Hi, I have just learned about phasor and laplace analysis of RLC circuits in my engineering course.

I am trying to use my knowledge to build an RLC oscillator in real life, and create a signal that will produce an electronic sound. I understand how an oscillator works. The resulting signal is something like A*cos(ωt+σ)e^-t

The ω tells you what the frequency will be of your decaying cosine.

I also understand that the smaller the capacitance and inductance of the capacitor and inductor, the larger the frequency ω will be, because it will take less time for the capacitor to charge and the inductor to build up a magnetic field. The larger the resistance, the bigger the damping is and the signal will die out faster.

Knowing all these things I began to search for components. I have many types of capacitors, but I went to radio shack to get an inductor. The best they had is a 100μH inductor. So I built my circuit on a breadboard.

The following circuit.

So then I closed the switch. Watched the voltage of the capacitor grow to 6 volts with my multimeter. Opened the switch and watched the voltage of the capacitor decrease. As soon as that happened, I would expect the inductor to recharge the capacitor and the oscillations to begin, but I didn't see the voltage of the capacitor increase again.

So I think whats wrong is, the inductor is so tiny that its mag field was built in microseconds, too fast for me to notice or even for the meter to pick up. Is this the reason? If not what else is wrong.

Another question.

Obviously I will need to amplify my signal with a BJT before I can input it into a speaker and hear the sound. Why is that? Why will the signal be so weak? I mean how strong does a current or voltage need to be for the sound to be loud enough? It probably depends on the resistance of the speaker somewhat.

Thank you.

I am trying to use my knowledge to build an RLC oscillator in real life, and create a signal that will produce an electronic sound. I understand how an oscillator works. The resulting signal is something like A*cos(ωt+σ)e^-t

The ω tells you what the frequency will be of your decaying cosine.

I also understand that the smaller the capacitance and inductance of the capacitor and inductor, the larger the frequency ω will be, because it will take less time for the capacitor to charge and the inductor to build up a magnetic field. The larger the resistance, the bigger the damping is and the signal will die out faster.

Knowing all these things I began to search for components. I have many types of capacitors, but I went to radio shack to get an inductor. The best they had is a 100μH inductor. So I built my circuit on a breadboard.

The following circuit.

So then I closed the switch. Watched the voltage of the capacitor grow to 6 volts with my multimeter. Opened the switch and watched the voltage of the capacitor decrease. As soon as that happened, I would expect the inductor to recharge the capacitor and the oscillations to begin, but I didn't see the voltage of the capacitor increase again.

So I think whats wrong is, the inductor is so tiny that its mag field was built in microseconds, too fast for me to notice or even for the meter to pick up. Is this the reason? If not what else is wrong.

Another question.

Obviously I will need to amplify my signal with a BJT before I can input it into a speaker and hear the sound. Why is that? Why will the signal be so weak? I mean how strong does a current or voltage need to be for the sound to be loud enough? It probably depends on the resistance of the speaker somewhat.

Thank you.

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