Hello,
I am trying to build my own ESC (Brushless DC controller) and I managed to get the motor running starting from a ramp to a steady PWM duty Cycle and Commutation period and these are the BEMF waveforms that I see. My question is, where is the "zero crossing event" and why is it different (somehow inverted) from the regular BEMF waveforms displayed on various application notes? Kindly refer the waveform images below.
http://static.rcgroups.net/forums/attachments/3/6/9/4/5/8/a4175768-10-NewFile0.jpg
http://static.rcgroups.net/forums/attachments/3/6/9/4/5/8/a4175769-43-NewFile1.jpg
Here-in, it is almost impossible to detect '0' crossing. Also, in my scheme I am PWMing the upper MOSFETS, with the lower ones being used/made high during relevant commutations.
I am trying to build my own ESC (Brushless DC controller) and I managed to get the motor running starting from a ramp to a steady PWM duty Cycle and Commutation period and these are the BEMF waveforms that I see. My question is, where is the "zero crossing event" and why is it different (somehow inverted) from the regular BEMF waveforms displayed on various application notes? Kindly refer the waveform images below.
http://static.rcgroups.net/forums/attachments/3/6/9/4/5/8/a4175768-10-NewFile0.jpg
http://static.rcgroups.net/forums/attachments/3/6/9/4/5/8/a4175769-43-NewFile1.jpg
Here-in, it is almost impossible to detect '0' crossing. Also, in my scheme I am PWMing the upper MOSFETS, with the lower ones being used/made high during relevant commutations.
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