摘要 |
<p>A microcontroller 4 provides the driving current to the windings of an electrical motor. The motor current is taken as one input 9 to a comparator 8 whose threshold input 10 is derived from a voltage divider circuit 11,12. In the event of an over-current condition the driving current to the windings in interrupted. Alternatively the threshold input may be a variable determined by the output of a low pass filter 14,15 which takes a variable frequency waveform as its input. The waveform is controlled by the microcontroller by output 16.</p> |