sensored BLDC Motor input signal (help)

[etiquoe]

hi everyone...

I have a 3-phase BLDC motor (24 V) with its dedicated driver. but i wanna make my own driver for the motor. it is sensored bldc motor. I have read some application notes and other kind of sources about controlling sensored BLDC motor and i found that it is controled by 6 commutation steps. A fundamental BLDC motor (with 3 coils and 1 pair of poles) need 2 cycles of 6 commutation steps for 1 motor rotation. My BLDC motor has 12 coil, but i don't exactly know how many pairs its pole.
how can i know the number of pole?
with different number of coil and pole, does it need different number of cycle too?

i have checked the signal on the BLDC I/O pins when it's run by its original driver. its I/O pins contain Hall sensor feedback pins and phase pins.

here is the results:

**broken link removed**

this is signal on the 3 pins which is known as phase pins. it is 24 v pwm signal. i got this when i only measure the signal on the phase pins, without measuring the signal on the hall sensor pins at the same time.



**broken link removed**

and this is signal on the phase pin too, when it's measured at the same time with the hall sensor pins. 1-3 are phase pins signals (24V), and 6-8 are hall sensor pins signals (5V).


there's different result on the phase pins. could anyone explain?
which one of the signals is input signal to the motor?
it's confusing for me, because i assume that the motor input signal should be same as with what the application notes has explained: commutation signal. seems it doesn't match to the theory i have read from any sources.

i need to know the motor signal input to make my own driver, don't i ?

anyone can help ???


thanks



best regards

 

[MikeMl]

The three Hall signals are the feedback signals (just logic levels). Since each Hall sensor is high for 180degrees of rotation, and low for the other half, and the three sensors switch 120degrees apart, the three signals are decoded to six states, each lasting for 60 degrees of rotation.

The drive signals are dependent on the instantaneous value of the decoded Hall sensors.

 

[etiquoe]

so, to build new driver,
whether i have to consider the measuring results from the original driver as i mentioned above, or just follow the theory as you explained: signal input = the six state based on hall sensors order ?

seeing the measuring results is confusing to me because it doesn't match to the theory.
and i don't exactly know which one of the signal is the actual input signal to the motor.

 

[MikeMl]

If there are three leads to the stator winding A, B, and C (it matters not if they are connected wye or delta), there are six current paths A>B, A>C, B>C, B>A, C>A, C>B and back to A>B... It takes three half H-Bridges to steer the currents through the windings. There is a one-to-correspondence between the six decoded Hall sensor states and the six stator drive patterns... I'm ignoring PWM in this simplified description.

 

[MikeMl]

Read this data sheet.

Read this ap note

 

[etiquoe]

There is a one-to-correspondence between the six decoded Hall sensor states and the six stator drive patterns... I'm ignoring PWM in this simplified description.

is there certain pattern for all bldc motor? i mean, is it same for all bldc motor?
the same 'hall sensor states' will give the same 'six stator drive patterns' for all bldc motor?