I'm trying to set up several RC522 RFID readers with an Arduino Uno but struggling to get it working.
I've gone back to just using 1 RFID reader and that works when i wire it directly to the Arduino. But when i then try to wire it through a breadboard the reader stops working. Even if i move just the 3.3v line to go through the breadboard as per the photo below it doesn't work. Ive tried different parts of the breadboard and different cables and still no good. Ive also tried just chaining together 2 jumper cables and that didnt work either.
What is causing the problem is that you seem to be coping the insane circuit that is rife on the Internet. The RFID card reader is a 3V3 device and you are feeding 5V signals into it. A sure fire way to damage most chips.
It won't happen immediately, it could take a few months of operation before it fails, even a few years but it will fall a lot sooner than it otherwise would. It ight be too late for your hardware.
Every output from the Arduino needs to pass through a voltage divider to cut the 5V signal down to 3V3. The output from the reader can be connected directly to the Arduino.
It could also be a bad on connection, as mentioned. This is something we get here about five times a week.
Yes that is maybe the best way to drive this. Although, as I said you can put a potential divider to cut down the signals from a 5V processor. Here is a diagram to help you.
How are you measuring this? you can't just test continuity across the wire, you have to test the connectors as well.
You can do this by removing all power and turning the boards upside down, and measuring the continuity from the soldered points of each connection between the boards. That way you check both the wires and the sockets.
Single wire lengths into single holes are the worst way of wiring things up. I always try to make my pin headers at least two pins wide, and wider than that if possible.
