Mars Rover Robot (MRR)

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RFP*: Mars Rover Robot (MRR)

* RFP is an acronym for Request For Proposal. Internationally, RFPs are called ITTs, an acronym for Invitation To Tender governmental agencies use RFPs to solicit new business.

This project reflects real life scenarios; the robot must be able to handle minor imperfections in the course.

Note: You should only use the materials contained in the Price list for Lego parts for robot projects. If you want to use other parts, get permission from your faculty member to do so, and also to determine the cost of the parts you want to use that are not in this price list.

Introduction and Overview

The United States National Aeronautics and Space Administration (NASA) has received increased funding and have been able to reinstate the Constellation program. To help accelerate the process of development, NASA has issued an RFP (request for proposal) for a rover that will be used in the first of the Constellation missions. This rover will provide data about the landing site and begin preparations of the surrounding area to aid the manned missions arriving 26 months later. The robot should be able to get an accurate salinity reading of any water source, collect soil samples, travel across uneven terrain, and return to the landing site.

The mission has two parts that must be completed. The first part uses a salinity sensor to measure the salt content of one water source and a soil collection module to collect a soil sample, both taken by an autonomous robot (see Course Specifications for more details). The second part of this mission involves analyzing a water source and a soil sample. The water must be tested for salt content. There are two soil tests that the robot can choose from: a pH test and a compounds separation test. Once the tests are done, a conclusion must be reached about whether life can exist in the water sources on Mars, and (depending on the soil test) whether plants can potentially grow in the soil and/or if there is enough Fe2O3 and Fe3O4 to produce an adequate amount of rocket fuel.

Course Specifications

Design a robot using Lego Digital Designer as your primary design tool. A model of your design must be built using the materials provided. A Mindstorms program that will direct the robot's movements must be created. A cost estimate of the robot's components must be provided. All revisions to the original design must be recorded and explained. This includes technical design drawings and cost estimates. All revisions to the Mindstorms program must be recorded and explained.

The Mars Rover Robot (MRR) must be able to move autonomously over the surface of Mars and collect salinity readings from a water source and a soil reading from a soil sample. Salinity readings will be taken using a salinity sensor while soil readings will be taken using a soil collection module. The robot must return to start to pick up the next module/sensor; if the robot can hold both the sensor and module while traversing the course, there is no need to go back to start between readings. The NXT adapter must be fixed to the robot at all times. The robot must finish in the start area, which is 11” by 11”. There is no height restriction. The part of the robot containing the Vernier sensor and collection modules must also fit within the size specifications.

Projectile (catapult, slingshot) designs are not allowed.

The robot program may not be altered or switched during any part of the mission. The robot must be fully autonomous and cannot be touched by any person during testing. Modules can be attached or placed on the robot so long as the robot is not shifted or altered in any way. Please refer to the course syllabus for all due dates.

The robot must return to the landing site to successfully complete the project.

Main Tasks

The first part of the mission requires the robot to:

  • Collect one water reading using the Vernier salinity sensor
    • Salinity sensor must be dipped into the water sample by the robot
  • Collect one soil sample from a dig site using a collection module
    • The robot must carry the collection module from the Start tile to the dig site
    • Soil collection modules can be placed by hand onto the soil sample once the robot comes within 2 cm of the sample
    • Collection modules are color coded; refer to the layout to determine which module to use
  • Return to the landing site between readings unless the robot can hold both a module and the salinity sensor
  • Return to the landing site after all readings are taken
Figure 1: Soil Collection Modules

Extra Credit

Extra Credit will be awarded if:

  • A second different type of soil sample is taken
    • The corresponding test must also be done to get extra credit
  • The robot takes a reading from an extra credit tile
  • The robot travels up mountain
  • The robot crosses the canyon
    • This means the robot completely enters on one side and exits from the opposing side
    • All four wheels must cross the canyon

Layout

Figure 2: Labeled Mars Rover Course Map

Microsoft Project

A time management plan using Microsoft Project (MS Project) must be created. You can learn Microsoft Project by doing the MS Project Skill Builder. This plan must include all tasks related to the project. The MS Project schedule should include the following:

  • Minimum of 20 tasks.
  • Milestones should be clearly indicated on the project plan (duration of zero days).
  • Each task must include the person responsible for completing the task (resource names).
  • Use the Copy Picture function to include the project plan in the presentations. DO NOT take a screenshot.
  • Gantt chart must be displayed alongside the tasks list (fit onto one slide).
  • Gantt chart must clearly show a progress line.
  • Clearly state during the presentation whether the project is on time, behind schedule or ahead of schedule

For help in planning the project, review the page called How to plan the schedule and calculate costs for a project.

Drawings

All drawings and sketches should be made using Lego Digital Designer.

Create four drawings of the robot: front, top, most detailed side, and a drawing of the gear trains. Sensors, motors, and gears must be included in each drawing. If the robot does not use any gears, make sure to explicitly state that during the presentations.

Each revision of the design must be documented and all changes must be presented during Milestone presentations.

Figure 11: Sample isometric image from Lego Digital Designer (without part numbers)

Model

Figure 3: Salinity sensor[1].
Figure 4: NXT Sensor Adapter[1].

The following materials will be provided:

  1. Mindstorms kit
  2. One EV3
  3. Sensors
  4. Motors
  5. Salinity sensor*
  6. NXT Sensor Adapter
  7. Two soil collection modules

* Please note that the salinity sensor and soil collection modules will only be available for use in the Model Shop. This is for safety purposes as we do not want the sensor to be misplaced or damaged in transit from school to home.

There is size limitation for the robot. Please note the size of the obstacles on the course when building the robot.

Additional materials can be supplied by a TA.

Cost Estimate

Once a robot design is complete, a cost estimate must be generated that specifies the cost of all the materials and labor required for the construction of the design. Tabulate this cost information clearly in an Excel spreadsheet, using the materials cost list provided. Help in calculating the cost is available by reviewing How to plan the schedule and calculate costs for a project. The costs for the parts can be found on the Price list for Lego parts for robot projects.

Note: You should only use the materials contained in the Price list for Lego parts for robot projects. If you want to use other parts, get permission from your faculty member to do so, and also to determine the cost of the parts you want to use that are not in this price list.

Create a cost estimate on a Microsoft Excel spreadsheet. The cost estimate should include the following:

  • Labor cost breakdown with hours and rates
  • Consolidate low-cost pieces: axles, beams, bricks, bushings, connectors, gears, plates
  • Itemize high-cost pieces: controllers (NXT/EV3), sensors
  • No decimal places; this is an estimate after all. Round appropriately
  • Total cost must be shown in the bottom right corner

Data Specifications

Overview

Part 2 is now available. Download the Part 2 Template and complete all applicable questions before submitting the final folder.

The second part of the mission is to:

  • Analyze 3 water samples' salinities and specific gravities to determine if life can exist in the waters of Mars
  • Analyze a soil sample depending on which dig site(s) the robot traveled to:
    • pH Test: Test the pH to determine if plants/vegetables can grow, and if possible, state 3 different potential plants/vegetables that could be planted
    • Fuel Test: Analyze a sample of Fe2O3 and a sample of Fe3O4 to determine how much rocket fuel can be made

Background Information

Salinity

Salinity is defined as the amount of salt dissolved in a solution. This can be seen in bodies of water throughout the world. Most of the oceans have salinity between 34 and 36 parts per thousand (ppt) while the Mediterranean Sea has a salinity of 38 ppt. One of the more salty bodies of water in the world is the Dead Sea which has a salinity of 342 ppt, which is 9.6 times higher than that of oceans.

The salinity sensor used in this project works by measuring the conductivity of the solution. The salt water can be measured in this way because there are ions in the water that can conduct electricity. In order to understand why this works, the basic chemistry of ionic and molecular compounds must be understood.

Salt is an ionic compound, which means that it is made up of two components, a metal and a non-metal. Some examples of salts are sodium chloride (NaCl), which is table salt, magnesium sulfate (MgSO4), potassium nitrate (KNO3), and sodium bicarbonate (NaHCO3). A molecular compound is made up of two components as well, but instead of it being a metal and a non-metal element like ionic compounds, it is two non-metals. A few examples of molecular compounds are carbon dioxide (CO2), water (H2O), and ethane (C2H6).

Ionic compounds are different from molecular compounds because molecular compounds are held together by bonds and ionic compounds are not. Non-metals have a tendency to gain electrons and have a little tendency to lose them. When two non-metals come together to make a molecular compound, they share electrons. This is because both non-metals want the other's electron(s) and do not want to give up their own; they form a bond to share those electron(s) between them. For ionic compounds, the metals have a tendency to lose electrons and the non-metals have a tendency to gain electrons, which sets up a perfect match. When the two are put near each other, the metal gives the non-metal an electron(s).

Figure 5: Ionic bonds[2].

These newer elements are called ions and they can either be positive or negative. The metal ion tends to be positive because it gave an electron away (electrons are negatively charged), and the non-metal tends to be negative because it accepted an electron from the metal. These ions are what conducts electricity and the more ions there are, the more electricity they can conduct. This conductive property of ions is what allows the salinity sensor to determine the salinity of a solution, based on the number of salt ions in the water. Figure 15 shows the dissociation or separation of the two elements in table salt, sodium (Na) and chlorine (Cl). Notice that the metal (Na) becomes a positively charged ion while the non-metal (Cl) becomes a negatively charged ion based on the electron exchange.

Figure 6: Dissociation of NaCl[3].

Salinity plays an important role is determining the chemistry of organisms that live in the oceans and seas that cover the Earth because it governs physical characteristics such as density and heat capacity. These physical characteristics also determine which organisms and plants can survive in a body of salt water. As described earlier, the Dead Sea has a very high salinity, causing the density to increase and creating a harsh environment that few life forms can survive in.

Although many organisms cannot survive in extremely high salinity bodies of water, such as the Dead Sea, some of them can still survive in lower salinity oceans and seas. Plants that can live in these very saline conditions are called extremophiles or halophiles, while those plants and organisms that can live in a wide range of salinities are called euryhalines. These species of plants have adapted to these harsher environments that are created by effects of salinity because even the slightest change in salt content can drastically change the temperature, density, or pressure of the body of water.

When describing the habitable properties for both freshwater and saltwater fish, many experts use the term specific gravity. Specific gravity is a ratio that can be determined by dividing the density of a substance by the density of a reference substance. Salt water is being used for this project so the reference density is the density of fresh water, which will be altered from the real value for the purposes of this project. The formula for specific gravity can be seen below where ρ (rho) is the density of a substance and ρreference is the density of the reference substance.

Specific Gravity = \frac{\rho}{\rho_{reference}}\!\,

Specific gravity ratios are used for many purposes in chemistry, but for this project it plays an important role in determining whether fish can survive in certain salinities. Freshwater fish can survive in bodies of water with a specific gravity ranging from 0.98 – 1.00 and saltwater fish can survive in water with a specific gravity ranging from 0.93 – 0.98. Plants and organisms that can live in a wide range of salinities can survive with specific gravities ranging from 0.90 – 0.95 and those that can survive in extremely saline conditions can live in waters with specific gravities ranging from 0.86 – 0.89. These conditions are specific to this project only and do not replicate the real ratios. In salinity (ppt) terms, freshwater fish can only survive in salinities less than 3 ppt. The salinities of bodies of water found on Earth are displayed below as a reference for other types of fish and organisms:

Figure X. Salinity values of various bodies of water on Earth, measured in ppt.
Body of Water Salinity
Baltic Sea 8 ppt
Black Sea 18 ppt
Average Seawater 34.7 ppt
Mediterranean Sea 39 ppt
Red Sea 40 ppt
Mono Lake >50 ppt

Typically, chemists use the density of a solution to estimate its salinity, but for this project, both the salinity and specific gravity will be used to determine whether a body of water can sustain life or not.

pH

In order to recognize the safety and viability of aqueous solutions in chemical reactions, the pH needs to be calculated. The pH numeric scale is used to determine the acidity or basicity of an aqueous solution. At the top of the scale, 14 is for very strong bases, and 0 is for the strongest acid. In the middle of the scale, 7 is for neutral aqueous solutions. To determine the pH, one must use an indicator. These indicators are halochromic chemical compounds added in small amounts to solutions to determine the pH visually. The different pH levels and their corresponding color can be seen in the picture below.

Figure 8: pH indicator colors and their corresponding pH values

pH plays a vital factor in Martian exploration due to the connection between the soil's pH and its ability to harbor vegetation. On Earth, agriculture usually occurs in soil with a pH between 5.5 and 7. However, on Mars the pH is considerably higher. In August 2008, the Phoenix Lander conducted basic chemical analysis and determined the pH of martian soil. It was found that the soil had a pH of 8.3 and contained salt perchlorate.

The samples in this test are aqueous solutions that have been mixed with Martian soil and filtered to be clear. pH indicator will be used to determine whether plants can grow on the surface of Mars.

Magnetite, Hematite, and Wustite

The issue that plagues a voyage to Mars is the amount of resources necessary for the astronauts to have a successful return trip. The inherent weight of the fuel alone makes the trip exceptionally difficult. However, as unmanned missions have progressed the presence of Hematite (Fe2O3) and Wustite (FeO) on the surface of Mars brings a new hope to a mission of this sort. For the majority of rockets, pressurized hydrogen is the main source of fuel. Its high potential energy, relatively low weight, and abundance make it an ideal choice. On Mars there is an abundance of both Hematite and Wustite. Hematite, a reddish black mineral consisting of ferric oxide, and Wustite, a greenish gray crystallite, are the two martian components required. Prior to the creation of the hydrogen fuel, the Hematite and hydrogen must be reacted to create Magnetite (Fe3O4). With Magnetite and Wustite, hydrogen can be created, which is a form of rocket fuel. On Mars this process is an in-situ, on location, production of oxygen, hydrogen, and carbon monoxide through a two-step thermochemical splitting process or redox cycle. In this process, hydrogen reacts with Hematite to form magnetite which is combined with water to create hydrogen. The chemical equations can be seen below:

  • Fe_3O_4 (+ energy) \rightarrow 3FeO + \frac{1}{2}O_2
  • 3FeO + H_2O \rightarrow Fe_3O_4 + H_2

The samples in this course consist of Fe3O4 and soluble compound. The amount of H2 (rocket fuel) can be determined from the amount of Fe3O4 found in the sample by using the above chemical reactions.

Figure 9: Space shuttle launch on May 31, 2008

Obtaining and Analyzing Data

For the second part of this project, calculations will be done on the water sources and soil samples from the course. This data will be used to answer each test's objective. This part requires the use of a robot and the EV3 program. The robot may be touched for this part only. It will also have to be done during an Open Lab session and a TA will the following materials:

  • For Salinity Test
    • One 100 mL beaker filled with salt water
    • Salinity sensor
    • A scale
  • For pH Test
    • One 100 mL beaker filled with solution
    • pH indicator
    • A stirring stick
  • For Fuel Test
    • One packet of Fe2O3
    • One packet of Fe3O4
    • One empty packet (to tare)
    • A scale

Testing Procedures

Depending on the samples the robot travels to, there are tests that must be done in order to complete the mission.

Fuel Test (Yellow Soil Sample)

  • A packet of Fe2O3 and a packet of Fe3O4 must be weighed in order to find out how much rocket fuel can be produced by the samples found on Mars
    • Tare the scale using the empty packet
    • Mass the packet of Fe2O3
    • Mass the packet of Fe3O4
    • Calculate how much rocket fuel can be created and answer Analysis questions accordingly

pH Test (Red Soil Sample)

  • A sample of soil must be tested to see if plants can grow
    • Use universal indicator to determine the pH levels of the soil on Mars
    • Answer Analysis questions using the results

Water Salinity

  • Three water samples must be tested to determine if life can exist in the water on Mars
    • Use the salinity sensor and EV3 program to determine salinity
    • Calculate specific gravity and answer Analysis questions accordingly
      • Note: The robot does not travel to both samples

Density can be recorded in grams per milliliter (g/mL) and salinity should be recorded in ppt. The formula for density is shown below for reference where m represents the mass and V represents the volume.

Density(\rho) = \frac{m}{V}\!\,

All of the information recorded in this part of the section should be typed up on a Word document. Please download the Part 2 template and refer to each test's set of questions to complete the document.

Analysis

In the Part 2 template, answer the following questions. Only answer questions for the tests performed:

  • Salinity Test
    • What are the salinities of the three samples?
    • Based off of the samples' salinities and specific gravities, which, if any, of the water samples are habitable for freshwater fish? saltwater fish?
      • Both the salinity and specific gravity must allow for life in order to conclude that life can exist.
    • Would euryhalines survive? How about halophiles?
  • pH Test
    • What is the pH of the sample?
    • Can plants survive in this pH? If so, name three plants that could potentially be planted.
  • Fuel Test
    • How much Fe2O3 (in grams) was found in the sample?
    • How much Fe3O4 (in grams) was found in the sample?
    • How much fuel (H2) can be produced (in grams) by the Fe2O3 and Fe3O4 found in the sample?
    • How much Fe2O3 is needed to produce 5kg of H2?

Show all the formulas and calculations used to answer the questions as well as a few sentences explaining the calculations and the thought process. A simple formula and calculation will not suffice. Please note that these questions do require some critical thinking.

* Please remember to save all documents from part two (questions and answers) because they are required for final submission.

Milestones and Benchmarks

As you work on your project, you will be required to present periodic reports on your progress. We call these Milestones. All the items assigned in each Milestone are called deliverables. These deliverables often consist of a combination of written submissions, presentations, and demonstrations.


Milestone 1

Prepare a preliminary sketch of the design, a cost estimate, and an MS Project plan.

Look Ahead: What tasks are planned between now and Milestone 2?

See How To Give a Milestone Presentation for the format of a Milestone presentation.

Milestone 1 Deliverables:

  • Presentation:
    • Project description
    • Design approach
    • Mission statement
    • Preliminary CAD drawing of robot
    • Cost estimate
    • MS Project schedule
    • Progress update: current state of the project

Benchmark Assessment A

Benchmark assessments evaluate the progress of the project. Benchmark Assessment A is due at the end of Model Shop Session 1. There are penalties for not completing on time. Refer to the EG1003 Grading Policy for more information.

To pass, the design must complete all of the following:

  • Obtain one soil reading from any of the four available soil sources

Milestone 2

Using Lego Digital Designer, prepare four views of the latest design: front, top, most detailed side, and an isometric drawing. Also, create a drawing of the gear trains. Complete the latest Mindstorms program and the latest MS Project plan reflecting any schedule changes. Finally, calculate a revised cost estimate.

Look Ahead: What tasks are planned between now and Milestone 3?

See How To Give a Milestone Presentation for the format of a Milestone presentation.

Milestone 2 Deliverables:

  • Presentation:
    • Project description
    • Design approach
    • Design changes since Milestone 1
    • Mission statement
    • CAD drawings: top, front, most detailed side, isometric, gear train
    • Mindstorms program
    • Cost estimate (previous and current). What changes were made?
    • MS Project schedule (previous and current). What changes were made?
    • Progress update: current state of the project (time, budget, etc.)

Benchmark Assessment B

Benchmark Assessment B is due at the end of Model Shop Session 2. There are penalties for not completing on time. Refer to the EG1003 Grading Policy for more information.

To pass, the design must complete all of the following:

  • Obtain a first soil reading from any of the four available soil sources
  • Return to the landing site to pick up salinity sensor if necessary
  • Obtain a second reading from a water source

Milestone 3

Using Lego Digital Designer, prepare four views of the latest design: front, top, most detailed side, and an isometric drawing. Also, provide a drawing of the gear trains. Complete the latest Mindstorms program and the latest MS Project plan reflecting any schedule changes. Finally, calculate a revised cost estimate.

Look ahead: What tasks are planned between now and the completion of the project?

See How To Give a Milestone Presentation for the format of a Milestone presentation.

Milestone 3 Deliverables:

  • Presentation:
    • Project description
    • Design approach
    • Design changes since Milestone 2
    • Mission statement
    • CAD drawings: top, front, most detailed side, isometric, gear train
    • Mindstorms program
    • Cost estimate (previous and current). What changes were made?
    • MS Project schedule (previous and current). What changes were made?
    • Progress update: current state of the project (time, budget, etc.)

Commissioning

Refer to the syllabus for the commissioning deadline. There are penalties for not completing on time. Refer to the EG1003 Grading Policy for more information.

To pass, the design must complete all of the following:

  • Obtain a first reading from any of the four available soil sources
  • Return to landing site to pick up salinity sensor if necessary
  • Obtain a second reading from a water source
  • Return to landing site
  • Completed Part 2 Template of test results from Data Specifications: Analysis


Final Presentation

The final presentation will be a technical briefing, similar to the milestones, but also serves as a sales presentation explaining why your company should be selected instead of the competition. Please include the following:

  • Problem statement
  • Solution overview
  • Company description and qualifications
  • Drawings
  • Mindstorms program
  • Cost estimate
  • Microsoft Project schedule
  • Video demonstration
  • Why should the company be awarded this contract?

Submission

Beginning Fall 2016, students will be able to submit online. Please visit https://eg.poly.edu/finalSLDP.php for login information and the link to the Project Submission form.

Students must be logged into the account provided at https://eg.poly.edu/finalSLDP.php. Submitting with your NYU account or any other account will generate an error.

Submissions may be edited at any time before the deadline. Please note that submission times are based on the last submission. Submissions that qualify for Early Submission will lose the Early Submission Extra Credit if the submission is edited after the Early Submission deadline.

Please note the deliverables for this project are as follows. If any of the following items are omitted, you will be penalized. Be sure to click SUBMIT at the bottom of the form.

  • Project deliverables:
    • Final presentation
    • Cover page and table of contents
    • Final Mindstorms program
    • Initial sketch
    • All the drawings of your design (initial through final)
    • Video
    • Final MS Project Schedule
    • Final cost estimate
    • Resume(s) (No fictitious resumes will be accepted.)
    • Completed Part 2 Template of test results from Data Specifications: Analysis

Early Acceptance

If you submit your project one week early, you are eligible for a bonus that will be added to your final semester-long project grade. You must submit all deliverables one week before the submission deadline (see syllabus for exact date). To submit early, all required information on the form titled Project Submission Form, found on the EG web site, must be approved, accepted, and signed by a TA. The deliverables received early are the ones you will use in your presentation. No adjustments to the deliverables submitted will be accepted.

Late Delivery

Late delivery is not allowed. If you do not commission by the deadline set forth in the syllabus, you will not receive full credit for commissioning. In order to receive partial credit, all deliverables except the commissioning statement must be submitted by the submission deadline. Please refer to the EG1003 Grading Policy for more information.

Frequently Asked Questions

Could we take readings from both the regular and extra credit options of a sample?

No. You can only go for one sample in each category (i.e. cannot get both regular water and extra credit water)

Can we bump the course if the robot gets stuck?

No. You can't bump Mars, so bumping the course is not an option.

Can we rubber band the soil collection module to the robot?

No. The module has to be fixed to the robot using only EV3 pieces that came in your kit. Regular Legos cannot be used.

Can we put the soil collection module back on the robot once it's been placed on a soil sample?

No. The soil collection module must remain on the soil sample for the rest of the robot's run.

Appendix: Programming with Vernier Sensors

In order to program the EV3 to obtain a reading using a Vernier sensor, a special sensor block that must be used. This block does not initially come with the EV3 programs, but can be easily downloaded. The computers in the Model Shop and all the EG lab rooms already have this sensor block on the programs. If you would like to download it onto your own computer, please look at the instructions below.

Downloading the Sensor Block: EV3

The instructions are the same for downloading the EV3 sensor block. On [www.vernier.com www.vernier.com], search for "Vernier EV3 Sensor Block" and click on the first link on the search results page.

Once at this webpage, click on "Download Vernier EV3 Sensor Block – Version 0.79" and save the "Vernier Sensor Block.ev3b" folder to a place where it can be accessed easily.

Start the EV3 software on your computer. At the top of the screen click on "Tools" -> "Block Import." A screen will pop up that looks very similar to the one in Figure 18. Click on "Browse" and search for the "Vernier Sensor Block.ev3b" file that was recently downloaded from the website. After a few seconds, the words "Vernier Sensor Block.ev3b" will appear in the box under "Name." Click on the name and hit import; the file will be downloaded.

Using the Sensor Block: EV3

Start the EV3 software on your computer and open a new program. On the bottom of the window, click on the yellow sensors palette, different sensors should be visible at the bottom of the screen. Click and hold on to the Vernier Sensor icon and drag it onto the main frame.

On the Vernier sensor block there should be button that says "Raw" right underneath the green picture that says Vernier. This button is shown in Figure 21.

Figure 21: Vernier sensor block (EV3).

After the button is pressed go to "Measure" -> "More Sensors" -> "Salinity ppt." You should see that the image looks similar to the one in Figure 22.

Figure 22: Salinity sensor block.

Now, we are going to create a program to make the robot continuously measure the salinity and display the reading on the EV3 brick. To do this, we must input a loop that can be found under the orange palette. Drag the loop onto the main frame. It should now look like the program in Figure 23.

Figure 23: Loop with salinity sensor block.
  • To change the runtime to a specific amount of time, click on the infinity symbol under the red arrows on the loop switch and change it to time, which can be found all the way at the bottom. Change the number to the right of the button to the desired time.

We are now going to have the salinity reading display on the EV3 brick. Go to the green palette at the bottom of the program, click on the display block and drag it onto the main frame. On the display block, click on the image folder and go to text, then pixels. The block should look like the one in Figure 24.

Figure 24: Display block.

At the top of the display sensor block, the name "MINDSTORMS" is displayed. Click on the name and change it to "Wired." The block should look exactly the same except with one more slot immediately to the left of the spot with the check mark. Input the display block into the loop previously made and wire it like the picture in Figure 25. This program will now allow the salinity sensor to read the measurement and display it on the brick until the program is stopped.

Figure 25: Sample salinity reading program.
  • Note: For measuring salinity for Part 2, it's recommended to run the loop continuously in order to continuously display the salinity until the program is stopped.

References