Build Your Own Programmable Lego® Submersible FAQ

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 Yellow Pages™ or ordering from catalogues or on the web. (See below for catalog/website sales.)

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 searching the web and ordering online from companies such as All Electronics (www.allcorp.com) or www.supercircuits.com.

You can make your own floats 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 pumps” 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 are 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.

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.

What serves as waterproof housing for this tetherless 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.

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 just as easily but if they differ in size you will need to alter the structural dimensions and waterproof housing suggestions given in this project.

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.

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