There are some old and some new low wattage lights and night lights out there. I just want people to beware of possible disappointments and to know of some of the better ones.
Please note that all models described below are made for use in the USA, and require 120 volts. Some models require specifically 60 Hz AC. Most 120VAC LED models and in general 120 VAC electroluminescent models will work safely at 50 Hz 110-120 VAC with slightly reduced light output. Most fluorescent models requiring AC should only be operated at their rated frequency, however.
Contents:
The usual 1/4 watt neon night lights
The dual neon daylight-shutoff white oblong model
Those 3.5 and 4 watt fluorescent models
General Electric 1.5 watt fluorescent models
"Limelight", "Indiglo" and other electroluminescent models
Black And Decker daylight-shutoff model
General Electric / U.S. Energy Technologies 1.5 watt Mini Guide Light
GE, Dollar Store and Similar single-LED Nightlights
Target roundish-oval LED Nightlights
"Sweet Dreamers" dollar store LED Nightlights
Some LED Nightlights that I Like
LED "lightbulbs" in general
The NE-2H neon lamp is also rated for use with a 22K resistor to use 1/3 of a watt. However, the life rating drops to 5,000 hours. If you try to get really long life by hacking out the resistor and replacing it with one over 33K or adding additional resistance, you may be disappointed. Life increases only roughly proportionately with resistance as resistance is increased above 33K.
UPDATE 4/1/2004 - These are less common than they used to be and are often now called "guide lights". They are available at Target and some/most places where GE nightlights are sold.
The unit consists of two A1B neon lamps and a 10K resistor all in series, with a cadmium sulfide cell in parallel with the pair of neon lamps. Another problem with this unit is unreliable light output at low voltages. This unit will not light during a significant brownout.
The American Power Products 3.5 watt unit that I have also flickers slightly.
1. A very rounded triangular or triangle-egg-shaped one with a blue push-on-push-off switch, which glows an icy cold pure white to "daylight" color.
2. A different shape white one with a "1-0" switch, which glows a roughly incandescent yellowish warm-white color.
3. A green model which is labelled as "neon".
I purchased the yellowish-glowing model on July 1 2002 and the pure-white-glowing model on July 8 2002 and have been running them 24 hours a day ever since with few breaks.
The yellowish-glowing model produces more light than the pure white model, but to night vision it may be the other way around. The yellowish model produces approx. 9 lumens of light, which is a little less than half as much light as is produced by a typical 4 watt 120V incandescent lamp. To night vision, light output may be more than half that of a 4 watt incandescent. Efficiency is about that of 7-7.5 watt 120V incandescents. Miniaturized fluorescent lamps, especially when miniaturized in length, are inherently less efficient than longer ones.
No claims are made as to light output nor life expectancy except that life expectancy is longer than that of 4 watt incandescent.
UPDATE 5/7/2003 - The warmer color one burned out on 5/4/03, which is approx. 7400 hours. It has experienced approx. 100 starts.
UPDATE 4/1/2004 - The cooler white one largely conked out in mid-March 2004, with two distinct major decreases in brightness about a week apart. It lasted a little over 20 months of operation 24 hours per day with only a few hours per year of off time.
The yellower one and the pure/cool white one appear to have different circuits inside.
As for efficiency? The efficiency is comparable to incandescent, and the light output is comparable to the usual 1/4 watt orange neon models. But the light is mostly of wavelengths that night vision is sensitive to, and these illuminate dark rooms much more than 1/4 watt orange neon models do.
These do have impressive warranties against burning out. But there is one dark side of electroluminescent night lights: They do deteriorate with use. I have no hard figures, but I hear horror stories about their "half life" being only a couple to a few years. Sometimes their light-emitting areas develop dark spots.
The bulb in the Mini Guide Light is a low voltage incandescent lamp that is built in and not intended to be replaceable. I could make out the filament, and think the bulb may be an 1829 or an 1819 or something similar. This light has a built-in electronic ballast to power a low voltage incandescent lamp. There is an efficiency advantage, since a shorter, thicker filament can be operated at a higher temperature for the same lifetime than a thinner filament can.
From the color of the filament, I expect a lifetime of at best several thousand hours. Since it costs about US$ 7 and could easily burn out in a couple years, I think it is no bargain.
NEWS 1/10/2004, updated 1/16/2004 - I purchased late in December 2003 a few LED nightlights from a dollar store. Claimed power consumption is usually 1/3-1/2 watt. Actual power consumption so far in my experience has mostly been around .3-.33 watt.
A majority of the power consumption in these models is in circuit components other than the LED.
The white versions will fade over the years, with a "halflife" of only a few years or more likely even around a year, due to phosphor degradation that is normal in white LEDs.
There is a green version (with a green InGaN LED) that both outperforms (in terms of illumination as sensed by night vision) and outlasts the white version. There is also a blue verson.
White, green and blue units are brighter than neon and electroluminescent units, though dimmer than 4 watt incandescents. White, green and blue LED units stimulate night vision well and allow most people to easily see in rooms at nighttime.
Red and yellow LED nightlights are less common, since they are dimmer than white and green ones and also do not stimulate night vision well. Yellow ones are a little brighter than neon "guide lights", while red ones are about as bright as neon "guide lights". Red ones often effectively illuminate rooms even less than neon "guide lights" do.
A review is available HERE in Craig Johnson's world-famous site for LEDs and LED products, mostly flashlights.
GE produces a similar white LED nightlight, which I believe these are a knockoff of.
These are the ones reviewed by Craig Johnson as noted below. Target now sells other LED nightlights.
They are attractive, roughly of the shape and size of an egg, and have a round
dome. Power consumption is claimed to be 1 watt. They have a photocell to shut
them off when bright light is present, although the current draw (but possibly
not the actual power consumption) does not change much when this happens.
Light output is much more than that of neon "guide lights" and somewhat more
(only slightly more to night vision) than that of electroluminescent models,
but much less than that of 4-watt incandescent models.
Craig Johnsom has a more extensive review of these at:
http://ledmuseum.thefire.us/tpnight.htm
One note: I have found these to noticeably lose light output and become more blue in color after just a few months of operation. I suspect the phosphor in the white LEDs is a lower quality one that fades from just a few thousand hours of operation.
The circuit is the 3 LEDs, a diode, and a 15K-ohm 1/2-watt resistor all in series. The 15K resistor typically dissipates .4 watt. My experience with electronics repair makes me uneasy with resistors dissipating more than 70% of their power rating in heavy, continuous or long-term use.
"Crude measurement of light output" indicates half a lumen - with the front cover removed. The scotopic/photopic ratio is fairly high, and ability to stimulate night vision is likely comparable to that of 1 lumen of light from white LEDs and 2 lumens of incandescent light. The front cover blocks about or somewhat more than half the light.
The front cover comes off easily without tools, exposing the LEDs. This is a very minor shock hazard. Gripping the unit by the LEDs (somewhat easy to do with the front cover removed) is not recommended, since that can lead to eventual breakage of the LED leads by "metal fatigue".
This is an LED "bulb" that can be used in place of 4-7 watt candelabra screw base incandescents. Power consumption is approx. .45 watt. Light output is fairly usual for LED nightlights. It has 3 white LEDs that have a very cool bluish white color. I estimate the color temp. to be about 8,000-9000 K. Light output is somewhere around "crude measurement" 1-2 lumens. Efficiency is in the "low end of incandescent" range, though better than that for night vision.
A shade is unlikely to be necessary in a usual candelabra base nightlight. The light output pattern is different from that of incandescents, due to the light output being more through the tip of the bulb. However, there is no well-defined beam.
The LEDs are being provided much less power than usual, so they should fade more slowly than most low power white LEDs do. As a result, I consider the claim of 50,000 hour life expectancy to be realistic.
2. Amertac Green/Blue switchable model 71381, available at Home Depot:
This is an LED model that resembles electroluminescent ones. Power consumption is stated as .3 watt. It is somewhat brighter than electroluminescent units. It has a switch for green, blue and off. It is available in 2-packs at Home Depot.
Although this unit provides less light than 4-7 watt incandescents, it is plenty bright for most nightlight use since green and blue LEDs provide wavelengths of light that night vision is sensitive to.
Light output in lumens so far, according to actual measurements although likely to not be very accurate, are approx. .2 lumen for green and approx. .1 lumen for blue. Although with power consumption of .3 watt the photometric energy efficiency is less than that of incandescents, these lights can easily replace incandescent nightlights with achievement of energy savings, since their light output is likely to be adequate, especially considering the high sensitivity of night vision to the mid-blue to mid-green wavelengths produced by these and most other blue and green LED nightlights.
To night vision, the blue LED used here actually outshines the green LED despite lower photometric results.
I consider this unit notable for being reasonably economically priced for a non-dollar-store unit, and also for having blue/green LEDs instead of an aging-prone white LED. Expect the LEDs to give many years of service with little fading.
Buyer beware of any or any combination of the following disappointments in many, probably most models as of 3/2/2008:
* Light output claim has a big number due to apples-to-oranges comparison
(usually from the LED one having a beam)
* Light output is less than claimed by all measures
* Light from white units has an icy cold color
* Warm white version is even dimmer than icy cold color version
* Many white units will fade over the years
Beware that many low power white LEDs, even good ones, fade significantly within 10,000 operating hours at "normal power". There are high power white LEDs that honestly achieve 50,000 hours before "fading excessively" (over 30%), notably many recent "Luxeon" ones by Lumileds, but even those can fade faster if they are overpowered or have insufficient heatsinking.
Green units will tend to work well for good illumination efficiency and lack of fading. Red and blue units also resist fading, but generally provide less illumination.
Copyright (C) 2003, 2004, 2008 Donald L. Klipstein. Please read my Copyright and authorship info.
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