Maker Pro
Maker Pro

Connecting two (or more) incandescant bulbs in series.

F

Frank Martin

Jan 1, 1970
0
I want a low-level mood light occasionally, but not often.
If I connect two bulbs in series I get about 1/4 the wattage rating and
light output.
Is there a simple switching scheme to switch from parallel to series, that
will fit in a small space?
Or will I have to go to a relay?
Regards, Frank
 
J

JM

Jan 1, 1970
0
quoting:
I want a low-level mood light occasionally, but not often.
If I connect two bulbs in series I get about 1/4 the wattage rating and
light output.
Is there a simple switching scheme to switch from parallel to series, that
will fit in a small space?
Or will I have to go to a relay?


Put a switch across one of the bulbs. When the switch is on, one bulb will
get full voltage, when it is off, the two bulbs will be in series. Don't do
that with once one bulb though, it makes a short.
 
V

Victor Roberts

Jan 1, 1970
0
I want a low-level mood light occasionally, but not often.
If I connect two bulbs in series I get about 1/4 the wattage rating and
light output.

With two lamps of the same voltage rating wattage in series you
actually get 8.8% of the rated light from each lamp, and use 33% of
the rated power for each lamp. So, two lamps in series will use 66% of
the power of one lamp while producing only 17.7% of the light.
Is there a simple switching scheme to switch from parallel to series, that
will fit in a small space?
Or will I have to go to a relay?

You might want to try a series diode. This will give you about 85
volts on one lamp (assuming you have 120 volts power lines), which in
turn gives 30.8% of the light that this same lamp would produce at
rated voltage and consumes 57.4% of the power this same lamp would
produce at rated voltage. Using one lamp and a diode gives just about
the same amount of light for just about the same amount of power as
you get with your two-lamp series connection and a simple single-pole
switch can be used to short out the diode when it is not needed.
 
J

jriegle

Jan 1, 1970
0
Why can't you use a light dimmer? they are not very expensive and can be
adjusted to the level you want.
John
 
D

Don Klipstein

Jan 1, 1970
0
In said:
It depends upon the type of dimmer. A resistive or "rheostat" dimmer does
not save any power regardless of the dimming level, but the newer
Pulsewidth Modulation (PWM) dimmers can show actual power savings at
lower-than-full-intensity dimming levels.

It seems to me that over 99% of dimmers in use nowadays or in the past
decade or two use a waveform chopping technique and less than 1% use
rheostats. There is a third class which is also rare for "permanently
installed" ligt dimmers - variable autotransformer, mostly a little worse
than the common kind of dimmer for energy efficiency, but mostly not as
bad as a rheostat.

Rheostats decrease power consumption, but substantially less than the
usual kind of dimmer does (and the usual kind when adjusted to reduce
light output by 80% reduces power consumption by around 30%). A rheostat
reduces light output by something like 90% when adjusted to reduce power
consumption by 30%, or when adjusted to reduce light output by 80% reduces
power consumption by roughly 22%.

- Don Klipstein ([email protected])
 
F

Frank Martin

Jan 1, 1970
0
Many thanks for all replies.

Frank Martin said:
I have heard that dimmers use as much power, whatever the setting.
 
J

JM

Jan 1, 1970
0
quoting:
I guess 'newer' has to be anything past 1980...

In any case efficiency goes down as you dim. Thus it is better to switch
from a 60 watt to a 5 watt bulb, than to use a dimmer.


A 60 watt "A" lamp drivin at 33% power will be on the order of 7.6 lpw, While
a 7 watt clear night light lamp is 6.5 lpw. Not a big enough difference to
really care, but it does show that a dimmed "A" lamp is actually more
efficiant.
 
Z

Zak

Jan 1, 1970
0
JM said:
A 60 watt "A" lamp drivin at 33% power will be on the order of 7.6 lpw, While
a 7 watt clear night light lamp is 6.5 lpw. Not a big enough difference to
really care, but it does show that a dimmed "A" lamp is actually more
efficiant.

This is really strange. Maybe no-one cares about efficiency of 7 watt
bulbs. And while a 7 watt at 100% is much less efficient than a 60 watt
at 100%, that situation should be reversed when they end up at the same
power or the same light output.



Thomas
 
Top