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Old 11-27-2009, 12:35 PM   #2636 (permalink)
MPaulHolmes
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Interesting, Jack! So, the LEM output goes to the comparator. You would just connect the LEM output to the output of the frequency to voltage converter. What is the affect of having 2 different voltages tied to the same point? (LM393 pin 2) I guess it would cause current to flow into the LEMs output if the LEM output was at a lower voltage than the LM2917 output, and vice versa. What does the LM393 pin 2 see if you give it 2 separate voltages. Is it the average of the 2, or how the heck does that work?! I've never thought of that before! But if you do that, you might need to increase the time that the hardware shuts off the mosfet driver. Right now it's for about 1/4000 of a second. Maybe increased to a whole second?

Hey! Alternatively (not recommended), you could just cut the line from the current sensor to the LM393 right near the LM393 pin 2. Then just have the lm2917 go into that input. The hardware overcurrent doesn't ever come on after the PI loop is tuned to the motor.
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