measuring currents with the st7mc

[bigsmile]

Posted on December 20, 2004 at 06:49

measuring currents with the st7mc

[bigsmile]

Posted on May 17, 2011 at 10:18

hi

I'm using the st7mc to control a AC motor. I want to generate a closed loop vector orientated control. therefor i need to measure all the currents in the phases. does anyone of you know if the st7mc coprozessor is able to do that in ca mode? I want the coprozessor to do that, because I don't habe enough calculation time left to measure the currents by ADC. On the evaluation kit I'm using is a current sensing application. but this one is only sensing the total current of the motor. does anyone of you know if I can use this measure application together with the st7mc to calculate the three independent phase currents? thanks a lot for your help! bigsmile

[gaetano]

Posted on May 17, 2011 at 10:18

Hi bigsmile,

what you are trying to do (FOC) seems very hard to be realized in one 8-bit core based MCU with 2MIPS!! Moreover, you should have some peripherals to do that: at least one ADC with 2 sample and hold circuitry, plus the capability to perform your current samplings at the very beginning of PWM cycle, that means in centered pattern, when all the low side switches are closed; ST7MC doesn't know how to trigger on this such a kind of event. Based on these limitations, for me it should be hardly to implement a vectorial control on a ST7MC. Neverthless, if you have some ideas on mind let us know about them. In each case, the starter kit has only one resistor, as you said, and for sure, one needs 3 resistors to start with FOC. Best regards, Tanio