Transportation Scenario I
September 2001
Goal:  Count Cars
Materials: LEGO DACTA Cities and Transportation set 
     or similar LEGO elements
Instruction book #2
RoboLab 2.0 or 2.5 Investigator
RCX
Program: Add 1 to counter each time car passes light sensor on input 1.
Upload: Data and compare with actual count.
The LEGO CITY is set up much like the speed trap in instruction booklet #2 of the Cities and Transportation sets.  Instead of having many cars pass in front of the light sensors, one car is continually circling around so that it passes through the photo gate of a light sensor and a lamp.

Build a similar set up using the pictures.
The motor to run the car is in the middle of where a 16-stud beam was in the instruction booklet #2.  Replace the 16-stud beam with two 6-stud beams. Place the motor set up as pictured. Build a car and connect to motor set up with axles.  A 10 and a 12 axle connected by an axle connector is sufficient.

Program the RCX to gather light sensor readings. 
Try out your set up at school (or home) to get an idea of what the light readings will be.  Note that graphing light sensor at one second can miss many passes of the car.

Write and run a program to save to add 1 to the red container each time there is a decrease in light sensor reading. 
Pictures of set up.
Pictures of example programs
Transportation Links
SENSORSCITY
LEGO Links of  Linda Hamilton