RC522 RFID module powered but not scanning cards

[marcyvz]

Hello everyone,

I’m having trouble with my RC522 RFID reader. I’m using pins D9 to D13 on my Arduino, and I’m powering the module with 3.3V (not 5V). The code I’m using has been part of my project for a while and it always worked fine before.

Recently I had some issues with loose connections on the Arduino pins, but I fixed them. Now the LED on the module lights up, but it doesn’t scan any cards or tags anymore. This is already the second module I’ve bought with a similar problem.

Has anyone experienced something like this? Could it be a wiring/soldering issue, or does the module itself usually get damaged easily? Any tips for testing if the antenna or chip is broken would be really helpful.

Thanks in advance!

[van_der_decken]

@marcyvz

I’m using pins D9 to D13 on my Arduino, and I’m powering the module with 3.3V (not 5V).

You're giving the module 3.3V power, with 5V signals apparently - as you didn't mention any of the required level shifting. Eventually, the IC on the module (which is not 5V tolerant, despite what you may have read elsewhere - check the data sheet) will protest at such mistreatment. And it sounds like it has.

Here's one way to connect a 3.3V RC522 to a 5V board. There are others, some simpler.

[Grumpy_Mike]

This is the way I do this:-