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Electrical and Electronic Components Available in National Instruments Multisim
Summary: This module provides a brief introduction to electrical and electronic components available in National Instruments Multisim. Multisim is fully featured SPICE schematic capture and simulation tool used for circuit design, simulation, and in combination with Ultiboard for layout of custom PCBs.
Components
Components Overview
Components comprise the basis for any
schematic. A component is any part that can be placed onto the
schematic. Multisim defines two broad categories of parts: real and
virtual. It is important to understand the difference between these
parts, in order to fully utilize their advantages.
Real components can be differentiated from
virtual parts because real components have a specific value that
cannot be changed, and a PCB footprint.
Virtual components are simulation-only
components, which can be assigned user-defined characteristics. For
example, a virtual resistor can take on any resistance (such as
3.86654 Ohms). Virtual components help designers to check
calculations by simulating designs with precise component values.
Virtual components can also be idealized components such as the
4-pin Hex display shown in Figure 1.
Multisim also provides other classifications
of components: analog, digital, mixed-mode, animated, interactive,
multi-section digital, electromechanical, and radio-frequency (RF)
components.
 Figure 1:
Various Component Symbols:
7-Segment Display, Diode D1, Voltage Source V1, NAND gate U2A,
Microcontroller U3 and Transistor Q1
|
Interactive Components
Multisim provides a method for interacting
with certain components that are placed on the schematic. Changes
to these components will affect the simulation results on-the-fly.
Components are controlled by pressing the key listed beside the
component.
For the components shown in Figure 2 below,
pressing the A keywill increase the resistance of the potentiometer
toward 100% of the shown value (1kΩ); to decrease the resistance,
hold the Shift key then press the A key. Pressing the Spacebar will
toggle the switch to be either closed or open.
The keyboard shortcut key can be changed by
double-clicking on the component, and choosing the desired key from
the drop-down box as shown below.
 Figure 2: Examples Interactive
Components |
Component Characteristics
The following fields are visible from the
Component Browser.
 Figure 3: Component Information |
The Component Browser
The Component Browser is used to select
components for placement onto the schematic. To access the
Component Browser, click on any icon in the parts bin, or select
Place/Component. The default keyboard shortcut to place a component
is Ctrl-W.Double-click on the desired component to place it on the
schematic. The component will “ghost” the mouse cursor until the
left mouse button is clicked again to place the component.
 Figure 4: The Parts Bin or Component Toolbar |
 Figure 5: The Component Browser |
To search this view, simply start typing the
name of the desired component, and the browser will automatically
display matching candidate parts. Optionally, for a more detailed
search, click on the Search button.
The Component Browser shows the current
database in which the displayed parts are stored. Multisim
organizes the parts by group, and family. The browser also shows
the symbol, a description of the component in the Function field,
the model, and the footprint / manufacturer.
The wildcard character ‘*’can be used to
match any set of characters. For example “LM*78” would match
components “LM*AD” would return both “LM101AD” and “LM108AD”, among
others.
Note:Any component may have multiple models
associated with it. Each model may account for varying physical
characteristics of the component. For example, the LM358M opamp has
five visible pins, but only three of them are used in one model,
ignoring the power supply terminals. More information about models
can be found by selecting the desired model from the Model
Manuf.\ID field, and click on the Model button.
Databases
There are three levels of database provided
by Multisim:
- The Master Database is read-only, and contains components supplied by Electronics Workbench.
- The User Database is private to the individual user logged onto the computer. It is used for components built by an individual that are not intended to be shared.
- The Corporate Database is used to store custom components that are intended to be shared across an organization. The Corporate Database can be shared on a network.
Database management tools are supplied in
order to move components between databases, merge databases, and
edit them. All the databases are divided into groups and then into
families within those groups. When a designer chooses a component
from the database and drops it onto the circuit, a copy of the
component is placed onto the circuit. Any edits made to the
component in the circuit do not affect the original database
copy.
Edits made to the component in the database do
not affect the previously placed components, but will affect all
subsequently placed components of that type. When a circuit is
saved, component information is saved in the Multisim file. On
load, the user has the option to keep the loaded parts as is, to
make copies to place into their user or corporate database, or to
update similarly-named components with the latest values from the
database. Note: The Database Manager can be opened by selecting
Tools/Database/Database Manager. To edit Master Database parts,
copy them to the User or Corporate Database.
 Figure 6: Database Manager |
Creating Custom Components
Multisim includes the ability to create and
edit components to satisfy the needs of any design. The two methods
available are the Component Wizard, and the Component Properties
dialog box.
To access the Component Wizard, select
Tools/Component Wizard. The component wizard allows designers to
enter all pertinent component information, such as symbol, and
SPICE model (Figure 7).
To access the Component Properties dialog box,
double-click on a placed component, click on the Value tab, and
click the Edit Component in DB button (Figure 8).
 Figure 7: Component Wizard |
 Figure 8: Component Properties Dialog Box |
More details on creating custom components
are available in the helpfiles.
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This work is licensed by Janell Rodriguez and Erik Luther. See the Creative Commons License about permission to reuse this material.
Last edited by Janell Rodriguez on Aug 3, 2006 11:34 am GMT-5.
"This course introduces National Instruments Multisim through instructional modules and hands-on exercises. Multisim is an interactive, graphical schematic capture tool and SPICE simulator that […]"