We'll continue to modify our Jumping Jack sprite that's configured to work with sensors A, B, and C:
- Plug the fourth alligator clip into sensor D on the PicoBoard.
- In the Scratch project, add a forever block to the second script of the Jumping Jack sprite.
- From the Sound palette, add the play note block to the forever block.
- We'll use the resistance value to select the note to play. From the Sensing palette, add the sensor value block to the play note block. Select sensor D from the list of options.
- Click the flag, and let's test some resistance. In turn, attach the foil, the wet napkin, and the pencil to the alligator clips attached to sensor D.
- If you want to watch the resistance values, enable the sensor value monitor for sensor D.
Feels like science class, doesn't it? Not surprisingly, our test materials showed various levels of resistance, and as we connected the alligator clips to each material, a different note played.
Actually, the tinfoil didn't play a note, and if you watched the sensor values, you noted that sensor D reported zero when we connected the foil. This means that the current flowed through without resistance. At the other extreme was our pencil; it reported a resistance value of 100, and the music played steadily.
We know that current flows through foil easily, but not wood. Our tests confirm that water conducts a current, but not as well as foil, for example. When we measure electrical resistance, we want to know by how much the material impedes an electrical current. In the case of our PicoBoard sensor, the higher the value, the more the material impedes the current. How we use that value is left to our imagination.
Using the PicoBoard sensors allows our kids to experiment with the electrical properties of various materials.