Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default flashing strobe like street light, failure mode?

There is a street light I pass frequently that occasionally flashes like a strobe.

I've seen a bright flash at that corner a number of times over the past year or two, but never saw the source. Usually there's a building blocking it and all I see is the street light up.

This past week I was coming from the other direction and clearly saw the street light flash twice, very brightly.

These lights are bluish white, I've always assumed they were mercury vapor, but don't really know. It's not a city likely to have moved to LED.

Is there a failure mode for a discharge lamp that would produce that?
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Default flashing strobe like street light, failure mode?

There is a street light I pass frequently that occasionally flashes like a strobe.

I've seen a bright flash at that corner a number of times over the past year or two, but never saw the source.
Usually there's a building blocking it and all I see is the street light up.

This past week I was coming from the other direction and clearly saw the street light flash twice, very brightly.

These lights are bluish white, I've always assumed they were mercury vapor, but don't really know. It's not a city
likely to have moved to LED.

Is there a failure mode for a discharge lamp that would produce that?


High-pressure sodium lights exhibit a "cycling" on-and-off behavior when
they reach end of life. However, when I've seen this it's been a
fairly slow cycle, and didn't exhibit the sort of bright strobe-like
flash you describe.

I suppose that you could be seeing a mercury-vapor lamp with a failing
bulb and/or ballast, where the ballast sends a strong pulse to
"strike" the lamp and get the arc flowing (hence the flash) and a
fault in the bulb causes an over-current or under-current condition
which then shuts down the arc almost immediately.

Pragmatically, you might want to write down the streetlamp pole number
(if it has one) and contact the city's public-works department and
report the problem.







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Default flashing strobe like street light, failure mode?



This past week I was coming from the other direction and clearly saw the street light flash twice, very brightly.


red light cam?

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Default flashing strobe like street light, failure mode?

On Monday, February 1, 2016 at 9:32:39 AM UTC-5, wrote:

This past week I was coming from the other direction and clearly saw the street light flash twice, very brightly.


red light cam?


I'll have to drive past there on the other road. My impression was street light, not near the traffic signal.

It's a part of town not conducive to hanging around watching for it to recur.
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Default flashing strobe like street light, failure mode?

On Monday, February 1, 2016 at 12:34:58 PM UTC-5, Tim R wrote:
On Monday, February 1, 2016 at 9:32:39 AM UTC-5, wrote:

This past week I was coming from the other direction and clearly saw the street light flash twice, very brightly.


red light cam?


I'll have to drive past there on the other road. My impression was street light, not near the traffic signal.

It's a part of town not conducive to hanging around watching for it to recur.


It seems thats were "they" like to put the red light cams.





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Default flashing strobe like street light, failure mode?

Dave Platt wrote: "High-pressure sodium lights exhibit a "cycling" on-and-off behavior when
they reach end of life. However, when I've seen this it's been a
fairly slow cycle, and didn't exhibit the sort of bright strobe-like
flash you describe. "

There's a street light across from our house that cycles on
and off over a period of 30-40 sec., but does it on random
nights(!). We might see it do it repeatedly for one night,
then do it again a week or a month later, no pattern.
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Default flashing strobe like street light, failure mode?

On Tuesday, February 2, 2016 at 5:00:31 PM UTC-5, wrote:
On Monday, February 1, 2016 at 12:34:58 PM UTC-5, Tim R wrote:
On Monday, February 1, 2016 at 9:32:39 AM UTC-5, wrote:

This past week I was coming from the other direction and clearly saw the street light flash twice, very brightly.


red light cam?


I'll have to drive past there on the other road. My impression was street light, not near the traffic signal.

It's a part of town not conducive to hanging around watching for it to recur.


It seems thats were "they" like to put the red light cams.


I got a better look yesterday. It's a street light, no camera. Besides, I see the flash when I'm stopped at a red light, so the cross traffic would have a green.

Good thinking though.
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Default flashing strobe like street light, failure mode?

On Tuesday, February 2, 2016 at 7:51:28 PM UTC-5, wrote:
Dave Platt wrote: "High-pressure sodium lights exhibit a "cycling" on-and-off behavior when
they reach end of life. However, when I've seen this it's been a
fairly slow cycle, and didn't exhibit the sort of bright strobe-like
flash you describe. "

There's a street light across from our house that cycles on
and off over a period of 30-40 sec., but does it on random
nights(!). We might see it do it repeatedly for one night,
then do it again a week or a month later, no pattern.


Yeah, that sounds like normal failure mode. I've not seen one flash and stay lit though.
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Default flashing strobe like street light, failure mode?

Tim R wrote:


I got a better look yesterday. It's a street light, no camera. Besides,
I see the flash when I'm stopped at a red light, so the cross traffic
would have a green.

It is a worn-out lamp. When they get old, they start to run hot and the
ballast cycles power every few minutes. The repeated starting, maybe 10
times an hour, increases the wear on the lamp. When they get really bad,
the ignitor can't strike the arc, and so the ignitor keeps trying. The
strobe effect, maybe a couple flashes a second, is the ignitor trying to get
the lamp to restart.

Jon
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Default flashing strobe like street light, failure mode?

On Wednesday, February 3, 2016 at 4:26:44 PM UTC-5, Jon Elson wrote:
Tim R wrote:


I got a better look yesterday. It's a street light, no camera. Besides,
I see the flash when I'm stopped at a red light, so the cross traffic
would have a green.

It is a worn-out lamp. When they get old, they start to run hot and the
ballast cycles power every few minutes. The repeated starting, maybe 10
times an hour, increases the wear on the lamp. When they get really bad,
the ignitor can't strike the arc, and so the ignitor keeps trying. The
strobe effect, maybe a couple flashes a second, is the ignitor trying to get
the lamp to restart.

Jon


You could be right. I need to get a better look at this one.

It doesn't sound like that to me, because a lamp that old shouldn't stay normally lit most of the time. It should be burned out trying to start most of the time. But I haven't heard a better explanation either.

I might call the city engineer and just ask.
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