Circuits
Circuits are the an integral part of human life in this day and age. Radios, televisions, phones, computers, etc., are complex circuits. However, they are based on simple physical principles. That is the purpose of this lab, to teach you the basic principles behind circuits. We will also introduce how to use your Arduino and computer as a virtual oscilloscope.
- Lab 3A: RC Circuits
- Lab 3B: RLC Circuits
Physics Background
To review physics laws on mechanics, please check out OpenStax texbook. Here are important Chapters:Please also refer to Wikipedia:
Lab 3A/B: Arduino Oscilloscope and RC Circuits
We are going to start with a simple RC circuit. We will see a capacitor charge and discharge using this circuit. The timing of the charging is referred to as the RC time constant.
In many circuits, a time varying current is present. We observe oscillations in the voltage of these circuits when an inductor is introduced. Since all circuits have some form of resistance and capacitance, it is important to understand the fundamentals of RLC circuits. In this lab we will examine the most basic RLC circuits.
In many circuits, a time varying current is present. We observe oscillations in the voltage of these circuits when an inductor is introduced. Since all circuits have some form of resistance and capacitance, it is important to understand the fundamentals of RLC circuits. In this lab we will examine the most basic RLC circuits.
Our study of circuits begins with RC circuits and the measurement of the RC time constant, τ. This time constant is the amount of time required for the capacitor in the RC circuit to charge up to ~63% and conversely, discharge to ~37%. The analytical solution for this circuit is simply and exponential. Furthermore, when an inductor is introduced, the RC circuit begins to resonate with the inductor introducing a sinusoidal function. Complete the following pre-lab to gain an understanding on how to fit functions to complex data-sets like damped oscillations.
Lab 3C/D: RLC Circuits, Damped Oscillations and RC Filtering
Now that we have studied RC circuits, we will continue to the study of RLC circuits. We will examine the concept of resonance by applying a range of frequencies to our RLC circuit. When a system is on resonance, the amplitude of the oscillations will increase drastically. In mechanical systems this amplitude increase can be very destructive, with a common example shown being the collapse of the Tacoma Narrows Bridge due to the wind. In a much less frightening way, this lab will look for the resonance by sweeping over the frequencies applied to an RLC circuit.
When an inductor (L) is added in series to the RC circuit a phenomena known as oscillation begins to occurs. The reason is because the capacitor and the inductor are out of phase in their voltages, therefore they begin to oscillate when supplied with a step function voltage, better known as "ringing."
For 3C, you will study how to create RLC circuits and supply a square wave or step voltage to create this oscillation. In addition, you will determine what effect a resistor has on this oscillation.
In addition, for 3D, you will take a step back and enjoy the application of RC circuits. You will create a filtering device that will smooth out the pseudo analog voltage produced by your Arduino. This voltage modulation is known as pulse modulation by which the electronic device you power (for example an LED or motor) thinks that is receiving a constant DC voltage when in fact it is now. Instead, the Arduino is rapidly turning off and on in digital fashion, however, ratio of how long its on vs off is the pulse width which mimics the voltage. In order to create a TRUE DC signal, you will filter out the higher frequency components of the pulse with an RC circuit.
When an inductor (L) is added in series to the RC circuit a phenomena known as oscillation begins to occurs. The reason is because the capacitor and the inductor are out of phase in their voltages, therefore they begin to oscillate when supplied with a step function voltage, better known as "ringing."
For 3C, you will study how to create RLC circuits and supply a square wave or step voltage to create this oscillation. In addition, you will determine what effect a resistor has on this oscillation.
In addition, for 3D, you will take a step back and enjoy the application of RC circuits. You will create a filtering device that will smooth out the pseudo analog voltage produced by your Arduino. This voltage modulation is known as pulse modulation by which the electronic device you power (for example an LED or motor) thinks that is receiving a constant DC voltage when in fact it is now. Instead, the Arduino is rapidly turning off and on in digital fashion, however, ratio of how long its on vs off is the pulse width which mimics the voltage. In order to create a TRUE DC signal, you will filter out the higher frequency components of the pulse with an RC circuit.