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The Life of Neil in a Nutshell
We approached the building of a firefighting robot in a series of small steps. While the three of us had been in EGR 100 together, where we built Lego robots with RCX processors and programming, we had never had much experience with the Handy Board.
We began by learning how to wire and solder the motors and sensors, and spent a lot of time in the machine shop perfecting them. (The soldering guide is available here.) Then we got to know the board itself, by downloading Interactive C onto it and working with its connection to the computer. Some simple programs were tried next, to test its sensors and motors. At first we tried programs found on Shana's page and others, but they needed small modifications. The programs we used are available here. Next we worked on how calibrating the light sensor would work, which proved somewhat difficult.
Once we had a handle on small programs and how the Handy Board worked, we had to adapt the board's sensors and motors to fit into the Lego parts we would be using for the chassis. We went back to the machine shop to attach the motor axles to Lego ones. (The details on this are in the components section.) To attach sensors to Lego pieces we used a very sophisticated method - Scotch tape.
The first chassis built was a modified version of the Lego bug, available in the resources section. It consisted of a very boxlike structure that held motors reduced with worm gears, one set of wheels with tires and one set without, and two bumpers with touch sensors on the front. We later modified it to hold the Handy Board on top with a structure to keep it in place and also a structure on the front to hold a light sensor. More details are here, in the building section.
Once we had a working Handy Board and body, we decided to try a very simple programming task, similar to our first tasks in Engineering 100, consisting of path-following. The Lego Mindstorms kit comes with a black line path in a circle to test path-following robots. A program was written that would theoretically do this, and we started to calibrate the light sensor. This proved to be very difficult, because even though we found an area with uniform diffused light, variations in brightness from one side of the path to the other made it very challenging to find a happy medium of settings to program, because some of the light areas were registering in the upper 50s with dark areas on the other side of the maze registering in the lower 50s. After many attempts, we discovered that the placement of the light sensor is highly important. We tried lowering the sensor, which was taped to a Lego block, but the robot would sometimes hit a crease in the maze and knock the sensor sideways.
To combat this problem, we went back to the machine shop and drilled a hole in a 3x2 Lego block through which to thread the sensor and a notch across the top to secure its wire. This kept the sensor at a uniform height and orientation and was a great help to our calibration efforts.
With the light sensor properly calibrated, we worked with the program until we had a viable path-following robot. The program is in the programming section, and the movie of Neil following the path is available on this page.
Now that we had a handle on how to build a robot using the Handy Board kit, it was time to focus on the competition. We began designing a new body for the Handy Board in a design we were told had worked rather well at previous competitions. The XY robot was to have had a set of wheels oriented one way and another at a ninety degree angle, with the necessary set snapping into place depending on which direction the robot needed to go. Despite many long hours spent on this design, it never quite worked right. More details are here.
Around this time we decided that we wished to blow out the candle using a fan. We tried various commercial fans, including those designed for computers, but ended up making our own. It was made by Greg in the machine shop and consisted of a simple piece of metal cut into a fan shape with the blades angled, attached to the axle of another motor. It was very fast and extremely efficent at putting out candles from up to about 14 inches away. As the robot must be within 12 inches of the candle to blow it out (rules of the competition) this is an excellent design for the fan.
Desperately trying to have a viable robot for the Penn State Abington competition, we switched back to using our previous Lego Bug design. The holders for the Handy Board were perfected as well as a mechanism to the top that swiveled back and forth using a design similar to the one that moved a Lego project from our engineering class, Flik's, head back and forth. Flik can be found here. Upon this we attached the pyroelectric sensor and the fan. The motor was too heavy to be put here, we discovered.
We tried to working with pyroelectric sensors to find the candle, as they were recommended to us. If working with pyroelectic sensors is something you want to do, be very sure they are wired correctly as they are extremely sensitive. The little notch is very important. There is more discussion of the sensor in the sensors section of the components page, but because of their sensitivity to body heat, overall sensitivity, calibration problems, and cost, we do not recommend them for the competition.
At this point we planned to simply hard code the design of the maze into the Handy Board rather than navigate, with plans for navigation later. Unfortunately, the night before the competition, Neil was dropped in a parking lot and was not salvageable for the competition. Upon viewing the competition, we decided that there was very little chance our dear Neil would be ready in time for Trinity. There were many designs that gave us incredible ideas, but nothing we felt could be accomplished within three weeks, so we switched our focus to research and a guide to those who might come after us. We then worked with more possible body designs, and worked more rigorously with how each sensor works. The most important advice we could give, however, would be to be in contact with other schools such as Penn State who have programs in building these robots. The ability to bounce ideas off of other people is something we wished we could have had.