Line Follower Robot

After many years of interest, I finally decided to start building robots. I bought the best book I could find on robot building because I wanted a strong foundation for the nuances of building robots. The book I bought was Robot Building for Beginners, by David Cook.

Here are some images of the first robot I built totally based on this book. I had to get creative when I added the motors and wheels to the chassis, but it works. The motors only run about 14 or so RPM so, it’s really slow, but it follows lines effectively.

In this first picture, you can see the battery connector and the wheels. This was my first time mounting wheels to a motor shaft and since the motor shaft was very small and short, I bought a set of those plastic carpet protectors for furniture. This was used as the hub for the wheel. A 2.5 inch flexible hose was cut down to about a half-inch length to use as the tire mount and a rubber plumbing gasket was used for the tires as it just happened to fit perfectly around the flexible tubing. I just glued the carpet protectors onto the tube, ground it down to the size of the tube and slipped on the tires.

The hard part was mounting the wheels the the motor shafts. The motor shaft was about 1/16th inch with a little slot in it. So I placed a hole in the wheel hub, mounted it on the motor shaft and melted a metal staple into the plastic to provide drive power. Then I epoxied the staple in place and also inside the wheel bythe shaft. I keep waiting for the wheels to fall off, but it was fun to build this little robot.

In this picture you can see the line following sensors underneath the Sandwich robot. The sensors were installed with 2 sensors on each side of a voltage comparator mounted on the circuit board. When the cadmium sulfide photo sensors are exposed to light or dark, they change their resistance. When a dark line is detected, the sensors allow their respective motor to turn on or off, depending if it senses the dark line. The voltage divider in the circuit board acts as a negotiator between the two sets of sensors. If one side has more resistance than the other side, the side with more resistance gets turned on and the robots subsequently tracks lines.

You can also see two bright white LEDs underneath the robot. These are used to even up the lighting conditions on the line-following track so that the sensors can be more accurate in sensing whether they see light or dark. In other words, the headlights prevent ambient light from interfering with the sensitivity of the sensors.

Here, you can see, the circuit board. the yellow and green LEDs turn on when their respective sensors have more resistance than the other side. The voltage comparator chip is in the middle and the two trimmer potentiometers in the middle are for adjusting the resistance between the two sides so they are as even as possible before starting to follow lines. The other trimmer potentiometer is for adjusting the brightness of the headlights on the bottom of the robot.