Industrial LED Lighting

I have a special-application installation that I've been asked to spec out. I need to set up the equivalent of a street lamp (okay, walkway lamp) that will not be tied into mains power. This would be mounted on a post where no power is available. Ideally it would last through the night but even 5 hours of illumination would be satisfactory.

My thoughts turned to the latest generation of high-intensity LEDs. I figure that I could design a fixture of some sort that would have a solar charger sitting on top along with a photocell to know when it gets dark and a battery mounted to the post.

Does anyone know of a unit such as this already in existence or where I might turn to figure out such a setup? I'm not looking for those weak little lights available at Home Depot that people use to line their walkways. I want a larger unit that will light up an area equivalent to say a 100w tungsten bulb and figured that LEDs would be the most efficient way to go.

Any ideas?

Mitch Gross
NYC DP

Mitch Gross wrote:

>My thoughts turned to the latest generation of high-intensity LEDs.

You could try one of these

http://www.lumileds.com/luxeon/products/flood_index.html

The 18 LED unit has a fairly high output, but it's also pretty thirsty for power. Although LEDS are pretty efficient, at this end they still pull a fair whack. You'd need a pretty substantial battery to keep it going...

there are also some thermal issues you'd need to deal with. The light itself is *cool* but there is so much energy going through the LED die that they get pretty hot and you need to reject quite a bit of heat from the pack. if you don't then you will drastically impair the brightness and efficiency.

These are available in the usual colours but be aware that the white LEDs are usually pretty cool. Lumileds claim 6000K but I find they are more like 7-8000k.

This package has a very wide 110deg lens single so the light falls off pretty quickly as well. You can also get 3rd party collimating optics which will correct this and give you more light projection (down to 5 deg), but they can't be used with the specific package above because of size and proximity of the LEDS on the PCB. Contact me if you want that info.

Cheers...

John Brawley
V:Media
Melbourne Australia
www.viciousmedia.com

Mitch Gross writes :

>I have a special-application installation that I've been asked to spec out. >I need to set up the equivalent of a street lamp (okay, walkway lamp) >that will not be tied into mains power.

The latest LEDs are just about on a par with tungsten halogen in terms of efficiency. It would be just as efficient (and a lot cheaper) just to use one or two halogen reflector lamps running on a very big battery.

100W's worth of power for five hours or so isn't too dramatic, and could be realised with a decent car/truck battery. 100W @ 12V = 8.5A for five hours equals 45Ah minimum battery capacity.

For much greater efficiency, you could use electronically ballasted fluorescents. An invertor could be connected to a vehicle battery and used to power a decent number of standard compact fluorescents, or more suitable colour specific tube arrangements.

Clive Mitchell
http://www.bigclive.com

Mitch Gross writes :

>I need to set up the equivalent of a street lamp (okay, walkway lamp) >that will not be tied into mains power.

One option would be to use a ~100-W equivalent (about 25-30 watts draw) compact fluorescent bulb. Make sure it has an electronic (not magnetic) ballast, to avoid any flicker issues. You can get 'em at Home Depot -- go for brand names, like Philips.

You can safely power the bulb from a cheap 12V->120V inverter that has at least 50 watts of rated capacity. (Radio shack has some decent ones. Go to radioshack.com and search on "inverter.")

You can plug the inverter into an automobile cigarette lighter socket, and then run the inverter's 120-volt AC output to your lamp via a long extension cord. Depending on the car, you may have to keep the ignition key on or in the Accessory position to power-up the lighter socket.

A typical car battery, in good condition and fully charged, should hold at least 600 watt-hours of power. In five hours this inverter/fluorescent rig will draw under 200 watt-hours. These are conservative figures.

Dan Drasin
Producer/DP
Marin County, CA

Let me note that this will be a semi-permanent installation, at least six to eight months (it's an art piece). So it needs to be something that is self-powered and can be generally left to itself to function. That's why I'm figuring large lead-acid battery and a solar cell. The solar cell would have to be powerful enough to recharge the batt during an overcast winter's day in the NY area. I'm told that the latest generation of cell panels can do quite nicely. But I'll need to determine how big a batt I'll need so that I know how big a solar panel I'll need, so it goes back to figuring out first the lighting fixture itself.

This is functionally to act as a sort of walkway lamp, something that illuminates the area around it for say 25'. Not photographically per se, but at least enough for human vision straining into the darkness. Yes this is CML related as it is part of a larger art piece that I'll be shooting film & video for. Thanks for any suggestions.

Mitch Gross
NYC DP

Mitch, I remember reading something about Ski-mountains that were offering night skiing finding that 1 to 3 foot candles were sufficient, and preferred. That of course had to do with giving contrast to the down hills, so skiers could tell the shape of the snow, but if it isn't necessary to illuminate for filming/taping, then you might not need that much.

Hope this helps.

Steven Gladstone
www.gladstonefilms.com
Cinematographer - Gladstone Films
Cinematography Mailing List - East Coast List Administrator
Better off Broadcast (B.O.B.)
New York, U.S.A.

>Mitch, I remember reading something about Ski-mountains that were >offering night skiing finding that 1 to 3 foot candles were sufficient...

Yes, I would think this would be an acceptable light level, which is why I figured something around a 100w bulb could cover a 25' radius.

Mitch Gross
NYC DP

Don't forget that was on nice, white, 90-95 percent reflecting snow.

Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614

>Mitch, I remember reading something about Ski-mountains that were >offering night skiing finding that 1 to 3 foot candles were sufficient...

Don't forget that was on nice, white, 90-95 percent reflecting snow.

Still, when I go out on the streets of NYC at night with my lightmeter, 1-2 footcandles is what I find on sidewalks that are illuminated properly for my purposes. And the sidewalks & streets of New York City have been called many things, but nice & white ain't one of 'em!

Mitch Gross
NYC DP

>The solar cell would have to be powerful enough to recharge the batt >during an overcast winter's day in the NY area.

I'm not sure how much sun you have in the NY area, but you'd be surprised at just how large the solar array would have to be to provide even a modest amount of power. They work fine in direct sunshine, but put out virtually nothing on a grey winters day.

Then there's the complexity of charge monitoring so that the (deep discharge) lead acid battery doesn't get over discharged (which results in damage). This would mean that the load could only be run for as much time as the days "sunshine" had allowed. This would be determined by an accurate voltage threshold cut-off point.

Is it a windy location? Could a small wind turbine be used?

Clive Mitchell

Mitch Gross writes:

>it needs to be something that is self-powered and can be generally left >to itself to function. That's why I'm figuring large lead-acid battery and a >solar cell.

For NYC in winter you'll have to over design your system pretty heavily.

To calculate the output of a non-tracking (fixed-mount) photovoltaic panel aimed at the proper elevation (to face the sun broadside at noon during that time of the year), you'll generate about five times the rated wattage in watt-hours per ideal day.

Translation: A 100-watt panel mounted so it's directly facing the sun at noon will produce 500 watt-hours of power on a perfectly clear, sunny day.

In addition to the panel(s), mount(s) and wiring you'll need a) a charge-controller designed for solar applications and for the particular type of battery you're using (wet-cell-vs. gel-cell), and b) a storage battery (preferably gel-cell, which is much safer) with enough capacity to see you through X number of dark days.

Note that even the slightest amount of shading (relative to bright sun) will radically reduce the output of solar panels. So mount any panels on a rooftop or open area where nothing can shade them -- even partially -- for as much of the day as possible. Mounts should be sturdy and solid -- nothing that can possibly be picked up by strong winds. Feeder cables should be heavy enough (relative to their length) not to impose excessive resistance.

Best would be to engage a solar-power consultant to do the math and recommend the hardware.

As for the light itself, don't count on a single LED source to illuminate a broad area. Most are fairly directional, so you might use several, mounted in a divergent array. Compact fluorescents might be a better bet.

Dan Drasin
Producer/DP
Marin County, CA