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Filters are a rather useful tool. They are frequently used in many applications. One such example is a problem which I have recently come across. From plans found on the internet I built an encoder-less encoder. What this device does is measure the inductive kick back of the dc motor to which it is applied. However, this motor is being powered with a pulse width modulated signal. And when the output of the encoder is viewed on the oscilloscope, it is clear that the carrier signal is being superimposed upon the signal from the inductive kickback of the motor. The solution to this problem, then, is to pass the signal through a low pass filter before it enters the encoder circuit. This would filter out the noise from the carrier frequency, and then allow the signal from the noise on the motor to pass through the encoder circuit thus allowing us to count the number of revolutions of the motor. Using the facilities at the McNaughton centre, the filter could be easily developed and tested. All that is needed to make the circuit would be some resistors and capacitors. Then the oscilloscope and function generator at the McNaughton centre can be used to make sure the filter is not letting any signals with a frequency which are greater than or equal to that of the carrier frequency, thus eliminating the noise from the circuit, and allowing us again to use the encoder circuit on our dc motor. |