Low Voltage D.C. Lighting & Color Temperature of Light

electricity from the sun by John Drake II | home

Where do I start?

In the early to mid-seventies when I was playing around with small solar panels,

the only lights I knew about were ones that used tail light bulbs.

These draw over an amp and produced a dim yellow light.

In the late seventies I picked up some incandescent fixtures from the

local trailer supply house.

Then in the early eighties I discovered 12 volt d.c. fluorescent lights.

I did not realize that they had been around since 1969 when Thin-Lite

(their product line was then called REC Specialties) opened their doors.

We started using the Thin-Lite fixtures as well as the Mclean Electronics line.

There is still a four foot Mclean light in our main storage building that I

installed in 1986 that we use every day. Mclean closed their doors

many years ago.

Around 2001 I learned about 12 and 24 volt d.c. compact fluorescent,

flood, and area lights by

LIght It Technologies (later they changed their name to Montana Light) .

These made setting up an off-grid or back up lighting system a snap.

They made the compact fluorescent light, with many upgrades through

the years, but always had to compete with imported compact fluorescent

lights whose lifespan most times could be measured in weeks - while

the LIT lights lasted years and did not make the strange noises like the imports

did.

Many times samples were sent to us out of the blue by importers trying to

get us to sell their goods. We played with them and chuckled at the

funny smells they made and the annoying whistling sounds coming from them.

The fluorescent lights were light-years ahead of the incandescents.

Brighter, a cleaner light and they did not beat up batteries.

For a few decades fluorescent lights ruled the roost, except in applications

where the light would be turned on and off throughout the day.

This is where the quartz halogen Edison base 12 and 24 volt light by

Low Voltage Lighting (in Vermont) were a good choice.

They made floodlights and lights that looked just like an ordinary light

bulb but with a quartz halogen bulb inside.

In a hallway, closet or pantry where the light was constantly being

cycled on and off the life span of a fluorescent light was greatly

shortened.

Low Voltage Lighting closed their doors many years ago because

the halogen lights could not compete with the low voltage energy

efficient d.c. compact fluorescent lights.

Then came along the LED (light emitting diode) lights.

They had a rough start: high cost , low light output and in some

cases they were very delicate.

Montana Light started building Edison base (screw in) led lights as

well as small flat plate lights around 2006.

We have many of the in use here for security lighting and a few have

been run continuously for several years.

Some Edison base lights started coming into the U.S. which were

made in the Far East and had a German name on them.

Most of these had to be repaired right out of the box.

The Montana Light leds were well made and extremely durable,

they also made some 2-1/2 to 3 watt screw-in lights.

It is sad to say that Montana Light closed its doors in

March, 2014.

LED lights struggled for some time.

There were many claims made about them, life spans of up to

100,000 hours, high output and low power draw.

Yes, if you did not over-drive (run a high voltage) them, the life

spans were incredible but the technology was not there for a

bright led with a long life span.

Some manufacturers took large leds, ran the voltage high to

increase brightness, and claimed the high life span.

Well they were bright and ran very hot which in many cases

reduced the life span to around 1200 hours.

Yup, light emitting diodes (led's) do produce heat and if driven

hard a heat sink is required to prevent early failure.

As time has passed, the led technology has improved light output,

color saturation consistency and longevity.

Thin-Lite's "P" led lights operate from 8 to 30 volts d.c. and are

dimmable.

As of November, 2014, Thin-Lite's light fixture production is close

to sixty percent led models.

Pros and Cons of different light sources.

light source type	pros	cons
standard incandescent	cheap, on/off cycles do not greatly affect life span, can be dimmed	high amp draw for low light output, produces a lot of heat, yellowish light color, if dimmed the light color becomes muddy
quartz halogen	can handle many on/off cycles, not as yellow as other incandescents	very high heat output (the quartz halogen cycle requires high temperatures to operate), high cost, can not be dimmed successfully
linear (straight tube) and Edison base compact fluorescents	long life span, energy efficient, can be had in cool white which is no color	produces some heat, tubes last from approximately 2000 to 9000 depending on how they are used, many on/off cycles reduce both the tube and electronics life span, low voltage damages the electronics, can not be dimmed
Edison base led	very efficient, generates small amount of heat, no tubes to replace, more durable than other types of lights, can be dimmed	high cost when compared to a fluorescent but less in the long run, limited light output because of the limited size of the led cluster as led's are directional does not have the coverage of a fluorescent light
linear (or straight strips) led light	high light output for the amount of power used, low heat output, no tubes to be replaced, can be dimmed, they give the user great bragging rights	high cost
fluorescent to led conversions	more efficient than a fluorescent when done properly	not as durable as a factory complete led fixture, usually no warranty and usually not dimmable, Thin-Lite looked into making conversion kits - the cost when compared to a complete fixture (with warranty) was equal or slightly more for the conversion, after looking at the cost and liability concerns they took a pass

Color Temperature of Light

The color temperature of light, from yellow (warm like an incandescent light bulb)

to blue (daylight) is measured in degrees Kelvin.

The lower the number, the warmer the light.

The higher the number, the cooler the light.

Incandescent light bulbs produce light by heating a tungsten filament which

produces a warm colored light which is around 2700 to 3000 degrees K.

The quartz halogen lights operate hotter so their color temperature can run

up to 3500 degrees K in some cases.

Fluorescent lights, depending on the gas mixture in the tubes, can run

from 2700/3000 degrees (warm white) through 4000/4100 degrees

(cool white - no color) to 5500/6500 degrees (daylight with some blue to very blue).

LED lights, depending on the chemistry of the diode, can run the gamut

from 2700 degrees up to 6500 degrees.

Just what does this mean to us?

Much of it is personal preference.

Some folks light the warm white light - it reminds them of incandescent lights

without the drawbacks.

A downside is that in a room with wood surfaces, the light is soaked up by the

wood.

If you want the illuminated surfaces to retain their color you might want to

consider cool white - it changes color very little and provides good contrast.

In a recreational vehicle or boat it is usually the best choice.

If you want a daylight like light, and don't mind a bluish tinge in the light,

the 5500 degrees light source might work for you.

The 6500 degree LED's may be fine for a flash light but for area illumination

they can get on your nerves in a hurry.

When Montana LIght came out with their first high powered screw-in led

lights they were around 6000 degrees.

I put one over my desk, for a couple of minutes, then pulled it out for use

in our outdoor security lighting.

Not for me.

An important concern, I hear this from many of our customers, is that as

we age we need more light along with a decent amount of contrast.

This is why all of our instock fluorescent and led lights are 4000 to 4100 cool white.

To be continued.

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