This book provides plans for building a tetherless, shallow-diving robot. By programming and waterproofing a microprocessor, the robot can carry out simple underwater missions to a depth of 3 meters (10 feet). This basic AUV (Autonomous Underwater Vehicle) is called SEA ANGEL and its “brain” is the LEGO® MINDSTORMS™ or ROBOLAB™ RCX controller brick that is housed inside a modified Model 350 waterproof Otter Box™. These well-illustrated plans can be adapted to use other brands of microprocessors.

Power for this underwater vehicle comes from 8 AA batteries that are hooked up to inexpensive hobby motors with small propellers. SEA ANGEL’s slow speed and small size means it can be used in a tank of water only 1 cubic meter in size, something that can easily be brought into the classroom environment.

• This booklet details basic skills required to build this underwater robot as well as the tools required and a complete parts list.
• It discusses how to waterproof motors, lights and cameras for use on a small underwater robot.
• There’s also a section on how to build a deeper-diving, faster-traveling AUV.

CAUTION:
While the projects in this book are fun to build, they are more than challenging toys and constructing them is not play. Some projects involve real tools and utilize procedures that require skill and care.

In all cases, it’s important to use common sense, work under experienced adult supervision and follow safe working practices. The authors and publisher assume no responsibility for injuries or other occurrences.

Number of FAQs for this book: 6

If you’d like to ask a question about this or any other book, please contact us. Popular questions will be posted here.

1. How deep can this submersible go?

The SEA ANGEL robot is a shallow diving tetherless submersible rated to 10 meters. It has four 2.5 cm (1”) diameter motors powered by a total of 8 AA batteries.

2. How do I find the materials and supplies needed for building an underwater robot?

Almost all of the parts needed for building the projects listed in the book are easily available at any local hardware and electronics store. We’d also suggest checking out the internet, company catalogues, or the Yellow Pages™. There are several excellent underwater robot sites, such as www.ronsrovs.com, that are excellent and provide amazing resources.

Each project has a complete list of parts—read it over first to make sure you understand what is needed and in what quantity. Many people dramatically cut the cost of building projects by scrounging and adapting parts—that’s part of the challenge!

Most electrical and electronic supplies can be found at local electronic component suppliers, hardware stores or even automotive supply shops. For CCD cameras and video monitors, you can try electronic supply shops and businesses that supply burglar alarms and security electronics. You will probably find the cheapest prices by checking the internet and ordering online from companies such as All Electronics or Supercircuits.

You can make your own floats from PVC pipe and end caps or buy them at a commercial marine supply store or ships chandlery. In the same store you should be able to locate small bilge pumps or you can order them online. For example, if you do an online search by typing “Rule Industries” you’ll come up with the websites of several companies that carry the 360 and 500 gph Rule bilge pumps. Similarly, Johnson Pump of America makes the 500 gph Mayfair bilge pump inserts. If you do an internet search for “Mayfair bilge pump” you’ll find several companies that carry this product.

Hobby shops have a variety of motors and props. (Surprisingly electronic shops do not really have a good supply of motors.) Props for hobby airplanes can easily be cut down for use on thrusters. Or you can use props from a toy boat or construction set. The important thing is to buy or make a prop with the correct-sized shaft hole.

Waterproof underwater lights from underwater robotic manufacturers can be very expensive. It’s possible to make your own from halogen bulbs or white LEDs. You can also use waterproof flashlights available from hardware stores, outdoor stores, and scuba shops, although these will cost more.

Automotive shops have simple compasses that will work well for an underwater vehicle. Depth gauges and diver compasses come from scuba shops.

3. What serves as waterproof housing for this tether-less underwater robot?

The plans for SEA ANGEL call for the robot’s basic vehicle platform to be constructed around an extremely reliable waterproof housing. We use the Model 3500 clear plastic Otter Box™ that is rated to 30 meters (100 ft). Check out the Otter Box Company’s website in the U.S. or Canada for prices and availability. Other waterproof boxes are available, as well.

4. What kind of computer microprocessor do I need for building a tetherless submersible?

The plans for the SEA ANGEL tetherless submersible call for a LEGO® RCX™ brick microcomputer. Certainly you can use other brands of microcomputers (Stamps, __________, __________) just as easily. If they differ significantly in size, you will need to alter the structural dimensions and waterproof housing suggestions given in this project.

5. About how much does it cost to build an underwater robot?

The cost of any project depends on a number of factors. If you go out and purchase all of the parts and supplies off the shelf, the SEA ANGEL project will cost approximately $100 (U.S.), depending on how many sensors you choose to add. This presumes that you already have the microprocessor components. Of course, you can significantly reduce costs by scrounging materials or by comparison shopping. For example, you could pay more for ready-made underwater lights or you could adapt a cheaper diver’s flashlight. Note that reliable underwater housing is an absolute necessity to protect your microprocessor components. Otter Box™ is the only reliable waterproof housing that we’ve tested that will keep water out. Of course, this presumes that you will have adapted and used it properly, according to instructions in this booklet.

6. What do I have to know to get started?

You need to know a variety of basic skills for this project or else you need to ask someone for help. The basic skills are:

• simple soldering
• following simple wiring schematic diagrams and devising a wiring layout on the vehicle
• understanding simple construction sketches
• using hand tools and a power drill
• drilling and tapping a hole for screw threads
• basic wiring skills such as wire stripping, splicing, using heat-shrinkable tubing and plastic cable tie connectors, running conductors neatly and logically
• using a multimeter to measure DC voltage, current and resistance through a conductor
• understanding basic buoyancy and stability concepts and how they effect submerged objects
• understanding basic programming