Designer circuit using optocoupler
PHOTOCOUPLER
PS2501-1,-4,PS2501L-1,-4
CTR = 80%  to 600%

You must use the worst case 80%

Typically If input is listed in the tables here, If=10 mA @ Vf=1.14V

So you only expect 8mA out and or even 80% of your 15mA.

Generally for Q2 if need Ib=5~10% of Ic when Vce=Saturated

So an additional transistor is needed. and then configure as a Darlington.







simulate this circuit &ndash; Schematic created using CircuitLab

You can drive the opto with 10mA from PIO port on Anode or cathode depending on power on state or preference for positive or negative logic.

I assume you have decoupled V+ nearby and a reverse clamp diode for the Q2.  The funny schematic just shown here ( dont draw yours this way) just add a note to minimize the loop area. (twisted pair or short wires.)