mikereidis wrote:I checked the hall sensor holes 2 days ago to confirm for myself it matches C1246 pinout:
A: goes to pins 1 and 4
B: to 3 and 6
C: to 2 and 5
So it appears to me it differs a bit from the schematic you show for 40a version. Instead of a voltage divider giving about 5 volts on negative side of comparators, these hall sensor lines seem to be setup in a differential mode. Perhaps this gives better EMF/noise immunity ? BTW, to hookup I used a few feet of cat5 network cable with 4 twisted pairs and each hall sensor pair is ground and sensor twisted.
Hall sensors need pullups ? If so, I'd think they'd be on the board. I will check.
If the immediate start version still has those BEMF sensing resistors, then I'd hope there was some way to disable them (or just disable their connection to C1246) without removing/destroying them. There MUST be a jumper somewhere or I won't be entirely happy. Would be nice, but not essential, if pedal first still worked if one or more of the hall sensors go bad.
Yes, halls need pullups.
I tried some random 1-5K resistors pulled up to +5v but didn't work. Interesting observation: once I fixed one bad hall connection solder joint (insulation in hole ! My eyes aren't so good no more), then the pedal first still worked with the halls connected, with or without pullups. So at least it doesn't interfere (but does if one hall line breaks ?).
This didn't give me instant start however. I still think that no matter the combination, the motor should do something, even if just a growl or a bang or two when throttle twisted. Spinning the wheel a little will give all 6 combinations of 3 halls and at least one or two of those should make some noise.
Is pedal first minimum start speed enforced by a minimum AC voltage produced by motor ? Or does something measure pulse frequency to set the min start speed ? I think, at least, I should be able to replace BEMF sensing with hall sensing and have a hall driven pedal first setup. (I'm assuming I can make the phase offsets correct.) Once I do that, I can look for what to mod to reduce the start speed (to 1 KMH say, real easy to do) or eliminate the need for prior rotation.
I traced the connections to those 6 BEMF sensing resistors. The tap between them connects directly to the hall sensor holes and the comparator pins on c1246. Pins 1 and 4 are both negatives, 3 and 6 are both positives and 2 and 5 are one of each.
Each top resistor (I measured 38Kohms) goes directly to motor lead. Each bottom resistor (13Kohms) goes to negative bus/ground. So it seems like a simple 25% voltage divider, although probably more complex than that since 3 phase AC comes in here, and it's relative to all 3 phases, and not really relative to the negative bus/ground.
I could use the top resistors as pullups, and cut traces or whatever to disconnect them from motor. But it would be REALLY nice if I didn't have to cut components or traces, and still leave BEMF sensing there as a full time non-interfering thing, or switch selectable.
So I'm off to read C1246 app notes and learn what I can to go farther.
EDIT: Dagnab it ! The notes are in Japanese only: http://www.necel.com/cgi-bin/nesdis/o00 ... le=UPC1246http://www.necel.com/nesdis/image/IEP-651.pdfhttp://www.necel.com/nesdis/image/IEP-653.pdf
Datasheet is available in English but I already have that. Anyone know of English app-notes for this chip or very similar chip ?