PRADIS Qucs is schematic preprocessor for PRADIS
Getting Started with PRADIS Qucs
Short Description of Actions
Working with Subcircuits
List of Special Characters
Description of Qucs file formats
When you start Qucs the first time, it creates the directory ".qucs" within your home directory. Every file is saved into this directory or into one of its subdirectories. After Qucs has been loaded, one sees the main window looking simular like the one in figure 1. On the right side, there is the working area (6) containing the schematics, data displays and so on. Using the tabular bar (5) above this area, you can quickly switch to every document currently open. On the left side of the Qucs main window, there is another area (1), whose content depend on the status of the above-lying tabular bar: "Projects" (2), "Content" (3) and "Components" (4). After running Qucs, the "Projects" (2) tab is activated. As it is the first time you started this program, the area is empty because you haven't yet any project. Press the "New" button right above the area (1) and a dialog opens. Enter the name for your first project, e.g. "firstProject" and press the "Ok" button. Qucs creates a project directory into the ~/.qucs directory, for this example "firstProject_prj". Every file belonging to this new project will be saved within this directory. The new project is immediately opened (as can be read on the window title bar) and the tabular bar is switched to "Content" (3), where the content of the currently opened project is displayed. You do not yet have any document, so press save button on the toolbar (or use the main menu: File->Save) in order to save the untitled document that still fills the working area (6). You will be ask for the name of your new document. Enter "firstSchematic" and press the "Ok" button.
Figure 1 - Qucs main window
Now we want to make a simple DC simulation, i.e. we want to analyse the circuit in figure (1). Activate the "Components" tab ( (4) in figure 1). There, you see a combo box where you can choose a component group and, below, the components of the chosen component group. Choose "lumped components" and click on the first symbol: "Resistor". Moving the mouse cursor into the working area (6) you are carrying a drawing of a resistor symbol. Pressing the right mouse button rotates the symbol, pressing the left mouse button places the component onto the schematic. Repeat this process for all components shown in figure 1. The voltage source can be found in the "sources" component class, the ground symbol can be taken from "lumped components" class or from the toolbar, the wanted simulation is defined by the big simulation blocks found in the "simulations" component class. To edit the parameters of the second resistor, double-click on it. A dialog opens where you can change the resistance. Enter "100 Ohm" into the edit field on the right side and press enter.
To connect the components, press the wire toolbar button (or use the main menu: Insert->Wire). Move the cursor onto an open port (marked by the small red circles). Clicking on it starts the wire. Now move to the end point and click again. The components are now connected. If you want to change the corner direction of the wire, click on the right mouse button before setting the end point. You can also end a wire without pressing on an open port or on a wire: Just double-click the left mouse button.
Last but not least, you must label the node where you want Qucs to caculate the voltage. Press on the label toolbar button (or use the menu: Insert->Wire Label). Now click on the chosen wire. A dialog opens and you can enter the node name. Type "divide" and click the "Ok" button. Now the circuit should look like the one in figure 1.
To start the simulation press the simulate toolbar button (or use the menu: Simulation->Simulate). A window opens and shows the progress. After finishing the simulation successfully, the data display is opened. Normally, all this happens so fast that you only see a short flickering. Now you have to place a diagram to see the simulation results. On the left side the "diagrams" component class has already chosen automatically. Press on the "Tabular" item, move to the working area and place it by clicking the left mouse button. A dialog opens where you can choose what should be displayed by the new diagram. In the left area you see the node name you have defined: "divide". Double-click on it and it will be transfered to the right area. Leave the dialog by clicking the "Ok" button. Now you see the simulation result: 0.666667 volts. Wonderful, give yourself a clap on the shoulder!
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Short Description of Actions
(Menu: Edit->Select)
(Menu: Insert->Wire)
(Menu: Edit->Paste)
Mouse in "Content" Tab
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Working with Subcircuits
Subcircuits are used to bring more clarity into a schematic. This is
very useful in large circuits or in circuits, in which a component
block appears several times.
In Qucs, each schematic containing a subcircuit port is a subcircuit. You can get a subcircuit port by using the toolbar, the components listview (in lumped components) or the menu (Insert->Insert port). After placing all subcircuit ports (two for example) you need to save the schematic (e.g. CTRL-S). By taking a look into the content listview (figure 1) you see that now there is a "2-port" right beside the schematic name (column "Note"). This note marks all documents which are subcircuits. Now change to a schematic where you want to use the subcircuit. Then press on the subcircuit name (content listview). By entering the document area again, you see that you now can place the subcirciut into the main circuit. Do so and complete the schematic. You can now perform a simulation. The result is the same as if all the components of the subcircuit are placed into the circuit directly.
Figure 1 - Accesing a subcircuit
If you select a subcircuit component (click on its symbol in the
schematic) you can step into the subcircuit schematic by pressing
CTRL-I (of course, this function is also reachable via toolbar
and via menu). You can step back by pressing CTRL-H.
If you do not like the component symbol of a subcircuit, you can draw your own symbol and put the component text at your favourite position. Just make the subcircuit schematic the current and go to the menu: File->Edit Circuit Symbol. If you have not yet drawn a symbol for this circuit. A simple symbol is created automatically. You now can edit this symbol by painting lines and arcs. After finished, save it. Now place it on another schematic, and you have a new symbol.
Just like all other components, subcircuits can have parameters. To create your own parameters, go back to the editor where you edited the subcircuit symbol and double-click on the subcircuit parameter text. A dialog apperas and you now can fill in parameters with default values and descriptions. When you are ready, close the dialog and save the subcircuit. In every schematic where the subcircuit is placed, it owns the new parameters which can be edited as in all other components.
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List of Special Characters
It is possible to use special characters in the text painting and
in the text of the diagram axis labels. This is done by using
LaTeX tags. The following table contains a list of currently
available characters.
Note: Which of those characters are correctly displayed depends on the font used by Qucs!
Small Greek letters
Capital Greek letters
Mathematical symbols
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Schematic File Format
This document describes the schematic file format of Qucs.
This format is used for schematics (usually with suffix ".sch")
and for data displays (usually with suffix ".dpl").
The following text shows a short example of a schematic file.
<Qucs Schematic 0.0.6>
<Properties>
<View=0,0,800,800,1,0,0>
</Properties>
<Symbol>
<.ID -20 14 SUB>
</Symbol>
<Components>
<R R1 1 180 150 15 -26 0 1 "50 Ohm" 1 "26.85" 0 "european" 0>
<GND * 1 180 180 0 0 0 0>
</Components>
<Wires>
<180 100 180 120 "" 0 0 0 "">
<120 100 180 100 "Input" 170 70 21 "">
</Wires>
<Diagrams>
<Polar 300 250 200 200 1 #c0c0c0 1 00 1 0 1 1 1 0 5 15 1 0 1 1 315 0 225 "" "" "">
<"acnoise2:S[2,1]" #0000ff 0 3 0 0 0>
<Mkr 6e+09 118 -195 3 0 0>
</Polar>
</Diagrams>
<Paintings>
<Arrow 210 320 50 -100 20 8 #000000 0 1>
</Paintings>
The file contains several section. Each of it is explained below. Every line consists of not more than one information block that starts with a less-sign "<" and ends with a greater-sign ">".
<type name active x y xtext ytext mirrorX rotate "Value1" visible "Value2" visible ...>
<x1 y1 x2 y2 "label" xlabel ylabel dlabel "node set">
<x y width height grid gridcolor gridstyle log xAutoscale xmin xstep xmax yAutoscale ymin ystep ymax zAutoscale zmin zstep zmax xrotate yrotate zrotate "xlabel" "ylabel" "zlabel">
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Getting Started with PRADIS Qucs
Short Description of Actions
Working with Subcircuits
List of Special Characters
Description of Qucs file formats
Getting Started with PRADIS Qucs
This document should give you a short description on how to use Qucs.When you start Qucs the first time, it creates the directory ".qucs" within your home directory. Every file is saved into this directory or into one of its subdirectories. After Qucs has been loaded, one sees the main window looking simular like the one in figure 1. On the right side, there is the working area (6) containing the schematics, data displays and so on. Using the tabular bar (5) above this area, you can quickly switch to every document currently open. On the left side of the Qucs main window, there is another area (1), whose content depend on the status of the above-lying tabular bar: "Projects" (2), "Content" (3) and "Components" (4). After running Qucs, the "Projects" (2) tab is activated. As it is the first time you started this program, the area is empty because you haven't yet any project. Press the "New" button right above the area (1) and a dialog opens. Enter the name for your first project, e.g. "firstProject" and press the "Ok" button. Qucs creates a project directory into the ~/.qucs directory, for this example "firstProject_prj". Every file belonging to this new project will be saved within this directory. The new project is immediately opened (as can be read on the window title bar) and the tabular bar is switched to "Content" (3), where the content of the currently opened project is displayed. You do not yet have any document, so press save button on the toolbar (or use the main menu: File->Save) in order to save the untitled document that still fills the working area (6). You will be ask for the name of your new document. Enter "firstSchematic" and press the "Ok" button.
Figure 1 - Qucs main window
Now we want to make a simple DC simulation, i.e. we want to analyse the circuit in figure (1). Activate the "Components" tab ( (4) in figure 1). There, you see a combo box where you can choose a component group and, below, the components of the chosen component group. Choose "lumped components" and click on the first symbol: "Resistor". Moving the mouse cursor into the working area (6) you are carrying a drawing of a resistor symbol. Pressing the right mouse button rotates the symbol, pressing the left mouse button places the component onto the schematic. Repeat this process for all components shown in figure 1. The voltage source can be found in the "sources" component class, the ground symbol can be taken from "lumped components" class or from the toolbar, the wanted simulation is defined by the big simulation blocks found in the "simulations" component class. To edit the parameters of the second resistor, double-click on it. A dialog opens where you can change the resistance. Enter "100 Ohm" into the edit field on the right side and press enter.
To connect the components, press the wire toolbar button (or use the main menu: Insert->Wire). Move the cursor onto an open port (marked by the small red circles). Clicking on it starts the wire. Now move to the end point and click again. The components are now connected. If you want to change the corner direction of the wire, click on the right mouse button before setting the end point. You can also end a wire without pressing on an open port or on a wire: Just double-click the left mouse button.
Last but not least, you must label the node where you want Qucs to caculate the voltage. Press on the label toolbar button (or use the menu: Insert->Wire Label). Now click on the chosen wire. A dialog opens and you can enter the node name. Type "divide" and click the "Ok" button. Now the circuit should look like the one in figure 1.
To start the simulation press the simulate toolbar button (or use the menu: Simulation->Simulate). A window opens and shows the progress. After finishing the simulation successfully, the data display is opened. Normally, all this happens so fast that you only see a short flickering. Now you have to place a diagram to see the simulation results. On the left side the "diagrams" component class has already chosen automatically. Press on the "Tabular" item, move to the working area and place it by clicking the left mouse button. A dialog opens where you can choose what should be displayed by the new diagram. In the left area you see the node name you have defined: "divide". Double-click on it and it will be transfered to the right area. Leave the dialog by clicking the "Ok" button. Now you see the simulation result: 0.666667 volts. Wonderful, give yourself a clap on the shoulder!
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Short Description of Actions
General Actions
(valid in all modes)| mouse wheel | Scrolls vertically the drawing area. You can also scroll outside the current size. |
| mouse wheel + Shift Button | Scrolls horizontally the drawing area. You can also scroll outside the current size. |
| mouse wheel + Ctrl Button | Zooms into or outof the drawing area. |
| drag'n'drop file into document area | Tries to open file as Qucs schematic or data display. |
"Select"-Mode
(Menu: Edit->Select)| left mouse button | Selects the element below the mouse cursor. If several components are placed
there, you can clicking several times in order to select the wanted one. Keeping the mouse button pressed, you can move the component below the mouse cursor and all selected ones. If you want to fine position the components, press the CTRL key during moving and the grid is disabled. Keeping the mouse button pressed without any element below it opens a rectangle. After releasing the mouse button, all elements within this rectangle are selected. A selected diagram or painting can be resized by pressing the left mouse button over one of its corners and moving by keeping the button pressed. After clicking on a component text, it can be edited directly. The enter key jumps to the next property. If the property is a selection list, it can only be changed with the cursor up/down keys. Clicking on a circuit node enters the "wire mode". |
| left mouse button + Ctrl Button | Allows more than one element to be selected, i.e. selecting an element does not deselect the others. Clicking on a selected element deselects it. This mode is also valid for selecting by opening a rectangle (see item before). |
| right mouse button | Clicking on a wire selects a single straight line instead of the complete line. |
| double-click right mouse button | Opens a dialog to edit the element properties (The labels of wires, the parameters of components, etc.). |
"Insert Component"-Mode
(Click on a component/diagram in the left area)| left mouse button | Place a new instance of the component onto the schematic. |
| right mouse button | Rotate the component. (Has no effect on diagrams.) |
"Wire"-Mode
(Menu: Insert->Wire)| left mouse button | Sets the starting/ending point of the wire. |
| right mouse button | Changes the direction of the wire corner (first left/right or first up/down). |
| double-click right mouse button | Ends a wire without being on a wire or a port. |
"Paste"-Mode
(Menu: Edit->Paste)| left mouse button | Place the elements onto the schematic (from the clipboard). |
| right mouse button | Rotate the elements. |
Mouse in "Content" Tab
| left click | Selects file. | ||||||||
| double-click | Opens file. | ||||||||
| right click | Displays menu with:
|
Keyboard
Many actions can be activated/done by the keyboard strokes. This can be seen in the main menu right beside the command. Some further key commands are shown in the following list:| "Delete" or "Backspace" | Deletes the selected elements or enters the delete mode if no element is selected. |
| Cursor left/right |
Changes the position of selected markers on their graphs. If no marker is selected, move selected elements. If no element is selected, scroll document area. |
| Cursor up/down |
Changes the position of selected markers on more-dimensional graphs. If no marker is selected, move selected elements. If no element is selected, scroll document area. |
| Tabulator | Changes to the next open document (according to the TabBar above). |
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Working with Subcircuits
Subcircuits are used to bring more clarity into a schematic. This is
very useful in large circuits or in circuits, in which a component
block appears several times.In Qucs, each schematic containing a subcircuit port is a subcircuit. You can get a subcircuit port by using the toolbar, the components listview (in lumped components) or the menu (Insert->Insert port). After placing all subcircuit ports (two for example) you need to save the schematic (e.g. CTRL-S). By taking a look into the content listview (figure 1) you see that now there is a "2-port" right beside the schematic name (column "Note"). This note marks all documents which are subcircuits. Now change to a schematic where you want to use the subcircuit. Then press on the subcircuit name (content listview). By entering the document area again, you see that you now can place the subcirciut into the main circuit. Do so and complete the schematic. You can now perform a simulation. The result is the same as if all the components of the subcircuit are placed into the circuit directly.
Figure 1 - Accesing a subcircuit
If you do not like the component symbol of a subcircuit, you can draw your own symbol and put the component text at your favourite position. Just make the subcircuit schematic the current and go to the menu: File->Edit Circuit Symbol. If you have not yet drawn a symbol for this circuit. A simple symbol is created automatically. You now can edit this symbol by painting lines and arcs. After finished, save it. Now place it on another schematic, and you have a new symbol.
Just like all other components, subcircuits can have parameters. To create your own parameters, go back to the editor where you edited the subcircuit symbol and double-click on the subcircuit parameter text. A dialog apperas and you now can fill in parameters with default values and descriptions. When you are ready, close the dialog and save the subcircuit. In every schematic where the subcircuit is placed, it owns the new parameters which can be edited as in all other components.
back to the top
List of Special Characters
It is possible to use special characters in the text painting and
in the text of the diagram axis labels. This is done by using
LaTeX tags. The following table contains a list of currently
available characters.Note: Which of those characters are correctly displayed depends on the font used by Qucs!
Small Greek letters
| LaTeX tag | Unicode | Description |
| \alpha | 0x03B1 | alpha |
| \beta | 0x03B2 | beta |
| \gamma | 0x03B3 | gamma |
| \delta | 0x03B4 | delta |
| \epsilon | 0x03B5 | epsilon |
| \zeta | 0x03B6 | zeta |
| \eta | 0x03B7 | eta |
| \theta | 0x03B8 | theta |
| \iota | 0x03B9 | iota |
| \kappa | 0x03BA | kappa |
| \lambda | 0x03BB | lambda |
| \mu | 0x03BC | mu |
| \textmu | 0x00B5 | mu |
| \nu | 0x03BD | nu |
| \xi | 0x03BE | xi |
| \pi | 0x03C0 | pi |
| \varpi | 0x03D6 | pi |
| \rho | 0x03C1 | rho |
| \varrho | 0x03F1 | rho |
| \sigma | 0x03C3 | sigma |
| \tau | 0x03C4 | tau |
| \upsilon | 0x03C5 | upsilon |
| \phi | 0x03C6 | phi |
| \chi | 0x03C7 | chi |
| \psi | 0x03C8 | psi |
| \omega | 0x03C9 | omega |
Capital Greek letters
| LaTeX tag | Unicode | Description |
| \Gamma | 0x0393 | Gamma |
| \Delta | 0x0394 | Delta |
| \Theta | 0x0398 | Theta |
| \Lambda | 0x039B | Lambda |
| \Xi | 0x039E | Xi |
| \Pi | 0x03A0 | Pi |
| \Sigma | 0x03A3 | Sigma |
| \Upsilon | 0x03A5 | Upsilon |
| \Phi | 0x03A6 | Phi |
| \Psi | 0x03A8 | Psi |
| \Omega | 0x03A9 | Omega |
Mathematical symbols
| LaTeX tag | Unicode | Description |
| \cdot | 0x00B7 | multiplication dot (centered dot) |
| \times | 0x00D7 | multiplication cross |
| \pm | 0x00B1 | plus minus sign |
| \mp | 0x2213 | minus plus sign |
| \partial | 0x2202 | partial differentiation symbol |
| \nabla | 0x2207 | nabla operator |
| \infty | 0x221E | infinity symbol |
| \int | 0x222B | integral symbol |
| \approx | 0x2248 | approximation symbol (waved equal sign) |
| \neq | 0x2260 | not equal sign |
| \in | 0x220A | "contained in" symbol |
| \leq | 0x2264 | less-equal sign |
| \geq | 0x2265 | greater-equal sign |
| \sim | 0x223C | (central european) proportional sign |
| \propto | 0x221D | (american) proportional sign |
| \diameter | 0x00F8 | diameter sign (also sign for average) |
| \onehalf | 0x00BD | one half |
| \onequarter | 0x00BC | one quarter |
| \twosuperior | 0x00B2 | square (power of two) |
| \threesuperior | 0x00B3 | power of three |
| \ohm | 0x03A9 | unit for resistance (capital Greek omega) |
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Schematic File Format
This document describes the schematic file format of Qucs.
This format is used for schematics (usually with suffix ".sch")
and for data displays (usually with suffix ".dpl").
The following text shows a short example of a schematic file.
<Qucs Schematic 0.0.6>
<Properties>
<View=0,0,800,800,1,0,0>
</Properties>
<Symbol>
<.ID -20 14 SUB>
</Symbol>
<Components>
<R R1 1 180 150 15 -26 0 1 "50 Ohm" 1 "26.85" 0 "european" 0>
<GND * 1 180 180 0 0 0 0>
</Components>
<Wires>
<180 100 180 120 "" 0 0 0 "">
<120 100 180 100 "Input" 170 70 21 "">
</Wires>
<Diagrams>
<Polar 300 250 200 200 1 #c0c0c0 1 00 1 0 1 1 1 0 5 15 1 0 1 1 315 0 225 "" "" "">
<"acnoise2:S[2,1]" #0000ff 0 3 0 0 0>
<Mkr 6e+09 118 -195 3 0 0>
</Polar>
</Diagrams>
<Paintings>
<Arrow 210 320 50 -100 20 8 #000000 0 1>
</Paintings>
The file contains several section. Each of it is explained below. Every line consists of not more than one information block that starts with a less-sign "<" and ends with a greater-sign ">".
Properties
The first section starts with "<Properties>" and ends with "</Properties>". It contains the document properties of the file. Each line is optional. The following properties are supported:- <View=x1,y1,x2,y2,scale,xpos,ypos> contains pixel position of the schematic window in the first four numbers, its current scale and the current position of the upper left corner (last two numbers).
- <Grid=x,y,on> contains the distance of the grid in pixel (first two numbers) and whether grid is on (last number 1) or off (last number 0).
- <DataSet=name.dat> contains the file name of the data set associated with this schematic.
- <DataDisplay=name.dpl> contains the file name of the data display page associated with this schematic (or the file name of the schematic if this document is a data display).
- <OpenDisplay=yes> contains 1 if the data display page opens automatically after simulation, otherwise contains 0.
Symbol
This section starts with "<Symbol>" and ends with "</Symbol>". It contains painting elements creating a schematic symbol for the file. This is usually only used for schematic files that meant to be a subcircuit.Components
This section starts with "<Components>" and ends with "</Components>". It contains the circuit components of the schematic. The line format is as follows:<type name active x y xtext ytext mirrorX rotate "Value1" visible "Value2" visible ...>
- The type identifies the component, e.g. "R" for a resistor, "C" for a capacitor.
- The name is the unique component identifier of the schematic, e.g. "R1" for the first resistor.
- A "1" in the active field shows that the component is active, i.e it is used in the simulation. A "0" shows it is inactive.
- The next two numbers are the x and y coordinates of the component center.
- The next two numbers are the x and y coordinates of the upper left corner of the component text. They are relative to the component center.
- The next two numbers indicate the mirroring about the x axis ("1" for mirrored, "0" for not mirrored) and the counter-clockwise rotation (multiple of 90 degree, i.e. 0...3).
- The next entries are the values of the component properties (in quotation marks) followed by an 1 if the property is visible on the schematic (otherwise 0).
Wires
This section starts with "<Wires>" and ends with "</Wires>". It contains the wires (electrical connection between circuit components) and their labels and node sets. The line format is as follows:<x1 y1 x2 y2 "label" xlabel ylabel dlabel "node set">
- The first four numbers are the coordinates of the wire in pixels: x coordinate of starting point, y coordinate of starting point, x coordinate of end point and y coordinate of end point. All wires must be either horizontal (both x coordinates equal) or vertical (both y coordinates equal).
- The first string in quotation marks is the label name. It is empty if the user has not set a label on this wire.
- The next two numbers are the x and y coordinates of the label or zero if no label exists.
- The next number is the distance between the wire starting point and and the point where the label is set on the wire.
- The last string in quotation marks is the node set of the wire, i.e. the initial voltage at this node used by the simulation engine to find the solution. This is empty if the user has not set a node set for this wire.
Diagrams
This section starts with "<Diagrams>" and ends with "</Diagrams>". It contains the diagrams with their graphs and their markers.<x y width height grid gridcolor gridstyle log xAutoscale xmin xstep xmax yAutoscale ymin ystep ymax zAutoscale zmin zstep zmax xrotate yrotate zrotate "xlabel" "ylabel" "zlabel">
- The first two numbers are x and y coordinate of lower left corner.
- The next two numbers are width and height of diagram boundings.
- The fifth number is 1 if grid is on and 0 if grid is off.
- The next is grid color in 24 bit hexadecimal RGB value, e.g. #FF0000 is red.
- The next number determines the style of the grid.
- The next number determines which axes have logarithmical scale.
Paintings
This section starts with "<Paintings>" and ends with "</Paintings>". It contains the paintings that are within the schematic.back to the top
