A pal of [Kyle’s] was regularly leaving his sprinkler on for too long. He also had forgotten to turn the water off while topping off his pool a couple of times, an embarrassing and wasteful situation.

The ATtiny85 microcontroller doesn’t have all that much of anything: 8 KB of flash, an 8-bit architecture, and only eight pins (three of which are taken up with power and reset duties). And that’s ...