I have a hard wired smoke detector that is connected to the same circuit breaker as the two hallway lights. The two switches at the end of the hallway do not turn the smoke detector on and off, however before I added a three-way dimmer to the circuit, the alarm would chirp whenever switching the hallway lights on and off. I didn't quite understand what was happening, so I went ahead with my plan to install a three-way dimmer. Now with the dimmer switch installed, the smoke alarm turns on when I'm at any setting other than full brightness. I believe this can be explained by a voltage drop causing the alarm to trip.
This perplexes me because no switch position can turn the smoke alarm on or off, however it's acting like one end of the circuit connection is experiencing extra resistance whenever the dimmer is activated, or as previously when the circuit was inturrupted briefly when the switch was flipped.
The hallway switches behave as you would expect, turning alternately on and off when one or the other is flipped.
I was hoping for some suggestions as to how the alarm or switches might be wired to explain this, and how I could fix the problem so that the alarm doesn't do that.
Best Answer
I think I have figured it out. One of the guys in the comments suggested that it chirps every time it switches between current and battery. What I think was happening was not that the lines were directly connected to the switches, but that they were getting EM interference from the current changes on the switched lines. I took apart the old detector and determined that it was too old to keep using. I installed a new one, and the problem disappeared. I would need an oscilloscope to confirm the interference theory, but it makes the most sense.