Well, spent an hour messing tonight, i have no doubt it can be done, but its not going to happen by trial and error i think - too many variables and unless you know what effect each one has your'e just pissing in the wind Wink

Pretty certain now that steps/per and acceleration does nothing, this makes sense as we are on PWM so I think that can be taken out of the equation.

That just leaves Min PWM, base frequency, pulley min and pulley max.

Unless there is a setting on the VFD, i guess there might be, might be worth checking that 5v does give 50% speed.