Two Arduino pins instead of four.The opto LEDs for Q1 and Q4 can be driven by one Arduino pin, by connecting the LEDs in series.The single CL resistor for the two LEDs must be reduced to 100 or 120ohm to keep LED current the same.Same for the Q2, Q3 pair.
Where to put the opto transistor. As in the diagram for Q3 or for Q4.Not conducting transistor is almost ideal open circuit, but conducting has a saturation voltage.Fet Vgs 'off' voltage range is small, but Vgs for 'on' can be anything between 6volt and 12volt.I think it's therefore better to have the resistors between gate and source, and the transistor between gate and ground/12volt.Leo..
My Idea was to turn on the High side and apply PWM to the other to avoid that.
Ao you're saying i should rather do it like I drew it on O3 rather than how I drew it on Q4?