What you have just learned in Chapter 4 are the most elementary operations we can do in Arduino: controlling digital output and reading digital input. If Arduino were some sort of human language, those would be two letters of its alphabet. Considering that there are just five letters in this alphabet, you can see how much more work we have to do before we can write Arduino poetry.
Now that you’ve learned how to use a pushbutton, you should know that there are many other very basic sensors that work according to the same principle:
Just like a pushbutton, but doesn’t automatically change state when released
A switch that opens when the temperature reaches a set value
Has two contacts that come together when they are near a magnet; used by burglar alarms to detect when a window is opened
Small mats that you can place under a carpet or a doormat to detect the presence of a human being (or heavy cat)
A simple electronic component that contains two contacts and a little metal ball (or a drop of mercury, but I don’t recommend using those) An example of a tilt switch is called a tilt sensor. Figure 5-1 shows the inside of a typical model. When the sensor is in its upright position, the ball bridges the two contacts, and this works just as if you had pressed a pushbutton. When you tilt this sensor, the ball moves, and the contact is ...