Hi, I’m using Arduino UNO and built an object placement puzzle. It has 4 Rfid sensors which unlocks the relay if puzzle solved properly. Problem is that everything works perfectly if Arduino UNO is connected with USB cable. If I connect it with external power supply it looks like it’s working (lights on Rfid sensors, relay and arduino is lit), but after solving the puzzle signal from first analog output doesn’t drop and relay is not switched. I’m using DC lab power supply. I’ve tried different voltages from 7v up to 12v. It doesn’t change anything.
The only way I managed it to work was connect 5v directly from the other arduino to first arduino 5v pin. If I connect 5v to that pin from other power supply it doesn’t work the way it should.
If anyone could help me with a problem that would be nice. I can upload a code, but I’m assuming problem is not with a code, because it works with USB powered arduino.