One final thought -
I looked at the spec sheets for the Arduino MKR1000 and the UNO.
The MKR1000 is showing a rated I/O pin current of 7 mA, and the UNO does show between 20 and 50 mA depending on the output voltage.
Will the 7mA be enough to switch the gates on the 2n2222 transistor?
The UNO data sheet
The MKR1000 data sheet:
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