LM324N op amp and toolchanger sensors

Hello,
On an existing lathe and sensor circuit board I have 4x, forked,
optical sensors and an LM324N op amp. This circuit is used to sense
the position of my tool turret. There are 6 output wires, 2 are
power wires, and the other 4 are for each sensor.

On my PMDX 120 breakout board, wiring to the inputs requires two
wires, one into the input and the other into the common return. With
the optical sensors and LM324N, I will only have one wire for each
sensor, no common return. How can I wire this to my PMDX 120
breakout board to get the sensor input without a common return wire
to complete the circuit?

Is it possible that the - supply wire going into the sensor
circuit board could be used as the common return for all 4 sensors??

Any help would be appreciated.