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Loading and Simulating

Let's load the PSPICE file dc1.sch.

If you have not done so already, you will need to download (using your web browser) and save this file into your PSPICE directory. Now you can load this file from your directory into PSPICE. From the SCHEMATICS window:

File $\to$ Open
go to your PSPICE directory
click on the file dc1.sch
click Open

The schematic diagram will appear in the window, Figure 2.

  

Figure 2: File dc1.sch in the SCHEMATICS window.

The circuit consists of a 9 V DC voltage source, three resistors, and a ground (analog). A ground must appear on all PSPICE schematics. The ground is used as a reference point (0 V) for nodal analysis. Note that all components have a label, and the values are shown (labels and values can easily be changed).

The simplest way to simulate (i.e. do a DC analysis in this case) is to click the simulate button, as shown in Figure 3.

  

Figure 3: Simulate button.

Alternatively, you can do the following:

Analysis $\to$ Create Netlist
Analysis $\to$ Simulate

Either way, you will see (by default) the nodal voltages marked on the schematic, and a PSPICE window with information about the outcome of the simulation, Figure 4.

  

Figure 4: Schematics window after simulation.

You can also see the branch currents marked on the schematic:

Analysis $\to$ Display Results on Schematic $\to$ Enable Current Display

Of course, display of voltages and currents can be disabled (on/off toggle).

Exercise. Calculate the nodal voltages and branch currents using nodal or mesh analysis and compare your answers with the PSPICE values.

Now that you know how to do DC simulations to find voltages and currents, lets do some more simulations with different component values.

To change the voltage of the DC voltage source, click on the 9 V value label next to the battery. A box will appear called Set Attribute Value, Figure 5.

  

Figure 5: Set Attribute Value dialog box.

Type in a new value, say 18V (include the units V). Press OK, the box will dissappear, and the new voltage should be shown on the schematic. Now save the changes to the schematic by pressing the save (disk) button, or by using the menu:

File $\to$ Save

Now simulate the circuit - the voltages and currents will be updated.

Another way to change the voltage is to edit a more detailed list of part values via the PartName dialog box, Figure 6. To open this box, click on the battery itself. Then click on DC in the box and edit the top line to the voltage you want. Press Save Attr, and then OK.

  

Figure 6: PartName dialog box.

Now try changing resistor values and simulating the resulting circuit. The method is the same, using either the Set Attribute Value or PartName dialog boxes. In general the PartName box is useful when the value does not appear on the schematic or when multiple attributes are to be set or changed.

Note that all PSPICE operations can be performed using menus, and many (but not all) operations have shortcut buttons, as we have seen. Keyboard shortcuts are also provided.

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