12V relay with nfc door


at the momant our frontdoor opend with the fingerprint, but this wouldn’t work 100%. Now I’m looking for a solution. My idea is a 12v relay with a potentialfree contact. Outside a bring a NFC stiker near the frontdoor and wenn only I scan the tack the door open.

The 2 question are is a 12v relay with a potentialfree contact supportet in home assistant?
And is it possible to trigger the automation from the nfc only with my smartphone?


ESP32 running ESPHome, with 12vdc - 5vdc buck converter, and 4x potential free (dry contact) relays.

  • Relays are controlled through MQTT to ESPHome over wifi.
  • Use NFC tags automation from Home assistant to drive the relays.
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I love these. been using them for years. Not this specific brand but exactly how ours work.

Thanks, but i will it in a flush-mounted box.
Is it possible to get only 1 relay?

We have already a fingerprint but after the work with little dirty finger it wouldn’t work 100%

Thanks but is there no all in one solution?

Today my devices arrived.
Can I use the 3,3V input pin as output for my relay?

If you bought the one from the link. The input side should work with 3.3v.

Yes and this
That mean I use the 5v input and then I can use te 3.3v as output

Do you have a schematic on what your final circuit should achieve?

From the 12v to the buck converter (12->5v) this powersupply to the esp. From the esp 3.3v and ground to the relay and the pin 5 use for the in from the relay.

Hi, today I have installed the relay and the esp.
All works fine.

Now a short question, is it possible to open the door per NFC tag. I mean if only I scan the NFC then open the door?

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Should be. You need to have the automation set up and the ha app running on your phone. Also being connected to ha the time you do the scan (probably via wifi) would be mandatory that your “call” reaches ha to trigger the automation to open your door. :door:

That way of setup might be smarter safer than using a nfc/rfid reader on the door that opens when a specific uid is presented. That’s because many readers don’t even check cryptographic signatures of tags (or they don’t have one at all) or even when they do the implemented way can have it’s own weaknesses (like mifare classic)… :put_litter_in_its_place:

The way you do is that you keep all the “secretes” with you in your pocket (your phone stores the passwords etc.) and they actually never get “read out” but just trigger something if you give the input (in that case reading a nfc tag) :star2:

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