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Forum Post: RE: Real current feedback requirements - Hall sensors

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Thank you, Jorge.

I added the DC bus sensor - as I mentioned before, my system does not contain DC bus measurement. Well, now it does.

Using your calculations, I confirm that voltage offsets corresponds to the Vbus. Now I'm using voltages 20-30V , and all offsets scale accordingly. I had no idea it is centered like that! Being named as offsets, I suspected them to be an ADC offset with transistors grounded. That cost me quite some time, trying to figure out why my system is not measuring near-zero offset values. Now when you say that those are offsets related to the Vbus, it makes sense.


I fixed my user.h file to be more close to the reality (IQ scaling)

Yes, inverter has 50% duty cycle during offset calc.

Now my problem is definitely in the current sensing. I would like to ask you for a definite guide to the current polarity and offsets. Just say which direction should be sensor mounted to keep the default (inverting) behavior, meaning:

bias += OFFSET_getOffset(obj->offsetHandle_I[cnt]);

....

  pAdcData->I.value[0] = value;


PS: Could there ever be a situation in which bias sign is "-" and value sign "+" ?

While randomly changing the current feedback polarity, I either get Rs in very small numbers (>0.0001Ohm even with motor disconected), or very high currents and Rs in kOhms. My current sensors are working well, tested by other instruments.


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