In said:
Why not try TWO 4W incandescents in series? Lasts forever since each
bulb is at half voltage and gives more than half the light a regular 4W
does.
Lasting forever is nearly enough true.
As for light output and power consumption:
A pair of 4w bulbs in series consumes approx. 2.7 watts. But I doubt a
watt or two one way or another is that big an issue.
A pair of 4w bulbs in series produces only about 20% as much light as
one bulb does. This may well be an adequate amount of light for a night
light, but please consider this fact when contemplating doing such a thing
with higher wattage lightbulbs where energy consumption expense is
significant.
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As for an LED nightlight: I am afraid you will have to homebrew one and
the budget gets sort of high for a nightlight.
To do this I would get a few superduperultrabright green LEDs of InGaN
chemistry and wavelength preferably in the 520's of nm. Feed a series
string of a a few of these LEDs by a bridge rectifier - voltage is not
critical, since the diodes will only have reverse voltage similar to the
voltage drop of the LED string if you do as I describe below.
A capacitor of a few hundred microfarads and voltage at least that of
the LED string (allow 4 volts per LED), added in parallel with the LED
string, will usually help since this chemistry of LEDs prefers lower
instantaneous current (or instantaneous current closer to a few
milliamps).
In series with one of the AC legs of the bridge rectifier, put a
capacitor with value around .047 to .1 microfarad (.022-.047 uF for
220-240 volts AC) and being rated for continuous duty with AC line voltage.
(CAUTION - some nonpolarized and even some non-electrolytic capacitors can
only take intermittent duty of AC whose peak voltage is within the DC/peak
voltage rating.)
In series with the capacitor put a power resistor with a value around
10-100 ohms or so, to reduce sparking when you connect the whole thing to
line voltage.
Be amazed at what a few milliamps through a few really bright green LEDs
can do once you are even somewhat dark adapted. I can see my way around
and through 2 rooms with just one of these LEDs running at just a couple
to a few milliamps. Wavelengths in the low 500's nm are especially
favorable to night vision! And power consumption (at 4 mA, roughly the
current with a .1 uF capacitor at 120V, is roughly .0125 watt per LED plus
perhaps .01 watt for everything else.
If you make an LED nightight and want more brightness, then get a higher
value capacitor that must have an explicit AC voltage rating in excess of
your line voltage. Up to .15 uF with 220-240V or .33 uF for 110-120V is
OK.
I would add a fuse in series with one of the line connections.
Electroluminescent nightlights, such as those of the "Indiglo" and
"Limelight" brands, are less efficient than really good
nightlight-favorable LEDs. However, you can outperform neon nightlights
(assuming dark-adapted eyes) with only something like 1/16 watt of power
consumption. And these are widely enough available and do not require any
homebrewing.
- Don Klipstein (
[email protected],
http://www.misty.com/~don/led.html,
http://www.misty.com/~don/ledx.html)