We are going to use the light sensor to detect if a train is passing. We will do this by detecting the shadow of the train.
Let’s first explore how the light sensor works by downloading the following program onto our micro:bit.
Now press button A and the micro:bit responds with a number. This number indicates the amount of light that falls on the LEDs (yes, LEDs can also be used to detect light). If the number that you receive is either 255 or 0 it means the brightness sensor is initializing, so you need to press the button once more.
NOTE: If you do not possess a train, you can also use a car or even your hand to create a shadow.
Detecting a shadow can be a bit tricky. For this to work we need to have a bright lamp on the other side of the train, that is not too high. A desk lamp should work. Furthermore, we do not want too much light from other light sources, so you may have to close curtains or blinds and dim ceiling lamps.
You should now see a shadow of the train that is big enough to place your micro:bit in. Make sure the board is laying down flat on the table and write down the amount of light that is measured in the shadow and the amount of light that is measured when there is no shadow. The number in the light should be at least 2 times the number in the shadow.
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