joins the wifi network would be an option, but I don't take my phone with me always and the router has quite a long range.

What is the best and safe way to have a passive device with me that would trigger my presence to the RPi?

  • Interesting task but the Pi is irrelevant.
    – joan
    Commented Dec 8, 2020 at 20:45
  • Well, you’re right, but where would be a better place to ask/migrate this? Commented Dec 9, 2020 at 5:06

2 Answers 2


You might look into a Passive IR sensor. You don't need to carry anything with you :) They're extremely simple (hardware-wise), and many relevant "How-To" articles are available for interfacing with RPi, and coding examples. There was another question on PIR sensors posted here recently - you may wish to have a look at those answers.

PIR isn't going to identify you specifically - if that's your aim. However, there was an excellent, well-researched answer posted here years ago that used the RPi for speech recognition.

And finally - there is facial recognition: RPi hardware several years ago may have lacked the horsepower to do facial recognition, but there are several projects available today that apparently do that rather easily.

  • Umm, I don’t want to detect when someone else enters the room but only when I enter the room (or specifically, that portable device). Voice/facial recognition would not be the right thing because I want it to be fast enough and not have to talk. Thanks! Commented Dec 9, 2020 at 8:42
  • @IonicăBizău: a system to automatically detect when I am in the range of the Raspberry Pi. Writing good questions is hard. You also didn't like the other answer. Perhaps give this some thought next time?
    – Seamus
    Commented Dec 9, 2020 at 9:27

There’s some instructions you might want to look at here - https://magpi.raspberrypi.org/articles/create-a-raspberry-pi-3-bluetooth-tag

  • I mentioned this solution but I don’t take my phone always with me. I’d rather use a passive tag/device instead. Thanks! Commented Dec 9, 2020 at 5:05

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