So, as I mentioned earlier today, over the past few days, I had an idea to automate the lighting in my apartment. After talking with some friends of mine, I finally decided on a rather simple implementation, wiring relays in parallel with the existing lightswitches (so all the lightswitches will continue to operate normally). The relays aren't entirely necessary, since the MicroLogix PLC I'm using has relay outputs, but they do provide an extra layer of safety (not to mention all the signalling is low-voltage, 24vdc). Relays themselves were squeezed into the electrical box where the switches are. Also, all the contacts on the relay use crimp-on quick disconnects.
The ladder logic program I'm using is fairly simple: use timers to create a maximum length of time any light can be on, and also provide an automated mode where the lights cycle between on/off periods. Inputs are wired like pushbuttons to toggle each light, as well as the manual/auto mode. The whole thing works as expected, blinking lights and all. Enjoy some pictures after the break.