This is the same idea as the pull up resistor, except now it is attached to GND. The hook up is shown below.
Again, we use the alligator clips to set this up.
Run the sketch again and touch the BLUE clip with your finger. As before, it should not detect any changes. It is being held LOW and is happy there.
It should see the change and report it.
Note that the only thing different between this and the pull up configuration is the order of the values.
- A pull up is normally HIGH and goes LOW when the alligator clips are touched together.
- A pull down is normally LOW and goes HIGH when the alligator clips are touched together.
And remember that our touching of the alligator clips is like pressing a button. So the same logic applies for button presses as well.