Hi, Please suggest me a method of testing the phase currents without running the actual motor. There is hardware based offset voltage using resistors, which i can read when connected and it corresponds to x volts = 0Amps, but i want to confirm that adc reading of phase currents is correct before i actually run the motor. Is there a method? Please advise.
Why not just connect three through-hole resistors in a wye, with value similar to your winding resistance?
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You would want some inductors too because they smooth the current out. Without them the current reading could end up all over the map as the high frequency of the pwm will be applied.
They would have to be large resistors though (in terms of power dissipation capability). The motor is the biggest resistor your are going to get and has the inductor built in already. I just used a current limited power supply and set the voltage way down at the power supply, in the code in two different places, to prevent disasters. As long as things don’t overheat you can take your time observing.
I was also cautious and it is a good idea, monitor the motor closely on first turn on with your finger on the power switch for sure. I probably would have added some resistors in series with the motor however I didn’t have any with suitable power rating and that would probably be overkill.
As for actually measuring the current, well I had good success with the IN169 current sensor from adafruit, don’t try to buy an IN216 unless you can get direct from adafruit or digikey etc., they are all counterfeit trash that doesn’t work with the drivers available.
Or, ideally, an actual proper current probe for an oscillosope.
At higher frequencies AC you could use a current transformer, they do sell small ones.