MATLAB

3/17 Thevenin's and Norton's Theorem

Here we try to simplify all the resistors as simple as possible.

We are introduced to Thevenin's Theorem where we treat the load resistor have an infinite resistance and remove it from the circuit. We then find the voltage where the load resistor would be as labeled in the bottom circuit and that gives us our Vth.

Using Thevenin's Theorem, we solve a different problem with a circuit where the load resistor varies in resistance. Rather than solving for Vth 3 times, we found it only for when the load resistor is at 36 ohms.

We are assigned a lab where we construct the circuit drawn above. Before we do that, we are asked to find the currents in the circuit using any method we have learned. We found that mesh analysis was easiest and found the currents using that method.

We check our answer using EveryCircuit and found that our calculated currents are accurate.

Here we measured the actual resistances of each resistor. On the left is the theoretical value of the resistor and on the right is the actual.

Here we setup the circuit for our lab and use our Analog Discovery to power the circuit to find the voltage drop across our load resistor.

We are given a new element to add to our circuit, a potentiometer. Rather than swapping resistors in and out of our breadboard, the potentiometer can change its resistivity based on how it is turned. 

We found the voltage across the potentiometer at various resistances and the power using the formula P = V^2/R

We graphed the power vs resistance from the data before and found that the graph is a root curve.

3/15 Super Position and Source Transformation

We start the day with a lab where we have two 10k ohm resistors and we are asked to find the potential drop between the resistors.

Here we have the graphs of the voltage going in and voltage going out. We have two graphs of sinusoidal, square, and triangle graphs, once with an amplitude of 2V and another with an amplitude of 1V.

We are introduced to the idea of superposition. This idea takes one independent source from a circuit and analyzes the currents and voltages associated with that independent source. Current sources are replaced with an open circuit and voltage sources are replaced with a wire.

Here we have a circuit where we have two different dependent sources, We used mesh analysis to find the different currents/ 

Using the idea of superposition, we are asked to find the current based on the voltage source and current source. 

We are given a more difficult superposition problem where we are asked to find the equivalent resistance and calculate the voltage and current from Req.

Here we are measuring the potential between one of the resistors.

We record the resistance of each resistor as measured from the multimeter and the voltage from each source.

Here we calculate our theoretical values for potential from the given resistance.

We are introduced to the idea of source transformation. This concept allows us to convert voltage sources to current sources and vice versa to make finding the equivalent resistance easier. 

3/10 Super Mesh

Here we are introduced to the idea of node voltage analysis. The super node we found was the current source which re removed to define the super mesh which we used to solve for the different currents.

We went over the benefits of using Node Analysis vs, Mesh Current Analysis

We use mesh analysis to find the i1, i2, and i3.

Here is the lab we did in class where we hooked up the Analog Discovery to power the circuit and measure potentials across resistors.

These are the values of the resistors that we used in our circuit.

We measured the actual resistance of the resistors using the multimeter. On the left is the circuit we setup for the experiment.

For channel 1, we made the voltage increase linearly in a step function. In channel 2, (not in the picture), the function we used was shaped like a pyramid starting from 0 and ending at the same place as channel 1.

After we measured the voltages, we plotted them in a XY plot and got this graph as a result. Our graph did not come out very accurate. The graph we were suppose to have gotten was something called a Gummel Plot which measures current going into the collector vs current coming out. 

3/8 Mesh Current Method

We are introduced to the idea of a supernode that exists when a voltage source exists between two nodes. We can say that the potential difference between the nodes surrounding the supernode is the same as the voltage from the supernode and makes it easier when calculating for the different currents in the circuit.

We are given a circuit problem with givens and asked to identify each current and voltage in the circuit by using the mesh current method.

From the same problem, we are told that each resistor can be increased and decreased by 10% and asked to find the different currents in the circuit when the resistors are +10% and -10%.

Rather than calculating by hand the different current values 3 different times from the equations, we plug in the equations and values into MATLAB to solve the system of equations.

Here we have a circuit where we use the mesh current method of finding the different currents in the circuit.

This is the circuit from before put into the breadboard.

We used a website called EveryCircuit and calculated the theoretical values of the circuit and found them to match our calculations.

Here we are given resistors and asked to determine its resistivity based on its color code.