The Raspberry Pi is the small box indicated by the red arrow. On the left are the keyboard and monitor.
On screen is the code (program), written in Python, which controls the water-drops (following the work of David Hunt).
To the right of the Pi is the home-made interface between the Pi and the water-drop system.
(The device behind the monitor is my Dali Katch bluetooth speaker, probably the best of it's kind in the world,
which I use with the Pi as an internet radio!)