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The purpose of this video is to give a brief introduction to a Spice tool, specifically
beige bag spice. Spice programs are a class of programs that
can simulate circuits. Most SPICE programs also have a graphical
interface that allows us to draw schematics. Beige bag spice is one such program.
In this introductory video you will learn how to draw a basic schematic and do a dc
simulation. The handout corresponding to this video can
be found in D2L, or on the instructor’s webpage.
To begin we need to open b2 spice. This is done by going to the start menu under
all programs and selecting B2 Spice A_D v5. Under this menu item, select B2 Spice V5.
If you are at a streaming video location, you will need to log into the VM Ware View
Client in order to find this menu item. Once you’ve started the program you will
see a grid; this is the schematic background. This schematic that we’re going to construct
consists of a DC voltage supply, two resistors and a current source.
This schematic is on the second page of the SPICE handout.
To add parts to a schematic we have several options:
On the left hand side of the screen we have a parts tab that will allow us to access all
parts that are available in this program’s library.
Additionally, there is a ‘common parts’ menu item. This will allow us to access the
most frequently used parts. If we click on the’ common parts’ menu
item we also see that there are a variety of shortcut keys that can be used access parts.
For instructional purposes, we will add parts in all three ways to this schematic.
To begin lets add the 24 volt DC Power Supply. This can be found by clicking on the add part
tab and selecting virtual components. We then select voltage sources, followed by
battery. The part is placed in the schematic simply
by clicking in the schematic background where we want the part placed.
Next we will want to change the value of the voltage source to 24V.
The default value of the voltage source is one volt.
The value of the source can be modified by double clicking on the part and entering the
appropriate value in the ‘value’ box, in this case 24. One to have clicked OK, you’re
ready to add the next part. I will add the current source from the common
parts menu. Click on ’common parts’ and select current
source. The current source comes in oriented to the
right. In order to align it oriented up, simply a
right click until it appears as you would like it oriented.
The part can then be placed by left clicking. This is to be a two amp source.
The value can be edited by double clicking on the part and entering two for the value
and clicking OK. If we click on the common parts menu item
we can see some of the shortcuts that are available to us to place parts.
We can see that in order to place a resistor F4 is the shortcut.
Place the resistors in the schematic, right clicking when necessary to reorient the part.
For aesthetic purposes, when placing parts, they should be fairly uniform in spacing.
They should also not be too close to each other, nor too far apart from each other.
A rule of thumb I use when drawing a schematic is to place parts that are at a right angle
to each other two grid spacings in each direction from the previous component.
The component values can be edited by double clicking on the parts.
R1 should be changed to 3 ohms, and R2 should be changed to 6 ohms.
The last necessary part before wiring is the ground.
A ground is necessary in all schematics. This provides a reference node for the simulator.
To place the ground, simply press F3. Wiring can be accomplished by clicking on
the toolbar item for wiring or by pressing the letter W.
Once the wiring tool is selected, simply click on the green parts connector and draw a line
to connect the desired parts. To end of a particular line double click on
the endpoint. Begin a new wire by clicking on the next component
to be connected and double clicking on the endpoint.
Continue this process until all lines are drawn. Exit wiring mode by clicking on the
arrow in the toolbar. The labels for the nodes can be displayed
by clicking on the node icon in the toolbar. At this point, you may want to change the
default names of the nodes of the circuit. To do this simply right click on the node
you want to change the name of and select 'Rename Net'. You can then type in whatever
name you wish for the selected node. Now that our schematic is drawn and all the
component values are correct, the circuit is ready for simulation.
For this circuit we will find the DC bias point.
To begin, click on the ’tests’ tab. Since we’re doing a simple DC analysis,
all we need to select is the basic DC bias box.
Once this is selected, click on ‘Run enabled tests’.
Once this is done the DC bias data will appear on the screen.
We can also have these data appear in the schematic by clicking on the V, I or P in
the toolbar and clicking on ‘Run enabled tests’ again. Since I have selected V, now
the 24 volts and the 20 volts both appear on the schematic at the respective nodes.
More information about the current and voltage can be displayed by clicking on the animation
tab. Under the operating point tab select to show the voltage text, show the voltage
graphically show the currents text and graphics. When these boxes are checked, each of the
nodes appear as a different color (nodes with positive voltages appear in red, nodes with
negative voltages appear in blue), and arrows appear indicating the direction of each of
the currents displayed. Note that the values for the currents are the currents leaving
the particular part terminal, so currents that enter a terminal are labeled as negative.
Once you are comfortable with the process for creating a schematic, and doing a DC bias
analysis, you are ready to move on to more complicated circuit and simulations. The next
video will show you how to include a dependent source in your schematic.