Day 25 - Filters

Topics Discussed

On day 25 of the ENGR 44 course, we were introduced to filters and the different types of filters would could make in a circuit. Essentially, there are four types of filters one could create: High-Pass, Low-Pass, Band-Pass, and Band-Stop. (Fig. 1)

Fig. 1

Each type of filter has its own corresponding transfer function which can describe it. We did some practice finding bandwidth and the quality factor as well from the previous lecture. (Fig. 2)

Fig. 2

Passive RL Filter Lab

In lab, we created a passive RL filter. The circuit would act as either a low-pass or high-pass filter depending on whether or not the voltage is measured across the inductor or resistor. We calculated the specific cut-off frequency for this circuit. (Fig. 3)

Fig. 3

Once we found our cut-off frequency we proceed to actually build the circuit. (Fig. 4)

Fig. 4

We then proceed to analyze the voltage across the entire circuit and the voltage across the inductor and resitor at different frequencies. We tried frequencies ranging from 1/10 the cut-off frequency to 10 times the cut-off frequency. (Fig. 5)

Fig. 5

We then calculated the gain, phase shifts, and determined if the circuit behaved as intended. (Fig. 6)

Fig. 6

Summary

On the final day of lecture for the ENGR 44 class, we were able to successfully build a circuit that filter out high frequencies and low frequencies according to whether we were measuring across the inductor or capacitor. This premise is what allowed Tony and I to create a color organ for our final project, as the circuit intended to filter out different frequencies to play specific color lights for the bass, mids, and highs. The semester has been interesting, and the class has been a challenge and kind of rewarding in a sense. God bless America.