Knob
Change parameter or variable value using knob with customizable appearance
Since R2021a
Libraries:
Simulink /
Dashboard /
Customizable Blocks
Description
Use the Knob block to tune the value of a variable or block parameter to during simulation. When you use the Knob block in the Customizable Blocks library, you can customize the appearance of the block so that it looks like a control in a real system. You can modify the range and tick values on the Knob block to fit the desired range for the value you want to tune. Use the Knob block with other dashboard blocks to create an interactive dashboard to control your model.
To tune a value when the simulation is running, use your pointer to drag the handle to the scale value to which you want to set the connected variable or block parameter. To tune a value when the simulation is not running, select the Knob block, and then drag the handle to the scale value to which you want to set the connected variable or block parameter.
Note
Double-clicking a connected Knob block during simulation does not open its dialog box. Clicking a connected Knob block to select the block, and then double-clicking the block also does not open its dialog box. To edit the block parameters in these cases, use the Property Inspector or right-click the block and select Block Parameters from the context menu.
Customize Knob Blocks
When you add a Knob block to your model, the block is preconfigured with a default design. You can use the block with the default design or customize the appearance of the block.
To customize the appearance of the block, use design mode. After selecting the block, you can enter design mode in one of three ways:
In the Simulink® Toolstrip, on the block-specific tab, under Design, click Edit.
In the Property Inspector, on the Design tab, click Edit.
Pause on the ellipsis that appears over the block and click the Edit Custom Block button
.
In design mode, you can use the toolbar above the block to customize the circular gauge. To access additional customization options or to enter exact values for design settings, use the Design tab in the Property Inspector.
Design Mode Actions
| Action | Available in Toolbar | Available in Design Tab |
|---|---|---|
Upload a handle image. | Yes | Yes |
Upload a background image. | Yes | Yes |
Set a solid background color. | No | Yes |
Upload a foreground image. | No | Yes |
Change the color and opacity of the scale tick marks, scale labels, or value bar. | Yes | Yes |
Change the arc length of the scale. | No | Yes |
Specify the scale direction as clockwise or counterclockwise. | No | Yes |
Specify the location of the origin from which the value bar grows. | No | Yes |
Change the size of the scale and handle. | No | Yes |
Change the position the scale and handle. | No | Yes |
To change the color and opacity of the scale tick marks, scale labels, or value bar using the toolbar, in the second section of the toolbar from the left, select the component whose color you want to change. To change the color, click the color wheel. To change the opacity, move the slider.
In addition to customizing the block design using the toolbar and Design tab, you can also resize and reposition components interactively in the canvas. The movement of the handle is limited to the line that passes through the center of the block and the minimum value on the scale.
When you finish editing the design, to exit design mode, click the X in the upper right of the canvas.
Connect Dashboard Blocks
Dashboard blocks do not use ports to connect to model elements. To connect a dashboard
block, use connect mode. To enter connect mode on an unconnected block, pause on the block
you want to connect and click the Connect button 
. To enter connect mode on a connected block, select the
block, pause on the ellipsis that appears (…), and in the action menu that expands, click
the Connect button.
To connect a control block to a parameter in your model or to change the connection of a
control block, enter connect mode. Select the block to whose parameter you want to connect.
From the list that appears, select the parameter to which you want to connect. Then, pause
on the dashboard block and click the Done Connecting button .
The control block cannot connect to a parameter defined by a variable until you update the model diagram. To connect to a parameter defined by a variable or to modify the value of a variable that defines the value of a connected parameter when the simulation is not running, update the model diagram by pressing Ctrl+D.
You can connect to a parameter with a scalar value or to an element of a matrix or structure. For more information, see Connect Dashboard Blocks to Simulink Model.
You can also connect dashboard blocks to a Stateflow® chart. For more information, see Connect Dashboard Blocks to Stateflow (Stateflow).
This animation shows how to connect the Knob block to your model.
Parameter Logging
Tunable parameters connected to dashboard blocks are logged to the Simulation Data
Inspector, where you can view the parameter values along with logged signal data. You can
access logged parameter data in the MATLAB® workspace by exporting the parameter data from the Simulation Data Inspector
by using the UI or the Simulink.sdi.exportRun function. For more information about exporting
data using the Simulation Data Inspector UI, see Export Data to Workspace or File. The
parameter data is stored in a Simulink.SimulationData.Parameter object, accessible as an element in the
exported Simulink.SimulationData.Dataset.
Examples
Design Custom Knobs
Design knobs using the customizable Knob block.
Limitations
Except for the Dashboard Scope block and the Display block, dashboard blocks can only connect to real scalar signals.
You cannot use the Connection table in the Block Parameters dialog box to connect a dashboard block to a block that is commented out. When you connect a dashboard block to a commented block using connect mode, the dashboard block does not display the connected value until the you uncomment the block.
Dashboard blocks cannot connect to model elements inside referenced models.
When you simulate a model hierarchy, dashboard blocks inside referenced models do not update.
Dashboard blocks do not support rapid accelerator simulation.
When you connect a dashboard block to a variable or parameter during simulation, the data for that variable or parameter is not logged to the Simulation Data Inspector. To log variable and parameter data to the Simulation Data Inspector, connect the dashboard block to the variable or parameter prior to simulation.
When you simulate a model in external mode with the Default parameter behavior set to Inlined, dashboard blocks can appear to change parameter and variable values. However, the change does not propagate to the simulation. For example, Gain blocks display changes made to the Gain parameter using the dashboard blocks, but the Gain value used in the simulation does not change.
Parameters
Use the Property Inspector and the Block Parameters dialog box to specify the values of the block parameters. To set the core parameters of the dashboard block, use the Block Parameters dialog box or the Parameters tab in the Property Inspector. To customize the block, use the Design tab in the Property Inspector. To open the Block Parameters dialog box for a block, double-click the block. To open the Property Inspector, on the Modeling tab, under Design, select Property Inspector.
Parameters
To set the core parameters of the dashboard block, open the Property Inspector and click the Parameters tab.
ConnectionConnection — Block parameter value to connect
parameter value connection options
Dashboard blocks do not use ports to connect to model elements. To connect dashboard blocks to parameter values in your model, use connect mode, the Simulink Toolstrip, or the Connection table in the Block Parameters dialog box. You can connect to a parameter with a scalar value, or to an element of a matrix. For information about connect mode and how to connect using the toolstrip, see Connect Dashboard Blocks to Simulink Model.
To connect a control block to a parameter with a scalar value or change the connection of a control block to a parameter with a scalar value using the Connection table:
Select the block.
To connect the block, in the Property Inspector, on the Parameters tab, click Connect. To change the connection of the block, click Change instead.
Select the block to whose parameter value you want to connect.
In the table, select the parameter to which you want to connect.
Click Apply.
The control block cannot connect to a parameter defined by a variable until you update the model diagram. To connect to a parameter defined by a variable or to modify the value of a variable that defines the value of a connected parameter when the simulation is not running, update the model diagram by pressing Ctrl+D.
You can also connect dashboard blocks to a Stateflow chart. For more information, see Connect Dashboard Blocks to Stateflow (Stateflow).
Programmatic Use
To programmatically connect a dashboard block to a tunable parameter, use a
Simulink.HMI.ParamSourceInfo object. The
Simulink.HMI.ParamSourceInfo object contains four properties.
Some properties apply to connecting dashboard blocks to parameters defined by
values, and some apply to connecting dashboard blocks to parameters defined by
variables. Not all fields have a value for a connection because a given dashboard
block connects to either to a parameter defined by a value or to a parameter defined
by a variable.
Block Parameter:
Binding |
Type:
Simulink.HMI.ParamSourceInfo |
Default:
[] |
Minimum — Minimum tick mark value
0 (default) | scalar
Finite, real, double, scalar value specifying the minimum tick mark value for the scale. The parameter value must be less than the value of the Maximum parameter.
Programmatic Use
To programmatically set the Minimum parameter, use a
1-by-3 vector containing values for the
Minimum, Tick Interval, and
Maximum parameters, in that order. To use the
auto value for the Tick Interval, leave
the Tick Interval position in the vector empty, or specify
-1.
Block Parameter:
Limits |
Type:
1x3 vector |
Default:
[0 -1 100] |
Maximum — Maximum tick mark value
100 (default) | scalar
Finite, real, double, scalar value specifying the maximum tick mark value for the scale. The parameter value must be greater than the value of the Minimum parameter.
Programmatic Use
To programmatically set the Maximum parameter, use a
1-by-3 vector containing values for the
Minimum, Tick Interval, and
Maximum parameters, in that order. To use the
auto value for the Tick Interval, leave
the Tick Interval position in the vector empty, or specify
-1.
Block Parameter:
Limits |
Type:
1x3 vector |
Default:
[0 -1 100] |
Tick Interval — Interval between major tick marks
auto (default) | scalar
Finite, real, positive, whole, scalar value specifying the interval of major tick
marks on the scale. When set to auto, the block automatically adjusts
the tick interval based on the values of the Maximum and
Minimum parameters.
Programmatic Use
To programmatically set the Tick Interval parameter, use a
1-by-3 vector containing values for the
Minimum, Tick Interval, and
Maximum parameters, in that order. To use the
auto value for the Tick Interval, leave
the Tick Interval position in the vector empty, or specify
-1.
Block Parameter:
Limits |
Type:
1x3 vector |
Default:
[0 -1 100] |
Direction — Direction of increasing scale values
Clockwise (default) | Counterclockwise
Set the direction of increasing scale values.
Programmatic Use
Block Parameter:
ScaleDirection |
| Type: character vector |
Values:
'Clockwise' | 'Counterclockwise'
|
Default:
'Clockwise' |
Label — Position of label displaying name of connected element
Hide (default) | Bottom | Top
You can display the name of the element to which the dashboard block connects in a
label positioned at the top or bottom of the block, or you can hide the label. If you
want the label to be visible, specify the position. If you do not want the label to be
visible, select Hide.
Note
When the dashboard block is not connected to an element, the label is blank.
Programmatic Use
Block Parameter:
LabelPosition |
| Type: character vector |
Values:
'Hide' | 'Bottom' |
'Top' |
Default:
'Hide' |
Lock Aspect Ratio — Option to maintain block aspect ratio
on (default) | off
Select this parameter to maintain the aspect ratio when resizing the block in the Simulink canvas.
When the aspect ratio is locked, adding a new background image changes the aspect ratio of the block to match the aspect ratio of the background image. When the aspect ratio is unlocked, adding a new background image does not change the aspect ratio of the block, but instead changes the aspect ratio of the background image to fit the size of the block.
When the aspect ratio is locked, pressing the Shift key while resizing a block temporarily unlocks the aspect ratio. When you release the Shift key, the aspect ratio locks. When the aspect ratio is unlocked, pressing the Shift key while resizing a block temporarily locks the aspect ratio. When you release the Shift key, the aspect ratio unlocks.
Design
To customize the dashboard block, open the Property Inspector, click the Design tab, and click Edit.
KnobLock Aspect Ratio — Option to maintain block aspect ratio
on (default) | off
Select this parameter to maintain the aspect ratio when resizing the block in the Simulink canvas.
When the aspect ratio is locked, adding a new background image changes the aspect ratio of the block to match that of the background image. When the aspect ratio is unlocked, adding a new background image does not change the proportions of the block but instead stretches or scales the background image to fit the size of the block.
When the aspect ratio is locked, pressing the Shift key while resizing a block unlocks the aspect ratio. When you release the Shift key, the aspect ratio locks. When the aspect ratio is unlocked, pressing the Shift key while resizing a block locks the aspect ratio. When you release the Shift key, the aspect ratio unlocks.
Minimum — Minimum tick mark value
0 (default) | scalar
Finite, real, double, scalar value specifying the minimum tick mark value for the scale. The parameter value must be less than the value of the Maximum parameter.
Programmatic Use
To programmatically set the Minimum parameter, use a
1-by-3
vector containing values for the
Minimum, Tick
Interval, and Maximum
parameters, in that order. To use the
auto value for the
Tick Interval, leave the
Tick Interval position in the
vector empty, or specify
-1.
Block Parameter: Limits |
Type: 1x3 vector |
Default: [0 -1 100] |
Maximum — Maximum tick mark value
100 (default) | scalar
Finite, real, double, scalar value specifying the maximum tick mark value for the scale. The parameter value must be greater than the value of the Minimum parameter.
Programmatic Use
To programmatically set the Maximum parameter, use a
1-by-3 vector containing values for the
Minimum, Tick Interval, and
Maximum parameters, in that order. To use the
auto value for the Tick Interval, leave
the Tick Interval position in the vector empty, or specify
-1.
Block Parameter: Limits |
Type: 1x3 vector |
Default: [0 -1 100] |
Tick Interval — Interval between major tick marks
auto (default) | scalar
Finite, real, positive, whole, scalar value specifying the interval of major tick marks on the scale. When set to auto, the block automatically adjusts the tick interval based on the values of the Maximum and Minimum parameters.
Programmatic Use
To programmatically set the Tick Interval parameter, use a
1-by-3 vector containing values for the
Minimum, Tick Interval, and
Maximum parameters, in that order. To use the
auto value for the Tick Interval, leave
the Tick Interval position in the vector empty, or specify
-1.
Block Parameter: Limits |
Type: 1x3 vector |
Default: [0 -1 100] |
Origin — Value on scale from which handle moves and value bar grows
auto (default) | scalar
Specify the value on the scale from which the handle moves and the value bar grows.
When set to auto, the Origin is the minimum of
the scale.
Example: 0
Direction — Direction of increasing scale values
Clockwise (default) | Counterclockwise
Set the direction of increasing scale values.
Programmatic Use
Block Parameter:
ScaleDirection |
| Type: character vector |
Values:
'Clockwise' | 'Counterclockwise'
|
Default:
'Clockwise' |
Arc — Arc length of scale
270 (default) | scalar
Specify the arc length of the scale as a scalar value, measured in degrees.
Example: 90
Start Angle — Angular location of scale minimum
135 (default) | scalar
Specify the angular location of the minimum scale value, measured in degrees clockwise from the horizontal axis pointing right.
Example: 0
Inner Radius — Radius of free end of scale tick marks
scalar
Specify the radius of the free end of the scale tick marks as a ratio of the
smaller of the two dimensions of the bounding box of the scale, width or
height. The Inner Radius can be larger than the
Outer Radius.
Example: 0.5
Outer Radius — Span line radius
scalar
Specify the span line radius as a ratio of the smaller of the two dimensions
of the bounding box of the scale, width or height. The Outer
Radius can be smaller than the Inner
Radius.
Example: 0.5
X Offset — Horizontal offset of left edge of scale bounding box from left edge of block
scalar
Specify the horizontal offset of the left edge of the bounding box of
the scale from the left edge of the block as a ratio of the
block width. Relative to the position of the scale when the
offset is 0, an offset with a negative value
moves the scale left, and an offset with a positive value moves
the scale right.
Example: 1
Y Offset — Vertical offset of top edge of scale bounding box from top edge of block
scalar
Specify the vertical offset of the top edge of the bounding box of the scale from the
top edge of the block as a ratio of the block height. Relative to the position of the
scale when the offset is 0, an offset with a negative value moves the
scale up, and an offset with a positive value moves the scale down.
Example: 1
Width — Scale width
scalar
Specify the width of the bounding box of the scale as a ratio of the block width.
Example: 2
Height — Scale height
scalar
Specify the height of the bounding box of the scale as a ratio of the block height.
Example: 2
Lock Aspect Ratio — Option to maintain scale aspect ratio
on (default) | off
Select this parameter to maintain the aspect ratio when resizing the scale using the Property Inspector.
Tick Color — Color of scale tick marks, span line, and block name
[r g b] vector
Set the color of the scale tick marks, the span line, and the block name. Choose a color from the palette of standard colors, or specify a custom color.
Tip
You can also set the Tick Color by choosing a Foreground Color on the Format tab of the Simulink Toolstrip.
To specify the color of the block text, use the Label Color parameter.
Programmatic Use
Specify the ForegroundColor parameter for the block as a string
or a character vector that defines a 1-by-3
[r g b] vector with values between 0 and
1.
Block Parameter:
ForegroundColor |
| Type: character vector | string |
Values:
[r g b] vector |
Label Color — Scale label font color
[r g b] vector
Choose a font color for the scale label from the palette of standard colors, or specify a custom color.
Tip
To specify the color of the scale, use the Tick Color parameter.
Label Radius — Distance of labels from scale center
scalar
Specify the distance of the labels from the center of the scale as a ratio of the smaller of the two block dimensions, width or height.
Example: 0.5
Width — Handle image width
scalar
Specify the width of the handle image as a ratio of the smaller of the two dimensions of the bounding box of the scale, width or length.
Example: 1
Height — Handle image height
scalar
Specify the height of the handle image as a ratio of the smaller of the two dimensions of the bounding box of the scale, width or length.
Example: 1
Lock Aspect Ratio — Option to maintain image aspect ratio
on (default) | off
Select this parameter to maintain the aspect ratio when resizing the image using the Property Inspector.
Rotate Image — Rotation of handle image
180 (default) | scalar
Rotate the handle image about its center in 90 degree increments.
Example: 90
Offset from Center — Offset of handle image center from scale center
0 (default) | scalar
Specify the distance from the center of the handle image to the center of the scale as a ratio of the diameter of the scale.
Example: 1
Use Background Color — Option to specify solid block background color
off (default) | on
For the block background, you can provide a background image, or to select a solid color. To select a solid background color, turn Use Background Color on. To provide a background image, turn Use Background Color off.
Note
Changing the background color using the toolstrip removes the background image and enables the Use Background Color option.
When you use a solid background with the Circular Gauge block, you can design noncircular gauges. When the scale arc angle is 180° or smaller, the background shape conforms to the scale.
Example: on
Background Color — Block background color
[r g b] vector
To select a solid background color, enable the Use Background Color parameter. Then, choose a background color from the palette of standard colors, or specify a custom color.
Note
When you use a solid background with the Circular Gauge block, you can design noncircular gauges. When the scale arc angle is 180° or smaller, the background shape conforms to the scale.
Programmatic Use
Specify the BackgroundColor parameter for the block as a
1-by-3
[r g b] vector with values between 0 and
1 that is formatted as a string or a character vector.
Block Parameter:
BackgroundColor |
| Type: character vector | string |
Values:
[r g b] vector |
Opacity — Block background opacity
1 (default) | scalar
Specify the block background opacity as a scalar value from 0 to
1.
Example: 0.5
Corner radius — Offset of outer edge of area with block background color from tick marks
scalar
Set the offset of the outer edge of the area covered by the block background color
from tick marks, specified as a scalar value from 0 to
1.
Example: 0.1
X Offset — Horizontal offset of left edge of foreground image from left edge of block
scalar
Specify the horizontal offset of the left edge of the image from the left edge of the
block as a ratio of the block width. Relative to the position of the image when the
offset is 0, an offset with a negative value moves the image left,
and an offset with a positive value moves the image right.
Example: 1
Y Offset — Vertical offset of top edge of foreground image from top edge of block
scalar
Specify the vertical offset of the top edge of the image from the top edge of the
block as a ratio of the block height. Relative to the position of the image when the
offset is 0, an offset with a negative value moves the image up, and
a positive value moves the image down.
Example: 1
Width — Foreground image width
scalar
Specify the width of the foreground image as a ratio of the block width.
Example: 0.5
Height — Foreground image height
scalar
Specify the height of the foreground image as a ratio of the block height.
Example: 0.5
Lock Aspect Ratio — Option to maintain foreground image aspect ratio
on (default) | off
Select this parameter to maintain the aspect ratio when resizing the image using the Property Inspector.
Block Characteristics
Data Types |
|
Direct Feedthrough |
|
Multidimensional Signals |
|
Variable-Size Signals |
|
Zero-Crossing Detection |
|
Extended Capabilities
Version History
Introduced in R2021aR2023b: Open panel in new window
Starting in R2023b, you can open a dashboard panel in a new window. To do so, select the
panel and pause on the ellipsis that appears. In the action menu that expands, click Open In
New Window 
.
You can minimize and restore the new window containing the panel separately from the model window. From the panel window, you can run, pause, stop, and step through the simulation. In the panel window, you can edit the panel and the blocks it contains.
To return the panel to the model canvas, in the panel window toolstrip, click Open in
canvas 
.
For more information about opening a panel in a new window, see Open Panels in New Window.
See Also
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