#4 is key to simplicity. The ST method looks at the current profile (integrates current) for the energized coil. In the stalled condition, the period of EMF is less. It seems to me that just looking at the non-energized coil is simpler.
As a first approximation, though, I am just going to drive 600+ steps to ensure I am past the FS stop and then back off 300 full steps. The exact number will be determined by experiment. As Pommie noted, this is not for a run of >100,000 devices. And, as for Nigel's comment, these devices are considerably quieter than the old disk drives. I think driving to FS stop rather than to zero stop has more panache.
I took the day off for other things. Tomorrow will be a "go to Cleveland" day with mowing afterwards, if it doesn't rain. When I get back to it, I will look at how to implement the bridge arrangement using just the PIC. A smart chip with dual bridge and drivers combined for that level of current may still be the easiest way to go.
John
As a first approximation, though, I am just going to drive 600+ steps to ensure I am past the FS stop and then back off 300 full steps. The exact number will be determined by experiment. As Pommie noted, this is not for a run of >100,000 devices. And, as for Nigel's comment, these devices are considerably quieter than the old disk drives. I think driving to FS stop rather than to zero stop has more panache.
I took the day off for other things. Tomorrow will be a "go to Cleveland" day with mowing afterwards, if it doesn't rain. When I get back to it, I will look at how to implement the bridge arrangement using just the PIC. A smart chip with dual bridge and drivers combined for that level of current may still be the easiest way to go.
John