STM32 12v relay driver circuit
how much current will transistor pull?
Ic =approx= (gain) x (current in 22k)
= (100 min) x ((3.3V-0.6V)/22000R)
= 100 x 2.7V/22000R
= 12mA min
Is this enough to close your relay? Maybe not.
Note also that the assumption that the pin actually produces 3.3V at the output could be lower.