Not Shocking People After Spring Break
1. Measure the resistance of the speaker.
We measured 8.6 Ohms, while online is says this model of speaker offers 32 Ohms.
2. Build the following circuit using a function generator setting the amplitude to 5V (0V offset). What happens when you change the frequency? (video)
Figure 1: Frequency of AC Voltage applied to a speaker.
Figure 2: Circuit Layout
Figure 3: Frequencies compared speaker output.
3. Add one resistor to the circuit in series with the speaker (first 47 Ω, then 820 Ω). Measure the voltage across the speaker. Briefly explain your observations.
Figure 4: Observations while placing resistors in parallel with speaker. The higher the resistor, the lower the amplitude. Therefore, the lower the volume.
4. Build the following circuit. Add a resistor in series to the speaker to have an equivalent resistance of 100 Ω. Note that this circuit is a high pass filter. Set the amplitude of the input signal to 8 V. Change the frequency from low to high to observe the speaker sound. You shouldnot hear anything at the beginning and start hearing the sound after a certain frequency. Use 22 nF for the capacitor.
Figure 5: Video explaining the operation of the high pass filter connected to the speaker.
b. & c.
Figure 6: V_out measured and V_out/V_in Calculated with respect to frequency increasing.
d. It looks like the cutoff frequency is 5000 with the voltage V_out capping off at 0.014V.
Figure 7: Plot of Frequency v. Output. The climax of the curve shows the critical frequency of the circuit.
f. The Cutoff Frequency according to our plot and theoretical calculations is 5000 Hz.
g. As the frequency increases, to a high 2000 Hz, the voltage amplitude takes on a significant enough value to be audible to human ears. However, when the frequency reaches 5000 Hz, the voltage reaches its cutoff point and begins to decrease.
5. Design the circuit in 4 to act as a low pass filter and show its operation. Where would you put the speaker? Repeat 4a-g using the new designed circuit.
We would place the speaker in parallel with a capacitor, the pair of which would be in series with a resistor.
Figure 8: Video explaining the operation of the low pass filter.
b. & c.
Figure 9:V_out measured and V_out/V_in Calculated with respect to frequency increasing in a low pass circuit.
d. The cutoff frequency is at 1000, capping off at .596 V.
Figure 10: Plot of Frequency v. Output of a low pass circuit. The climax of the curve shows the critical frequency of the circuit.
f. According to the plot, our cutoff frequency is at 1000.
g. The low pass filter works in a way where the capacitor works as an extremely high resistance to low frequency signals, making them pass to the speaker, whereas high frequency will pass through the capacitor, and not to the speaker, as can be seen above.
6. Construct the following circuit and test the speaker with headsets. Connect the amplifier output directly to the headphone jack (without the potentiometer). Load is the headphone jack in the schematic. “Speculate” the operation of the circuit with a video.
Figure 11: Video with speculation of the operation of the circuit.