Isolated RS-485

To avoid potential ground loops, the RS-485 line drivers and line receivers are optically isolated at both ends. The circuit can utilize three power supplies; one non-isolated supply for the Arduino bar code reader circuitry feeding the line driver, one Isolated supply for the line driver / line receiver pairs, and one non-isolated supply for the buffer circuitry feeding the 7-segment shift register boards. See image below for the concept: