Well, I built these things: 1. A mechanical/environmental monitor/display for a grinding/polishing machine for telescope mirrors. It measures the rotation spee

Well, I built these things: 1. A mechanical/environmental monitor/display for a grinding/polishing machine for telescope mirrors. It measures the rotation speed of two key machine parts; also measures ambiental temperature and humidity. It displays all these parameters on a front panel. http://florin.myip.org/blog/making-tachometer-grinding-polishing-machine-telescope-mirrors http://florin.myip.org/blog/making-tachometer-grinding-polis... 2. Lights control for an aquarium Regular fish tank, LED lights with timer. The lights would turn on or off suddenly, scaring the fish. :) I used pulse-width modulation and a MOS-FET to gradually fade the lights in and out over 1 hour. 3. PC clock I've setup time limits on PC usage for my kids. But before Windows 10 the login screen on Windows 7 didn't have the time displayed, so they didn't know when their accounts would actually let them log in. I've found a big LED display that fits almost exactly in a CD-ROM bay, and built a clock with it. It's synced to the PC every time the OS boots up.