Where is the Back-EMF on the STEVAL-ESC001V1 schematics ?

[GMich.4]

Hello,

I am trying to develop my own sensorless motor control using the STEVAL-ESC001V1 Board. The motor used is a 6 poles BLDC motor. I have successfully been able to run the motor in open loop and it’s running well.

In order to have feedback and estimate the rotor position, I want to measure back-EMF voltages, however I can’t really tell where is the back-EMF voltage. 

I have measured the (curr_fdbk1, curr_fdbk2, curr_fdbk3) and (PHASE_1, PHASE_2, PHASE_3) pins and both of them almost have the same output which is the current feedback. I find this weird because, from my understanding the PHASE_x pins should be the back-EMF voltages.

So my question is: from the schematics of the board, which point should be measured in order to have the 3 Back-EMF voltages on the oscilloscope?

Attached are the adc measurements of the curr_x pins using ADC in open loop as well as screenshots from the relative schematic parts. Attached is also the schematics pdf of the STEVAL-ESC001V1 board.

Thanks in Advance !

Regards,

George

[mimho]

Hello @GMich.4 

I think the PHASE.x pins are fed to the MCU because we have a resistive divider before it, so they must be the three phase voltages of the motor being scaled-down.

If you want to observe the real phase voltages of the motor you should connect the probes to the OUT.x pins.

Regards.