3.3 Vdc for Opto Switches.
I left a diagram and ProtoBoard with an OPB816 in the PCB Mill goody box. It needs to be modified.
P/S Volts need to be 3.3Vdc, not 5V
Pull-up Resistor for PhotoTransistor = 3k3, not 4k7
CurrentLimit Resistor for IR LED = 100 Ohm, not 170
The leads for the Optos are already attached, and a legend marking on the Diagram. Maybe just put the Resistors on the leads where they plug into TinyG