Trouble on switching a 3V relay with Arduino digital pins
The Arduino pins can only source a small amount of current (40mA per pin, 200mA total). You will want to use a low side switch with a transistor to satisfy the current demand of your relay. My go-to circuit for this problem is as follows (using a 1N4001 diode and a 2N3904 transistor). 







simulate this circuit &ndash; Schematic created using CircuitLab