DrDAQ is a versatile instrument that connects to the USB port of any PC. Using the supplied PicoScope software it can be used as an oscilloscope, spectrum analyzer and signal generator.
The general idea was to track the time taken for the car to complete a circuit. See the PicoScope display below for an example of how it works:
Notice the two different peaks. The lower peaks represent the car on the inside track, the larger peaks represent the car on the outside track. It can be seen that the car on the inside was overtaken by the car on the outside. The reason for the difference in signals is that the nearer the car is to the light sensor the less light reaches it, thus the resistance is greater which makes for a bigger voltage drop.
The above display shows that the car on the outside overtakes the car on the inside.
From the above screen capture in PicoScope it is possible to calculate the speed of the Scalextric cars using the following equation:
Velocity = Distance / Time
The car on the inside can be seen to take 2997 ms to travel 3.7 metres. The first stage is to identify the units, to compare the car to the real thing we should use mph and hours.
Distance (km) = (3.7/1000) = 0.0037
Time (Hours) = (2997/(1000*60*60)) = 0.0008325
The average velocity can now be calculated:
Velocity = 0.0037 / 0.0008325 = 4.44 km/h
There are 1609 metres to the mile so:
Velocity = 4.44/1.609 = 2.759 mph
If the same calculations are performed for the car in the outside lane then its average velocity is seen to be 3.698 mph.
The above speeds do not seem very fast, however this is just a demonstration of how to log the average speed of the devices. In practice the staff here at Pico managed to get a top average speed of around 8 mph with the car on the inside lane.
Following on from this experiment there are a number of other parameters that can be recorded: