LabVIEW Experiment 1 Light Sensor Calibration Using Arduino Data Acquisition (Arduino DAQ)

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1 Spring 2015 LabVIEW Experiment 1 Light Sensor Calibration Using Arduino Data Acquisition (Arduino DAQ) Experiment Objectives Experience LabVIEW capabilities through learning exercises that design and implement several Virtual Instruments (VIs) to meet specified requirements. Utilize and implement a data acquisition system to collect data from several different light sensors; to understand their differences and how they could be used to accurately measure light intensity. Design your own experimental procedures and conduct experiments to gather and analyze data according to a given set of experimental objectives. Analyze light sensor data and present calibration plots using Excel to relate measured data to light intensity. Understand and use the Arduino_Communication_SubVI to communicate between LabVIEW and the Arduino DAQ. Continue to develop your abilities to function on teams, act cooperatively and honor individual commitments to team members and the team project. Continue to develop your abilities to generate good technical reports. Experiment Overview LabVIEW will be programmed using several different front panel designs to collect data from three light sensors measuring varying intensities of light. A test setup housing the light source and sensors will be provided. Data calibration plots (sensor output vs. light intensity) using Excel will be generated for each sensor over a full range of intensities, and a study of how light intensity varies with distance will be conducted. Design requirements for a baseline and three enhanced LabVIEW front panels will be provided. The baseline front panel will form the basis upon which the enhanced panels will be built. A step-by-step programming procedure will be provided for the baseline panel, and everyone will walk through this procedure simultaneously with your instructor to become familiar with using the LabVIEW interface. Each student on a team will then be assigned one of the three enhanced panels. Each student will develop their own Virtual Instruments (VI) according to the design requirements given them. Guidance will be provided suggesting which LabVIEW functions could be used to satisfy those requirements, however, a step-by-step programming procedure will not be provided. Requirements for data collection, analysis and presentation will also be provided, however, a step by step procedure will not be provided. You must develop and document your own experimental procedure. A written lab report (team effort) will be due on the date specified by your instructor. Page 1 of 13

2 Of the three light sensors under test, two will be the same Cadmium Sulfide (CdS) type used in the Design I course on the robot project. The third sensor will be a new solid state device. All three will be connected to different analog input channels on the Arduino DAQ. LabVIEW will communicate and request data from the Arduino DAQ via a serial communication link established between your laptop and the Arduino. A communication protocol implemented by a predefined sub Virtual Instrument (SubVI) will be called in LabVIEW to communicate with the Arduino. A SubVI is analogous to a subroutine in a text based programming language, such as C or BASIC. You will learn how to use this SubVI, named the Arduino_Communication_SubVI. The Arduino DAQ will be preloaded with a program that recognizes and responds to data requests from LabVIEW. No programming of the Arduino will be required for this experiment. The experiment will be conducted in a four foot long wooden enclosure designed to block out ambient light. A white LED light source will be located at the end of the enclosure. The intensity of the LED can be varied by turning a knob (a potentiometer) on the controlling circuit board. The Arduino microcontroller with attached sensors will be placed into the open end of the chamber where it can be moved closer to, or further from the light source. Experimental Hardware Setup The experimental setup is for the most part intuitive and builds upon the knowledge you have gained in Design I (E121) relative to operation and connectivity of sensors to the Arduino microcontroller. The Arduino is now functioning as a Data Acquisition module (Arduino DAQ). All required hardware will be provided, one setup per group. Following is specific guidance. Light Source Control The light source, a white LED, and controlling circuitry are pre-mounted on one side of the light chamber. They get power from a 5VDC wall adapter that must be plugged into an available outlet on your workbench. The circuitry associated with the LED is a constant current source power supply. It monitors the current flowing into the LED and automatically makes adjustments when necessary to keep the current at a constant level. This in turn keeps the LED brightness constant. This circuitry is necessary to offset the dynamically changing electrical characteristics of the LED as it naturally heats up when generating light. Without it, intensities would vary and you could not take consistent light readings. The constant current source can be set to different levels (intensities) using a rotary knob. The knob is connected to a potentiometer (variable resistor) that changes the amount of current being delivered to the LED. Arduino Microcontroller Connections 1. Power Different from Design I, the Arduino DAQ will get power through the USB port connected by a USB cable to your computer. For this experiment the position of the power switches does not matter. Once the USB cable is connected to your laptop power is supplied to the Arduino DAQ. Page 2 of 13

3 2. Communications -Your laptop must be connected to the Arduino microcontroller via the provided USB cable. The Arduino_Communication_SubVI will allow you to select which COM port on your laptop to use for the serial link. The serial link parameters (baud rate, parity, number of stop bits, etc.) will automatically be set by the SubVI to be compatible to those set in the Arduino DAQ. 3. Light Sensors Under Test - Three light sensors mounted in the experimental setup must be connected to the Arduino DAQ. The light sensor analog output signals will be read by the Arduino s analog input circuitry. Remembering the configuration of the Arduino module from last semester, there are six easily accessible analog input connections. It is up to you to select and remember how you have connected the devices. See Interfacing to the Arduino Microcontroller under Arduino Resources if you do not remember where/how to connect to the analog input channels. Before connecting the light sensors, you must configure the associated analog input jumper blocks, i.e., the red push-on shorting clips located next to each of the six analog input terminals. The Arduino DAQ was designed to accommodate two different types of analog sensor input sources: The first was specifically for a variable resistor, such as our Design I light sensors. This is called a passive sensor. It s called passive because it does not require its own power supply and it will not produce its own signal output. Rather it must be used in some external circuit capable of detecting its changing characteristic (i.e. resistance). The external circuit used is a voltage divider that is located on the Arduino DAQ. (See Light Sensor Theory of Operation under E121 Robot Project Resources). To configure the Arduino board for this type of sensor the jumper block next to the associated analog input channel must connect the center pin (either A0-A5) to the 5V pin. These designations can be found printed on the circuit board. Our experimental setup will use two of these type sensors. The second was for any analog sensor directly providing an output voltage in the range of 0-5 volts DC. This is called an active sensor. It s active because it receives its own power source, and then on its own it detects the parameter being measured and generates an output voltage proportional to the magnitude of the measured parameter. To configure the Arduino DAQ for this type of sensor the jumper block next to the associated analog input channel must be completely removed from the board. In our experimental setup we will have one active type light sensor. When connecting the passive CdS light sensors, the two same colored wires can be connected in any order to the selected input screw terminal (A0-A5) and the other to any GND screw terminal. Page 3 of 13

4 When connecting the active solid state light sensor, there are three wires. Since this device is an active type, it must get power via the red and black wires. The red wire must connect to 5 volts on the Arduino DAQ (screw terminal labeled VCC) and the black wire must connect to any GND screw terminal. The sensor output signal will be a voltage that will vary with light intensity. The output signal is on the yellow wire and it must connect to the selected Arduino analog input terminal (A0-A5). Remember to remove the jumper block for this active sensor. Experiment Requirements 1. Data Collection Requirements Remember as part of the written report you must fully describe your step-by-step data collection procedure, in sufficient detail so that a stranger could read it and be able to replicate exactly what you did without question or ambiguity. Be sure to record all relevant set-up parameters, measurements, distances, settings, etc. that are required to duplicate your experimental procedure. When defining your procedure, and when confronted with alternatives, be sure to select the procedure that best minimizes data collection errors, and maximizes reproducibility. (This step-by-step procedure refers only to the actual conduct of the experiment, i.e. how you connected all of the components in the experimental setup and how you moved things around and adjusted controls to collect data. You do not have to describe the steps you used to build your LabVIEW VIs. Once you have a working VI, it is just the tool you will use to collect data.) Procedure 1 Requirements - Fixed Distance, Variable Intensity Light sensor data from each of the three light sensors shall be recorded as the light source is gradually increased from off to full intensity. During this procedure, the light sensors shall be located in the light tunnel at a point furthest from the light source, where readings can be taken. The number of data points collected shall be sufficient to get a smooth data plot over the full range of intensity control. Measures shall be taken to minimize the intrusion of ambient light into the experimental setup. Procedure 2 Requirements - Variable Distance, Fixed Intensity Procedure 2 shall be run three times using three different light intensities. Three data sets shall result. The three different intensities shall be selected to get varying sensor data over the distance moved, i.e. avoid early saturation of the sensor data due to bight intensity. (Prior to taking data, determine the best three intensities to use experimentally by observing output data as the sensors move through the tunnel. Note the position of the intensity knob.) Page 4 of 13

5 At each of the three intensities selected: - Record data from each light sensor as the sensors are moved through the light tunnel towards the light source. - The sensors shall be moved through the full length of the light tunnel. - The number of data points collected shall be sufficient to get a smooth data plot over the full range of motion. - At each data collection point, the distance between the light source and the light sensors shall be recorded in inches (not in fractions of the light tunnel length). Measures shall be taken to minimize the intrusion of ambient light into the experimental setup. 2. Front Panel Design Requirements Note: When LabVIEW communicates to the Arduino DAQ, it must use the Arduino_Communication_SubVI. This is a predefined subroutine you must download onto your laptop and understand how to use, i.e., what are its inputs, what actions will it take based on those inputs, and what if any outputs will it return to LabVIEW. This SubVI is fully described in the Understanding the Arduino to LabVIEW Interface document under the LabVIEW Resources icon. You must read this document before beginning your front panel designs; otherwise you will not be able to implement your designs. Three different front panels shall be designed. Any of the three panels can be used to collect data, however data collection cannot begin until all three front panels have successfully been designed to stated requirements, and your instructor has verified their operation and assigned you credit for the accomplishment. The front panels have some common requirements as stated below. These common requirements form the baseline design. The baseline design will be demonstrated as a group class activity on the overhead projector by your instructor. Your instructor will also explain how to use the Arduino Communication SubVI during this exercise. Each team member must follow along with the instructor by constructing the design so that the baseline design will be available on every laptop computer. The baseline design is the starting point for each of the three final or enhanced designs. It is required that each person on the team design and implement one of the enhanced designs. It is up to the team to decide on how the design assignments will be distributed. Collaboration during the design efforts is allowed and recommended, however each person on the team must be responsible for completing their assigned front panel using their own laptop. Once a front panel design is complete and working, it must be demonstrated to your instructor, as well as included in your project report. Your instructor and T/A will help you accomplish your designs; however, you should also rely on the LabVIEW help feature to understand the operation of a particular function. Right clicking on a function when viewing the Block Diagram will bring up a Help and/or Properties Page 5 of 13

6 option that will provide a description of that function and show how to use/configure it. The help feature is extremely important and useful. Use it! The design requirements for the baseline and three enhanced front panels are present below. In general, required front panel control and indicator names are shown in bold type. Common (Baseline) Front Panel Requirements (Homework Assignment due at the start of Week 3) This baseline panel is a step above the SubVI. It provides a user friendly means for getting data from the Arduino DAQ. Using this panel, the person running the experiment would only need to know which analog channel to read. He/she would not have to know the technical details of the protocol (language) between LabVIEW and the Arduino DAQ. These details will be programmed into LabVIEW, and thus transparent to the user. The requirements for the baseline front panel are as follows: 1. As an input entitled Arduino Connection, the laptop COM port to use for connection to Arduino DAQ shall be selectable via a drop down menu. 2. As an input entitled Arduino Analog Channel, the analog channel to read from the Arduino shall be input as a number in the range of As an output entitled Communications Error, a red LED shall illuminate if the Arduino_Communication_SubVI returns a Hardware Error status. Otherwise the LED shall be off. 4. As an output entitled Data Entry Error, a red LED shall illuminate if the Arduino_Communication_SubVI returns a Data Input Error status. Otherwise, the LED shall be off. 5. As an output entitled Sensor Data, VDC, the numerical value of the raw data returned from the Arduino DAQ shall be displayed in DC Volts. The data shall be scaled to display output data in the following format- X.XXXX VDC. To start a new front panel design, the basic procedure is to open a blank VI in LabVIEW. A new blank VI will always display two screens, the Front Panel, and the Block Diagram. On the Front Panel, right clicking will display the Controls palette. From the Controls palette you will select the various input and output controls needed to satisfy requirements and place them on the front panel. In selecting the input and output controls, there is not always one right answer. If the requirements are not specific, you can use your creativity in designing the Front Panel. For example the size, shape, color, and location of a LED indicator are up to you (unless otherwise specified). Once the required controls and indicators are situated and configured on the Front Panel, you will then go into the Block Diagram and wire the data paths between inputs and outputs to achieve program objectives. Wiring the data paths on the block diagram may require data conversions, such as converting string data to numeric data, or other Page 6 of 13

7 data manipulations, such as arithmetic operations, or data comparisons. These data manipulations are represented by icons that are placed on the block diagram by grabbing them from the Functions palette made visible by right clicking on the Block Diagram. Once the Front Panel and Block Diagram designs are complete, run LabVIEW to see how the program operates, and to see if any runtime errors exist. Your instructor will go through the following step-by-step baseline front panel design with you. To implement the baseline front panel design (do this for homework): Open LabVIEW on your laptop and from the Files menu, open "New VI to start a new program. Address requirement 1. On the front panel, right click to show the Controls palette. Select the Modern, I/O, VISA Resource icon and place it on the front panel. (VISA is LabVIEW s standard application programming interface used to control your computer s USB serial port.) Double click on the text VISA resource name and change it to Arduino Connection Address requirement 2. On the front panel Controls palette, select the Modern, Numeric, Numeric Control icon and place it on the front panel. Right click on the text Numeric and make sure the Size to Text option is checked. (You should do this for all icons placed on the front panel.) Then double click on the text Numeric and change it to Arduino Analog Channel. Further configure this numeric control by right clicking on it (not the text box) and selecting Properties. In the Properties display, select Data Type. Left click on the representation icon, and Select U8. (This means data entered will be in unsigned integer format, and will have a length of 8 bits, the smallest possible.) Furthermore, select the Data Entry tab and unclick Use default limits, and set the minimum value to 0, the maximum value to 5, and the increment to 1. (This will limit data entry to only the valid range as required, i.e., as a 0, 1, 2, 3, 4 or 5.) Address requirement 3. On the front panel Controls palette, select the Modern, Boolean, Round LED icon and place it on the front panel. Change the text to Communications Error. Using Properties change the On color of the LED to red. Address requirement 4. On the front panel Controls palette, select the Modern, Boolean, Round LED icon and place it on the front panel. Change the text to Data Entry Error. Using Properties change the On color of the LED to red. Address requirement 5. On the front panel Controls palette, select the Modern, Numeric, Numeric Indicator and place it on the front panel. Change the text to Sensor Data, VDC. Using Properties, select Display Format, set the number of significant digits to 5, and uncheck the Hide Trailing Zeros box. (This will allow us to display data as required with five significant digits.) Page 7 of 13

8 You now have a front panel design that meets requirements, but there is no program knowledge of how data will flow from inputs to outputs. This will be entered on the block diagram panel. When you open the block diagram view, you should see all of the controls and indicators you just placed on the front panel. Open the block diagram view. (Note: Control-E can be used to toggle between the front panel and block diagram.) On the block diagram, arrange your program inputs to be on the left (i.e., Arduino Connection and Arduino Analog Channel) and your program outputs (the two error LEDs and Sensor Data) to be on the right. (This will not affect the layout of these items on the front panel.) This rearrangement will cause a natural flow of data from left to right, and is important for clarity and simplicity in troubleshooting problems. For LabVIEW to communicate with the Arduino DAQ, we need to get the Arduino_Communication_SubVI and place it on the block diagram. (You should have downloaded this SubVi to your laptop s hard drive following the procedure detailed in Understanding the Arduino to LabVIEW Interface. If not, you must do so now.) On the functions palette, select Select a VI... all the way on the bottom. Browse to and select the Arduino_Communication_SubVI.vi. Click OK and place it on your block diagram between the inputs and outputs. Expand the SubVI as detailed in Understanding the Arduino to LabVIEW Interface. Three front panel items can be wired immediately; that is there are no data conversions or mathematical operations required. Wire the: - Arduino Connection control to COM port on the SubVI (notice both have a purple color) - Data Entry Error LED to Data Input Error on the SubVI (notice both have a green color) - Communications Error LED to Hardware Error on the SubVI (notice both have a green color) Next, we would like to wire the Arduino Analog Channel selector to the input of the SubVI which is Message. However, their colors are different, which indicates they are different data types and generally cannot be connected. If you try to wire them together, you will get an error. Arduino Analog Channel is a numeric integer; Message is an ASCII string. Additionally the Arduino_Communication_SubVI needs to receive a specific sequence of string characters (the protocol described in Understanding the Arduino to LabVIEW Interface ) otherwise the Arduino DAQ will not understand what is requested. Hence, in the block diagram we must implement the data conversion and the required protocol string, as follows: - Convert the Arduino Analog Channel number into ASCII by selecting from the Functions palette the Programming, String, String/Number Conversion, Number to Decimal String Conversion icon. - Create the protocol string input required by the SubVI by selecting the Programming, String, Concatenate String icon. This icon simply merges Page 8 of 13

9 ASCII strings together. It will have a default input length of two (which is what we need), but it can be "stretched" down (left click/stretch) to any length desired. Connect the first input to an ASCII A constant. This can be done by pointing to the first (upper) input connection, right clicking, and selecting Create, Constant. Type the constant required into the box that appears. Connect the second (lower) input to the ASCII output coming from the icon that converted the Arduino Analog Channel from a number to ASCII. - Connect the output of the concatenated string to the SubVI input named Message. The final connection we need is to get the output from the SubVI, Arduino Reading, and display it on our Sensor Data, VDC numeric display. However, again the colors are different which indicates a conversion is needed, this time from ASCII to a numeric value. Also the data coming from the Arduino is an integer number in the range of to (recall the light sensor data in Design I). To convert this to Volts in X.XXXX format we need to divide by Hence, in the block diagram we must do these data conversions as follows: - Convert the Arduino Reading ASCII output into a number by using the Programming, String, String/Number Conversion, Decimal String to Number Conversion icon. Note the output of this icon is the terminal named Number. - Divide the resulting numeric output by using the Programming, Numeric, Divide icon. Connect a constant = to the denominator (y input) of the divide function. (Use Help, by right clicking on the function.) - Connect the Output of the divide function to the Sensor Data, VDC numeric display. You should now have a fully functioning LabVIEW program. Assign one of the three following enhanced front panels to each member on your team and proceed to design and develop them. Enhanced Front Panel #1 Requirements (Will be assigned to one team member during the week 3 class) This front panel makes selecting the analog channel even easier by incorporating a drop down menu. It also introduces the concept of warning/system status indicators by comparing sensor data to predefined/acceptable limits. The input Arduino Analog Channel numeric control shall be changed from the baseline design to a selectable drop down menu. (Hint: Combo Box) There shall be six selectable menu options: CdS #1, CdS #2, Solid State Sensor, Spare #1, Spare #2 and Spare #3. These menu options must be associated (Assigned) with the six available Arduino DAQ analog input channels 0, 1, 2, 3, 4 and 5. Three LED output indicators shall be added to the Front Panel to warn of certain conditions as follows: Page 9 of 13

10 - One LED labeled No Light Source shall be illuminated RED when the solid state light sensor indicates that the tunnel light source is off (has been turned off). Otherwise the LED shall be off (grayed). This LED shall be functional only when the Arduino Analog Channel input has selected the Solid State Sensor. If not selected, this LED shall be off. (Hint: You must experimentally determine a value from the Solid State Sensor that indicates the light source is off. Also the comparison functions equal to, equal to or less than, equal to or greater than and the logical AND function may be useful.) - One LED each shall be associated with the two CdS light sensors. A LED labeled Level #1 shall be associated with CdS#1 sensor and a LED labeled Level #2 shall be associated with CdS#2 sensor. The LEDs shall turn on Green when the associated CdS light sensor output indicates a predetermined light intensity level has been achieved or exceeded (greater intensity, brighter). The predetermined intensity for each LED shall be independently entered on an associated numeric input control. These inputs shall be labeled Operating Level #1, VDC and Operating Level #2, VDC. The input values for both operating levels shall have the same format as Sensor Data, VDC, that is X.XXXX Volts DC. If the associated intensity levels are not reached or exceeded, or if they had been reached or exceeded but then drop below them, the associated LED shall be off (grayed). The LED associated with CdS#1 shall be functional only when the Arduino Analog Channel has selected CdS#1. The LED associated with CdS#2 shall be functional only when the Arduino Analog Channel has selected CdS#2. If not selected, the associated LEDs shall be off. Enhanced Front Panel #2 Requirements (Will be assigned to one team member during the week 3 class) This front panel offers the user versatility to select any of the six analog channels available on the Arduino DAQ and display up to three of them simultaneously, i.e. it emulates a three channel display/monitoring device. It also introduces the graphical plotting of data in real time when LabVIEW is placed in the Run Continuously mode. The Front Panel shall be redesigned to include three identical (Hint: Copy and Paste after one is complete) monitoring panels. Each monitoring panel will have one input device and two output devices as follows: - One six position rotary switch input device labeled Select Sensor. This input selector shall select which one of the six Arduino DAQ analog channels to monitor. The first three position markers on the rotary switch shall be labeled CdS #1, CdS#2, and Solid State Sensor. (Hint: Right Click on the device and explore the available options.) The last three switch positions shall be labeled Spare#1, Spare#2 and Spare#3. Page 10 of 13

11 - In addition to the Sensor Output, VDC used in the baseline, a numeric output indicator labeled Raw Sensor Output shall display the associated sensors raw output, i.e., directly as sent from the Arduino DAQ. - A graph output display labeled Sensor Output shall plot the data associated light sensor. The x-axis shall be time, and be scaled so that data is displayed for approximately 3 seconds before it scrolls off of the graph. The y-axis shall be Raw Sensor Data, but calibrated in volts and scaled to range of volts DC to volts DC. (Hint: The Waveform Chart already has the x-axis setup for time.) When LabVIEW is placed in the Run Continuously mode, all three monitoring panels shall simultaneously and continuously display sensor data in real time as selected by the six position rotary switch, both on the numeric output indicator and on the graphical strip charts. The following controls and indicators should NOT be replicated for each monitoring panel. Only one of each is required to oversee operation of all three monitoring panels: Arduino Connection, Communications Error, Data Entry Error Enhanced Front Panel #3 Requirements (Will be assigned to one team member during the week 3 class) This front panel comes closest in configuration to a final user application, not a development version. It places controls of how to run program right in the front panel. Once the program is started, it should never have to be stopped. Continuous Read and Single Read modes of operation shall be implemented. The program shall be capable of switching between these two modes without stopping or restarting the program. Upon program start, the Single Read mode shall be the default operating mode. (Hint: Consider nesting of while and case structures. Use of Local Variable may ease implementation.) The modes shall be implemented with two pushbutton switches: - As an input entitled Take Reading, a momentary pushbutton switch shall when pressed cause the program to request one data reading from the Arduino DAQ, as selected by the Arduino Analog Channel input. The data reading shall be output to the Sensor Data, VDC display. After the reading is received and displayed, pressing the Take Reading pushbutton again shall request and display another reading. ( Hint: Consider changing the mechanical action of the switch to achieve the desired switch type) - As an input entitled Continuous Data, a lighted pushbutton switch shall when pressed light green and cause the program to exit the default Single Read mode and enter the Continuous Read mode. In this mode LabVIEW shall continuously request and receive data from the Arduino DAQ, as selected by the Arduino Analog Channel input. The data reading shall be output to the Sensor Data, VDC display. When the pushbutton switch is Page 11 of 13

12 pressed again, it will extinguish its light and the program shall return to the Single Read mode of operation. The front panel shall contain one graph that will display in real time the data being received from the selected Arduino Analog Channel when the program is operating in Continuous Read mode of operation. The x-axis shall be time and be scaled so that data is displayed for approximately 2 seconds before scrolling off of the chart. The y-axis shall be Sensor Data, VDC scaled to cover the range from VDC. (Hint: Use right click properties to change graph parameters) As designs are completed and tested successfully, alert your instructor so that credit can be assigned. 3. Written Report Requirements and Grading Each of three experiments conducted in Design II are group grades worth 6 points towards your final grade. This lab report will be graded to a maximum score of 60 that will then be scaled down to 6 and summed into your final grade. The organization, clarity, and presentation of your report shall count for 6 Points. When writing your report, structure it according to the Lab Report Template, Lab Report Format for Experiment 1. Within the template provide the following data and analysis: Present the step-by-step procedure you used to configure the experimental setup and carry out the data collection procedures. (Not the LabVIEW Front Panel or Block Diagram creation procedure.) (10 Points) Present depictions of your three Enhanced Front Panel designs. I.e., use the Print Window command to print out BOTH your three front panel designs AND the three associated block diagrams. (15 Points) Enter collected data into Excel and use the Excel graph function to generate x-y scatter plots of all light intensity data. BE SURE TO CLEARLY LABEL ALL AXES AND PLOTS. - Present one graph for Procedure 1 Requirements with light intensity as the independent variable (x-axis) and sensor outputs as the dependent variables (yaxis). Plot the output data for all three sensors on the one graph so that their data differences can be readily seen. Scale the graph to get good differentiation of the data. (5 Points) - Present three separate graphs for Procedure 2 Requirements. Each graph should associate to one of the three light sensors (I.e., one graph for data from CdS#1, one graph for data from Cds#2, and one graph for data from the Solis State light sensor). Each graph should plot distance from light source (independent variable, x-axis) vs. that sensor s output (dependent variable, y- Page 12 of 13

13 axis). Three lines should appear on each graph, all data from the same sensor but at the three different intensities you chose to run the experiment. (12 Points) Analyze the data by answering the following questions: - What differences in output readings do you see between the two Cds light sensors for the same light intensity? How could you have used these calibration plots to better compare sensor data from multiple light sensors during the Design I robot experiment? (3 Points) - What significant differences are clearly visible between the output of the CdS sensors and the solid state sensor? Identify at least two. (3 Points) - Based at looking at the data, for what situations would you more likely want to use the solid state technology sensor over the CdS technology sensor? (3 Points) - For all light sensors, what empirical observation can be made about how light intensity drops off with distance from the light source? (3 Points) Page 13 of 13