Setting up an initial ".tcshrc" file

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2 ECE445 Fall 2005 Introduction to SaberSketch The SABER simulator is a tool for computer simulation of analog systems, digital systems and mixed signal systems. SaberDesigner consists of the three tools, Saber Sketch TM, SaberGuide TM, and SaberScope TM. SaberSketch TM lets you create and edit designs. SaberGuide allows you to interactively control the simulation and analyses. SaberScope TM enables you to view and graphically analyze waveforms. How to start Saber? You have to set up a.tcshrc file in your ECE account before you can use saber. If you are working on a pc you can access ernie through Exceed. Setting up an initial ".tcshrc" file The.tcshrc (pronounced dot-t-c-s-h-r-c) file tells the shell (assuming you are using the tcsh shell environment all) sorts of setup parameters, most important of which are where to find certain programs. For some unknown reason, new accounts are not setup with any such file so the following is necessary. Directions: Click on the following link to view a basic tcshrc file. Create it in your home directory as.tcshrc (don't forget the dot in front). (i.e. save it as ~/.tcshrc) Finally, log out and log back in again. At the command prompt, type source.tcshrc. At the command prompt type sketch &. This brings up the SaberSketch Window.

3 ECE 445: FALL 2005 Getting Started With Saber Designer Starting Saber Designer If you are using a UNIX workstation the simplest way to run Saber Designer is to do the following: Click on a console (if it is not already available on the screen, Figure 1). At the Unix prompt type sketch & Click on this Console button Saber s Environment Figure 1: CDE Panel SaberSketch Design Editor A schematic capture utility for creating and editing designs. Designs created with SaberSketch can be both analog and digital, or can be a combination of electronic, electrical, mechanical, hydraulic, optical and magnetic symbols. Any devices that can be mathematically described can be included into a design. SaberGuide Toggle Button Zoom Icons Toggle Grids Parts Library Probes and Wiring Figure 2: SaberSketch Design Editor Tool/Icon Bar 1

4 SaberGuide Simulation Environment This is a set of tools that control the simulation process. The actual analysis are set up and executed from this environment. Among the available analyses are: DC operating point, transient, small-signal AC, DC transfer characteristics SaberGuide SaberSketch Figure 2: SaberGuide Simulation Environment SaberScope Waveform Analyzer -- is the post-processing and waveform analysis tool set that allows you to view and analyze simulation results in the form of waveforms displayed on graphs or values displayed in lists. It is menu-driven and can be controlled from the command line as well. Clear Graph Icon Measurement Tool Icon Signal manager Icon At X/Y Measurement Icon Figure 3: SaberScope Waveform Analyzer Creating Simple Projects Example #1: Construct and analyze a transistor based amplifier. Placing Symbols (Components) We will start by placing the symbols for the components onto the schematic block as follows: Click the Parts Gallery icon to get the Parts Gallery Window. 2

5 Set the fields as follows (type words that are in italic 1 ): Category Name: Leave unselected Search String: npn From the pull down menu, select (or make sure that they are selected): Options String match Type Containing Options Object Search Type Any Field Click the Search button. A list of parts that matches the string npn appears under the Available Parts list. In the Available Parts list, select BJT, 3 pin NPN Transistor. Place the npn symbol by clicking the Place button. You will have to go through the similar steps for placing other parts. We will now Search and Place other parts. The follows are the (Steps are similar to the above): Search String: res You don t have to type the whole word to search for a part; this will list all parts that have the string res in it. This can be too long of a list. To make it easier, change the option to the following: Options String match Type Beginning with Options Object Search Type Part Name Click the Search button At the Available Parts, select Resistor( ) Place five resistors by clicking the Place button five times. Turn on the grid in the Design window by clicking the Toggle Grid the SaberSketch Icon Bar. Position the five resistors relative to the transistor as shown on Figure. icon in You can use the Zoom displayed contents. icons to help manage the size of Find and place the Voltage Source, Pulse symbol using the Parts Gallery Search String: voltage source In the same search list, select the Voltage Source, Constant Ideal DC Supply to place into the Schematic. Find and place the capacitor symbol using the Parts Gallery by using cap as the key word. You might need to change the options as needed Select Capacitor (-) and click on Place. Move the mouse over the capacitor you just placed. Click and hold with the right mouse button and select Rotate 180. Position the capacitor as shown in Figure. Reposition symbol as necessary. 1 Bolded Words are usually available in the program, in this case Saber Designer. You might have to type in those Bolded Italic Words. 3

6 Find and place the vertical capacitor symbol as in the previous step except that in the Available Parts list, select Capacitor ( ). Now click on Place. Find the vcc symbol by changing the Search String to vcc Search String: vcc Select the vcc and place three times. Find and place the ground symbol Search String: ground Select Ground (Saber node 0) Place Ground six times. Your figure should look like Figure, (Move the symbols around as needed). Now close the Parts Gallery. Figure 4: Layout of example Symbol Properties Once all the parts are placed on the schematic, you can put property values that are specified for this example on each symbol. For those symbols that have property value place-holders (*opt*) already displayed such as the resistor and capacitor symbols, you can change the value on each by doing the following: 1. Position the mouse cursor at the end of the desired text field. 2. Click the left mouse button. 4

7 3. Change the *opt* to the desired value i.e. resistance, capacitance etc. This allows you to quickly change the value. However for this example you will be changing the value of each component through the Properties editor window, which allows you a complete access to all properties that described the component. To access Property Editor, position the mouse cursor over any of the passive component (e.g. a resistor), and double click on the component. The Property Editor should look like Figure. Locked: Indicate that the value is unchangeable. Name and Value Field Visibility: Fully filled: Name and Value are visible in Schematic. Half Filled: Only Value are visible in Schematic Empty (not filled): The property is not visible in Schematic. Figure 5: Property Editor Wiring The Schematics After the symbols are placed and the properties are set, you can wire all the parts together. The simplest way to create a wire between two ports is as follows: Position the mouse cursor over the first port (e.g. start with the top of the v_dc symbol) until the mouse cursor turns into a +. Click the left mouse button. Position the mouse cursor over the second (the vcc symbol above the v_dc symbol) until the mouse cursor turns into a +. Click the left mouse button again. Repeat these steps for all the separated symbols as shown in Figure 4. You can reposition either segment of the wire as follows: Move the mouse cursor to the wire segment that you want to move. Press-and-hold the left mouse button. Drag the wire segment to the desired location. Release the mouse button. To delete wire: Select a wire segment. 5

8 Right click and select Delete Segment. Figure 6 is the completed schematic on how it should look like after you have entered all the values. Figure 6: Completed Schematic Before Simulation Save the file with an.ai_sch extension. Simulating The Example The values assigned to the symbols may not be the desired value; you may have to adjust these values and simulates a few times in order to determine a desire design of the circuit (it is now up to you knowledge in circuit designs). To begin simulations Click on the SabeGuide Toggle button,. Click on the Transient Analysis button,. Type in the following values, in each of their respective field: End Time: 10u Time Step: 0.1u Click on OK or Apply to begin the simulation. Once simulations is completed (Provided there s no error in the setup of the schematics). Click on the Waveform Probe button,. Move the Pointer of the probe to any desire points of the circuit to view the outcome of the simulation. Double click on the plot graph to activate SaberScope. 6

9 Example #2: Creating a Buck Converter Circuit We will analyze a Buck Converter circuit with a resistive load. mp1 L2 V in pwld C2 R vpulse Fig. 7 Parts used in this circuit are listed below: Element Search String Resistor resistor Dc voltage source v_dc MOSFET mp1 Inductor inductor Capacitor capacitor Power diode pwld Voltage pulse v_pulse Ground ground, (saber node 0) Short short Values for the various components are as follows: Input Voltage: 48v Inductor : 30 µh Capacitor : 60 µf Resistor : 0.7Ω Vpulse V1 : 0 V2 : 15 Time Period : 10µ Width : 1.05µ 7

10 Transient Analysis Transient analysis refers to analysis in the time domain. Choose Analyses>Time-Domain>Transient. This opens Time-Domain Transient Analysis window. Enter the following values: End Time: Time Step: Run DC Analysis first: yes Plot after Analysis: yes, open only Click on run. Saber creates a netlist of your design and simulates the circuit. After the simulation is done signal Manager window showing the list of signals pops up. You can see the voltage at any point in the circuit by clicking on the corresponding net in the signal manager window. 8

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