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Instructions for building an under-water vehicle

To start off, get the stuff for the control box from Radio Shack.  What you need:

Project box  #2701807  $5.89

DPDT switch (3 or 4 each box)  #2750709  $3.29

In-line fuse holder  #2701217  $1.89

Four terminal bus strip  #2740658  $1.59

8 pos bus strip jumper  #2740650  $1.59

four pos fuse block  #2700742  $2.39

and a bunch of fuses, 4A, 8A, 10A, and 20A.  The 20A goes in the in-line fuse holder, the 4A go in the individual fuse block position, one for each motor. If you use bigger motors than the V-500’s, you will need bigger fuses.

One DPDT switch for each motor, you need at least 3 motors but most students want 4 motors per vehicle.  Drill holes in the project box for each switch, and 2 other holes, one for power in and one for power out.  Switches go on the flat top to the project box, the other two holes go into the front and back sides of the box. I usually glue the bus strip and the fuse block inside the box with epoxy.  Connect pos and neg power to each switch, use the switch to reverse the power for forward and reverse.  The switch is DPDT because it has to reverse both polarities. From each switch run two wires out the box for each motor, through the tether to the vehicle.  I usually make the tether (with 6 to 10 wires inside) separately from the box, then connect the tether to the control box. These wires go as a bundle with the rope as the tether out one hole, usually in the front. You will need 2 more wires, I use 12 gauge, for the battery connection. Ten to fifteen feet for the power wires is fine. Run these wires out the hole in the back, and put big battery clamps on the ends. Fuse the positive (red) wire with an in-line fuse holder, and put a 20 or 25 Amp fuse in there. I use the four terminal bus strip and the four position fuse holder as a power distributor (power bus) out to each switch. Fuse each motor with a 4 or 5 amp fuse in the fuse holder. That gets pos and neg to each switch, the switch is used for forward and reverse, with a center off position.

The tether:  Buy 50 foot lengths of hollow braided plastic rope from Home Depot (while there, get a bunch of electrical tape, plastic ties, and a variety of metal hose clamps.  You can get the 1/2" PVC and fittings here, too).  One rope will be for one tether.  Inside the hollow rope, thread 6 or 8 (2 for each motor) 50' lengths of wire.  I usually twist the wire together, then thread the wire through as a bundle.  You can use 14, 16 or 18 gauge wire, 16 is probably the best because its both flexible and heavy, 14 works but is a little too stiff, 18 is more than flexible enough and is easiest to work with, but is not good for bigger, high current motors.  Have a couple feet of wire sticking out each end of the rope (you can cut a couple feet off the rope, the total length doesn’t need to be much more than 40 feet long or so, but 50 feet is fine)  The tether (rope and wire) is now a single assembly with loose wires on each end (let the students figure out how to know which wire is which on each end).

I wire the box, make the tether, then connect the tether to the box through the front hole, and make the electrical connections. I try to use black for neg and red for pos.  So out of the box, one end has a 50 foot 6 or 8 conductor tether, the other end of the box has 2 - 12 gu wires for main power.  Twist these two wires together also (NOT the bare wire, twist the wire length that is insulated together to keep them neat as a single assembly).  One end connects (separately) to the pos and neg for the switches, the other end has battery clamps to connect to the terminals of the battery. Use 12 V car or marine batteries for the power, but be careful with these around the pool.  Use a battery box.

The vehicle is made out of 1/2" PVC pipe and fittings.  Just get a bunch of the PVC pipe and a bunch of fittings, and let the students figure out how to make the vehicle from them.  You need tee's, angles, crosses, and something called a 90 degree tee, which looks like a 90 degree corner with a third connection going straight down at another 90 degree angle.  These will be the corners, and so are important, but may have to be ordered.  Lowe’s may have them in stock, but Home Depot usually does not. Get some 45 degree angle fittings, too. Cut the pipe into lengths of 4", 6", 8", 10".  The lengths do not have to be too long or the vehicle will get too big.  A vehicle of a couple feet by a couple feet or so (can be smaller or bigger) is good.  One pipe length is not enough for one side, you need at least two lengths, remember that the motors should go in the middle, so you need fittings in the middle.  That is why you put two lengths together for each side.  Let the students experiment here on motor placement.  I also buy noodles (also called Wacky Noodles) from Wal-Mart as the buoyancy device.  You will need some type of foam like this to balance the weight and make the vehicle float.

Motors are Attwood bilge pumps, bought from either Wal-Mart or Academy.  (get the noodles while you are there)  Academy actually has a pretty good selection of a variety of bilge pump sizes, ranging from 10 to 20 bucks each.  I usually use the Attwood V-500's, because they are cheap, but these only work with smaller propellers.  (not enough torque for big propellers)  Bigger propellers need bigger motors, obviously.  The V-625’s or the V-750’s are good for bigger prop’s. Cut the plastic bilge pump housing off to get to the motors, which have o-rings in them to make them water resistant.  They are not water proof, and so will eventually burn out. In the meantime, they will work great.  Attach the motors to the frame using motor mounts made by cutting a cross in half, giving you a 1/2" pipe outlet and a fairly solid rounded part the motor kind of fits into.  One cross gives you two motor fittings.  Note: lately I have been using 1” crosses with a ½ inch outlet, and cutting through the 1” part lengthwise. The larger opening fits the motor better, and the ½” outlet attaches to the frame with the ½” pipe. Attach the motors to this piece with a two or three inch metal hose clamp.  Attach the tether to the vehicle frame with another cross, and then connect the wires to the motors.

Propellers are harder to find, I use three types.  Robbe, Octura, and Traxxas.  Order 3 bladed Robbe's (#1465 and #1464) from Harbor models in Ca, 626-292-1617.  Look around at local hobby stores for the Traxxas and Octura propellors.  The Traxxas prop’s are the easiest to use, but they are not made in very large sizes.  You can order them online (www.traxxas.com for about 3 bucks each. Get both right and left hand. The numbers are #1534 and 1533) The Octura's come in a variety of bigger sizes, but require an extra fitting to attach to the motor.  I use a propeller adaptor from Windsor Propellor Company, the number MA3200. Get some 10/32 nuts and bolts to attach the propeller to the adaptor. At about 5 bucks each, the fittings are expensive compared to about 3 or 4 buck for the prop itself, so I usually do not get a lot of these.  (If you get a good supplier, you can get the adaptors for about 3 bucks, and the propellers for less than 2) The propeller I am using lately is the Octura 1250. Have the students experiment with a variety of propeller sizes connected to a variety of motors to find the best combination.  Remember to test these in water!

Switches work fine, but are only good for on-off control.  For an advanced project, look for variable power control modules from Acroname (www.acroname.com). We have a project where we modify a PlayStation 2 controller, and use that instead of the switches. Unfortunately, this is a much more complicated process and is not easily described. You have to use a microcontroller between the PS-2 controller and the Acroname power module, and you have to do some programming. Basically, the idea is that the PS-2 controller has a variable, analog output that controls a pulse width modulator in the microcontroller. The microcontroller outputs the pulse width modulated signal to the power controller, which is usually an H-bridge. There are other ways of doing this, of course.

The other parts of the project also get a little more complicated. We use a waterproof camera that goes on the vehicle, and we have some projects that require the students to navigate using only the video output from the camera. The student basically watches TV and navigates the vehicle. In the real world, the vehicle is too far underwater to navigate by looking at the vehicle itself, so you need video from the ROV. I buy my camera from SeaView Video Technology, Inc. (727-866-7440). The model is the CSM-50-C SuperMini Color Camera with 50’ cable. This camera works off 12V DC, so runs off the battery. The video output is from an RCA connection, like the aux input to a TV. We put a TV near the pool, but have the students face away from the pool to the TV to navigate. There are lots of other underwater video camera’s, these cost about $240, and are the single most expensive item. In the past, I have
bought a few cheap X-CAM’s, and made my own waterproof housing. This is a good project, but expect to lose a few camera’s when the housing leaks.

We have a mission that requires some type of robotic actuator (an arm of some type) attached to the vehicle. One mission is just to drop a variety of items into the pool, and have the students retrieve the objects. Using pneumatics, or hydraulics, or little motors you can make a gripper or a sweeper pretty easy. There actuators can get pretty expensive, too, but a simple project is a scissors type gripper, spring return, with a 12 V DC solenoid to actuate. I have found that car door solenoids work very well, and can be found at any car alarm or auto stereo installer shop. Add an extra set of wires to the box with an extra on-off switch. You can use a motor to drive a screw type gripper, or a windshield wiper type motor for a sweeper.

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ROV Program Overview    Pre-class checklist

Key Contacts:

 Teacher                                          _________________________

 School Administration Contact          _________________________

 District Administration Contact         _________________________

Class Location:

 Lecture area                                   _________________________

 Lab / construction area                    _________________________

 Computer / printer for portfolio         _________

  ROV intermediate storage area         _________________________

 Construction tools access                  _________

Pool Access

 Pool contact                                     _________________________

 Pool requirements and constraints      _________________________                                                            _________________________                                                            _________________________

 Pool availability confirmed for dates    _________

Class schedule

 Class meeting time / day of week       ________________________

 Target start date                               ________________________

 Target end date                                ________________________

 ROV-in-a-Bag 3-hour block target date ________________________

  First pool access date                       ________________________

  Second pool access date                   ________________________

 Competition date                              ________________________

Class Assignments

 Teams assigned by teacher               _________  

Tools & Materials

Tool Kit Provided by Alvin CC  Safety Glasses     2 pair

 Hacksaw      2

 Wire nipper     2

 Wire stripper     2

 Crimping tool     2

 Straight blade screwdriver   2

 Phillips screwdriver    2

 Multimeter (Volts / Amps / Resistance)   1

Optional tools (school to provide if possible)

 Cordless or AC-powered drill and drill bit set

 Additional hacksaws, nippers and wire strippers, wire crimping tools

Materials Provided by Alvin CC

 ROV-in-a-Bag kits (For  use only during ROVIAB exercise)

 Materials to build 8 independent ROVs with off/on control systems

 Materials to build an additional 4 proportional control systems

 Storage bins for above material

 One 12V auto battery for in-class testing; additional batteries for pool tests

Optional materials (school to provide if possible)

 Additional PVC pipe and fittings if required

 Buoyancy foam, tape, misc supplies as necessary

 Robotics Project Timeline Overview  

ROV Program Overview       Week  1

Materials required:  ROV-in-a-Bag Kits (one for each team, 2-4 students per team)

Grant Instructor Classroom Instructor Lecture: Introduction + video Course schedule & objectives Team requirements (portfolio, report) Definitions & terminology Program management Competition plans Safety orientation

Lab: ROV – in – a – Bag demonstration

Lab: ROVIAB Exercise (requires 3hr block + pool access)

 Assign teams Participate in RIAB demonstration Distribute / monitor / collect pre-class survey info

Homework / classwork assignments 1. Commercial ROVs 2. Famous ROVs 3. ROV uses & jobs 4. ROV technology 5. ROV-related positions available 6. Team names(!)

Goals for Week 1:  Teams identified and assigned  Complete course introduction and ROVIAB exercise.

  ROV Program Overview       Week 2

Materials required:   Set of motors + propellers     Motor test setup (wet)     Materials for experiments (TBD)

Grant Instructor Classroom Instructor Discussion: Review of ROVIAB exercise

Lecture: Present scientific principles related to ROV performance  Buoyancy  Center of Gravity  Center of Flotation  Thrust & Drag  Pressure  DC Circuits & Ohm’s Law  DC Power

Lab: Perform motor / propeller optimization experiment Measure optimized motor thrust Measure optimized motor current & power Plot and summarize results

 Facilitate a representative from each team to detail hi’s / low’s; what worked and what didn’t.

Monitor and drive development of team portfolios

Prepare experiments / examples to demonstrate each scientific principle

Have a representative from each team give a short presentation on each topic and what would happen if the principle is not applied correctly

Additional instruction on scientific principles as needed / required, especially DC circuits

Support motor / propeller optimization experiment Goals for Week 2:  Complete class review of primary scientific principles that affect ROV behavior  Complete propeller performance & thrust experiment  Team portfolios started  

ROV Program Overview       Week 3

Materials Required:  ROV Kits     DC Supply (auto battery) for testing     Monitor for testing

Grant Instructor Classroom Instructor Lecture: Team ROVs  Design Goals  Competition Requirements & Mission Objectives  Design Constraints  Documentation Requirements  Safety Orientation (again)  Program Management:  Component Development Plan o Structure o Propulsion o Tether o Control  Team member component assignments

Discussion: ROV Structure Discussion ROV Propulsion Discussion ROV Tether Discussion ROV Control System Discussion

Lab: Team ROV construction begins

Facilitate team assignments

Host group discussions with key component representative from each team

Facilitates ROV construction

Students build ROV framework, mount motor and tether terminal strip; build tether cable; build on/off control box.

Goals for Week 3:  Complete classroom presentation on ROV construction  ROV construction underway  

ROV Program Overview       Week 4

Materials Required:  Multiple (2) DC supplies (auto batteries)         

Grant Instructor Classroom Instructor Lab: ROV Construction Continues Safety orientation (yet again)

Lab: First Pool Practice - Four ROV launching stations Students try out ROV designs in pool environment. 1. Thrust & power experiment using spring scale affixed to pool edge – does it generate as much thrust as expected? 2. Buoyancy experiment - does it sink / float as needed? 3. Center of Gravity / Flotation experiment - does it flop over and play dead or float right-side-up both on the surface and below the surface? 4. Pressure experiment – once on the bottom, can the ROV come back up?  Students build ROV framework, mount motor and tether terminal strip; build tether cable; build on/off control box.

Instructor facilitates trip to pool Goals for Week 4:  At least four ROVs, control boxes and tethers completed and tested by students  First pool test for completed ROVs (no cameras or monitors)

  ROV Program Overview       Week 5

Materials Required:  Advanced control boxes     Actuators      Cameras & lights (if available)     

Grant Instructor Classroom Instructor Discussion: Review experience from ROV pool test Review experimental results Discuss impact of tether on performance General progress report from teams that were not ready for pool test Update team portfolio

Lecture: Cameras and Video Systems for ROVs

Lab: Continued construction of ROVs Addition of cameras and lights to ROVs

 Facilitate pool test results by teams

Monitor and drive development of team portfolios

Facilitate continued construction and optimization of ROVs Goals for Week 5:  Review results from first pool test.  Complete lecture on advanced proportional control systems  All eight ROVs, on/off control boxes and tethers completed and tested by students  Begin integration of cameras and lights

  ROV Program Overview       Week 6

Materials Required:  Advanced control boxes     Actuators  (!)     DC Supplies (auto batteries)     

Grant Instructor Classroom Instructor Lecture: Advanced Control Systems for ROVs Proportional controller operation Intro to Basic Stamp-based  Proportional Controller

Lab: Demonstrate on/off and proportional controller Begin construction of proportional controllers

Lab: Second  Pool Practice - Four ROV launching stations Students try out ROV designs in pool environment. 1. Determine “real”  ROV performance 2. Practice flying using camera / monitor 3. Measure and track motor current 4. Begin limited practice with proportional controller

Facilitate continued construction and optimization of ROVs Goals for Week 6:  Complete lecture on advanced control systems  Complete one proportional control box and demonstrate  Demonstrate difference between on/off and proportional controllers  Complete second pool practice

  ROV Program Overview       Week 7

Materials Required:  Advanced control boxes     Actuators      

Grant Instructor Classroom Instructor Discussion: Review experience from ROV pool test Review experimental results Discuss impact of controller on performance and maneuverability. Team portfolio updated

Lab: Continue to work on ROVs and controllers. Complete team portfolios Facilitate pool test results by teams

Facilitate continued construction and optimization of ROVs

Monitor and drive development of team portfolios Goals for Week 7:  Finish all eight ROVs, four Advanced Proportional Control Systems.  Complete team portfolios

ROV Program Overview       Week 8

Materials Required:  TBD     

Grant Instructor Classroom Instructor Lecture: ROV career opportunities Science & Technology career opportunities

Team Presentations, including ROV demo, portfolio, construction details, advantages, challenges, expected performance

Lab: Third  Pool Practice - Four ROV launching stations

ROV Competition & awards ceremony 

Facilitate team presentations

Goals for Week 8:  Team presentations  ROV competition & awards ceremony

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These parts are suitable for a class of 20-25 students.

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ROV Project Parts List
Quantity Part Name Supplier Part Number Alternate Supplier Alternate Part
Quan   per school ind cost total
12 Control Box Radio   Shack 270-1807 ea $5.89 $70.68
12 Terminal Strip Radio Shack 89-210 ea $8.99 $107.88
77 PVC Tee Home Depot CP401-005 ea $0.16 $12.32
90 Hose Clamps 23-70mm Home Depot 300SS ea $1.06 $95.40
82 PVC 90 Elbows Home Depot 406-005P10 ea $0.14 $11.48
50 Propeller Hobby Center 1250 ea $1.49 $74.50
50 Propeller Adapter Hobby   Center MA3200 ea $3.00 $150.00
1 WirePro Crimp Tool Home Depot WP900 ea $8.99 $8.99
50 V625 Motor Academy Sports 4206 ea $12.60 $630.00 Bass Pro Shop Mayfair   Bilge Pump
70 PVC 45 degree elbow Home Depot 30605 ea $0.29 $20.30
10 PVC 1/2 inch Cap Home Depot 30155 ea $0.19 $1.90
50 PVC Lenova 1inch x 1/2inch Tee Home Depot 31475 ea $0.89 $44.50
13 PVC 4 way (cross) Home Depot 34405 ea $0.73 $9.49
2 7" Diagonal Pliers Home Depot 303518 ea $9.49 $18.98
3 PVC Tubing Cutter Home Depot H489743 O/M 1-5-25 ea $9.97 $29.91
12 HD Inline Fuse Holder Radio Shack 270-1217 ea $1.89 $22.68
12 Battery charging Clips pk of 2 Home Depot 14-530 pk $1.99 $23.88
41 Auto Flip Switch 6 way Radio Shack 275-709 ea $3.37 $138.17
1 #30 Drill Bit Home Depot 11830 pk $1.99 $1.99
4 Highland Terminals Spade Home Depot BFV18-6L bx $6.46 $25.84
1 Machine Screws Stainless 2 in Fastener supply 828514 bx $18.49 $18.49
1 Machine screw nuts Fastener supply bx $3.49 $3.49
3 Tartan 1710 Electrical Tape Home Depot 49656 ea $1.69 $5.07
1 Wire Nut box of 100 Home Depot 30-074 bx $6.10 $6.10
2 1/2" hollow plastic rope 250 ft Home Depot 10859 ea $45.00 $90.00
12 Sterilite 122 Qt Box Home Depot 1735 ea $8.99 $107.88
1 16 ga wire black 500 ft Electrical Supply 82656 roll $13.18 $13.18
1 16 ga wire brown 500 ft Electrical Supply 82405 roll $13.18 $13.18
1 16 ga wire red 500 ft Electrical Supply roll $13.18 $13.18
1 16 ga wire orange 500 ft Electrical Supply roll $13.18 $13.18
1 16 ga wire yellow 500 ft Electrical Supply 82559 roll $13.18 $13.18
1 16 ga wire green 500 ft Electrical Supply 82276 roll $13.18 $13.18
1 16 ga wire blue 500 ft Electrical Supply 82813 roll $13.18 $13.18
1 16 ga wire violet 500 ft Electrical Supply 81944 roll $13.18 $13.18
1 16 ga wire grey 500 ft Electrical Supply ???? roll $13.18 $13.18
1 16 ga wire white 500 ft Electrical Supply ???? roll $13.18 $13.18
1 12 ga wire red 100 ft Electrical Supply 41216 roll $10.99 $10.99
1 12 ga wire black 100 ft Electrical Supply 41211 roll $10.99 $10.99
4 digital fish scale Academy Sports ea $18.99 $75.96
12 PS-1 joystick controller Radio Shack 2600654 ea $7.97 $95.64
10 fuse (25 A) Radio Shack pk $1.78 $17.80
3 color video camera SeaView Video CSM-50-C ea $265.00 $795.00 Lights, Camera, Action LCA-7700C
6 compact jumpstart battery O'Reilly Auto Parts 2704123 ea $39.99 $239.94
90 side outlet   tee Home Depot ea $1.35 $121.50
50 threaded adapters Home Depot ea $0.19 $9.50
12 basic   stamp Parallax ea $41.65 $499.80
24 motormind Solutions Cubed ea $44.00 $1,056.00
12 custom circuit board Alvin CC MERV2845 ea $10.00 $120.00
12 electrical parts for board Jameco Supply misc $5.00 $60.00
20 PVC pipe 10 ft Home Depot ea $1.08 $21.60
4 Wire strippers Home Depot ea $8.47 $33.88
1 Tool box Home Depot ea $29.97 $29.97
2 Zip ties Home Depot pk $22.47 $44.94
2 Solder Station Radio Shack 6402184 ea $21.99 $43.98
SUM $837.02 $5,149.21

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