BLDC Back EMF Integration #2

In a previous article i was suprised by difference in BEMF signals, now i’ve got new PCB, reworked code, and made some investigationDSC_0433.JPG

I have connected hall sensors to the controller as a source of independent “threshold” signal to switch phases, and in this moment controller stores integration values. First i run both BEMF sensed as 1:1 duting top fet ON, and OFF:pwm hi-low.PNG
Red – integration value when switch OFF, blue – switch ON
I count the total average number for red as 0-7000, blue 7000-10000. This got me a difference as red:blue 2:3. About integration hit for blue at low erpm, it is too high, when im apply load these limit changes (for same erpm). Seems like it is coupled with duty cycle. Now test with 2/3 constant for switch ON applied:
pwm hi-low calibrated.PNG

Now much better! Switching from off-time integration to on-time will happen in range of 75-85% duty cycle. Everything said here refers to my motor. I need to run same test to other bldc’s


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