u/avenger524

https://preview.redd.it/51h1ddx5sh2h1.png?width=1513&format=png&auto=webp&s=89951d30266b3ed7455ed77fe6a30e6aa8adc514

I am using the STM X Nucleo IHM07 board i attached in the image. I am using trapezoidal driving of my bldc (1 phase floating, one gnd, onw pwm). I am sampling on a floating phase. The sampling happens in the middle of PWM HIGH (center aligned PWM). However my signal looks very bad. Its oscillating between 0 or max. So i was wondering if my sample timing is good. The circuit i attached is from the manual and shows what goes on back EMF pin im using for sampling. I don't really understand this circuit so i put it here hoping someone can explain. Does it make difference if i sample on PWM H or L? Again im sampling floating phase.

https://preview.redd.it/2cu6ubpash2h1.jpg?width=640&format=pjpg&auto=webp&s=c242121205c08a886bea4444f0984c73928e3fb4

I am trying to use this board with STM32 Nucleo F446RE to run BLDC with trapezoidal, step by step commutation. The commutation should be based on back emf measurement of the floating phase. However i am struggling to get a meaningful measurement. My pwm is center aligned and ADC sampling happens exactly on middle of PWM HIGH time, but it happens on floating phase. Is this how i am supposed to do it with this board? Or i should sample on PWM Low? I measure big oscillations even when motor is in place and the signal is unusable.

https://preview.redd.it/6r23olhk8h2h1.jpg?width=640&format=pjpg&auto=webp&s=cb1de4a6e5944295fca46c38422d9731fe4a66ea

https://preview.redd.it/712oa6cp7h2h1.jpg?width=640&format=pjpg&auto=webp&s=b4feee183b9fb64f2b234ccb6051094741881edc

I am trying to use this board with STM32 Nucleo F446RE to run BLDC with trapezoidal, step by step commutation. The commutation should be based on back emf measurement of the floating phase. However i am struggling to get a meaningful measurement. My pwm is center aligned and ADC sampling happens exactly on middle of PWM HIGH time, but it happens on floating phase. Is this how i am supposed to do it with this board? Or i should sample on PWM Low? I measure big oscillations even when motor is in place and the signal is unusable.

https://preview.redd.it/vesw6w6dxb2h1.jpg?width=1000&format=pjpg&auto=webp&s=1db00139685361b7ac0ac1ed5b7dd804734a6471

https://preview.redd.it/mbik85ghxb2h1.png?width=1167&format=png&auto=webp&s=3c1e15432281caffa5fcd26963affb38e6e689ef

I've been writing driver for this BLDC from the image. I am measuring mechanical angle with encoder and converting it to electrical angle. To test my setup i commanded my motor commutation steps, one by one with delay. And I am surprised to see that one step on this motor is not 60 electrical angle. As you can see on the other image its variable, one step is sometimes ~20 deg sometimes ~80. Is this normal? I don't think it is, I would expect 60 degrees eletrical angle.

Has anyone ever done BLDC commutation based on back EMF using IHM07 driver board from STM? I sample adc on middle of center aligned PWM but signal is very bad and I can not get a meaningful reading. If you have done this, write a comment and I will send you a message

Has anyone ever done BLDC commutation based on back EMF using IHM07 driver board from STM? I sample adc on middle of center aligned PWM but signal is very bad and I can not get a meaningful reading. If you have done this, write a comment and I will send you a message

I tried to plot on trace a 20kHz signal. It seems it is too fast for trace and what happens is that trace goes crazy and starts ahowing millions. Is it possible to set up trace to plot 20kHz signal? I tried to increase memory of trace but didnt help