Analog and Digital Filter for 100Hz Pulse Train

A 100Hz pulse train was filtered with an analog and digital filter to remove all but the first harmonic. The 100Hz pulse train was generated with the LM555 chip. The output was fed through a bias circuit on the LM324 Quad Op Amp chip to bring the voltages away from the rails. The analog filter, consisted of a 4th order Butterworth filter built from 2 Sallen-Key circuits. The analog filter’s input was filtered with a DSO-X-2024, a digital scope with sampling rate of 1kHz. A modified comb filter was designed in MATLAB to keep the first harmonic at 100Hz and remove the DC component and subsequent harmonics. The sampled data was run  through the digital filter to obtain the final results, a signal with all but the first harmonic attenuated.

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