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SCHEMATIC ENTRY
This section heralds a series of sections detailing operations involved when entering a circuit. At the end is an example that goes through the entry and simulation of a new circuit.
Entering new components
Components are pre-selectable from the Parts-Bin . Below this there are related buttons. Up and Dn scroll through the current page, and PAGE toggles between sub-circuits and primitives . The bottom box displays the name of the currently selected class.
- Available primitive components depend upon those specified for the target simulator and which level of software you have.
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To edit a components symbol, double-click on the component's symbol in the Parts-Bin .
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To draw a component, ensure that DRAW is selected (in the left hand menu), click on the required component in the Parts-Bin, position the mouse pointer at the required start position, press the left button and move the mouse.
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- If you draw a two terminal component over another of the same size, the original is deleted.
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Do it again and the original is replaced.
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Components are entered in the direction you draw them.
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Manipulating components
This section details all aspects of component manipulation from dragging them around to setting their parameters. All drawing actions use the left mouse button only.
Selecting components
Components can be selected whilst either the DRAW or SELECT button is selected:
- Drawing mode selection
Click the mouse near a component to select it. New components are already selected and - unless a SHIFT key is held down - are de-selected when you start drawing something else. To prevent others from being de-selected at the same time, hold down a SHIFT key while clicking.
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Select mode selection
Components are selected in this mode by outlining them. To Outline an area;- position the mouse pointer at one corner, press and hold the left mouse button while moving the mouse pointer to the opposite corner, release the button.
Moving components
Before one or more components are dragged, they must be selected. Selected components can be dragged whilst either the DRAW or SELECT button is selected.
- Drawing mode dragging
If you are close to a selected component, press the left button and do not move the mouse for one second. All selected components then change colour as SUMO enters drag mode. They can now be dragged around the screen until dropped.
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Selection mode dragging
Press the left mouse button near a selected component. Immediately all selected components then change colour as SUMO enters drag mode. They can now be dragged around the screen until dropped.
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Cutting and Pasting
To copy or cut a selection of components from the circuit, the buttons COPY and CUT, in the EDIT menu (accessed by pressing ALT-E) are required. First select the required component(s) and then COPY or CUT them. Both of these operation cause the components to be stored in the paste-buffer, a file that survives until another item is pasted, even though SUMO may be exited and the machine switched off. CUT will then remove all of the selected components from the circuit.
INSERT and PASTE (also found in the EDIT menu), work in similar ways. They both insert the relevant circuit or circuit fragment such that bottom left hand corner is at the cursor position. See above for information about the cursor.
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Rotating and Mirroring
To rotate or mirror a selection of components from the circuit, the buttons ROTATE and MIRROR, in the EDIT menu (accessed by pressing ALT-E), or the MIR and ROT buttons on the left hand menu, are required. First select the component(s) that you wish to operate upon, then click-on the required function. Both operations align the rotated or mirrored component(s) with the new left-bottom corner at the position of the previous left-bottom corner.
Deleting components
Pressing DEL deletes all selected components. An alternative way is to CUT the components out. This uses the CUT button in the EDIT menu, entered by clicking upon EDIT in the top menu-bar, or pressing ALT-E.
If you have accidentally deleted components by using the DEL key, clicking on UNDO in the EDIT menu will restore them. UNDO deletes selected components and selects deleted components.
Use of the circuit cursor
The cursor is a small green square on the circuit area, and is used as a reference point for paste, insert and annotate functions. The cursor always has a position, whether or not it is visible, at the last place that the mouse was clicked at on the circuit area. To toggle the cursor's visibility, from the OPTIONS menu (opened from the FILE menu, or ALT-F, T keys) the CURSOR option must be selected.
Panning and Zooming
>><< and <<>> zoom in and out, whereas PAN and [FRAME] select operations to be carried out by future mouse actions on the circuit drawing. To pan across a circuit, select the PAN button. Then put the mouse cursor on the circuit and press the left button. Move the pointer to where you wish that part of the circuit to be and release the button.
[FRAME ] has a similar action, but the outlined area will then fill the whole picture - allowing for any aspect ratio correction.
Annotation
ANNOTATE, in the EDIT menu, is used to put text onto the circuit to the right of the current cursor position. See above for information about the cursor. Open the ANNOTATE menu by pressing ALT-E and selecting ANNOTATE . Type in the required string and then press ENTER or click-on OK.
To edit text already put down, double-click on the left-hand end of the string, or select it and click-on PARAMS . To drag it, select it from the left-hand end and drag it. Text annotations are treated exactly like any other component in SUMO, but you must remember that they originate from the left.
Assigning values and models
Components generally have a main or primary value, and other optional parameters. If the component is a diode or transistor, the parameters are encapsulated into models, and it is the model that is chosen as its 'value'. If the component is a sub-circuit, the first parameter is its 'value'.
To alter a components value or parameters, the PARAMS menu is usually used. This is called up for the currently selected component by clicking on the PARAMS button (in the menu on the left-hand side of the screen), or by double-clicking on the selected component.
There are two methods to set a component's primary value or model:
- Once the component has been drawn, double-click on it with the mouse, or (making sure that it is selected first) click-on the PARAMS button near the Parts-Bin . The PARAMS menu will display the current value or model in a table. Select and double-click on it, or press the SET button. Enter the new value or model and press OK .
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Before the component has been drawn, the default value for that class can be set by selecting the button at the bottom of the menu containing the Parts-Bin. Enter the pre-set value or model required, and press OK .
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Method 1 is used to set all parameters associated with a component.
Note:
Models can be manually edited from the MODEL menu, and extracted from the SPICE libraries of the relevant manufacturer using the optional Extraction Tools . See the sections later for details...
Other parameters that are special are DEPENDENT and SOURCE . Source types are detailed in the Simulation section of this manual, Dependent sources are detailed just after the Sub-circuit section.
The Value menu/Scientific calculator
All values in the schematic section are entered via the VALUE menu.
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The VALUE menu has all the standard E24 component values, and you can type in values and expressions directly. <<<,<< and >>,>>> decrease and increase the current value by a factor of 2 and 10 respectively. The = button evaluates the expression.
To use this calculator - just type your equation straight in as text, then press the = button.
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Component values can be used by typing in the component names, e.g.:
"R1/R2" or 10k - R1.
When components are swept (with the M-Carlo /Sweeper option) these values hold true for the sweeps also.
Expressions can use any operator you like, as detailed below.
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Available Functions
| Function | Description
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| LOG | Natural log
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| LOG10 | log based on 10
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| EXP | Natural exponent
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| EXP10 | exponent based on 10
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| SQRT | Square root
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| SIN | Sine (radians)
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| COS | Cosine (radians)
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| TAN | Tangent
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| ASIN | Arc-sine (radians)
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| ACOS | Arc-cosine (radians)
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| ATAN | Arc-tangent
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| ABS | Absolute magnitude
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Available Operators
| Function | Operator
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| + | PLUS
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| - | MINUS
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| * | MULTIPLY
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| / | DIVIDE
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| ^ | POWER
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| (..) | Parenthesis (any depth)
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Naming components
All component names or instance names must be unique and have the correct prefix. NODE s however are the exception: see below.
Prefixes do not need to have any relation to the prefix required for netlisting. A components prefix can be set from the symbol editor .
A standard name is one like R1 etc., the prefix followed by a number. While using standard names it is useful is the sequence is complete, for one thing it makes the parts-list look better. SUMO can help in two ways. Firstly, if a component with a standard name is re-named to an existing standard name, the option of 'shuffling up' the other numbers is given. e.g.
Components R1, R2, R3 and R4 in a circuit
renaming R2 as R3, after the shuffle creates the names:
R1, R3, R4 and R5
Secondly, the sequence may be broken as a circuit is modified. SUMO can automatically 'condense' all of the standard names, using the CONDENSE function of the EDIT menu. Starting with the lowest standard name, components are re-named in sequence. Thus the sequence can start at any number, for example the first resister can be R400, and the rest will follow.
The visibility of names on the circuit can be toggled from the OPTIONS menu. This is accessed from the EDIT menu;- ALT-E.
Grounding the circuit
All circuit elements must have at least one path to ground (  ) This provides the absolute zero voltage reference, without which simulators do not work. Enter grounds just like any other single terminal component, attaching them to the appropriate wires.
Connecting wires and named nodes
All wire connections are shown by pads or blobs, which are rationalised after each drawing operation. To cross two wires (or components) without making contact, draw them straight across. To join them, draw the wire or component up to the junction, release (at which stage a blob will automatically be inserted,) then press and continue drawing.
Wires and components behave in the same way while drawing schematics. As far as SUMO is concerned there is no difference.
NODES with the same names are electrically connected, so you may use them to connect various points of your circuit.
 
The two circuits above are equivalent
The names of NODEs are case -insensitive for joining purposes.
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