When the outside lights in this apartment house come on at night by
photocell control they cause a loud buzzing noise in the buildings'
intercom system. These lights are the type that come on dim and warm up
to full brightness over several minutes. There are two large lighting
units mounted on the front of the building and three smaller units
mounted in the back. One of the large units is inoperatve in the front
and one small unit is also not working in the back. Are these what are
called "high pressure sodium"? Are these known to generate RF
interference? Is there a ballast in these things, and if so would a
defective bulb cause the the device to radiate energy into the air
instead of the load? Can someone please explain how these work and what
might be the most likely cause of this problem? Thanks for any opinions
on this. Lenny Stein, Barlen Electronics.

wrote in message
oups.com...
When the outside lights in this apartment house come on at night by
photocell control they cause a loud buzzing noise in the buildings'
intercom system. These lights are the type that come on dim and warm up
to full brightness over several minutes. There are two large lighting
units mounted on the front of the building and three smaller units
mounted in the back. One of the large units is inoperatve in the front
and one small unit is also not working in the back. Are these what are
called "high pressure sodium"?

It's impossible to say without a description of the bulbs and the light they
emit. They could be metal vapour lights like Sodium, Cadmium or Mercury,
but they could also be HID lamps.

Dave

is it a wireless intercom or wired?

Mark

Mark wrote:

is it a wireless intercom or wired?

Mark



If it's a wireless system I'd say you're out of luck unless you replace
the lights or get an intercom that can filter out the interference.

If it's a wired intercom, You may need to make sure the lights and the
intercom are fed their AC power from different branch circuits.
Also, you may need to replace the wiring between the intercom panel and
the individual receivers with shielded wire.

But first try something simpler - make sure all intercom wire
connections are clean and tight, and if there are any ground
connections, make sure they are secure.

wrote:
When the outside lights in this apartment house come on at night by
photocell control they cause a loud buzzing noise in the buildings'
intercom system. These lights are the type that come on dim and warm up
to full brightness over several minutes. There are two large lighting
units mounted on the front of the building and three smaller units
mounted in the back. One of the large units is inoperatve in the front
and one small unit is also not working in the back. Are these what are
called "high pressure sodium"? Are these known to generate RF
interference? Is there a ballast in these things, and if so would a
defective bulb cause the the device to radiate energy into the air
instead of the load? Can someone please explain how these work and what
might be the most likely cause of this problem? Thanks for any opinions
on this. Lenny Stein, Barlen Electronics.



Are these the crappy Lights of America wall packs with electronic
ballasts? A friend of mine had several of those and they failed one by
one, the ballasts were very cheaply made and it wouldn't surprise me if
they produced a lot of RFI.

Most HPS uses magnetic ballasts, those shouldn't cause interference,
except if a lamp is failed the igniter will pulse repeatedly and cause a
ticking sound to be picked up by nearby audio equipment.

It's impossible to say without a description of the bulbs and the light they
emit. They could be metal vapour lights like Sodium, Cadmium or Mercury,
but they could also be HID lamps.

Dave



Huh? HID is a broad category which covers high pressure sodium, mercury
vapor and metal halide lamps. There's no such thing as a cadmium vapor
lamp, at least not outside of specialized lab uses.

Either way, all HID lamps operate in a similar manner and the ballasts
are also very similar (though their characteristics must be a proper
match for the lamp.)

"James Sweet" wrote in message
news:Kb%lf.25094$SY.16950@trnddc06...


It's impossible to say without a description of the bulbs and the light
they emit. They could be metal vapour lights like Sodium, Cadmium or
Mercury, but they could also be HID lamps.

Dave

Huh? HID is a broad category which covers high pressure sodium, mercury
vapor and metal halide lamps.

I meant metal halide. Note the time I posted ;-)

Dave

We found that the problem was caused by a defective lamp. It was either
arcing (although that wasn't evident) or the fact that there was no
load to dump the energy into was the problem. In any case a new high
pressure sodium lamp fixed it. I learned something today...... Lenny
Stein, Barlen Electronics.