What are those little orange thingies on top of street lights?

[zev_steinhardt]

A friend of mine recently brought this question to my attention. I had no idea of the answer, but I figured that if anyone would be able to provide an answer, you guys would...

On the tops of many street lights in New York City, there are these little orange thingies. They sort of resemble little orange lights. What the heck are they?

Zev Steinhardt

[Q.E.D.]

They're photoelectric sensors. When it gets dark, they turn the lights on automatically, and turn them off when it gets bright enough. Usually not every lamp has one, and the sensor on one lamp can be used to control a bank of streetlights.

[zev_steinhardt]

They're photoelectric sensors. When it gets dark, they turn the lights on automatically, and turn them off when it gets bright enough. Usually not every lamp has one, and the sensor on one lamp can be used to control a bank of streetlights.

Thanks, Q.E.D., I knew someone would know.

This, however, adds a follow up question:

For many years (before those orange photoelectirc sensors) were installed, the lights would often go on and off at the appropriate times (including going on whenever it got extra dark on a cloudy afternoon). So, how did the lights go on/off by themselves before the sensors were installed?

Zev Steinhardt

[Squink]

So, how did the lights go on/off by themselves before the sensors were installed?Photosensors have been around a long time. They haven't always been orange.

[Q.E.D.]

Photosensors have been around a long time. They haven't always been orange.
Right, and they haven't always been on top of the lamps, either. Some were mounted as separate devices on top of a pole, for instance. Again, these would normally control a bank of lamps. I don't know specifically what benefit the newer sensor types offer, but my guess is that they are less prone to false "off" triggering by car headlights and other artificial light sources.

[zev_steinhardt]

Thanks a lot everyone. I appreciate the help and the quick answers.

Zev Steinhardt

[Mangetout]

Right, and they haven't always been on top of the lamps, either. Some were mounted as separate devices on top of a pole, for instance. Again, these would normally control a bank of lamps. I don't know specifically what benefit the newer sensor types offer, but my guess is that they are less prone to false "off" triggering by car headlights and other artificial light sources.
I remember seeing street lamps here where perhaps one in ten lamps had a bump on top - a single photosensor controlled a whole row of lights (although sometimes, judging by the way they used to switch on, it seemed like it wasn't a contiguous block of ten, but more like every third lamp in a row of thirty switching on at the same time.

I wonder what the economies were that drove such a system, maybe the sensors weren't very reliable/durable, so the extra cabling involved in patching them together would be cheaper than the cost of continually replacing ten times as many sensors...?

Anyway, nowadays, street lamps seem to be equipped with their own sensors each and the technology has improved so that things like dark clouds won't usually set them off; they have hysteresis to make them less sensitive to sudden brief changes (like a bird alighting on the sensor foir a minute) and they probably have some kind of circadian rythm thing; not so much a strict timer as a sense of whether it has been long enough since the last measured 'night'.

[stuyguy]

Wrong. Wrong. Wrong.

The glowing LED-filled orange thingees, roughly shaped like tennis ball cans, on top of steet corner light ploes indicate that a fire alarm box is located on the corner. I know this because I asked the same question of the NY Times "FYI" column, and that's what they told me.

It's sort of the modern day version of a similar system that has existed for decades but is being fast faded out. If you look closely you can still find some orange bullet-shaped incandecent lamps poking out of street light and telephone poles. They too indicate a fire alarm box on the corner.

[Q.E.D.]

The glowing LED-filled orange thingees, roughly shaped like tennis ball cans, on top of steet corner light ploes indicate that a fire alarm box is located on the corner.
Maybe4, but that doesn't seem to match the description in the OP. He said on top of the lights, which I took to mean on the topside of the lamp assembly, rather than the top of the pole. And he said they look like lights, but didn't say they were actually lit. I can't speak to the color of the fire alarm box indicator lamps in NYC, but in all the places I can recall seeing them they have been blue, not orange.

Perhaps some clarification on the details from the OP would help clear this up.

[stuyguy]

Look, I know exactly what the OP is talking about.

Sometimes the orange thingees are mounted on top of the poles; sometimes they are mounted on top of the streetlight "heads." It varies, but they are all the same. And they are the only orange thing out there.

[Q.E.D.]

If the OP is talking about something like these (http://members.tripod.com/~streetlights/lumes/327_mini_1099vw86avba.jpg), then they are not fire alarm box lamps, they are light sensors. This particular one is orange. As I said, some clarification from the OP is needed here.

[Q.E.D.]

Here (http://members.tripod.com/~streetlights/lumes/phgcpf5.htm) is a better view of one. Is this what you mean, zev?

[Dan Turk]

I know that if you fire a roman candle in an arc over a street light at night, you can turn off the entire string of lights connected to that sensor :)

[ticker]

So, how did the lights go on/off by themselves before the sensors were installed?

Zev Steinhardt

Showing my age here:

Back in the early 70's (73 I think) we in the UK had a period of industrial strife + oil crisis which lead to power shortages and planned power outages. In those days the street lights contained a timer mechanism to turn on and off. Trouble was the timer was electric so it got all screwed up during a power cut. I remember adults complaining that we were all being asked to use less electricity, yet the street lights were burning at lunch time.

[zev_steinhardt]

Here (http://members.tripod.com/~streetlights/lumes/phgcpf5.htm) is a better view of one. Is this what you mean, zev?

Yes, Q.E.D., that's exactly what I was talking about!

Zev Steinhardt

[GSV Consolation of Dreams]

I know that if you fire a roman candle in an arc over a street light at night, you can turn off the entire string of lights connected to that sensor :)

And a carefully aimed laser-pointer can do the same thing...I'm told.

[Eats_Crayons]

Is there a picture anywhere of stuyguy's tennis-ball-can fire thingy for comparisson? Now, I'm curious.

[manhattan]

Those things generally got their own branch off of a pole, like so (http://www.forgotten-ny.com/STREET%20SCENES/Fire%20Alarms%20page/Alarms.html) (about halfway down the page).

[stuyguy]

Ok, so I stand corrected. A million pardons for my smart-aleciness, especially to Q.E.D. whose request for clarification saved the day.

Manhattan's link shows the old-style, bullet-shaped fire signal lights that are currently being replaced by the longer, cylindrical ("tennis ball can") style I mentioned earlier. The new style does not appear on that page.

[Q.E.D.]

S'alright, stuyguy. Coulda gone either way. :)

[manhattan]

Is there a picture anywhere of stuyguy's tennis-ball-can fire thingy for comparisson? Now, I'm curious.Took one just for this thread. You have to have a free imagestation membership to see it, I think, but it's
here (http://www.imagestation.com/picture/sraid156/pf8be9f5b296ab31bd45a60209b40c2e9/f53dda92.jpg).

If someone wants to rehost it someplace more convenient, it ain't exactly gonna be a profit center for me, so no copyright worries. ;) Also, sorry for the quality -- I compressed it all to heck for space reasons and it lost a little something.

[Thinktank]

Wow, Pigeon Cameo and all! :Dlol... u dun guud, hahaha

[octothorpe]

Originally posted by Q.E.D.
Right, and they haven't always been on top of the lamps, either. Some were mounted as separate devices on top of a pole, for instance. Again, these would normally control a bank of lamps. I don't know specifically what benefit the newer sensor types offer, but my guess is that they are less prone to false "off" triggering by car headlights and other artificial light sources.

Generally speaking, the devices you refer to are used to control a series street light or 'arc' circuit. Series street lights use a constant-current transformer (also referred to as a regulated-output or 'RO' transformer) that operates at 6.6 amps and adjusts voltage to maintain that current. Although the voltage fluctuates dependent on the load, arc circuits operate on 'primary' voltage (nominally 2400v) and photocells designed to operate at that voltage would be cumbersome and expensive. As such, a photocell housed in a standard meter socket and operating on 120 or 240 volts controls a relay which switches the lights on or off. As this is a series circuit, you cannot switch the power off to an individual bulb as you would open the circuit and all lights would go off (for those of you old enough to remember, think of the Christmas lights you had as a kid and the frustration of locating the burnt-out bulb). This presented a bit of a problem in the early days of arc circuits in that a lamp burning out would cause the entire circuit to go out. This was solved ingeneously by placing a non-conductive disc between 2 contacts in the lamp housing. While the lamp was intact, the disc would keep the contacts apart. When the lamp burned out, the RO would raise the voltage in an attempt to maintain the 6.6 amps and once the voltage reached a high enough level, the disc would 'burn through' allowing the contacts to close and restoring the circuit; and serendipitously, allowing the utility workers to identify the lamp in need of replacement.

Arc circuits are being phased out across the US for safety reasons. Should a break occur in the circuit, the RO will raise the voltage on the circuit to the stops (2400 volts). While this doesn't present a problem as long as the conductor is in the air, if a wire should break or fall to the ground, it would not necessarily blow a fuse and pedestrians or motorists may come in contact with the energized primary. Cities across the nation are forgoing the installation of new arc circuits and are installing 120 or 240 volt parallel circuit street lights instead. They are both cheaper and safer in the long run.

Fiat Lux,
#

[hugo rodz]

A friend of mine recently brought this question to my attention. I had no idea of the answer, but I figured that if anyone would be able to provide an answer, you guys would...

On the tops of many street lights in New York City, there are these little orange thingies. They sort of resemble little orange lights. What the heck are they?

Zev Steinhardt

those orange lights on the lampost indicate there is a alarmbox or firebox to call the fire department

[Musicat]

those orange lights on the lampost indicate there is a alarmbox or firebox to call the fire departmentYou didn't actually read any posts in the thread past the first, did you? Or notice the dates? Or look at the pictures? Although I'll admit most pix are gone, due to the dates. NYC was different way back in 2005, and some of the posters were alive then.

[runner pat]

those orange lights on the lampost indicate there is a alarmbox or firebox to call the fire department

Why would anyone look put an indicator on top of a streetlight when a sign or marker at street level would be far more logical?

[johnpost]

zombie or no

these were identified in messages 11 and 12 and confirmed to be the object of the OP in message 15.

[postcards]

Why would anyone look put an indicator on top of a streetlight when a sign or marker at street level would be far more logical?
Because a street-level sign can't be seen from a distance of a block or more, whereas an indicator on high can.