after riding a zero-s (thanks again luke for that memorable night ride) i decided dogati NEEDS to go sensored. so..i picked up one of these capacitive commutation encoders: http://www.cui.com/product/components/e ... r/amt303-v
for a quick drop in solution. here are the steps i took to make it work (btw, these things are pretty tiny):
1. chucked the 3220 rotor onto my hobby lathe
2. drilled and tapped an M4 thread in the shaft (rear)
3. used a countersunk M4 screw to attach the encoder (the countersink helps secure the plastic encoder bushing firmly to the shaft axially and radially)
4. used some hot glue to temporarily secure the encoder housing.
5. connected the encoder to the programming board and set: direction (CCW), output (QAQB), resolution (1024), # poles (8) and left the commutation offset at 0.
this board has a nifty auto-zero function that gets stored into eeprom so you don't need to fiddle around with the alignment. however this only works if you know the correct commutation offset (for wye, offset is 0). i wasn't sure what the offset should be for my delta winded 3220 so i still had to adjust the encoder. running sensorless it draws 1.5A at WOT so i turned the encoder until it matched that. hooked it up to my kelly kbs controller and..the start-up is as smooth as margerine, niiiice
one thing to be aware of, you need to short GND_C with GND (pins 14 and 4) when hooking up to your motor to put it into normal operating mode (vs spi comm mode). it's written in really small print on the manual and easy to miss (this had me puzzled for a few hours).
so there you have it, a sensored 3220 for $35 bucks from digikey (http://www.digikey.com/product-detail/e ... 47?cur=USD
) and about 40 mins to set it up.
chucked back up onto the lathe to check commutation signals against BEMF on the scope. lookin good [thumbs up]