I got most the hack of the Hexbug Spider done last night, but broke one of the battery wires where it connected to the board. I checked the robot out by holding the wire to where it connects to the board, and the robot moved, so I figured all I needed to do was to solder it back onto the board, then aim the infared sensor and led. But it was late and decided to go to bed and finish it today.
I got back to it this afternoon and managed to solder the wire onto the board. I printed out a aiming diagram I'd drawn using Corel Draw. First time, I got the dimensions wrong, second drawing was good (jpg file attached below). I also drew and printed out some wide black lines to test the line following after the sensors had been aimed.
So, I aimed the sensors, but so far, the robot hasn't been able to sense the printed lines (0.65 inches wide). After attempting to aim the sensors for a while and not getting them to respond to the printed line, I tried darkening the line with a black permanent marker, but the robot still wouldn't sense the line, So, I decided to try something else. I had some black poster board (much darker than the line I had been using for checking out the robot) and decided to try cutting very thick lines from it. I started with a line about 3 1/2 inches (90 mm). I put it on my kitchen floor, set the spider robot at one end and turned the power on. IT WORKED! Using the same aiming that didn't work with the printed line. I then cut out some thinner lines of different shapes and the robot worked with all of them, down to a width of about 1/4 inch (6.5 mm). Really cool.
I plan on making a video of the robot following the lines cut from the black poster board and will either post them here or post a link to youtube.
This is the first robot I've built and very happy with the experience.
Target below. If you use this, be sure you print it out the correct size. The solid circle is 0.5 inch diameter and the dashed circle is 1.5 inch diameter, the horizontal lines are 2.5 + 1.5/2 = 3.25 inches apart.