Voltage divider tutorial outline

Sheila P. Werth/Kaung Myat Win
ECE2010 Alumni
Voltage divider tutorial outline
Outline
1. Introduction
2. Opening the library
3. Creating a new model
4. Converting from Simscape to Simulink
5. Example: Voltage divider
1. Introduction
In this course, you will be using Simulink and Simscape to model some of the circuits that
you will be building in lab and learning about in class. These tools can be very useful in
modeling electrical and mechanical systems.
Before beginning a model, it is important to understand the basic organization of Simulink
and Simscape. Because these products are created by MathWorks, you can open them from
MATLAB.
To familiarize yourself with the program, you will start by making a basic
voltage divider model.
2. Opening the library

Type‘simulink’in the MATLAB command window. This will open the
Simulink Library Browser. Despite the name, this browser contains components
from other toolboxes besides Simulink.
Figure 1: Simulink Library Browser
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Sheila P. Werth/Kaung Myat Win

ECE2010 Alumni
The library is organized into several different tool boxes.
Each toolbox in
composed of specific components.

Circuit building components can be found by expanding Simscape and looking
in the foundations library or the SimElectronics library. These components work
with physical signals. Physical signals have units, while Simulink signals do not.

Simulink blocks are used to process and view data. To view and analyze the
results of a model, you must convert the physical signal in your Simscape model
to a Simulink signal.
3. Creating a new model

To open a new model click on the ‘new model’
button just below the ‘file’ button in the Simulink
Library Browser.You can drag components from
the Simulink Library Browser into the new
modelwindow.
Figure 2: How to Create New
Model

To save a model, click
or you can go to
File Savefile_name.mdl . Be sure to save it in
a location where you can retrieve later.Save
your file asvoltage_divider.mdl.

In order to run, every Simscape model must
have a solver configuration block. This block can
be connected anywhere in the model. Because
every model also needs an electrical reference
(ground), it is good practice to begin by adding Figure 3: Solver with Electrical
and connecting both of these blocks in your
Reference
model.

Drag a solver configuration block and an electrical reference from the library
into your model. Connect them.
i. The solver configuration block can be found in the library browser:
Simscape Utilities  Solver Configuration
ii. The electrical reference (ground) can also be found in the library browser:
Simscape Foundation Library  Electrical Elements 
Electrical Reference

Blocks can be connected by dragging your curser from one input or output node
to another.
A complete connection will appear black while an incomplete
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Sheila P. Werth/Kaung Myat Win
ECE2010 Alumni
connection will appear red. Do not let red segments stay in your model because
it will not run.

Simulink blocks do not connect directly to Simscape blocks. To connect them,
see instructions in part 4.
4. Creating the voltage divider

Drag and drop two resistors from the library into
your newly created model window. You can change
the format or properties by right-clicking the model.
Right-click the resistor model, choose FormatRotate
BlockClockwise to rotate the resistor. You can also
use Crtl+R shortcut to do the same action.

Drag a source from the library into your model to Figure 4: Solver, Ground, and
power the resistors. Connect the components as shown Two Resistors
in Figure 5. There are two kinds of electrical sources in
the Simscape library. The first one is under Foundation
Library ElectricalElectrical Sources. The second
one
is
under
Foundation
LibrarySimElectronicsSources. You can use either
DC voltage source or Generic Battery. The only
difference is that when you use Generic Battery, you
can define the internal resistance and battery charging
capacity in Generic Battery. You should use DC voltage
Figure 5: Voltage divider
source under Electrical Sources for simplicity. By configuration
double clicking, you can access a model’s parameters
and you can change the parameters according to your needs. Clicking
in the parameters window directs you to online help page. Connect
DC voltage source to two resistors in series.

Make sure that the Solver Configuration and Electrical Reference are
connected to your circuit as shown in Figure 5.
Simscape portion of your model.
You have now built the
To run the model, you will need to convert
from Simscape to Simulink.
5. Converting from Simscape to Simulink

As discussed above, a Simscape model will create a physical signal. Examples of
physical signals include voltage, current, speed, etc. These signals have units
like Volts, Amps, Meters/s etc.
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Sheila P. Werth/Kaung Myat Win

ECE2010 Alumni
To view the results of your model you must convert to a Simulink signal. A
Simulink signal is simply numerical data with no units.

These are the steps to converting from Simscape physical signal to a Simulink
signal:
i. Connect a voltage sensor across the ports that you want to measure.
Electrical sensors include voltage and current sensors. There are other
types of sensors you may use in the future.
Simscape Foundation Library  Electrical Electrical Sensors
ii. Connect a PS-Simulink Converter block to the sensor block.
Simscape Utilities  PS-Simulink Converter
iii. Connect a Display block to view your results.There are other sinks that
you will use in the future.
Simulink  Sinks  Display
Figure 6: The Complete Model of Voltage Divider
6. Simulating the model
Change the resistor values and voltage source by double clicking on the block and typing
the desired value. Change the configuration parameters as shown in Figure 7 shown
below.

Set Stop time to 10. This is the amount of time you want the model to be simulated.
Since this circuit is only a DC analysis, the stop time does not matter and we will
leave it as it is.
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Sheila P. Werth/Kaung Myat Win

ECE2010 Alumni
Set Max step size to 1. Normally, the ‘auto’ step size is defined as the total simulation
time divided by 50, which would be equal to be 0.2. Since we are doing DC analysis,
we would not need this much step size as the values we get will be constant over
time.

Set the solver to ode23t (mod. stiff/Trapezoid). Since the model is stiff as it contains
Simscape components, we will use one of the solvers (ode23t, ode15s or ode14x
(fixed-step)) preferred for the stiff models.

Press OK button after you have changed the fields as shown in Figure 7.
Figure 7: Configuration Parameters for the voltage divider model

To run the model, click
from the tool bar to simulate the model. You can also
hit Ctrl+T or go to SimulationStart from the task bar. Does the answer meet your
expectations?
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