When using a relay breakout module with Opto-Isolation is an uln2003a needed? I am also using a GPIO expansion module driven by i2C, i.e. a PCF8475 module, and the relay can be low or high triggered (nice feature to have), so I don't see any benefit to using an uln2003a between the PCF8475 and the replay module. Or am I missing something of importance? Oh, and relays use separate PS, with no common GND between relay PS and Pi control logic circuit. If I was driving motors or such, then sure uln2003a would be needed, but not with a opto-isolation relay, right?