PTC Gizmo
This is the circuitry for the PTC exhibit. I won’t go into all the gory details. Look here to see the display that these circuits drive.
Sorry for grainy image - it’s the only one I could find. This is what it looks like from the front about halfway through its little cycle. See below to get a look at all the logic gates, relays, and timers that make it go.
The red arrow is pointing to the plastic dome as seem from behind. The blue arrow is pointing to the “brain”. The panel to the right contains some of the electronics. The remainder of the electronics can be seen below.
This was designed and wired before I knew about Arduino. Now I could do all this with two small circuit boards and about 50 lines of code. Below is a video of the display in action! Riveting!