A system includes a motor circuit and a calibration test circuit configured to be coupled to the motor circuit to calculate a nominal motor constant representing operation of a motor in a nominal mode, calculate a motor impedance function comprising one or more motor impedance values at one or more motor frequencies, store one or more values of the impedance function in a memory of the motor circuit, and calculate a range of acceptable motor constant values based on the nominal motor constant. The motor circuit may be configured to calculate an operating motor constant value for the motor while operating, wherein the operating motor constant value is based on at least one of the stored values of the impedance function and compare the motor constant value to the range of acceptable motor constant values stored in the memory to detect if a motor stall has occurred.