On-Line Companion: Pspice Using Schematics

On-Line Companion: PSpice Using Schematics

As you now know, to analyze a problem using PSpice, you must first create its circuit on your screen, a process referred to as “schematic capture”. The purpose of this web site is to show you how to use the PSPice Schematics editor for this task (see Background Notes).

Index

Section I: A Short Overview of Schematics

Section II: Worked Out PSPice Examples Using Schematics

·  Chapter 4

·  Chapter 5

·  Chapter 6

·  Chapter 7

·  Chapter 8

·  Chapter 9

·  Chapter 11

·  Chapter 14

·  Chapter 15

·  Chapter 16

·  Chapter 17

·  Chapter 18

·  Chapter 19

·  Chapter 20

·  Chapter 21

·  Chapter 22

·  Chapter 23

·  Chapter 24 (Vol 1)

·  Chapter 25 (Vol 2)

·  Chapter 26 (Vol 2)

·  Chapter 27 (Vol 2)

·  Chapter 28 (Vol 2)

·  Chapter 29 (Vol 2)

·  Chapter 30 (Vol 2)

Section I: A Short Overview of Schematics

Section I is for reference. If you are new to PSpice, you should browse through it for general information before you try the examples of Section II. (Because it is a reference document, you may find things that you have not yet covered. For example, if you are reading this while studying dc, you will not understand the comments regarding ac, etc. Just ignore these and return to them later when you get to that part of your course.). In what follows, we assume that you have PSpice loaded on your computer with the Schematics icon on your screen. (If you do not have the icon on your screen, click Start, select Programs, PSpice Student then Schematics.) To analyze a circuit, use the following general procedure:

1.  Click the Schematics icon on your screen. This opens the PSpice editor, Figure I-1.

2.  Create the circuit on your screen.

3.  Save your work to an appropriately named file – see box.

4.  Specify the type of analysis that you wish to perform

5.  Set up the analysis parameters, perform the analysis, then view the results

There are generally several ways to do many things. The approaches shown below will get you started.

The Schematics Screen

When you click the Schematics icon, a screen similar to that shown in Figure I-1 should open.

Note the menu items and icons. To familiarize yourself with these, place your mouse pointer over each in turn. As you do, a text box opens to tell you what the selected item’s function is. After you have familiarized yourself with these, review the PSpice information in Appendix A of the text, starting at the section entitled “Some Key Points for PSpice Users”.

Other Things to Note

Mouse Buttons: Use the left mouse button for all operations unless directed otherwise.

Keyboard entries: Frequently, you are instructed to type values into dialog boxes. In the examples that follow, these are shown in bold face. Thus, 25V indicates a value that you type in via the keyboard.

Get and Place a Part: To get and place a new part, click the Get New Part button and when the Parts Browser dialog box opens, select the desired part (source, resistor, capacitor, etc). You can do this by clicking on the item in the parts list, (or you can type in its abbreviation, R for resistor, C for capacitor, etc.), then click Place or Place & Close (or press the Enter key). Position the component as desired on the window, then click the left button. If you wish to place more than one instance of the component, repeat for each placement. When done, click the right button to end placement of that component.

Get Recent Part Bin: PSpice keeps track of the most recent parts used and lists them in the Get Recent Part bin. You can save time by selecting items from this bin. Simply double click the item then place as described above.

Meter Elements IPRINT, VPRINT1 and VPRINT2: These are general purpose metering components that you can use to measure voltage and current. To determine their readings, you must examine the output file. (Click Analysis, Examine Output, then scroll until you find them.) Note that IPRINT and VPRINT1 have a terminal marked with a - sign that corresponds to the COM terminal on a real physical meter. You must wire them into your circuit as you would a real meter, taking into account where you want the COM terminal. In addition, you must configure them for the type of measurement (dc or ac) that you wish to make. This is described in the examples that follow.

Netlists: When PSpice creates a circuit description from your schematic, it numbers nodes and for each component, lists the nodes to which it is connected as well as the value of the component. (For example, Node 1 is designated $N001, node 2 as $N002, etc.) These designations do not appear on your schematic screen but instead they reside in a file as a “netlist”. (To view, click Analysis, then Examine Netlist.) In the netlist, the “1” end of a component is connected to the first indicated node.) The netlist can serve as a useful troubleshooting aid; if PSpice displays an error message after simulation and you need more information, click Analysis, Examine Output then check for error details.)

Section II: Worked Out PSpice Examples Using Schematics

For the most part, Schematics screen displays are similar to those created by Capture and thus (except for the first few examples), we will rely on the photos in the book. For the instructions that follow, icons and menu items referred to may be identified by reference to the user interface screen of Figure I-1 shown earlier (Section I).

Chapter 4 Ohm’s Law

PSpice provides two methods for solving dc problems, the bias point method and the DC Sweep method. We illustrate both. Since this is our first look at computer simulation, we include considerable detail.

First Example (Bias Point Analysis)

Determine current for the circuit of Figure 4-27 of the book using the bias point method. Procedure: Click the Schematics icon to call up PSpice and get the opening screen on your computer. Now construct the circuit of Figure 4-29 of the text (also shown in Figure I-1 of these notes) as follows:

·  Click the Get New Part button and in the browser Part Name window, type vdc to select the dc source, then press the Enter key on your keyboard. (You can also click its name on the browser scroll list.) Alternately, if the source is already in the Recent Parts bin, you can get it from there by clicking it in the drop-down box.

·  Move the mouse pointer into the drawing area and position the source where you want it. Click the left mouse button to place, then click the right mouse button to end placement. (The battery has a default voltage of 0V. We will change it shortly.)

·  To get the resistor, repeat the first step above except type R in the Part Name window.

·  Rotate the resistor three times to provide for correct node assignments – see box, Note 1. Position the resistor where desired, click the left mouse button to place it, then click the right mouse button to end placement.

·  To get the ground symbol, repeat the first step except type egnd. A ground symbol appears. Position it on the screen with a left click then click right.

·  To wire the circuit, click the Draw Wire button. A pencil appears. Position it at the end of the lead protruding from the top of the battery, click left to start placement, then drag the pencil to the end of the lead at the top of the resistor. As you drag, a dashed line follows. Click left when you reach the resistor lead. This places the wire. (To help control routing, you can click the left button to freeze the wire in place as you drag it, as for example when you want to turn a corner.) Similarly, place a wire between the bottom of the source and the ground, then place a wire from the bottom end of the resistor to the wire just placed. (You should now have the circuit of Figure I-1.) Click right button to end placement.

·  If you want to reposition a component or wire to improve the layout of your circuit, select the component as in Operational Note 2, drag it to its new location then release the button. Repeat for any other items that need moved.

·  The battery default voltage is 0V. To change it, double click its voltage value. (Make sure you double click 0V, not the battery symbol.) A Set Attribute Value dialog box opens. Type 25V then press Enter or click OK. (The unit V can be omitted if desired. If you include the symbol V, do not leave a space. Thus, 25 V is unacceptable.) Repeat the process and set the resistor to 12.5ohm.

·  Click the Save button and save your work under an appropriate file name such as figure 4-29 in an appropriate file folder. (See Note 11 on page 105 of the text.)

·  Now run the simulation. To do this, click the Simulate button. After a short execution time, an inactive Output window may open. If so, close it.

·  On the menu bar, click the Enable Bias Current Display button. Computed currents are displayed as in Figure 4-29 of the text. Now click the Enable Bias Voltage Display button and circuit voltages will appear.

·  To exit from PSpice, click the ´ in the upper right hand corner of the screen and click yes to save changes (if asked).

Second Example (DC Sweep Analysis)

You can also solve the problem of Figure 4-27 using the DC Sweep method. First, call up PSpice to get the opening screen, then build the circuit as in Figure 4-30 of the text. (IPRINT is a general-purpose ammeter that you get by clicking Get New Part. Type IPRINT and place as indicated.)

·  You need to configure IPRINT for dc operation. Double click its symbol and a dialog box opens. Double click DC = and in the Value box type yes, click Save Attr, then click OK. The box closes. The meter has now been set for dc operation.

·  Click Setup Analysis and in the Analysis Setup dialog box that opens, click DC Sweep. A dialog box opens, Figure II-1. In the Name box, type the name of your source. (Check the schematic on your screen. The source is likely labeled V1. Enter this.) In the Start Value box type 25V, in the End Value box type 25V, in the Increment box type 1, click OK then Close. Click Save to save your work.

·  Click Simulate. After a short execution time, a Probe window may appear showing an empty set of axes. If so, close it.

·  On the menu bar, click Analysis, then Examine Output. Scroll through the file. Near the bottom, you should find the following:

I(V_PRINT1)

2.000E+00

This is the answer. The I(V_PRINT1) refers to the IPRINT meter and the answer 2.000E+00 is the current that it measured. Thus, for this circuit, PSpice determined I = 2 A as expected.

Third Example (Ohm’s Law Plot)

PSpice can graph results. By varying the voltage of the source and plotting current for example, you can get an Ohm’s law plot.

·  Build the circuit of Figure II-2(a). Click the Current Marker Probe button and place the marker at the top end of the resistor as shown. Save your work as file figure II-2 (or a file name of your own choosing).

·  Click Setup Analysis and choose DC Sweep. In the Name box, type the name of your source (e.g., V1), key in 0V as the Start Value, 100V as the End Value and 5V as the Increment size. Set Sweep Type to Linear. Click OK then Close.

·  Click Simulate. After a short execution time, the Ohm’s law graph of Figure II-2(b) will appear. You can read values from the graph using the cursor. To activate the cursor, click Trace (on the menu bar), Cursor then Display (or click the Cursor icon). Position the cursor where you want it on the screen and click left. The readings in the small box that opens are the cursor coordinates. The first number represents the x-axis reading (voltage) and the second the y-axis reading (current). Position the cursor at various voltages, read the results and verify using your calculator.

Chapter 5 Series Circuits (Example 5-15)

Using the bias point analysis technique, solve for circuit current and for each of the voltages of Figure 5-41.

·  Build the circuit on your screen as in Figure 5-43. Rotate components to provide for correct node assignments – refer to Appendix A and Chapter 4 of these notes for details if necessary. Click Save and save your work under an appropriate file name such as Ch 5 PSpice (or a file name of your own choosing such as figure 5-43).