Jim Beaver wrote:

"E Z Peaces" wrote in message
.. .
Jim Beaver wrote:
I've got my Christmas tree set up in my living room. A couple of
strings of lights (not those mini-lights, but the finger-tip size
bulbs). Here's the problem:

When I turn on the lights, a loud hum arises from the timer for my
yard sprinklers. This timer is mounted on the outside wall of the
living room. Obviously it's on the same circuit, as the hum comes and
goes when the Christmas tree lights are turned on or off.

The hum is loud. Probably loud enough indoors to wake a light
sleeper from a nap if it suddenly came on. It's even louder, of
course, outdoors near the timer.

The power cords, plugs, and receptacles all seem cool. So I'm
wondering: does this sound like an overloading problem, or more
likely some sort of simple harmonic vibration? Am I in danger of
fire, if everything I can get to seems cool?

I don't know anything much about electrical testing or I'd use a
tester on it somehow. But I don't really know what to look for.

Anyone NOT doing something more interesting on Christmas Eve who
wants to advise me here?

And with that in mind, happy holidays to all here. Thanks.

Jim Beaver

I haven't been able to imagine how the lights could affect voltage or
current in the timer.

Are there valves near the timer? Sometimes a solenoid valve can hum
loudly.

I discovered this morning that the hum doesn't happen in the daytime.
Which leads me, genius that I am, to conclude that it's not the
sprinkler timer but the low-voltage outdoor lighting system timer. I
have no idea whether this affects matters much in terms of safety, etc.

Jim Beaver

My idea light is flashing! Does an electric eye turn on the outdoor
lights? Maybe the eye is exposed to one of the outdoor lights as well
as light from your tree in the window, and together they hit it with
enough light to shut it off. That brings the light below the threshold
and it turns back on. The frequency of the hum would depend on how long
it took the outdoor filament to heat white hot.