Street Light Controllers

Most street lighting in the UK uses a photo-sensor to switch the light off when light levels rise, backed by a time-switch. There is a move afoot in the east of the UK to turn some street lights in residential areas off between 24:00 and 05:00 regardless, and it is gaining momentum.

In my old town (Garland, TX) the lights would blink (red in the lesser traveled direction, yellow in the more traveled one) from midnight to morning. Turning them entirely off seems dangerous. Maybe drivers are more polite in the UK.

Drivers have their own lighting - those on the road vehicle. The purpose of street lighting in residential areas is principally to assist pedestrians, the occurrence of which drops considerably between 24:00 and 05:00, and where road speeds are constrained to below 30mph/48kph, well within the capabilities of dipped headlights. Those few pedestrians that remain outside buildings at these times have been bathed in light for a significant carbon-footprint-per-person. Turning off the lights in residential areas is both experimental and a politically-sensitive issue, particularly in terms of local politics, though it looks to be gaining momentum on the basis of achieving more for the locality for the same levels of local taxes by reducing the costs of community lighting.

A local radio station recently broadcast a highly amusing sketch based upon the observations the presenter and some of the dimly-lit characters encountered during one of the switch-off periods. It served to illustrate the claims of the lobbyists for both sides of the debate whilst producing much light-hearted amusement.

There is currently no move to alter lighting arrangements at places where road speed limits are higher and vehicle movements more frequent.

Artificial lighting is impedimental to the work of astronomers, a significant pro lobby in the above moves. Crime protection and prevention agencies are in the con lobby, though there has been no significant change to levels of crime in these areas to justify their negation; certainly in the districts chosen, already low-crime areas, no report of any significance has been reported on local radio since the experiments began.

A flight over the UK on a clear night can introduce some worries to an on-board observer at the level of light reflected from the ground. Low efficiency low-pressure sodium discharge street lighting is gradually being replaced with high-efficiency high-pressure lighting with a better colour balance for lower cost.

There is a growing concern over the levels of light pollution generally, particularly from that which originates from neigbours insisting on using a multitude of 500W tungsten lamps for home security applications, with their associated carbon footprint. In contrast, a home at these co-ordinates now uses an 11W fluorescent lamp with bayonet-cap fitting for general use as a security lamp, switched by a passive infra-red sensor with run-on timer and over-ride switch, supplementing it with a 40W tungsten mounted in an appropriate decorative lantern just 1m above ground level, on a gate post ready for expected visitors and intended to light only the path to the door, not the district. An Engineer lives there.

There is a strong correlation between gross-national-product-per-person and energy-dissipation-per-person across a range of countries [citation needed]. Significant deviations from the correlation are Germany (energy higher) and France (energy lower), indicating the fundamental differences in those nations' economies.

Incidentally, statistically insignificant observations might indicate that politeness in the UK often extends beyond the perimeter of a vehicle...

We may be talking at cross purposes - I was talking about traffic lights.

Here, residential street lights are more an issue of crime prevention than pedestrian safety - the fewer people you have out and about, the more lights you want on, to deter criminals from lurking about. It's my personal experience that lighting does deter crime.

I'm all for reducing the reflected night glow, though, with better designed lighting systems.

I'm all for reducing light pollution - especially as most burglary-type crimes occur during the daylight hours.

What really aggravates me is all the energy wasted illuminating points well away from streets/intended area. The fact that I can look out my window and see a street light's globe directly speaks for itself: wasted light = light pollution = wasted energy = wasted money. Mine. Yours.

-e

Quite.

Where I live now is about two miles from a large petro-chemical port facility. Talk about light pollution! On a cloudy night it looks like it's on fire. Even more so when it actually is on fire.

If only they would make up their minds! All those lit-up refineries down around Clear Lake, Pasadena, Deer Park, etc. look really cool at night from the air. Like something out of Star Wars. But then, there's the smell. Ugh. Your neck of the woods is polluted on just about every "wavelength!"

-e

Luckily we live south on the refineries and the sea breeze keeps the smell up north. We only get the smell (a nasty caustic burning plastic smell) when a cold front blows in - maybe one day a month during the cooler months. But when it comes, it's really really bad.

Up here in the Allergy Capital of the World we smell only oaks and cedars - and Claritin junkies.

-e

In Garland it's quite a dilemma: there's a real need for shedding light on would-be crimes; at the same time, Garland is not really a place one wants to light up.

So in Garland it would make more sense not to follow the parable's advice? That you really would want to light a lamp and place it under a bushel? I thought only Ft. Worth had this problem.

-e

Precisely--with one exception. Garland can take pride in one fact: that, unlike Dallas, it not irremediably envious of Fote Wuth.

There are commonly available PIR sensors( Photo Intensity Resistor) which are already used for street light control.

Ashelec, "PIR" is commonly understood (at least here in the US) to stand for "Passive Infra Red." But technically, you're right - mostly. The light-sensitive element in a street-light controller is a photoresistor or, alternatively, a photoconductive cell. Some US engineers call it a "CdS cell" or just a "photocell." CdS = cadmium sulfide. The brighter the incident light, the lower the resistance. Typically the cell is connected to the heating element in a thermal relay. The switch contacts are operated by means of a bi-metallic strip which flexes one way (or not at all) when cool, and the other way when warmed. During the day, when light is falling on the cell, it allows enough current to flow through the heater to keep the relay open. Come nighttime, the cell's resistance goes way up and reduces the current available to the heater. The strip cools down and closes the contacts. Voila! Light! Raspy, buzzing, puke-orange light!

-e

I don't think he is asking about street lights or on/off control. He is asking about how to modulate the current flow in a circuit in proportion/relation to the variable of light intensity. Assuming a clear day, unless you're sensing UV light, then low flow at 8AM and high flow at 2PM or the inverse as an example. Without doing any research I believe the photovoltaic cells that convert light to DC voltage do so in proportion to the amount of light/intensity. Using that variance to drive a current regulation circuit would be the next step. Of course their is the different frequencies of light and so on.

Okay, I've used up what I think I know. Its someone elses turn.

Most street lights are some form of arc or discharge lamp which do not lend themselves to brightness control. You either get light or you don't, and once the lamp turns off it must cool down before it can be restarted; a cycle which can take several minutes. Consequently, it makes little sense for street-light controllers (photocontrols) to regulate intensity. They're just light-sensitive switches.

-e

You are right of course. I realize now that the question made me forget that the heading was Street Light Controllers when I wrote my response. Now, based on some of the other posts, is he asking about Street Lights or Traffic Lights?

I'm taking my cue from the thread's Title: "Street Light Controllers," and also that the O.P. mentions controlling the "intensity" of these lights. In my neck of the woods, "street lights" are designed to illuminate an area of a street. In other parts of the world (CR4 has a number of international members and guests) the term may mean traffic-control lights. Without further information I'm assuming the meaning is that of the former case.

Assuming illumination is the P.O.'s goal, I'd say that intensity control is presently irrelevant given the arc-lamp nature of most street light bulbs. LEDs, on the other hand, are rapidly making inroads into niches formerly held by incandescent and fluorescent lamps. I suspect that in a few years we'll begin to see widespread use of some form of LED lighting used to illuminate streets and car parks. The intensity of LEDs can easily be controlled using PWM techniques, should such control prove necessary for street lights. Personally, I don't think so. A more practical approach I think would be on-demand street and pedestrian lighting with the appropriate sensors in place.

-e

A traffic control light could do with light sensor control to reduce the intensity at night. light censors detecting vehicles can also be used to change the preprogrammed cycle in quiet periods.

In my area the most incidents of crime is after midnight, therefore street lights must stay on (at least to operate CCTV's watching up and down the street).

The light intensity can be lowered after midnight by running a dual system or by switching off alternative lights.

Those CCTVs could also be provided with their own IR lighting. As most CCTVs can see well into the infrared, they could operate without the use of street lights and their annoying glare.

-e

Are using IR fitted CCTV in other places.

The ones facing the street was used for there smaller size and IR range Independency. What range can newer IR's do?

Your question does not detail the type of lighting you wish to control so no answer can given please add more detail as to the nature of you problem.