I have a strange problem, I have built an rfid reader with an SD card connected to it. Everything works nice and dandy when i have it connected to USB, but when i connect it to a 9v/1A powersource the sdcard fails to read after the first read. everything else seem to get current and are working as it should.
I have hurd that the RFID can be sensitive to different currents. but 9v/1a should be enough for anything right?
Any ideas? anyone who have had similar problems?
Could it be for some other reasons it behaves like this? The USB port is 5v/900mA , right?