Prelab Part 1 Please follow all rules, procedures and report requirements as described at the beginning of the document entitled ECE 220 Laboratory 1. Always wear your safety glasses when performing your lab experiments. This part and the next part reinforce the circuit analysis techniques that we have learned in class. V1 Use mesh analysis to solve the circuit shown below in Figure 1. For the purpose of your analysis, assume that the LED is forward biased (turned on). As before, we will approximate its behavior by a constant voltage drop of 2.1 V. Hint: only two equations and two unknowns are required. a) Calculate i₁, I2, I3, V₁, V2, and 13. 12.5 mA( LED ECE 220 Laboratory 2 Mesh and Node Analysis, AC Sources, and d'Arsonval Meters KH T 470 Ω V2 47 Ω Michael W. Marcellin 100 Ω V3 i[1002 [>100 2 Figure 1. Solve using mesh analysis. We will now verify your calculations using PSpice. Start PSpice and create a new project as you did for the PSpice homework and Lab 1. Draw the circuit from Figure 1, as shown below in Figure 2. Again, we use three D1N4002 diodes in place of the LED. Note that the bottom node in Figure 1 has been labeled as the reference node (0 V). As discussed in the PSpice homework and in class, any essential node can be chosen as the reference node. The PSpice ground should be thought of as the reference node. This can be seen via a comparison of Figures 1 and 2. D1 D2 D3 11 D1N4002 D1N4002 D1N4002 + 12.5mAdc R1 ww 470 www R3 100 R5 ww 47 R2 ww 100 Figure 2. PSpice schematic. www Click PSpice -> New Simulation Profile Enter a name for this profile Click Create R4 We will use PSpice to find the DC voltages and currents in the circuit, as we did in the PSpice homework. Prelab Part 2 100 A new window will open. You might have to look at the icons at the bottom of the screen to find it. In the drop down menu entitled Analysis type:, choose Bias Point This tells PSpice that we are going to compute the static DC values of voltages and currents in the circuit. Check the box below the drop down menu that says "Save Bias Point." Click "OK" Click PSpice -> Run A new window will open. You may need to look at the icons on the bottom of the screen to find it. If there are no errors, you may close this window and return to your schematic. Near the top of the screen there are 2 green buttons, labeled V and I, respectively. Use these buttons to view the currents and voltages in your circuits. The values should be slightly different than your calculated values. b) Print a copy of your schematic with the voltage labels turned on (File -> Print). c) Print a copy of your schematic with the current labels turned on (File -> Print). d) Why do the PSpice values differ (slightly) from your calculations? Use node analysis to solve the circuit shown below in Figure 3. Hints: 1) Again, only two equations and two unknowns are required. 2) Recognize that 2sin(200ât) = 2cos(200ât — ñ/2) and use complex phasor analysis. a) Calculate i₁(t), i₂(t), i3(t), v₁ (t), v₂(t), and v3(t). v=2sin (200πt) V VOFF = 0 VAMPL = 2 FREQ=100 AC = V1 V1 द् 1.5 ΚΩ V2 R1 ww 1.5k 470 Ω 1 ΚΩ ia|é1.5 ka Figure 3. Solve using node analysis. Again, we will verify your calculations using PSpice. Start a new PSpice project as you have done before, and draw the circuit of Figure 3. The PSpice part name for the sinusoidal voltage source is VSIN. Set VAMPL=2, and FREQ=100, which is consistent with the sin in Figure 3. In that figure the angular frequency w = 200π radians/second. You must input the frequency to PSpice in Hz. Since w= 2πf, we have f = 100 Hz. VOFF is an optional DC offset. Set this to 0. Add voltage markers (PSpice -> Markers -> Voltage Level) at each of the three nodes of interest, as shown in Figure 4 below. PSpice -> New Simulation Profile Enter a name for this profile Click Create R3 ww 470 V3 ia|ફૅ2.2 ka R4 1.5k R2 1k ww R5 2.2k Figure 4. PSpice schematic. We will use PSpice to plot v₁ (t), v₂(t), and v3(t). We have not done this type of analysis in PSpice before. Click A new window will open. You might have to look at the icons at the bottom of the screen to find it. In the drop down menu entitled Analysis type:, choose Time Domain (Transient) This tells PSpice that we are going to create a time domain plot of the values associated with the markers in the circuit. Enter the following parameters: Run to time: 25m Maximum step size: 0.1m Click "OK" This tells PSpice we want to create 25 miliseconds worth of data for our graph, with data points no more than 0.1 miliseconds apart. Click PSpice -> Run A new window will open. You may need to look at the icons on the bottom of the screen to find it. This window should contain a time plot (of duration 25 ms) showing the three voltages associated with the markers. These plots should agree with your calculations in a) above. b) Print the plot. Prelab Part 3 In class, we learned how to make a simple (but not very good) voltage meter using a d'Arsonval meter movement. The circuit diagram for such a meter is shown below in Figure 5. This meter includes (of course) a d'Arsonval meter movement and a resistor. The purpose of the resistor is to limit the current through the meter movement. The meter movements that we have in the lab have a maximum current of imax = 1 mA. The internal resistance of the meter movements is Ra 155 . You are to design a volt meter that gives full scale reading (100% deflection of the meter needle) at 5 V. a) Calculate the required value for RA. = RA Figure 5. Voltage meter. The amount of deflection of the meter needle will now indicate the voltage being measured. Since we have designed for full (100%) deflection at 5 V, 25% deflection indicates 1.25 V, 50% deflection indicates 2.5 V, etc. It is worth noting that the current flow is actually what causes the needle deflection. Since imax 1 mA, 0.25 mA will cause 25% deflection, 0.50 mA will cause 50% deflection, etc. = We will now verify the operation of your meter design using PSpice. We will "connect" your meter to a voltage source. We will then sweep the value of the voltage source from 0 to 5 V and see that the current through the meter movement varies linearly from 0 to 1 mA. Create a new project in PSpice and draw the circuit shown in Figure 6 below. We model the meter movement as a resistor with value Rd. 3 {M} V1 Put the value you RA calculated for R here. Figure 6. Meter simulation. Rd www PARAMETERS: V = 5.0 155 We will now sweep the voltage source using a variable V. This is very similar to when we did a sweep of the pot value in Lab 1. If you have not already done so, place the "Part" PARAM, which appears as PARAMETERS in Figure 6. Double click on PARAMETERS to open the Property Editor Spreadsheet. Click the "New Property" button in the upper left portion of the screen. A new screen will open. Enter V in the field labeled Name:. Below that enter 5.0 for Value:. Click "OK" Click on the V Heading (that we just created) in the Property Editor Spreadsheet. You may need to scroll to the right or left to find this heading. Now click the button above labeled "Display..." A new window will open. Click the button for Name and Value and click "OK" Return to the schematic by clicking the tab marked "PAGE1" Below the PARAMETERS part, you should now see V=5.0 as in Figure 6. We now need to associate our parameter V with the voltage source. Double click carefully on the value of the voltage source (probably OVdc). A window will open. Replace the value OVdc with {V} Don't forget the {} braces. Click OK. On the circuit symbol for the voltage source, you should now see {V} as in Figure 6. Here we will specify the parameters to "sweep" the value of V from 0 to 5 in steps of 0.1. Click PSpice -> New Simulation Profile Enter a name for this profile Click Create A new window will open. You might have to look at the icons at the bottom of the screen to find it. In the drop down menu entitled Analysis type:, choose DC Sweep. Enter the following parameters: Sweep Variable: Global parameter