Real world adaptation - SSR

 Recently, I breadboarded and tested a four-channel mosfet pcb. The channels were not, as I had hoped, isolated, but share a common ground reference.

I made some changes and got the unit working as a reversible H-bridge motor driver.

However, after I installed the unit on the power panel, I discovered the unit was not functioning as expected. I ran some in-circuit tests on the pcb and everything seemed okay.

My observations of the unit led me to believe the opto-isolators were not being driven high enough by the RPi 3.3VDC GPIO pins. My last test was to substitute the 3.3VDC with the 5VDC, also from the RPi. Success. Now I'm examing the parallel mosfet pcbs I purchased earlier and rejected due to having no opto-isolator input buffer protection. Since those pcbs will drive an existing opto-isolator, there should be no problem.

The proposed level shifter pcb circuit: