I am working on a BLDC sensorless motor. I need to detect BEMF Zero-cross event. My Motor is working on 24 Volt power.
Now I need to detect the back E.M.F. As refered in this application note.
My MCU is working on 5V. And ADC range is 0 to 5V. I need to convert the BEMF feedback signal to ADC channed in this.
As we know voltage divider rule says: Vo = (R2/R1+R2)Vin
In Figure I :-- Now signal (U) which I need to feed is applied at the middle of the two resistors R1 & R7. So what is the value of voltage VU ?
In Figure II :-- Sum of U,V,W is applied at the middle of the two resistors R11 & R15. So what is the value of voltage VN ?
Also, what are the roles of capacitors C1 & C4?
Please can someone explain the MATH behind this ?