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TUTORIAL: A NEW CIRCUIT
TUTORIAL: A NEW CIRCUIT
Before drawing the circuit..
For the purposes of this exercise it is assumed that a simple low-pass filter will be drawn in.
To get a clean sheet to start drawing a new circuit onto:
If already editing files
Save/close any previous editing from the FILE menu, by pressing ALT-F then clicking-on SAVE to save the circuit and CLOS E to close it. Repeat until there are no more circuits open. If modified circuits (except the top one) are left open you will be forced to close them before simulation.
If in DOS
Start up SUMO with no arguments. i.e. change to the required directory (where you want this circuit file to live) and type SUMO.
Naming the circuit
Firstly, use SAVEAS in the FILE menu, to establish a new name for the circuit. Press ALT-F and then click on SAVEAS . Type in 'LOWP1' for this exercise.
Press the ENTER key or click-on OK to finish the saving operation. The name in the menu-bar at the top of the screen should now read 'LOWP1'.
Drawing the circuit in...
Select an AC voltage source from the Parts-Bin, called VAC . Click the right-hand mouse button to flick the mouse pointer back to the circuit screen. This is a useful way to rapidly switch between the two windows. Press the mouse button down, and move it by a dot-pitch in the direction you wish it to appear (upwards).
Select a RES (resistor) and a CAP (capacitor) and connect them up to the source with WIRE s. Ensure that the value of the RES is 1k, and the CAP is 100n.
To monitor the output of this circuit, select a PROBE from the Parts-Bin, and draw it at the point which you wish to examine. Connect a GND (ground) up to the bottom of the source and the capacitor, and it is now ready for simulation .
The circuit should now look like this:
Simulating the circuit...
Go to the top of the screen, to the top menu-bar, and click-on SIMULATE, or press ALT-S. It is possible to define output traces now because the circuit has a PROBE, but SUMO will add some defaults automatically as required, so it is not necessary to do it manually now.
In the SIMULATE menu, Click on AC, to select the frequency response analysis and then click-on SIMULATE . The screen should now change, and graphs will appear. If this is not the case, fix the problem or look at the Installation and Trouble-Shooting guides in the front and back of the manual.
Viewing the results...
From the displayed graph the roll-off characteristics are displayed, together with the phase data. The decibel and phase data are the default traces that SUMO automatically added in. They were added because the domain that was missing the traces was AC, and the PROBE was not used. To prevent SUMO automatically adding traces then the OPTIONS menu must be used to switch this option off.
Creating new graphs...
Another useful graph for AC simulation is the POLAR plot. To create one of these, click on the CREATE button near the CURSORS one. Then select AC.
The CREATE menu allows the plotting of one X trace against one or more Y traces. If POLAR is specified, the X-plot will be rotated into a circle with the minimum Y at the centre. Thus a regular polar plot involves selecting any Phase trace (one of type (VP)) on the X-axis and the magnitude(s) required on the Y axis (VM). In this case, use the (VDB) type as that is what is available. Select POLAR and press OK, and the new graph will appear.
Further details about defining traces and creating graphs are available elsewhere in this manual.
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