Difference between revisions of "Introduction to LabVIEW"

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= 3D Printing and Prototyping Video =
= Objective =
General Engineering has created a video that covers the fundamental concepts of 3D printing for the semester-long design project: [https://stream.nyu.edu/media/EG+1003+Lab+4A+3D+Printing+and+Prototyping/1_hb8q9n70 3D Printing and Prototyping Video]. This video provides the fundamental principles behind the engineering design process and will help determine the best practices for 3D printing objects to complete the semester-long design project. Material covered in the video will be on the lab 4 quiz. Viewing the video is a mandatory pre-lab assignment.


= MakerSpace Orientation =
The experimental objective of this lab is to use LabVIEW to design a heating and cooling system and a lighting system and to test both systems. Building these systems will demonstrate the potential for using simulated instruments in a laboratory. These programs will also obtain data from outside the computer and incorporate it into a program design.
Part of this lab session will be used to take a tour of the MakerSpace. This orientation will include basic training on some of the MakerSpace equipment you will be able to use in the future.  


= Objectives =
= Overview =
The experimental objective of this lab is to design two systems using LabVIEW: a digital calculator and a thermal control system that automatically operates heating and cooling equipment.
<!--''Adapted from Introduction to LabVIEW, Six-Hour Course.<ref name="one">''Introduction to LabVIEW, Six-Hour Course ''[Courseware]. (June 2003) Austin, TX: Worldwide Technical Support and Product Information, National Instruments Corporation</ref>''-->
 
The <b>Laboratory Virtual Instrument Engineering Workbench (LabVIEW)</b> is a development environment designed by National Instruments that creates graphic-based programs called virtual instruments (VIs) that simulate actual laboratory instruments. A VI consists of two parts: a front panel and a back panel (Figure 1). The <b>front panel</b> allows the user to interact with the VI by displaying outputs and allowing the user to supply the program with inputs. The <b>back panel</b> consists of the code used by the VI to obtain inputs from the front panel, operate on the inputs, and display the results.
 
[[Image:Lab 7 Figure 1.jpg|500px|thumb|center|Figure 1: Front Panel (Left) and Back Panel (Right)]]
 
The front panel is built using controls and indicators. <b>Controls</b> are inputs that allow a user to supply information to the VI. <b>Indicators</b> are outputs that display the results based on the inputs given to the VI. Controls can be switches, knobs, dials, and buttons. Indicators can be meters, gauges, LEDs, and displays. These are located on the Controls palette and are placed on the front panel (Figure 2).
 
[[Image:Lab 7 Figure 2.jpg|225px|thumb|center|Figure 2: Controls Palette]]
 
The back panel, which is also known as the block diagram, contains the graphic-based source code. The environment of the back panel is navigated using the <b>Tools palette</b> (Figure 3).
 
[[Image:Lab 7 Figure 3.png|99px|frame|center|Figure 3: Tools Palette]]
 
In Figure 3, only the icons in colored boxed will be used in this experiment. The <b><span style="color:red">operating tool</span></b> changes the value of a control (such as a switch or LED). The <b><span style="color:orange">positioning tool</span></b> positions, resizes, and selects objects. The <b><span style="color:green">labeling tool</span></b> is used to create and edit all labels in the VI, such as the name of a Boolean control. The <b><span style="color:blue">wiring tool</span></b> wires objects together on the back panel. The <b><span style="color:purple">scrolling tool</span></b> allows scrolling the window by clicking and dragging.
 
All of the objects placed on the front panel will appear on the back panel as terminals. <b>Terminals</b> are the ports that exchange information between the front panel and back panel, and appear with small triangles in the icons to indicate that they can be used to process information (Figure 4). A control terminal has the triangle to the right to indicate that it sends data to be processed. An indicator terminal has the triangle to the left to indicate that it receives data.
 
[[Image:Lab 7 Figure 4.jpg|500px|frame|center|Figure 4: Control and Indicator Terminals]]
 
The back panel also contains structures and functions that perform operations on controls and supply data to indicators. Structures and functions are found on the Functions palette and are placed on the back panel (Figure 5).
 
[[Image:Lab 7 Figure 5.jpg|225px|thumb|center|Figure 5: Functions Palette]]
 
<b>Structures</b> are process control elements, such as while loops and for loops. The structure to be used in this experiment is the <b>case structure</b> (Figure 6), which is essentially multiple if-statements. A case structure contains multiple subdiagrams (or cases), and a case will be executed depending on the input to the case structure.
 
[[Image:Lab 7 Figure 6.jpg|400px|thumb|center|Figure 6: Case Structure]]
 
In Figure 6, Item 1 is the selector label, which displays the input value for which the associated case will execute. The black arrows on the side of the selector label toggle between the different cases. Item 2 is the area for the code that executes for the specific input in the selector label. When the selector label is toggled, the code in this area will also change. Item 3 is the case selector, which gives the input value to the case structure. The data type that is wired to the case selector will determine the possible cases. For example, if a Boolean data type is wired to the case selector, the possible cases will only be true and false.
 
<b>Functions</b> are the fundamental operating elements of LabVIEW, and have input and output terminals to pass data in and out. They are indicated by a pale yellow background in the icon (Figure 7).
 
[[Image:Lab 7 Figure 7.jpg|200px|thumb|center|Figure 7: Examples of Functions]]


Building these systems will demonstrate the potential for using simulated instruments in a laboratory. These programs will also obtain data from outside the computer and incorporate it into a program design. In contrast to the more common text-based languages, LabVIEW uses a graphical programming language. The logic of graphical programming will be shown during the course of this lab.
Functions have a certain number of inputs and outputs, depending on the type of function. For example, the addition function (leftmost icon in Figure 7) has two inputs as it will add the two inputs together, and it will have one output, which is the sum of the inputs. The inputs are wired to the left side of the function, and the outputs are wired to the right side of the function. The number of inputs and outputs of a function can be observed by hovering over the icon with the wiring tool and observing the terminals that appear (Figure 8).


= Overview =
[[Image:Lab 7 Figure 8.jpg|113px|thumb|center|Figure 8: Function Terminals]]
''Adapted from Introduction to LabVIEW, Six-Hour Course.<ref name="one">''Introduction to LabVIEW, Six-Hour Course ''[Courseware]. (June 2003) Austin, TX: Worldwide Technical Support and Product Information, National Instruments Corporation</ref>''


LabVIEW is a development environment for creating graphical programs called '''''virtual instruments (VI)''''', that simulate actual laboratory instruments. A VI consists of two parts: a '''''front panel''''' and a '''''back panel'''''. The '''''front panel''''' allows the user to interact with the VI by displaying output and allowing the user to supply the program with input. The '''''back panel''''' consists of the code used by the VI to obtain input from the '''''front panel''''', operate on the input, and display the results.
Collectively, controls, indicators, structures, and functions are referred to as nodes. <b>Nodes</b> are connected to one another using the wiring tool. For example, two controls and an indicator can be wired to the addition function so that the indicator displays the sum of the two controls (Figure 9).


The '''''front panel''''' is built using '''''controls''''' and '''''indicators'''''. '''''Controls''''' are '''inputs''' that allow a user to supply information to the VI. '''''Indicators''''' are '''outputs''' that display the results based on the inputs given to the VI. Controls can be switches, knobs, dials, and buttons. Indicators can be meters, gauges, LEDs, and displays. These are located on the '''''controls palette''''' and can be placed on the front panel.
[[Image:Lab 7 Figure 9.png|226px|thumb|center|Figure 9: Wiring Nodes]]


The '''''back panel''''', which is a '''''block diagram''''', contains the graphical source code. All of the objects placed on the '''''front panel''''' will appear on the '''''back panel''''' as ''terminals''. The '''''back panel''''' also contains '''structures''' and '''functions''' that perform operations on controls and supply data to indicators. '''Structures''' and '''functions '''are found on the '''''functions palette''''' and can be placed on the '''''back panel'''''. Collectively, controls, indicators, structures, and functions are referred to as '''''nodes'''''. '''''Nodes''''' are connected to one another using wires. For example, two controls and an indicator can be wired to the addition function so that the indicator displays the sum of the two controls.
The <b>toolbar</b> at the top of the front panel is used to execute and stop the program (Figure 10). The run tool (white arrow) runs the program once. The run continuously tool (two white arrows in a circle) keeps the program running continuously until the program is paused or stopped. This tool should be used when executing programs in this experiment. The abort execution tool (red stop sign) stops the VI immediately. The pause button (two vertical black rectangles) pauses the program, and can be clicked again to continue the program.


In any programming language, structures are used to create conditions. In LabVIEW, structures are accessed by opening the '''''functions palette''''' and selecting '''''Structures'''''. The following are some examples of structures:
[[Image:Lab 7 Figure 10.png|87px|thumb|center|Figure 10: Toolbar]]
* The '''''while loop''''' is similar to the ''do loop'' or ''while'' in text-based programming languages. It executes its subdiagram (or subroutine) until it receives a false value
* The '''''for loop''''' executes a subdiagram a set number of times specified by the value in the count terminal
* The '''''case structure''''' is similar to ''if/else'', ''switch/case'', or ''match/with'' in text-based programming languages. It contains multiple subdiagrams &mdash; one for each possible value of the input to the case structure


National Instruments' '''''Educational Laboratory Virtual Instrumentation Suite''''' (NI-ELVIS) board is one solution LabVIEW can utilize to physically interface with the outside world. Keep in mind that National Instruments offers different hardware solutions to meet clients' individual needs.
<b>National Instruments' Educational Laboratory Virtual Instrumentation Suite (NI ELVIS) board</b> (Figure 11) is one solution LabVIEW can utilize to physically interface with external devices. It is a modular engineering device that includes a breadboard, power supply, ground, thermocouple, oscilloscope, function analyzer, and other common lab instruments. In this experiment, an NI ELVIS board will be used to provide inputs and display outputs for the VIs that will be created.


Some useful key shortcuts when working in the LabVIEW environment are:  
[[Image:Lab 7 Figure 11.jpg|400px|thumb|center|Figure 11: NI ELVIS II+ Board]]
* CTRL+H: Show/hide context help
* CTRL+B: Clean up broken wiring
* CTRL+E: Toggle between front/back panels
* CTRL+Z: Undo last action


= Materials and Equipment =
= Materials and Equipment =
* A lab PC
 
* LabVIEW software
* Lab PC
* An NI-ELVIS II+ prototyping board
* LabVIEW 2019 software
* NI ELVIS II+ prototyping board
* Wires
* Two 100 kΩ resistors (brown, black, yellow)


= Procedure =
= Procedure =
# Open LabVIEW and select '''''Blank VI''''' under '''''Create Project'''''
# Click on '''''Window''''' and select '''''Tile Left &amp; Right''''' to set the front panel (left window) and back panel (right window) side by side. This will make them visible at the same time, making it easier to work
# On the right window, pull down the '''''View''''' menu, select '''''Tools Palette'''''
# On the left window, pull down the '''''View''''' menu again, select '''''Controls Palette'''''. At this point, the screen should look like Figure 1. Note the '''''Controls Palette''''' and the '''''Tools Palette''''', and their icons


[[Image:lab_labview_1.png|thumb|720px|center|Figure 1: LabVIEW workspace.]]
Note: Some tasks will be repeated and the same icons will be used. A LabVIEW digest of common tasks at the bottom of the page contains references for faster navigation.


For help with the operation of any LabVIEW icon, select Help from the main menu bar, choose Show Context Help, and click the icon for the operation that is unclear. It will be explained in the open window.
== Setting up a Blank VI ==


The approach for each of these projects is to place items on the front panel that the user will see and interact with. The corresponding items on the back panel will make the device work if the wiring is correct.
# Open LabVIEW and select Blank VI under Create Project.
# Click Window > Tile Left and Right to display the front panel (left window) and back panel (right window) side by side. This will make them visible at the same time, making it easier to work.
# With the back panel selected, click View > Tools Palette to open the Tools palette.
# With the front panel selected, click View > Controls Palette. The workspace should look like Figure 12. To open the Controls palette in the future, simply right click in the front panel.  Similarly, to open the Functions palette, simply right click in the back panel.


'''Note:''' Some tasks will be repeated and the same icons will be used. A LabVIEW digest at the end of this lab has references for faster navigation.
[[Image:lab_labview_1.png|thumb|500px|center|Figure 12: LabVIEW Workspace]]


== Design 1: Simple Calculator ==
For help with the operation of any LabVIEW icon, select Help > Show Context Help > click the icon for the operation that is unclear. It will be explained in the Context Help window.
Create a program that simulates a calculator that can add, subtract, and multiply.


# The '''''front panel''''' must contain:
== 1. Heating and Cooling System ==
## One slide to control the arithmetic operation to be performed. The instructions are:
### Select the '''Numeric''' icon [[Image:lab_labview_2.png]] under '''Modern''' on the '''''Controls Palette''''' (Figure 2). This will bring up the window shown in Figure 3
###: [[Image:lab_labview_3.png|frame|center|Figure 2: Controls palette.]]
###: [[Image:lab_labview_5.png|frame|center|Figure 3: Modern numeric controls.]]
### Select Horizontal Pointer Slide from the icons shown. Click on the left window to place the slide on the front panel at any location.
###: Note: The slide may be moved by clicking on it and holding down the left mouse button to drag the control to a preferred location. When correctly located, let go of the left mouse button. This will work for all items in both the front and back panels
###: Note: When items are placed on the front panel (left window), symbols corresponding to each item will appear on the back panel (right window). When the front panel is complete, the items on the back panel will be wired to make the calculator work.
### Click on the number 10 and change it to 2. Now the slide control will look like Figure 4
###: [[Image:lab_labview_6.png|frame|center|Figure 4: Slide control with range changed from 10 to 2.]]
### Right click on the slide to bring up a pull down menu. Select '''Representation''' and choose the '''I8''' icon. Figure 5 shows the pull down menu and the I8 icon. This completes the slide control on the front panel
###: [[Image:lab_labview_7.png|frame|center|Figure 5: Data type representation pull down menu.]]
## Select three Boolean indicators to specify the operation. The instructions are:
### On the '''''Controls Palette''''', select the '''Boolean''' icon [[Image:lab_labview_8.png]] under '''Modern'''. This will bring up the window shown in Figure 6
###: [[Image:lab_labview_9.png|frame|center|Figure 6: Modern Boolean controls.]]
### Select the '''Round LED''' icon from the icons shown. Click on the left window to place the LED on the front panel at a specific location. The best place to put it is centered under the slide. Do this two more times, placing the LEDs so there are three lights in a row under the slide
### Rename the three LEDs to correspond to the functions the calculator will be performing: add, subtract, and multiply. To rename each LED, click on the '''Edit Text''' icon [[Image:lab_labview_10.png]] on the '''''Tools Palette'''''. Then click on the labels on each LED and replace it with the proper text: "Add" for the left LED, "Subtract" for the center LED, and "Multiply" for the right LED.
## Two numeric controls will allow the user to input data from the keyboard. The instructions are:
### On the '''''Controls Palette''''', click on the '''Numeric''' icon under '''Modern'''. This will bring up the window shown in Figure 3
### Click on the '''Numeric Control''' icon and click on the left window to the left of the slide to place a numeric control there. This will create a window that allows data input. Click the '''Numeric Control''' icon again, and place another numeric control on the right side of the slide
## A numeric indicator to display the output. The instructions are:
### On the '''''Controls Palette''''', click on the '''Numeric Indicator''' icon and click on the left window centered below the three LEDs. This numeric indicator will display the answer from the calculator
###: '''Note''': The numeric indicator used for output is a different object from the two numeric controls which are for input that were constructed earlier in Item c.
### The finished front panel should look like Figure 7
###: [[Image:lab_labview_13.png|frame|center|Figure 7: Finished front panel.]]
#: As stated earlier, on the back panel there are icons corresponding to the controls and indicators that were placed on the front panel. They will be arranged, additional objects will be added, and they will be wired to make the calculator work.
# The '''''back panel''''' must contain:
## At least one case statement to control the arithmetic operations. This case statement will be the heart of the calculator. The instructions are:
### Drag all the Boolean nodes to the right edge of the window and all numeric controls and indicator to the bottom of the window. Place the slide node on the left edge of the window. This will leave a large area in the middle that will be filled in with the next steps. The back panel should look like Figure 8
###: [[Image:lab_labview_14.png|frame|center|Figure 8: Rearranged back panel.]]
### In the block diagram (back panel) of LabVIEW, go to the menu bar, select View, and choose '''''Functions Palette'''''. This will bring up the '''''Functions Palette''''', shown in Figure 9
###: [[Image:lab_labview_16.png|frame|center|Figure 9: '''''Functions palette'''''.]]
### Click on the '''Structures''' icon [[Image:lab_labview_17.png]] under '''Programming'''. This will bring up the window shown in Figure 10
###: [[Image:lab_labview_18.png|frame|center|Figure 10: Programming structure functions.]]
### Click on the '''Case Structure''' icon. Click on the right window to locate it on the back panel. It is a very large object and will have many connections. The best strategy is to locate it in the middle of the panel. Note that at the top of the object there a caption box with the value '''''True''''' in it. On each side of the caption box are arrows pointing to the left and right. Note also the question mark on the left side of the case structure object; any control outside of the case structure wired to the question mark determines which case is executed
### On the '''''Tools Palette''''', chose the Connect Wire icon [[Image:lab_labview_19.png]]. Connect the slide to the case structure by clicking on the slide object and then on the question mark on the left side of the case structure. The back panel should now look like Figure 11
###: [[Image:lab_labview_20.png|frame|center|Figure 11: Back panel slide to case structure connection.]]
### When the case statement is created, it only has two cases. Since there are three operations for the calculator, another case is needed. To add the third case operation, right-click the caption at the top of the case structure and select Add Case After, as shown in Figure 12
###: [[Image:lab_labview_21.png|frame|center|Figure 12: Adding another case.]]
### Now add the mathematical operations that the calculator should perform for each case. On the '''''Functions Palette''''', click on the '''Numeric''' icon [[Image:lab_labview_33.png]] under '''Programming'''. This will bring up the window shown in Figure 13
###: [[Image:lab_labview_23.png|frame|center|Figure 13: Numeric programming functions.]]
### Click on the left arrow at the top of the case structure box until the caption for the case structure changes to '''''0'''''. In the '''''Numeric Programming''''' window, click on the Add icon [[Image:lab_labview_26.png]], and click on a location in the middle of the case structure box to place it there
### Click on the right arrow at the top of the case structure box. This should change the caption for the case structure to '''''1'''''. In the '''''Numeric Programming''''' window, click on the Subtract icon [[Image:lab_labview_27.png]], and click on a location in the middle of the case structure to place it there
### Click on the right arrow at the top of the case structure box one more time, changing the number in the caption to '''''2'''''. In the '''''Numeric Programming''''' window, click on the Multiply icon [[Image:lab_labview_28.png]], and click on a location in the middle of the case structure to place it there. At this point, each case should look like the ones shown in Figures 14a-c. Check each case by clicking on the left and right arrows to change the case number in the caption
###: <div style="text-align: center; margin: 0px auto;"><div style="float: left; display: inline;">[[Image:lab_labview_29.png|thumb|240px|none|Figure 14a: Case structure: addition case.]]</div><div style="float: left; display: inline;">[[Image:lab_labview_30.png|thumb|240px|none|Figure 14b: Case structure: subtraction case.]]</div><div style="float: left; display: inline;">[[Image:lab_labview_31.png|thumb|240px|none|Figure 14c: Case structure: multiplication case.]]</div></div><br clear="both" />
### Wire the inputs to the calculator. Set the case structure case to zero by clicking on the left arrow until the caption reads '''''0'''''. The triangle inside should be addition, with a plus sign in the middle. Click on the Connect Wire icon [[Image:lab_labview_19.png]] on the '''''Tools Palette'''''. Click on the leftmost numeric control on the back panel, and click on the top left side of the operation triangle to wire the first numeric input to the input of the addition operation. Click on the other numeric control on the back panel, and on the left bottom of the addition triangle, establishing the second input. Click on the right side of the triangle, and click on the numeric indicator on the back panel. This will display the output of the addition calculation in the Numeric 3 box on the front panel. The addition function is complete. The back panel should look like Figure 15.
###: [[Image:lab_labview_32.png|frame|center|Figure 15: Completed back panel for addition.]]
###: '''Note''': Tunnels are created where the input and output wires cross into and out of the case structure; they are signified by squares along the border of the case structure where the wires cross the border. Input wires create complete tunnels, but output wires create tunnels that are incomplete. To complete output tunnels, there must be an output wired to the tunnel for each case of the case structure.
### To complete the other cases, click on the right arrow next to the case structure caption. This will change the caption to '''''1''''', and the subtraction triangle will be in the middle of the case structure. Connect the tunnel from the first numeric control to the top left of the triangle, the tunnel from the second numeric control to the bottom left of the triangle, and the right of the triangle to tunnel to the Numeric 3 box at the bottom of the back panel. Click the right arrow next to the case structure caption one more time. This will change the case number to '''''2''''', and the multiplication triangle will be in the middle of the case structure. Wire the numeric objects to the triangle as was done for the other two cases. The output tunnel is now complete and filled with a solid color. The numeric inputs and outputs are done.
### To illuminate the LED corresponding to each operation, click the left arrow to the left of the caption of the case structure until the caption reads 0, Default. On the '''''Functions Palette''''', under '''Programming''', click on the '''Boolean''' icon [[Image:lab_labview_36.png]], which will bring up the '''''Boolean Programming''''' window shown in Figure 16.
###: [[Image:lab_labview_37.png|frame|center|Figure 16: Boolean programming functions.]]
### Add three Boolean constants to the case structure. Since this is Case 0, which corresponds to add, the add indicator must be true, and the other two must be false. Click on the '''''True Constant''''' icon [[Image:lab_labview_42.png]], and then click inside the case structure on the right side to the left of the add indicator that is outside of the case structure. Select the '''''False Constant''''' icon [[Image:lab_labview_43.png]] and place it inside the case structure on the right side next to the subtract and multiply indicators
### To wire the constants to their respective indicators, click on the '''''Connect Wire''''' icon [[Image:lab_labview_19.png]] on the '''''Tools Palette'''''. Click on the right side of the top constant inside the case structure and connect it to the top indicator by clicking on the indicator. Do the same for the other two constants and their corresponding indicators. Three incomplete output tunnels have been formed. The add operation is complete
### Click on the right arrow next to the case structure icon. The caption should now show '''''1'''''. To have the subtract indicator illuminate for this case, place a '''''True Constant''''' inside the case structure on the right side to the left of the subtract LED. Place a '''''False Constant''''' inside the case structure on the right side to the left of the add LED, and again to the left of the multiply LED. Click on the '''''Connect Wire''''' icon [[Image:lab_labview_19.png]] on the '''''Tools Palette'''''. Click on the right side of the constant at the top inside the case structure and connect it to the output tunnel at the top. Do the same for the other two constants and their corresponding output tunnels. The subtract operation is complete
### To finish the calculator, click on the right arrow next to the case structure icon. The caption should now show '''''2'''''. The multiplication indicator should illuminate for this case. Add a '''''True Constant''''' to the right side of the case structure to the left of the multiplication LED. Place a '''''False Constant''''' inside the right side of the case structure to the left of the add LED, and again to the left of the subtraction LED. Click on the '''''Connect Wire''''' icon [[Image:lab_labview_19.png]] on the '''''Tools Palette'''''. Click on the right side of the constant at the top inside the case structure and connect it to the output tunnel at the top. Do the same for the other two constants and their corresponding output tunnels. The multiply operation is complete and all output tunnels have been filled
# The VI must be tested:
## Enter different input numbers through the control icon on the front panel
## Make sure the output is correct
## Make sure the correct LED lights up for the operation
## Have the TA test the VI
#: [[Image:lab_labview_50.png|frame|center|Figure 17: Completed and working VI.]]
# Once testing is completed, take a screenshot the VI
# Save the VI


== Design 2: Heating and Cooling System ==
Build a VI that simulates a heating and cooling system. The system must be able to be controlled manually or automatically. The VI’s specifications are listed below.
Build a VI that simulates a heating and cooling system. The system must be controlled manually or automatically. Design the VI so that:
* Must be able to be controlled automatically or manually
* The air conditioner is turned on when the temperature is above 80°F
* In manual mode, the heater and air conditioning (AC) can be switched on/off by the user
* The heater is turned on when the temperature is less than 60°F
* In automatic mode, the heater and AC turn on/off based on the following conditions:
* The heater and the air conditioner are turned off when the temperature is between 60°F and 80°F
** The air conditioner is turned on when the temperature is above 80°F
** The heater is turned on when the temperature is below 60°F
** The heater and the air conditioner are turned off when the temperature is between 60°F and 80°F


# The '''''front panel''''' must contain:
# In the front panel, drag and drop three Round LEDs and three Slide Switches by going to the Controls palette > Modern tab > Boolean (Figure 13). Each round LED and each slide switch will represent the AC, heater, and manual mode. The round LEDs will indicate if the item is on, and the slide switches will toggle the items on/off.
## Three LEDs: one to represent the AC, one to represent the heater, and one to show that the system is being operated manually
#: [[Image:Switches.PNG|thumb|400px|center|Figure 13: Slide Switches and Round LEDs in the Controls Palette]]
## Three switches: one to control the AC, one to control the heater, and one to control manual or automatic operation
# Rename the LEDs and their corresponding switches "Manual," "AC," and "Heater" to make building the system clearer (Figure 14). This can be done by using the editing text tool in the Tools palette.
## A thermometer to set the temperature of the system. By default, the thermometer is an indicator; right-click on it and select ''Change to control''. The thermometer should be set to 70°F
#: [[Image:Code_switches_leds.PNG|thumb|400px|center|Figure 14: Named Switches and LEDs in the Front Panel]]
# The '''''back panel''''' must contain:
# Drag and drop a thermometer (Figure 15) into the front panel (Controls palette > Modern tab > Numeric > Thermometer).
## A Boolean case statement to control the manual and automatic operation of the AC and the heater
#: [[Image:thermometer.PNG|thumb|400px|center|Figure 15: Thermometer Control]]
# After the VI is completed, it must be tested:
# In the back panel, right click the thermometer terminal and select Change to Control, and observe how the arrow switches from the left side to the right side (Figure 16). This makes the thermometer a control that will give an input to the program, which in this case is temperature.
## Using the slide bar on the thermometer, change the system temperature. Make sure the AC and heat come on as directed
#: [[Image:control_vs_indicator.PNG|thumb|400px|center|Figure 16: Indicator (Left) vs Control (Right)]]
## Test the program's manual operation by turning the manual switch on and then turning the AC and heat switches on. Each of the LEDs should light up when its corresponding switch is in the '''''On '''''position
# In the back panel, insert a case structure to control the manual and automatic operation of the heating and cooling system (Functions palette > Structures > Case Structure). To place the case structure, click once to place one corner of the case structure, and once more to place the other corner of the case structure (Figure 17).
## Have the TA test the VI
#: [[Image:Lab 7 Figure 17.PNG|thumb|400px|center|Figure 17: Case Structure]]
# Once testing is completed, take a screenshot of the VI
# Wire the slide switch designated as Manual to the case selector on the case structure (Figure 18). This should automatically change the selector label values to True and False, if they were not already, because the slide switch is a Boolean data type. The true value corresponds to manual mode being on (where the user can directly toggle the heater and AC), while the false value corresponds to manual mode being off (where the heater and AC are automatically toggled by the system).
# Save the VI
#: [[Image:Case_structure_wired.PNG|thumb|400px|center|Figure 18: Manual Switch as Case Selector]]
# Because the temperature of the room is input into the system only when the system is not in manual mode (the false case), the thermometer terminal should be moved into the false subdiagram (Figure 19).
#: [[Image:Thermometer_in_structure.PNG|thumb|400px|center|Figure 19: Thermometer in the False Subdiagram]]
# In the true subdiagram, wire the AC and heater switches directly to their corresponding LEDs (Figure 20). This allows the switches to directly toggle their corresponding LEDs.
#: [[Image:Lab 7 Figure 20.PNG|thumb|400px|center|Figure 20: Wiring the Switches to the LEDs]]
# Staying in the true subdiagram, insert a True Constant (Functions palette > Programming tab > Boolean > True Constant). Wire the true constant to the manual LED to turn the manual LED on and indicate that the system is in manual mode (Figure 21).
#: [[Image:Lab 7 Figure 21.PNG|thumb|400px|center|Figure 21: Subdiagram for True Case]]
# In the false subdiagram, insert two Numeric Constants (Functions palette > Programming > Numeric > Numeric Constant), one Greater? function and one Less? function (Functions palette > Programming > Comparison). These will be used to build the program for the heating and cooling system in automatic mode (Figure 22).
#: [[Image:Lab 7 Figure 22.PNG|thumb|400px|center|Figure 22: Terminals for False Subdiagram]]
# The less and greater functions compare what is wired to the upper input terminal to what is wired to the lower input terminal. Wire the thermometer to the upper input terminals of the less and greater functions. Set a numeric constant to 60 and the other to 80. Wire the 60 numeric constant to the lower input terminal of the less function and the 80 numeric constant to the lower input terminal of the greater function. Wire the output terminal of the greater function to the AC LED and wire the output of the less function to the heater LED  (Figure 23).
#: [[Image:Lab 7 Figure 23.PNG|thumb|400px|center|Figure 23: Wiring to Heater and AC LEDs]]
# In the false subdiagram, Insert a False Constant (Functions palette > Programming > Boolean > False Constant) and wire it to the manual LED (Figure 24). This is to turn off the manual LED and indicate that the system is in automatic mode.
#: [[Image:Lab 7 Figure 24.PNG|thumb|400px|center|Figure 24: Subdiagram for False Case]]
# The system is now complete. Click the continuously run button to control and test the VI. If the continuously run button is faded out, that means the system is wired completely. When successfully running the system, the gridlines in the background of the front panel should disappear (Figure 25). Click the switches and thermometer on the front panel to test the system.
#: [[Image:Lab 7 Figure 25.PNG|thumb|400px|center|Figure 25: Running Heating and Cooling System]]
# Have a TA check the VI. Once testing is complete, take a screenshot of the VI. Save the heating and cooling system as a VI file (saving the file will save both the front panel and back panel in one file). Send the VI file to you and your teammates via email.


The VI will be altered to interact with a '''heat cube''' &mdash; which is a physical device that houses a heating element, a fan, and a thermocouple &mdash; and LEDs located on an NI-ELVIS board.
== Interfacing with a Heat Cube ==
# Include the pre-written sub-VIs provided to interface with the circuit on the NI-ELVIS board.
## Insert the sub-VIs into the back panel by right-clicking on the back panel and clicking on '''Select A VI''' from the context menu that pops up. Open the Heating Control, Cooling Control, and Temperature Reading VIs located in the EG MENU shortcut on the Lab PC desktop
## Wire the output tunnels of the case structure for the heating and cooling indicators to the green terminals labeled ''Heat'' on the Heating Control and ''Cooling'' on the Cooling Control, respectively
## Connect the orange terminal labeled ''Result'' on the Temperature Reading node to the comparison operators used in the ''Automatic'' case. The Temperature Reading sub-VI will effectively replace the thermometer control
# Change the thermometer node to an indicator and connect the ''Result'' terminal on the Temperature Reading sub-VI to the thermometer. Since the Temperature Reading sub-VI replaces the thermometer, the thermometer will be used to monitor the temperature being read.
# Define a device constant for each of the pre-written sub-VIs. The device constant will determine the device(s) the sub-VIs read from and write to.
## Right-click on the purple ''Device Name'' or ''device name'' terminals on the sub-VI nodes using the '''Connect Wire''' tool. Mouse over ''Create'' on the context menu, and select ''Constant''
## Verify that all three device constants are equivalent
# Ask the TA to check over the modifications. If correct, the TA will supply an NI-ELVIS board with a pre-built circuit.
# Connect the '''heat cube''' and its circuit to the NI-ELVIS board.
## Using two 100,000 &Omega; resistors (Brown, Black, Yellow), insert one end of each resistor into AIGND (row 18) of the NI-ELVIS board
## Using a wire, connect the AI 7+ port (row 15) to the screw terminal 1 port (row 46)
## Using a wire, connect the AI 7- port (row 16) to the screw terminal 2 port (row 47)
## Insert the other end of one of the resistors into the AI 7+ (row 15), and the end of the other resistor into AI 7- (row 16)
## Insert the positive and negative wires from the fan into Variable Power Supplies SUPPLY+ (row 48) and Variable Power Supplies GROUND (row 49) at the lower-left-hand corner of the NI-ELVIS board
## Connect the positive wire from the heating pad to DC +5V (row 54) on the lower-right-hand corner of the NI-ELVIS board
## Connect the "source" of the MOSFET from the heat cube circuit to DC ground (row 53) on the lower-right-hand corner of the NI-ELVIS board
## Connect the "gate" of the MOSFET from the heat cube circuit to DIO 19 (row 20) on the upper-right-hand corner of the NI-ELVIS board
##: [[Image:lab_labview_68.jpg|frame|center|Figure 18: Mosfet.]]
# Attach the USB cable to the NI-ELVIS board, and power it. The device constants on the back panel should update to reference the NI-ELVIS device
# Run the VI


The lab work is now complete. Please clean up the workstation. Return all unused materials to the TA. Refer to [[#The Assignment|The Assignment]] section for the instructions needed to prepare the lab report.
The VI will now be altered to interact with a <b>heat cube</b>, which is a physical device that houses a heating element, a fan, and a thermocouple, and LEDs located on an NI ELVIS board. The heat cube will take the ambient temperature of the room and input it into the heating and cooling system. The fan (i.e. the AC) and heater in the heat cube can be turned on/off manually or automatically using the heating and cooling VI that was just created. This will be done by uploading pre-written sub-VIs that will interface the heating and cooling VI with the circuit on the NI ELVIS board.
 
# [[Media:Sub-VIs.zip | Download the sub-VIs onto the desktop.]] Unzip the folder. There should be three sub-VIs – Cooling Control.vi, Heat Control.vi, and Temp Reading.vi.
# Insert the sub-VIs into the back panel by right-clicking on the back panel > Select a VI… > click the sub-VI. Click on the back panel outside of the case structure to place the sub-VIs. They should appear as small boxes with text and an icon (Figure 26).
#: [[Image:Lab 7 Figure 26.PNG|thumb|center|Figure 26: Sub-VI Terminals]]
# In the automatic subdiagram, wire the output tunnel (green box along the border of the case structure) of the less function to the input terminal of the Heat Control sub-VI labeled Heat. Wire the output tunnel of the greater function to the input terminal of the Cool Control sub-VI labeled Cooling.
# Delete the orange wiring from the thermometer terminal to the upper input terminals of the less and greater comparison functions. Wire the output terminal of the Temp Reading sub-VI labeled Result to the upper input terminals of the comparison functions. The Temp Reading sub-VI will effectively replace the thermometer control terminal.
# Change the thermometer node to an indicator similarly to how it was earlier changed to a control.
# Wire the Result output terminal on the Temp Reading sub-VI to the thermometer indicator terminal. The thermometer indicator terminal will be used to display the temperature being read by the thermocouple in the heat cube.
# A device constant must be defined for each of the pre-written sub-VIs. The device constant selects the external device the sub-VIs transmit data to and receive data from, similar to selecting a port for an Arduino program.
# With the wiring tool selected, right click on the input terminal of the sub-VIs labeled Device Name > Create > Constant.
# Verify that all three device constants are equivalent. The device constant can be changed using the operating tool in the Tools palette.
# Ask the TA to check over the modifications to the VI. If correct, the TA will supply an NI ELVIS board, a heat cube, two 100 kΩ resistors, and electrical wires.
# Using two 100 kΩ resistors (Brown, Black, Yellow), insert one end of each resistor into AIGND (row 18) of the NI ELVIS board.
# Insert the other end of one of the resistors into the AI 7+ (row 15), and the end of the other resistor into AI 7- (row 16).
# Using a wire, connect the AI 7+ port (row 15) to the screw terminal 1 port (row 46).
# Using a wire, connect the AI 7- port (row 16) to the screw terminal 2 port (row 47).
# Insert the positive and negative wires from the fan into Variable Power Supplies SUPPLY+ (row 48) and Variable Power Supplies GROUND (row 49), respectively, at the lower-left-hand corner of the NI ELVIS board.
# Connect the positive wire from the heater to DC +5V (row 54) on the lower-right-hand corner of the NI ELVIS board.
# Connect the source of the MOSFET from the heat cube circuit to DC ground (row 53) on the lower-right-hand corner of the NI ELVIS board.
# Connect the gate of the MOSFET from the heat cube circuit to DIO 19 (row 20) on the upper-right-hand corner of the NI ELVIS board.
# Power the NI ELVIS board with the power cable and also connect it to the PC with the USB cable. The device constants on the back panel of the VI should update to reference the NI ELVIS board.
# Run the VI. Observe how the fan and heater in the heat cube can be turned on manually and automatically. Observe how the thermometer indicator in the front panel displays the actual temperature of the room.
 
== 2. Lighting System ==
 
Build a VI that simulates a lighting system in a house with four rooms. The design must use four lights (LEDs) and at least five switches — one switch per light and one master switch that will turn all of the lights off simultaneously (think of this as a circuit breaker). The program should also interact with real LEDs located on the NI ELVIS board.
 
# The front panel of the program should use five switches and four LEDs.
# The back panel requires a case structure for the master switch to turn off all the lights. Think of the cases that will be required for the function of the master switch.
# Create the program in the case structure using the appropriate functions and wiring. Use knowledge acquired from creating the heating and cooling system, information from the Overview, and the LabVIEW Digest at the bottom of the page.
# After completing the program, the VI must be interfaced to the physical NI ELVIS board. The VI is interfaced to the NI ELVIS board using a function called the Digital Writer, which writes data to the DIO (Digital Input and Output) pins on the board, and can display outputs on the board’s built-in LEDs from the VI. To access the  Digital Writer node, go to the Functions palette > Measurement I/O tab > NI ELVISmx > Digital Writer (Figure 27). Place the Digital Writer node on the back panel.
#: [[Image:Lab 7 Figure 27.png|225px|frame|center|Figure 27: NI ELVISmx Digital Writer]]
# Hover over the blue square at the bottom of the Digital Writer node, click, and drag down. Six colored lines should appear (Figure 28). If this cannot be performed, double click on the Digital Writer node and click OK in the NI ELVISmx dialog that pops up. Try to expand the node again.
#: [[Image:Lab 7 Figure 28.png|frame|center|Figure 28: NI ELVISmx Digital Writer Node]]
# Only two of the lines in the Digital Writer node will be used in this experiment. The <b>Lines to Write</b> determine which group of eight DIO pins will be used in the VI. The Lines to Write come in groups of eight (starting at 0) because the program works in 8-bit. The <b>DO (Digital Output) Lines</b> input the Boolean values into the DIO pins.
# For the purposes of this lab, DIO lines 0–7 will be utilized (Figure 29). To establish this setting, right-click Lines to Write on the Digital Writer node > Create > Constant. By default, the constant  is set to 0–7. The operating tool in the Tools palette can be used to change this value.
#: [[Image:Lab 7 Figure 29.png|145px|frame|center|Figure 29: Lines to Write]]
# The DO Lines require an input for each of the eight DIO lines, indicating whether each one is true or false (on or off), but the Digital Writer can only receive one input for the DO Lines (as observed by the one input terminal for the DO Lines on the Digital Writer node). Therefore, the eight Boolean values will be placed in an array, and the array will be input to the DO Lines.
# A Build Array function will be used by going to the Functions palette > Programming > Build Array (Figure 30). The array should be eight indices long to represent each DIO line. When first placing the array, it only appears as one index. Hover over the bottom of the array until a two-sided arrow appears, then click and drag down until the array is eight indices long.
#: [[Image:Lab 7 Figure 30.png|225px|frame|center|Figure 30: Array Function]]
# Each LED should be wired to an individual index in the array, at the element terminal on the left side of the array node. The remaining four indices in the array should be wired to false constants, as those DIO lines should remain false at all times as they are not in use.
# The resulting array should be wired to the Lines to Write of the Digital Writer node, from the appended array terminal on the right side of the array node (Figure 31).
#: [[Image:Lab 7 Figure 31.png|145px|frame|center|Figure 31: Completed Digital Writer Node]]
# For the LEDs on the NI ELVIS board to light up, wires must be used to connect the DIO lines (rows 0–7) directly to the LEDs on the NI ELVIS board (rows 35–42).
# Test the VI. Double click the Digital Writer node. Ensure the correct Device and Lines to Write are selected under Configuration of the NI ELVISmx dialog. Click OK. Run the VI in LabVIEW. Ask a TA to check the program.
# Take screenshots of the lighting system. Save the lighting system as a VI file.
# Submit a ZIP file of both the heating and cooling system and the lighting system to the EG1003 website before 11:59PM the night before the next lab.
 
The lab work is now complete. Please clean up the workstation. Return all unused materials to the TA. Refer to the Assignment section for the instructions needed to prepare the lab report.


= Assignment =
= Assignment =
== Individual Lab Report ==
'''A zip file including all LabVIEW programs (.vi) must be submitted to the [http://eg.poly.edu EG Website]'''. To create a zip file, read the page [[How to Compress Your Files]] in the ''Instructional Presentations'' section.


Follow the lab report guidelines laid out in the page called [[Specifications for Writing Your Lab Reports]] in the ''Technical Communication'' section of this manual. The following points should be addressed in the appropriate section of the lab report:
<b><span style="color:red">A ZIP folder containing both LabVIEW programs (in VI format) must be submitted to the [http://eg.poly.edu EG1003 Website] by 11:59PM the night before the next lab. There is no Team PowerPoint Presentation for this lab.</span></b>
 
== Team Lab Report ==
 
{{Labs:Lab Report}}
* How is LabVIEW important today?
* How is LabVIEW important today?
* Explain what LabVIEW is and describe how it helps engineers and scientists with their work
* Explain what LabVIEW is and describe how it helps engineers and scientists with their work
Line 173: Line 181:
* What are structures and functions?
* What are structures and functions?
* What is the front panel used for? The back panel?
* What is the front panel used for? The back panel?
* Discuss what an NI-ELVIS board is
* Discuss what an NI ELVIS board is
* Were the objectives of the experiment achieved? If not why?
* State whether the VIs were successful or not. If not, explain why.
* State whether interfacing the VIs with the NI ELVIS board was successful or not
* Describe the advantages and disadvantages of using LabVIEW
* Describe the advantages and disadvantages of using LabVIEW
* Suggest some improvements for the lab procedure
* Suggest some improvements for the lab procedure
* Suggest improvements for each VI
* Because the procedural elements in this lab are extensive, please include only the procedures employed to build the lighting system in the lab report. Do not document the procedures followed to build the heating and cooling system
* Though the Procedure section is limited to the lighting system, discuss both of the designs in the Data/Observations and Conclusion sections of the lab report
* Please consider the value of LabVIEW as a substitute for actual instruments and systems. The Data/Observations section should include information on ease of use, the LabVIEW user interface, and the available help options
* In describing the design of all the systems, present screenshots in the lab reports showing the VIs that were designed


<span style="color:#ff0000;">'''IMPORTANT: Because the procedural elements in this lab are extensive, please include only the procedures employed to build Design 2, the heating and cooling system in the lab report. Do not document the procedures followed to build Design 1: the simple calculator.'''</span>
{{Labs:Lab Notes}}
 
'''Note:''' Though the Procedure section is limited to the heating and cooling system, discuss '''ALL''' the designs in the Data/Observations, and Conclusion sections of the lab report.
 
Please consider the value of LabVIEW as a substitute for actual instruments and systems. The Data/Observations section should include information on ease of use, the LabVIEW user interface, and the available help options.
 
In describing the design of all the systems, show the screenshots in the lab reports showing the VIs that were designed. Look at the Online Manual under "Instructional Web Pages" for [[Screenshots|instructions on how to take a screen shot and use it]].
 
{{Lab notes}}


<!--
== Team PowerPoint Presentation (EGED I Only) ==
== Team PowerPoint Presentation (EGED I Only) ==
Follow the presentation guidelines laid out in the page called [[EG1003 Lab Presentation Format]] in the ''Introduction to Technical Presentations'' section of this manual. When preparing the presentation, consider the following points:
Follow the presentation guidelines laid out in the page called [[EG1003 Lab Presentation Format]] in the ''Introduction to Technical Presentations'' section of this manual. When preparing the presentation, consider the following points:
* What is the importance of LabVIEW?
* What is the importance of LabVIEW?
* Discuss some ways LabVIEW can be used in industry.
* Discuss some ways LabVIEW can be used in industry.
-->


= LabVIEW Digest of Common Tasks =
= LabVIEW Digest of Common Tasks =


== Front Panel Controls and Indicators ==
== Front Panel ==
 
 
* <b>How to get a slide control:</b>
** Controls palette > Modern tab > Numeric [[Image:lab_labview_2.png]]
** Select Horizontal Pointer Slide [[Image:Slide Control 2.png|55px]]
** Click on the front panel to place the slide at a specific location
 
* <b>How to get an LED indicator:</b>
** Controls palette > Modern tab > Boolean [[Image:lab_labview_8.png]]
** Select the Round LED [[File:LED 1.png|55px]] or Square LED [[File:LED 2.png|55px]]
** Click on the front panel to place the LED at a specific location
 
* <b>How to get a numeric control:</b>
** Controls palette > Modern tab > Numeric [[Image:lab_labview_2.png]]
** Click on Numeric Control [[Image:NC.png|55px]]
** Click on the front panel to place the numeric control at a specific location


=== How to get a slide control: ===
* <b>How to get a numeric indicator:</b>
# On the Controls Palette, select the '''Numeric''' icon [[Image:lab_labview_2.png]] under the Modern category
** Controls palette > Modern tab > Numeric [[Image:lab_labview_2.png]]
# Select Horizontal Pointer Slide
** Click on Numeric Indicator [[Image:NI.png|55px]]
# Click on the front panel to place the slide on the front panel at a specific location
** Click on the front panel to place the numeric indicator at a specific location


=== How to get an LED indicator: ===
== Back Panel ==
# On the Controls Palette, select the '''Boolean''' icon [[Image:lab_labview_8.png]] under the Modern category
# Select the '''Round LED''' icon from the icons shown
# Click on the front panel to place the LED at the location selected
# Rename the LED with a label that indicates what the LED stands for. To rename the LED, click on the '''Edit Text''' icon [[Image:lab_labview_10.png]] on the '''Tools Palette'''. Then click on the default '''Boolean''' label on each LED and replace it with the proper text


=== How to get a Numeric Input Control ===
* <b>How to define an arithmetic operation:</b>
# On the '''Controls Palette''', click on the '''Numeric''' icon under the Modern category
** Functions palette > Programming tab > Numeric [[Image:lab_labview_33.png]]
# Click on the '''Numeric Control''' icon and click on the location the control is to be placed
** Click on the function of the desired arithmetic operation [[Image:Arithmetic.png|300px]]
** Click on the back panel to place the arithmetic function at a specific location


=== How to get a Numeric Indicator Output ===
* <b>How to define Boolean constants (usually used to turn on/off LEDs):</b>
# On the Controls Palette, click on the '''Numeric''' icon under the Modern category.
** Functions palette > Programming tab > Boolean [[Image:lab_labview_36.png]]
# Click on the '''Numeric Indicator''' icon and click on the front panel location where the indicator is to be placed
** Click on the True Constant [[Image:lab_labview_42.png]] or False Constant [[Image:lab_labview_43.png]]
** Click on the back panel to place the Boolean constant at a specific location


== Back Panel Objects ==
* <b>How to wire:</b>
** Tools palette > Wiring tool [[Image:lab_labview_19.png]]
** Click the desired object output terminal (on the left side) to wire from
** Click the desired object input terminal (on the right side) to wire to


=== How to define a case structure ===
= References =
# On the Functions Palette, click on the '''Structures''' icon under the Programming category.
# Click on the '''Case Structure''' icon. Click on the back panel to place it at the desired location.
# By default, the case structure assumes it is being controlled by a Boolean control. What controls the case structure is any control that is wired to the question mark along the border. When being controlled by a Boolean control, the default cases are False and True; when being controlled by a numeric control, the default cases are 0 and 1. To add more cases, right-click anywhere on the '''Case Structure''' and select '''Add Case After'''.
# Define what happens for each case. Use arrows on each side of the caption to switch between cases. Switch to the case that is to be defined and fill the case structure with whatever needs to be done for that case. Make sure each case is fully defined. When output wires cross the border of the case structure, incomplete tunnels will be created. To complete the tunnels, an output wire must be wired to the tunnel for each case.


=== How to define an arithmetic operation ===
Introduction to LabVIEW, Six-Hour Course [Courseware]. (June 2003) Austin, TX: Worldwide Technical Support and Product Information, National Instruments Corporation.
# On the '''''Functions Palette''''', click on the '''Numeric''' icon [[Image:lab_labview_33.png]] under the Programming category
# On the Numeric Programming window, click on the icon for the desired arithmetic operation. Click on the front panel location where the icon goes


=== How to define Boolean constants (usually used to illuminate LEDs) ===
“LabVIEW Block Diagram Explained.” National Instruments, National Instruments, 4 Feb. 2020, www.ni.com/en-us/support/documentation/supplemental/08/labview-block-diagram-explained.html.
# On the '''''Functions Palette''''', click on the '''Boolean''' icon [[Image:lab_labview_36.png]] under the Programming category.
# Click on the True Constant icon [[Image:lab_labview_42.png]] or False Constant icon [[Image:lab_labview_43.png]], and then click the location of the constant on the back panel


=== How to wire ===
“Case Structure.” National Instruments, National Instruments, 4 Feb. 2020, www.zone.ni.com/reference/en-XX/help/371361R-01/glang/case_structure/.
# Objects have inputs on their left side and outputs on their right side. The output (right side) of one object is always wired to the input (left side) of another object
# On the Tools Palette, chose the "Connect Wire" icon [[Image:lab_labview_19.png]]
# Click the object output that is to be wired from. Click the desired object input to wire to. The first object's output is now connected to the second object's input


= Footnotes =
“LabVIEW Front Panel Explained.” National Instruments, National Instruments, 4 Feb. 2020, www.ni.com/en-us/support/documentation/supplemental/08/labview-front-panel-explained.html.
{{Reflist}}


{{Laboratory Experiments}}
{{Laboratory Experiments}}

Latest revision as of 02:49, 7 April 2020

Objective

The experimental objective of this lab is to use LabVIEW to design a heating and cooling system and a lighting system and to test both systems. Building these systems will demonstrate the potential for using simulated instruments in a laboratory. These programs will also obtain data from outside the computer and incorporate it into a program design.

Overview

The Laboratory Virtual Instrument Engineering Workbench (LabVIEW) is a development environment designed by National Instruments that creates graphic-based programs called virtual instruments (VIs) that simulate actual laboratory instruments. A VI consists of two parts: a front panel and a back panel (Figure 1). The front panel allows the user to interact with the VI by displaying outputs and allowing the user to supply the program with inputs. The back panel consists of the code used by the VI to obtain inputs from the front panel, operate on the inputs, and display the results.

Figure 1: Front Panel (Left) and Back Panel (Right)

The front panel is built using controls and indicators. Controls are inputs that allow a user to supply information to the VI. Indicators are outputs that display the results based on the inputs given to the VI. Controls can be switches, knobs, dials, and buttons. Indicators can be meters, gauges, LEDs, and displays. These are located on the Controls palette and are placed on the front panel (Figure 2).

Figure 2: Controls Palette

The back panel, which is also known as the block diagram, contains the graphic-based source code. The environment of the back panel is navigated using the Tools palette (Figure 3).

Figure 3: Tools Palette

In Figure 3, only the icons in colored boxed will be used in this experiment. The operating tool changes the value of a control (such as a switch or LED). The positioning tool positions, resizes, and selects objects. The labeling tool is used to create and edit all labels in the VI, such as the name of a Boolean control. The wiring tool wires objects together on the back panel. The scrolling tool allows scrolling the window by clicking and dragging.

All of the objects placed on the front panel will appear on the back panel as terminals. Terminals are the ports that exchange information between the front panel and back panel, and appear with small triangles in the icons to indicate that they can be used to process information (Figure 4). A control terminal has the triangle to the right to indicate that it sends data to be processed. An indicator terminal has the triangle to the left to indicate that it receives data.

Figure 4: Control and Indicator Terminals

The back panel also contains structures and functions that perform operations on controls and supply data to indicators. Structures and functions are found on the Functions palette and are placed on the back panel (Figure 5).

Figure 5: Functions Palette

Structures are process control elements, such as while loops and for loops. The structure to be used in this experiment is the case structure (Figure 6), which is essentially multiple if-statements. A case structure contains multiple subdiagrams (or cases), and a case will be executed depending on the input to the case structure.

Figure 6: Case Structure

In Figure 6, Item 1 is the selector label, which displays the input value for which the associated case will execute. The black arrows on the side of the selector label toggle between the different cases. Item 2 is the area for the code that executes for the specific input in the selector label. When the selector label is toggled, the code in this area will also change. Item 3 is the case selector, which gives the input value to the case structure. The data type that is wired to the case selector will determine the possible cases. For example, if a Boolean data type is wired to the case selector, the possible cases will only be true and false.

Functions are the fundamental operating elements of LabVIEW, and have input and output terminals to pass data in and out. They are indicated by a pale yellow background in the icon (Figure 7).

Figure 7: Examples of Functions

Functions have a certain number of inputs and outputs, depending on the type of function. For example, the addition function (leftmost icon in Figure 7) has two inputs as it will add the two inputs together, and it will have one output, which is the sum of the inputs. The inputs are wired to the left side of the function, and the outputs are wired to the right side of the function. The number of inputs and outputs of a function can be observed by hovering over the icon with the wiring tool and observing the terminals that appear (Figure 8).

Figure 8: Function Terminals

Collectively, controls, indicators, structures, and functions are referred to as nodes. Nodes are connected to one another using the wiring tool. For example, two controls and an indicator can be wired to the addition function so that the indicator displays the sum of the two controls (Figure 9).

Figure 9: Wiring Nodes

The toolbar at the top of the front panel is used to execute and stop the program (Figure 10). The run tool (white arrow) runs the program once. The run continuously tool (two white arrows in a circle) keeps the program running continuously until the program is paused or stopped. This tool should be used when executing programs in this experiment. The abort execution tool (red stop sign) stops the VI immediately. The pause button (two vertical black rectangles) pauses the program, and can be clicked again to continue the program.

Figure 10: Toolbar

National Instruments' Educational Laboratory Virtual Instrumentation Suite (NI ELVIS) board (Figure 11) is one solution LabVIEW can utilize to physically interface with external devices. It is a modular engineering device that includes a breadboard, power supply, ground, thermocouple, oscilloscope, function analyzer, and other common lab instruments. In this experiment, an NI ELVIS board will be used to provide inputs and display outputs for the VIs that will be created.

Figure 11: NI ELVIS II+ Board

Materials and Equipment

  • Lab PC
  • LabVIEW 2019 software
  • NI ELVIS II+ prototyping board
  • Wires
  • Two 100 kΩ resistors (brown, black, yellow)

Procedure

Note: Some tasks will be repeated and the same icons will be used. A LabVIEW digest of common tasks at the bottom of the page contains references for faster navigation.

Setting up a Blank VI

  1. Open LabVIEW and select Blank VI under Create Project.
  2. Click Window > Tile Left and Right to display the front panel (left window) and back panel (right window) side by side. This will make them visible at the same time, making it easier to work.
  3. With the back panel selected, click View > Tools Palette to open the Tools palette.
  4. With the front panel selected, click View > Controls Palette. The workspace should look like Figure 12. To open the Controls palette in the future, simply right click in the front panel. Similarly, to open the Functions palette, simply right click in the back panel.
Figure 12: LabVIEW Workspace

For help with the operation of any LabVIEW icon, select Help > Show Context Help > click the icon for the operation that is unclear. It will be explained in the Context Help window.

1. Heating and Cooling System

Build a VI that simulates a heating and cooling system. The system must be able to be controlled manually or automatically. The VI’s specifications are listed below.

  • Must be able to be controlled automatically or manually
  • In manual mode, the heater and air conditioning (AC) can be switched on/off by the user
  • In automatic mode, the heater and AC turn on/off based on the following conditions:
    • The air conditioner is turned on when the temperature is above 80°F
    • The heater is turned on when the temperature is below 60°F
    • The heater and the air conditioner are turned off when the temperature is between 60°F and 80°F
  1. In the front panel, drag and drop three Round LEDs and three Slide Switches by going to the Controls palette > Modern tab > Boolean (Figure 13). Each round LED and each slide switch will represent the AC, heater, and manual mode. The round LEDs will indicate if the item is on, and the slide switches will toggle the items on/off.
    Figure 13: Slide Switches and Round LEDs in the Controls Palette
  2. Rename the LEDs and their corresponding switches "Manual," "AC," and "Heater" to make building the system clearer (Figure 14). This can be done by using the editing text tool in the Tools palette.
    Figure 14: Named Switches and LEDs in the Front Panel
  3. Drag and drop a thermometer (Figure 15) into the front panel (Controls palette > Modern tab > Numeric > Thermometer).
    Figure 15: Thermometer Control
  4. In the back panel, right click the thermometer terminal and select Change to Control, and observe how the arrow switches from the left side to the right side (Figure 16). This makes the thermometer a control that will give an input to the program, which in this case is temperature.
    Figure 16: Indicator (Left) vs Control (Right)
  5. In the back panel, insert a case structure to control the manual and automatic operation of the heating and cooling system (Functions palette > Structures > Case Structure). To place the case structure, click once to place one corner of the case structure, and once more to place the other corner of the case structure (Figure 17).
    Figure 17: Case Structure
  6. Wire the slide switch designated as Manual to the case selector on the case structure (Figure 18). This should automatically change the selector label values to True and False, if they were not already, because the slide switch is a Boolean data type. The true value corresponds to manual mode being on (where the user can directly toggle the heater and AC), while the false value corresponds to manual mode being off (where the heater and AC are automatically toggled by the system).
    Figure 18: Manual Switch as Case Selector
  7. Because the temperature of the room is input into the system only when the system is not in manual mode (the false case), the thermometer terminal should be moved into the false subdiagram (Figure 19).
    Figure 19: Thermometer in the False Subdiagram
  8. In the true subdiagram, wire the AC and heater switches directly to their corresponding LEDs (Figure 20). This allows the switches to directly toggle their corresponding LEDs.
    Figure 20: Wiring the Switches to the LEDs
  9. Staying in the true subdiagram, insert a True Constant (Functions palette > Programming tab > Boolean > True Constant). Wire the true constant to the manual LED to turn the manual LED on and indicate that the system is in manual mode (Figure 21).
    Figure 21: Subdiagram for True Case
  10. In the false subdiagram, insert two Numeric Constants (Functions palette > Programming > Numeric > Numeric Constant), one Greater? function and one Less? function (Functions palette > Programming > Comparison). These will be used to build the program for the heating and cooling system in automatic mode (Figure 22).
    Figure 22: Terminals for False Subdiagram
  11. The less and greater functions compare what is wired to the upper input terminal to what is wired to the lower input terminal. Wire the thermometer to the upper input terminals of the less and greater functions. Set a numeric constant to 60 and the other to 80. Wire the 60 numeric constant to the lower input terminal of the less function and the 80 numeric constant to the lower input terminal of the greater function. Wire the output terminal of the greater function to the AC LED and wire the output of the less function to the heater LED (Figure 23).
    Figure 23: Wiring to Heater and AC LEDs
  12. In the false subdiagram, Insert a False Constant (Functions palette > Programming > Boolean > False Constant) and wire it to the manual LED (Figure 24). This is to turn off the manual LED and indicate that the system is in automatic mode.
    Figure 24: Subdiagram for False Case
  13. The system is now complete. Click the continuously run button to control and test the VI. If the continuously run button is faded out, that means the system is wired completely. When successfully running the system, the gridlines in the background of the front panel should disappear (Figure 25). Click the switches and thermometer on the front panel to test the system.
    Figure 25: Running Heating and Cooling System
  14. Have a TA check the VI. Once testing is complete, take a screenshot of the VI. Save the heating and cooling system as a VI file (saving the file will save both the front panel and back panel in one file). Send the VI file to you and your teammates via email.

Interfacing with a Heat Cube

The VI will now be altered to interact with a heat cube, which is a physical device that houses a heating element, a fan, and a thermocouple, and LEDs located on an NI ELVIS board. The heat cube will take the ambient temperature of the room and input it into the heating and cooling system. The fan (i.e. the AC) and heater in the heat cube can be turned on/off manually or automatically using the heating and cooling VI that was just created. This will be done by uploading pre-written sub-VIs that will interface the heating and cooling VI with the circuit on the NI ELVIS board.

  1. Download the sub-VIs onto the desktop. Unzip the folder. There should be three sub-VIs – Cooling Control.vi, Heat Control.vi, and Temp Reading.vi.
  2. Insert the sub-VIs into the back panel by right-clicking on the back panel > Select a VI… > click the sub-VI. Click on the back panel outside of the case structure to place the sub-VIs. They should appear as small boxes with text and an icon (Figure 26).
    Figure 26: Sub-VI Terminals
  3. In the automatic subdiagram, wire the output tunnel (green box along the border of the case structure) of the less function to the input terminal of the Heat Control sub-VI labeled Heat. Wire the output tunnel of the greater function to the input terminal of the Cool Control sub-VI labeled Cooling.
  4. Delete the orange wiring from the thermometer terminal to the upper input terminals of the less and greater comparison functions. Wire the output terminal of the Temp Reading sub-VI labeled Result to the upper input terminals of the comparison functions. The Temp Reading sub-VI will effectively replace the thermometer control terminal.
  5. Change the thermometer node to an indicator similarly to how it was earlier changed to a control.
  6. Wire the Result output terminal on the Temp Reading sub-VI to the thermometer indicator terminal. The thermometer indicator terminal will be used to display the temperature being read by the thermocouple in the heat cube.
  7. A device constant must be defined for each of the pre-written sub-VIs. The device constant selects the external device the sub-VIs transmit data to and receive data from, similar to selecting a port for an Arduino program.
  8. With the wiring tool selected, right click on the input terminal of the sub-VIs labeled Device Name > Create > Constant.
  9. Verify that all three device constants are equivalent. The device constant can be changed using the operating tool in the Tools palette.
  10. Ask the TA to check over the modifications to the VI. If correct, the TA will supply an NI ELVIS board, a heat cube, two 100 kΩ resistors, and electrical wires.
  11. Using two 100 kΩ resistors (Brown, Black, Yellow), insert one end of each resistor into AIGND (row 18) of the NI ELVIS board.
  12. Insert the other end of one of the resistors into the AI 7+ (row 15), and the end of the other resistor into AI 7- (row 16).
  13. Using a wire, connect the AI 7+ port (row 15) to the screw terminal 1 port (row 46).
  14. Using a wire, connect the AI 7- port (row 16) to the screw terminal 2 port (row 47).
  15. Insert the positive and negative wires from the fan into Variable Power Supplies SUPPLY+ (row 48) and Variable Power Supplies GROUND (row 49), respectively, at the lower-left-hand corner of the NI ELVIS board.
  16. Connect the positive wire from the heater to DC +5V (row 54) on the lower-right-hand corner of the NI ELVIS board.
  17. Connect the source of the MOSFET from the heat cube circuit to DC ground (row 53) on the lower-right-hand corner of the NI ELVIS board.
  18. Connect the gate of the MOSFET from the heat cube circuit to DIO 19 (row 20) on the upper-right-hand corner of the NI ELVIS board.
  19. Power the NI ELVIS board with the power cable and also connect it to the PC with the USB cable. The device constants on the back panel of the VI should update to reference the NI ELVIS board.
  20. Run the VI. Observe how the fan and heater in the heat cube can be turned on manually and automatically. Observe how the thermometer indicator in the front panel displays the actual temperature of the room.

2. Lighting System

Build a VI that simulates a lighting system in a house with four rooms. The design must use four lights (LEDs) and at least five switches — one switch per light and one master switch that will turn all of the lights off simultaneously (think of this as a circuit breaker). The program should also interact with real LEDs located on the NI ELVIS board.

  1. The front panel of the program should use five switches and four LEDs.
  2. The back panel requires a case structure for the master switch to turn off all the lights. Think of the cases that will be required for the function of the master switch.
  3. Create the program in the case structure using the appropriate functions and wiring. Use knowledge acquired from creating the heating and cooling system, information from the Overview, and the LabVIEW Digest at the bottom of the page.
  4. After completing the program, the VI must be interfaced to the physical NI ELVIS board. The VI is interfaced to the NI ELVIS board using a function called the Digital Writer, which writes data to the DIO (Digital Input and Output) pins on the board, and can display outputs on the board’s built-in LEDs from the VI. To access the Digital Writer node, go to the Functions palette > Measurement I/O tab > NI ELVISmx > Digital Writer (Figure 27). Place the Digital Writer node on the back panel.
    Figure 27: NI ELVISmx Digital Writer
  5. Hover over the blue square at the bottom of the Digital Writer node, click, and drag down. Six colored lines should appear (Figure 28). If this cannot be performed, double click on the Digital Writer node and click OK in the NI ELVISmx dialog that pops up. Try to expand the node again.
    Figure 28: NI ELVISmx Digital Writer Node
  6. Only two of the lines in the Digital Writer node will be used in this experiment. The Lines to Write determine which group of eight DIO pins will be used in the VI. The Lines to Write come in groups of eight (starting at 0) because the program works in 8-bit. The DO (Digital Output) Lines input the Boolean values into the DIO pins.
  7. For the purposes of this lab, DIO lines 0–7 will be utilized (Figure 29). To establish this setting, right-click Lines to Write on the Digital Writer node > Create > Constant. By default, the constant is set to 0–7. The operating tool in the Tools palette can be used to change this value.
    Figure 29: Lines to Write
  8. The DO Lines require an input for each of the eight DIO lines, indicating whether each one is true or false (on or off), but the Digital Writer can only receive one input for the DO Lines (as observed by the one input terminal for the DO Lines on the Digital Writer node). Therefore, the eight Boolean values will be placed in an array, and the array will be input to the DO Lines.
  9. A Build Array function will be used by going to the Functions palette > Programming > Build Array (Figure 30). The array should be eight indices long to represent each DIO line. When first placing the array, it only appears as one index. Hover over the bottom of the array until a two-sided arrow appears, then click and drag down until the array is eight indices long.
    Figure 30: Array Function
  10. Each LED should be wired to an individual index in the array, at the element terminal on the left side of the array node. The remaining four indices in the array should be wired to false constants, as those DIO lines should remain false at all times as they are not in use.
  11. The resulting array should be wired to the Lines to Write of the Digital Writer node, from the appended array terminal on the right side of the array node (Figure 31).
    Figure 31: Completed Digital Writer Node
  12. For the LEDs on the NI ELVIS board to light up, wires must be used to connect the DIO lines (rows 0–7) directly to the LEDs on the NI ELVIS board (rows 35–42).
  13. Test the VI. Double click the Digital Writer node. Ensure the correct Device and Lines to Write are selected under Configuration of the NI ELVISmx dialog. Click OK. Run the VI in LabVIEW. Ask a TA to check the program.
  14. Take screenshots of the lighting system. Save the lighting system as a VI file.
  15. Submit a ZIP file of both the heating and cooling system and the lighting system to the EG1003 website before 11:59PM the night before the next lab.

The lab work is now complete. Please clean up the workstation. Return all unused materials to the TA. Refer to the Assignment section for the instructions needed to prepare the lab report.

Assignment

A ZIP folder containing both LabVIEW programs (in VI format) must be submitted to the EG1003 Website by 11:59PM the night before the next lab. There is no Team PowerPoint Presentation for this lab.

Team Lab Report

Follow the lab report guidelines laid out in the EG1003 Writing Style Guide in the Technical Writing section of the manual. The following points should be addressed in the appropriate section of the lab report.

  • How is LabVIEW important today?
  • Explain what LabVIEW is and describe how it helps engineers and scientists with their work
  • Explain what a VI is
  • What are controls and indicators?
  • What are structures and functions?
  • What is the front panel used for? The back panel?
  • Discuss what an NI ELVIS board is
  • State whether the VIs were successful or not. If not, explain why.
  • State whether interfacing the VIs with the NI ELVIS board was successful or not
  • Describe the advantages and disadvantages of using LabVIEW
  • Suggest some improvements for the lab procedure
  • Suggest improvements for each VI
  • Because the procedural elements in this lab are extensive, please include only the procedures employed to build the lighting system in the lab report. Do not document the procedures followed to build the heating and cooling system
  • Though the Procedure section is limited to the lighting system, discuss both of the designs in the Data/Observations and Conclusion sections of the lab report
  • Please consider the value of LabVIEW as a substitute for actual instruments and systems. The Data/Observations section should include information on ease of use, the LabVIEW user interface, and the available help options
  • In describing the design of all the systems, present screenshots in the lab reports showing the VIs that were designed

Remember: Lab notes must be taken. Experimental details are easily forgotten unless written down. EG1003 Lab Notes paper can be downloaded and printed from the EG1003 Website. Use the lab notes to write the Procedure section of the lab report. At the end of each lab, a TA will scan the lab notes and upload them to the Lab Documents section of the EG1003 Website. One point of extra credit is awarded if the lab notes are attached at the end of the lab report. Keeping careful notes is an essential component of all scientific practice.


LabVIEW Digest of Common Tasks

Front Panel

  • How to get a slide control:
    • Controls palette > Modern tab > Numeric Lab labview 2.png
    • Select Horizontal Pointer Slide Slide Control 2.png
    • Click on the front panel to place the slide at a specific location
  • How to get an LED indicator:
    • Controls palette > Modern tab > Boolean Lab labview 8.png
    • Select the Round LED LED 1.png or Square LED LED 2.png
    • Click on the front panel to place the LED at a specific location
  • How to get a numeric control:
    • Controls palette > Modern tab > Numeric Lab labview 2.png
    • Click on Numeric Control NC.png
    • Click on the front panel to place the numeric control at a specific location
  • How to get a numeric indicator:
    • Controls palette > Modern tab > Numeric Lab labview 2.png
    • Click on Numeric Indicator NI.png
    • Click on the front panel to place the numeric indicator at a specific location

Back Panel

  • How to define an arithmetic operation:
    • Functions palette > Programming tab > Numeric Lab labview 33.png
    • Click on the function of the desired arithmetic operation Arithmetic.png
    • Click on the back panel to place the arithmetic function at a specific location
  • How to define Boolean constants (usually used to turn on/off LEDs):
    • Functions palette > Programming tab > Boolean Lab labview 36.png
    • Click on the True Constant Lab labview 42.png or False Constant Lab labview 43.png
    • Click on the back panel to place the Boolean constant at a specific location
  • How to wire:
    • Tools palette > Wiring tool Lab labview 19.png
    • Click the desired object output terminal (on the left side) to wire from
    • Click the desired object input terminal (on the right side) to wire to

References

Introduction to LabVIEW, Six-Hour Course [Courseware]. (June 2003) Austin, TX: Worldwide Technical Support and Product Information, National Instruments Corporation.

“LabVIEW Block Diagram Explained.” National Instruments, National Instruments, 4 Feb. 2020, www.ni.com/en-us/support/documentation/supplemental/08/labview-block-diagram-explained.html.

“Case Structure.” National Instruments, National Instruments, 4 Feb. 2020, www.zone.ni.com/reference/en-XX/help/371361R-01/glang/case_structure/.

“LabVIEW Front Panel Explained.” National Instruments, National Instruments, 4 Feb. 2020, www.ni.com/en-us/support/documentation/supplemental/08/labview-front-panel-explained.html.