Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

405 TD Estate wrote:
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

My understanding is that the power consumption is reduced a bit, but
nowhere near as much as the light output is. i.e. 50% light output
reduction does not mean you are only using 50% of the power -- far from
it, iirc.

Styx

On Mar 6, 10:13*am, Styx wrote:

My understanding is that the power consumption is reduced a bit, but
nowhere near as much as the light output is. i.e. 50% light output
reduction does not mean you are only using 50% of the power -- far from
it, iirc.

You should always remember an incandesant light produces light purely
as a by-product. They are really designed to produce heat - lots of it
- enough to make the filament glow white hot at design voltage.

On Thu, 6 Mar 2008 00:52:51 -0800 (PST) someone who may be 405 TD
Estate wrote this:-

Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

At a guess when dimmed to say 50% of the light output the lamp will
still consume something like 55W.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

David Hansen wrote:
On Thu, 6 Mar 2008 00:52:51 -0800 (PST) someone who may be 405 TD
Estate wrote this:-

Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

At a guess when dimmed to say 50% of the light output the lamp will
still consume something like 55W.


Bad guess then.

Humans eyes are logarithmic..'half as bright' may mean something like
1/4 the light power or less.

Anyone who has used a manual camera knows that going from bright
sunshine to a cloud passing over is already 1/4 of the light..going down
to internal light levels may be HUGELY less..and teh point at which you
can't really see color, is absolutely amazingly low.

Whilst its true to say that light bulbs get less efficient at lower
outputs, the fact of the matter is that you can see alarmingly well at
very reduced light outputs, and a dimmer is a crude, but efficient way
to reduce input power.

I would guess, from a more educated perspective, that it's less than 15W
at 'half brightness', possibly a LOT less.

But then we know *you* 'don't count', and all of your judgments are
predicated on woolly minded emotive bases, and never on facts -
especially backed up with informed mathematical analysis.

I can imagine you as a WWI commander: 'keep together chaps when you go
over the top. Mutual protection and all that' and the opposition's
machined gunners chuckling as they see a tight knot of 'chaps' just
waiting to be scythed down in a single burst..

Styx wrote:
405 TD Estate wrote:
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

My understanding is that the power consumption is reduced a bit, but
nowhere near as much as the light output is. i.e. 50% light output
reduction does not mean you are only using 50% of the power -- far from
it, iirc.

Styx

50% less light output barely registers as any different.

You would need to be down about 90% to feel that 'half brightness' had
been achieved.

On Thu, 06 Mar 2008 13:14:58 +0000 someone who may be The Natural
Philosopher wrote this:-

At a guess when dimmed to say 50% of the light output the lamp will
still consume something like 55W.

Bad guess then.

Nice try, but you failed to make a convincing case. You may have the
last word.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

David Hansen wrote:
On Thu, 06 Mar 2008 13:14:58 +0000 someone who may be The Natural
Philosopher wrote this:-

At a guess when dimmed to say 50% of the light output the lamp will
still consume something like 55W.

Bad guess then.

Nice try, but you failed to make a convincing case. You may have the
last word.



Sorry, this isn't open to debate. Or debating points scoring. It's open
to either sticking a meter on it, or understanding how dimmers,
electricity and lightbulbs and the eye actually work.

If you want to stay in your fantasy land of subjective judgments and
opinions, fine, but please don't expect anyone to take you seriously.

I spent enough my life with my eyes glued to oscilloscopes, test
equipment and god know what understanding the theoretical and practical
aspects of semiconductor design, let alone many years as an amateur
photographer with a hand held light meter, to have ANY patience with
someone as ill informed and unscientific and as totally unversed in
practical real world engineering as you are, when it comes to an opinion
on something technical.


Nothing I say will convince you anyway. ~I could spend a day rigging up
a watt meter, and demonstrate it to you and it wouldn't budge you an inch.

Unlike you, I am less concerned with winning arguments, than with
achieving practical results that have meaning, and practical results
that are predictable in both performance and cost. Thats what being an
engineer is all about.

On Mar 6, 1:14 pm, The Natural Philosopher wrote:
David Hansen wrote:
On Thu, 6 Mar 2008 00:52:51 -0800 (PST) someone who may be 405 TD
Estate wrote this:-

Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

At a guess when dimmed to say 50% of the light output the lamp will
still consume something like 55W.

Bad guess then.
[snip]
I would guess, from a more educated perspective, that it's
less than 15W at 'half brightness', possibly a LOT less

Hmm. There are two (very) non-linear effects he
- a small change in input electrical power causes a large change in
output light power.
- a large change in output light power is required to cause a small
change in perceived brightness.

.... and finally, the efficiency needs to include the power consumed in
the dimmer (I know it isn't just a variable resistor, but even so
there has to be *some* power loss).

But that's 15W in the lamp.

Martin Bonner wrote:
On Mar 6, 1:14 pm, The Natural Philosopher wrote:
David Hansen wrote:
On Thu, 6 Mar 2008 00:52:51 -0800 (PST) someone who may be 405 TD
Estate wrote this:-
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?
At a guess when dimmed to say 50% of the light output the lamp will
still consume something like 55W.
Bad guess then.
[snip]
I would guess, from a more educated perspective, that it's
less than 15W at 'half brightness', possibly a LOT less

Hmm. There are two (very) non-linear effects he
- a small change in input electrical power causes a large change in
output light power.

cubic or 4th power I think roughly, buy not exponential whereas..

- a large change in output light power is required to cause a small
change in perceived brightness.


that is inverse exponential - i.e. logarithmic.

So I would aver that power goes down faster than 'perceived brightness'

It certainly doesn't go down SLOWER as 'dynamo Hansen' reckons..

... and finally, the efficiency needs to include the power consumed in
the dimmer (I know it isn't just a variable resistor, but even so
there has to be *some* power loss).

About a 2v drop when on, no power lost when off. Some switching losses

So about 95%-98% efficient more or less.


But that's 15W in the lamp.

In article ,
405 TD Estate writes:
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

Nearly.

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Mar 6, 2:57*pm, Martin Bonner wrote:
On Mar 6, 1:14 pm, The Natural Philosopher wrote:

David Hansen wrote:
On Thu, 6 Mar 2008 00:52:51 -0800 (PST) someone who may be 405 TD
Estate wrote this:-

Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

At a guess when dimmed to say 50% of the light output the lamp will
still consume something like 55W.

Bad guess then.
[snip]
I would guess, from a more educated perspective, that it's
less than 15W at 'half brightness', possibly a LOT less

Hmm. *There are two (very) non-linear effects he
- a small change in input electrical power causes a large change in
output light power.
- a large change in output light power is required to cause a small
change in perceived brightness.

... and finally, the efficiency needs to include the power consumed in
the dimmer (I know it isn't just a variable resistor, but even so
there has to be *some* power loss).

But that's 15W in the lamp.


Don't forget that running the lamp at lower power also alters the
colour balance (spectrum) of the light it emits. It not just a
qestion of the intensity.


Robert

RobertL wrote:
On Mar 6, 2:57 pm, Martin Bonner wrote:
On Mar 6, 1:14 pm, The Natural Philosopher wrote:

David Hansen wrote:
On Thu, 6 Mar 2008 00:52:51 -0800 (PST) someone who may be 405 TD
Estate wrote this:-
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?
At a guess when dimmed to say 50% of the light output the lamp will
still consume something like 55W.
Bad guess then.
[snip]
I would guess, from a more educated perspective, that it's
less than 15W at 'half brightness', possibly a LOT less
Hmm. There are two (very) non-linear effects he
- a small change in input electrical power causes a large change in
output light power.
- a large change in output light power is required to cause a small
change in perceived brightness.

... and finally, the efficiency needs to include the power consumed in
the dimmer (I know it isn't just a variable resistor, but even so
there has to be *some* power loss).

But that's 15W in the lamp.


Don't forget that running the lamp at lower power also alters the
colour balance (spectrum) of the light it emits. It not just a
qestion of the intensity.



Indeed. apples and oranges.

Warm orange glow as opposed to blazing white halogen.

I would say that my experience of dimming halogens and ordinary lamps
shows that the halogens lose light more rapidly than the standard bulbs..


Robert

On 6 Mar, 17:51, The Natural Philosopher wrote:
RobertL wrote:
On Mar 6, 2:57 pm, Martin Bonner wrote:
On Mar 6, 1:14 pm, The Natural Philosopher wrote:

David Hansen wrote:
On Thu, 6 Mar 2008 00:52:51 -0800 (PST) someone who may be 405 TD
Estate wrote this:-
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?
At a guess when dimmed to say 50% of the light output the lamp will
still consume something like 55W.
Bad guess then.
[snip]
I would guess, from a more educated perspective, that it's
less than 15W at 'half brightness', possibly a LOT less
Hmm. There are two (very) non-linear effects he
- a small change in input electrical power causes a large change in
output light power.
- a large change in output light power is required to cause a small
change in perceived brightness.

... and finally, the efficiency needs to include the power consumed in
the dimmer (I know it isn't just a variable resistor, but even so
there has to be *some* power loss).

But that's 15W in the lamp.

Don't forget that running the lamp at lower power also alters the
colour balance (spectrum) of the light it emits. It not just a
qestion of the intensity.

Indeed. apples and oranges.

Warm orange glow as opposed to blazing white halogen.

I would say that my experience of dimming halogens and ordinary lamps
shows that the halogens lose light more rapidly than the standard bulbs..

In what way?

Adam

Robert

Adam Aglionby wrote:
On 6 Mar, 17:51, The Natural Philosopher wrote:
RobertL wrote:
On Mar 6, 2:57 pm, Martin Bonner wrote:
On Mar 6, 1:14 pm, The Natural Philosopher wrote:
David Hansen wrote:
On Thu, 6 Mar 2008 00:52:51 -0800 (PST) someone who may be 405 TD
Estate wrote this:-
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?
At a guess when dimmed to say 50% of the light output the lamp will
still consume something like 55W.
Bad guess then.
[snip]
I would guess, from a more educated perspective, that it's
less than 15W at 'half brightness', possibly a LOT less
Hmm. There are two (very) non-linear effects he
- a small change in input electrical power causes a large change in
output light power.
- a large change in output light power is required to cause a small
change in perceived brightness.
... and finally, the efficiency needs to include the power consumed in
the dimmer (I know it isn't just a variable resistor, but even so
there has to be *some* power loss).
But that's 15W in the lamp.
Don't forget that running the lamp at lower power also alters the
colour balance (spectrum) of the light it emits. It not just a
qestion of the intensity.
Indeed. apples and oranges.

Warm orange glow as opposed to blazing white halogen.

I would say that my experience of dimming halogens and ordinary lamps
shows that the halogens lose light more rapidly than the standard bulbs..

In what way?

halogens run at half power appear a lot less bright than say
incandescents run at half power, when they look similar at full power.

I think its because the halogens are more efficient at full power due to
higher temps in the bulb..the incandescnets start from a lower level,
and fall away less.


Adam
Robert

On 6 Mar, 19:32, The Natural Philosopher wrote:
Adam Aglionby wrote:
On 6 Mar, 17:51, The Natural Philosopher wrote:
RobertL wrote:
On Mar 6, 2:57 pm, Martin Bonner wrote:
On Mar 6, 1:14 pm, The Natural Philosopher wrote:
David Hansen wrote:
On Thu, 6 Mar 2008 00:52:51 -0800 (PST) someone who may be 405 TD
Estate wrote this:-
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?
At a guess when dimmed to say 50% of the light output the lamp will
still consume something like 55W.
Bad guess then.
[snip]
I would guess, from a more educated perspective, that it's
less than 15W at 'half brightness', possibly a LOT less
Hmm. There are two (very) non-linear effects he
- a small change in input electrical power causes a large change in
output light power.
- a large change in output light power is required to cause a small
change in perceived brightness.
... and finally, the efficiency needs to include the power consumed in
the dimmer (I know it isn't just a variable resistor, but even so
there has to be *some* power loss).
But that's 15W in the lamp.
Don't forget that running the lamp at lower power also alters the
colour balance (spectrum) of the light it emits. It not just a
qestion of the intensity.
Indeed. apples and oranges.

Warm orange glow as opposed to blazing white halogen.

I would say that my experience of dimming halogens and ordinary lamps
shows that the halogens lose light more rapidly than the standard bulbs..

In what way?

halogens run at half power appear a lot less bright than say
incandescents run at half power, when they look similar at full power.

I think its because the halogens are more efficient at full power due to
higher temps in the bulb..the incandescnets start from a lower level,
and fall away less.

Think its possibly because halogen will start at a higher colour temp
than a standard incan so transistion to yellow is more marked.

Heres a couple of interesting references:

http://www.blue-room.org.uk/index.ph...#entry2026 29

http://www.blue-room.org.uk/wiki/Dimmer_Curves

Adam

Adam
Robert

On 06 Mar 2008 16:44:21 GMT someone who may be
(Andrew Gabriel) wrote this:-

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

It will be interesting to see if the usual suspects attack your
posting. Clearly your measurements must be wrong, as they do not tie
up with the usual suspects' assertions.

Looking at the times of your and their postings, if propagation is
reasonable they have had plenty of time to attack your posting, but
they have not done so yet.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On 7 Mar, 10:49, Huge wrote:
On 2008-03-06, The Natural Philosopher wrote:

I would say that my experience of dimming halogens

I though dimming halogens was A Bad Idea?

--
"Be thankful that you have a life, and forsake your vain
and presumptuous desire for a second one."
[email me at huge {at} huge (dot) org dot uk]

Your thinking of what is largely a theoretical problem, where the
internal tempertaure drops below that high enough to support the
halogen cycle, where the halogen, iodine or bromine, catches tungsten
molecules and redeposits them back on the filament.

Theory being that at low levels envelope temp isnt high enough to stop
the tungsten being deposited on the inside of the enevlope rather than
the filament , leading to lamp blackening.

Running lamps at full for few minutes is enough to counteract it, some
debate about wether its a real problem though.

Adam

On Mar 6, 4:44 pm, (Andrew Gabriel) wrote:
In article ,
405 TD Estate writes:

Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

Nearly.

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

Hey, no fair! How can we have a good theoretical discussion if you
confuse the issue with actual experimental results.
:-)

(One question: Was you measurement actually watts, or was it volt-
amps? If the power factor is significantly different between dimmed
and undimmed lights, then that would invalidate your results.)

On 7 Mar, 12:37, Martin Bonner wrote:
On Mar 6, 4:44 pm, (Andrew Gabriel) wrote:

In article ,
405 TD Estate writes:

Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

Nearly.

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

Hey, no fair! How can we have a good theoretical discussion if you
confuse the issue with actual experimental results.
:-)

(One question: Was you measurement actually watts, or was it volt-
amps? If the power factor is significantly different between dimmed
and undimmed lights, then that would invalidate your results.)

tungsten, halogen or not , is resistive load so power factor shouldn`t
come into it
--
Adam

http://www.keeplambin.co.uk

On 06 Mar 2008 16:44:21 GMT, (Andrew Gabriel) wrote:

In article ,
405 TD Estate writes:
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

Nearly.

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

Agrees with the figures at:

http://members.misty.com/don/bulb1.html#pay

where it tells all about how much light for how many hours to expect per watt,
and per applied voltage...


Thomas Prufer

Huge wrote:
On 2008-03-06, The Natural Philosopher wrote:

I would say that my experience of dimming halogens

I though dimming halogens was A Bad Idea?


It probably is. To be honest we seldom DO dim them..although we can..

Adam Aglionby wrote:
On 7 Mar, 12:37, Martin Bonner wrote:
On Mar 6, 4:44 pm, (Andrew Gabriel) wrote:

In article ,
405 TD Estate writes:
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?
Nearly.
One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.
Hey, no fair! How can we have a good theoretical discussion if you
confuse the issue with actual experimental results.
:-)

(One question: Was you measurement actually watts, or was it volt-
amps? If the power factor is significantly different between dimmed
and undimmed lights, then that would invalidate your results.)

tungsten, halogen or not , is resistive load so power factor shouldn`t
come into it
--
Adam

http://www.keeplambin.co.uk

Thats true enough. Although the resistor value is by no means constant
over the voltage range, or even over a complete mains cycle..its heating
and cooling noticeably and you can pick up the fluctuations on an
optical tacho.

On Mar 7, 1:01 pm, Adam Aglionby wrote:
On 7 Mar, 12:37, Martin Bonner wrote:



On Mar 6, 4:44 pm, (Andrew Gabriel) wrote:

In article ,
405 TD Estate writes:

Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

Nearly.

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

Hey, no fair! How can we have a good theoretical discussion if you
confuse the issue with actual experimental results.
:-)

(One question: Was you measurement actually watts, or was it volt-
amps? If the power factor is significantly different between dimmed
and undimmed lights, then that would invalidate your results.)

tungsten, halogen or not , is resistive load so power factor shouldn`t
come into it
Oh for sure. I was wondering if the dimmer introduced a power factor,
rather than reducing current.

Martin Bonner wrote:
On Mar 7, 1:01 pm, Adam Aglionby wrote:
On 7 Mar, 12:37, Martin Bonner wrote:



On Mar 6, 4:44 pm, (Andrew Gabriel) wrote:
In article ,
405 TD Estate writes:
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?
Nearly.
One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.
Hey, no fair! How can we have a good theoretical discussion if you
confuse the issue with actual experimental results.
:-)
(One question: Was you measurement actually watts, or was it volt-
amps? If the power factor is significantly different between dimmed
and undimmed lights, then that would invalidate your results.)
tungsten, halogen or not , is resistive load so power factor shouldn`t
come into it
Oh for sure. I was wondering if the dimmer introduced a power factor,
rather than reducing current.


Sort of..sort of not..

It chops the waveform. So the current is definitely out of phase with
the voltage..bein zero some of the time,and in phase the rest.

I'd hesitate to say what that means in terms of power factor though.

That is a term that is applied to liner combinations of L, C and R,
which a dimmer most certainly is not.

Andrew Gabriel wrote:

In article ,
405 TD Estate writes:
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

Nearly.

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

And for other figures the equations are he
http://www.wiki.diyfaq.org.uk/index.php?title=Lamp_Life
in the equations section.

Filament lamps are around 2% efficient, but when dimmed this
nosedives.


NT

Andrew Gabriel wrote:

In article ,
405 TD Estate writes:
Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

Nearly.

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

And for other figures the equations are he
http://www.wiki.diyfaq.org.uk/index.php?title=Lamp_Life
in the equations section.

Filament lamps are around 2% efficient, but when dimmed this
nosedives.


NT

PS the energy efficient alternative to dimmers:
http://www.wiki.diyfaq.org.uk/index....26_Switchbanks


NT

On Mar 7, 4:35 pm, Martin Bonner wrote:
On Mar 7, 1:01 pm, Adam Aglionby wrote:

On 7 Mar, 12:37, Martin Bonner wrote:

On Mar 6, 4:44 pm, (Andrew Gabriel) wrote:

In article ,
405 TD Estate writes:

Just wondered if the dimmer + light stilll consume 60w when the light
is dimmed?

Nearly.

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

Hey, no fair! How can we have a good theoretical discussion if you
confuse the issue with actual experimental results.
:-)

(One question: Was you measurement actually watts, or was it volt-
amps? If the power factor is significantly different between dimmed
and undimmed lights, then that would invalidate your results.)

tungsten, halogen or not , is resistive load so power factor shouldn`t
come into it

Oh for sure. I was wondering if the dimmer introduced a power factor,
rather than reducing current.

Good point, most dimmers have a choke in line with the load.

Adam

In article ,
Martin Bonner writes:
On Mar 7, 1:01 pm, Adam Aglionby wrote:
On 7 Mar, 12:37, Martin Bonner wrote:
On Mar 6, 4:44 pm, (Andrew Gabriel) wrote:

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

Hey, no fair! How can we have a good theoretical discussion if you
confuse the issue with actual experimental results.
:-)

(One question: Was you measurement actually watts, or was it volt-
amps? If the power factor is significantly different between dimmed
and undimmed lights, then that would invalidate your results.)

Measurement was Watts, using a true power meter.

tungsten, halogen or not , is resistive load so power factor shouldn`t
come into it

The load isn't resistive -- it's a resistance in series
with a dimmer, and will have a power factor 1 due to
the dimmer's switching action.

Oh for sure. I was wondering if the dimmer introduced a power factor,
rather than reducing current.

Yes it does.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
Adam Aglionby writes:
On 7 Mar, 10:49, Huge wrote:

I though dimming halogens was A Bad Idea?

Your thinking of what is largely a theoretical problem, where the
internal tempertaure drops below that high enough to support the
halogen cycle, where the halogen, iodine or bromine, catches tungsten
molecules and redeposits them back on the filament.

Theory being that at low levels envelope temp isnt high enough to stop
the tungsten being deposited on the inside of the enevlope rather than
the filament , leading to lamp blackening.

Also at low levels, filament evaporation reduces. In order
to get blackening, you need a lamp geometry such that the
filament can still be hot enough to cause significant
tunsgten evaporation whilst the bulb wall temperature has
dropped below 250C.

Running lamps at full for few minutes is enough to counteract it, some

I have seen some suggestions that it might, but usually
qualified with a comment along the lines of people not being
sure if the tungsten can recycle once it has condensed onto
the bulb wall.

debate about wether its a real problem though.

I've only had this happen once, with a couple of Ring 500W
halogens. I suspect a more likely explanation is that there
wasn't actually any halogen in the bulb in the first place.

Another cause of this can be a draft which causes the bulb
wall to drop below 250C during normal operating.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 06 Mar 2008 16:44:21 GMT someone who may be
(Andrew Gabriel) wrote this:-

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

Interestingly those usual suspects who claim to be very interested
in figures have not responded to your figures. I think this tells us
all we need to know.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On 8 Mar, 12:41, (Andrew Gabriel) wrote:
In article ,
Martin Bonner writes:

Oh for sure. I was wondering if the dimmer introduced a power factor,
rather than reducing current.

Yes it does.

I thought a dimmer just switched the supply by triggering at different
points in the sine wave. In which case, how can it introduce a non-
unity (ie voltage and current out of phase) power factor? The load is
still - bar a tiny effect from the coiled filament - purely
resistive.

Ian

On 6 Mar, 16:44, (Andrew Gabriel) wrote:

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

That's not surprising, really, since the light output - voltage
relationship for an incandescent bulb is extremely non-linear.
Something like (digs in memory) seventh power.

However, I'd like to know how you measured the power in this case.
Measurements on very jagged waveforms (ie very high bandwidth) are
notoriously tricky to do, as the peddlers of many perpertual motion
machines have strenuously resisted finding out.

Ian

On 6 Mar, 13:45, David Hansen wrote:

Nice try

Yes! We used to count David's "Nice try" postings over on uk.railway,
but gave up when he got to several hundred, Does he do "Excellent.
Personal abuse." here as well?

Bless him.

Ian

Sort of..sort of not..

It chops the waveform. So the current is definitely out of phase with
the voltage..bein zero some of the time,and in phase the rest.

I'd hesitate to say what that means in terms of power factor though.

That is a term that is applied to liner combinations of L, C and R,
which a dimmer most certainly is not.



Why is the current out ofm phase with the voltage?

The filament is overwhelmingly resitive so the current and votage must
be in phase. No voltage = no current however the voltade is applied.

On Mon, 10 Mar 2008 09:30:20 +0000, David Hansen
wrote:

On 06 Mar 2008 16:44:21 GMT someone who may be
(Andrew Gabriel) wrote this:-

One that I measured...
A 500W light dimmed to same output as a 40W light was consuming 300W.

Interestingly those usual suspects who claim to be very interested
in figures have not responded to your figures. I think this tells us
all we need to know.


What are you talking about? If you are going on about "usual suspects"
why don't you name them instead of trying to appear all knowing.


As far as the figures you copied go why should they be challenged? So
far in this topic no one seems to have taken into account that the
filament resitance drops if the temperature falls, and as less light
output = lower temperature the current will increase. So its possible
that a 500w light working at 40w will consume nearly full current.
Measurments would show this.

On Mon, 10 Mar 2008 03:35:00 -0700 (PDT), The Real Doctor
wrote:

However, I'd like to know how you measured the power in this case.
Measurements on very jagged waveforms (ie very high bandwidth) are
notoriously tricky to do, as the peddlers of many perpertual motion
machines have strenuously resisted finding out.

Ah, but this depends on what one wants to do!

One thing to measure accurately for purposes of knowledge, scientific
advancement, or the satisfaction of curiosity, another to devise a waveform
which will allow power to be transferred without a given power meter indicating
accordingly.

That is, there's two ways one can interpret "free power": either violate the
laws of thermodynamics, or others...

ISTR some very modern rollercoaster -- using linear motors and very high surge
currents -- registered surprisingly little electricity use. Eventually they
adapted the meters accordingly.



Thomas Prufer

On Mon, 10 Mar 2008 10:46:02 +0000, Chris Charles
wrote:



Sort of..sort of not..

It chops the waveform. So the current is definitely out of phase with
the voltage..bein zero some of the time,and in phase the rest.

I'd hesitate to say what that means in terms of power factor though.

That is a term that is applied to liner combinations of L, C and R,
which a dimmer most certainly is not.



Why is the current out ofm phase with the voltage?

The filament is overwhelmingly resitive so the current and votage must
be in phase.

Even if the current is not switched on until it's 90 degrees out of
phase ?

No voltage = no current however the voltade is applied.

That's so inaccurate as to be no use whatsoever.

DG

On 10 Mar, 11:11, Huge wrote:
On 2008-03-10, The Real Doctor wrote:

On 6 Mar, 13:45, David Hansen wrote:

Nice try

Yes! We used to count David's "Nice try" postings over on uk.railway,
but gave up when he got to several hundred, Does he do "Excellent.
Personal abuse." here as well?

All the time. And very wearisome it is, too.

"Some of us are asking questions about the proportionality of the
police response"

Ian

On 10 Mar, 12:12, Derek Geldard wrote:
On Mon, 10 Mar 2008 10:46:02 +0000, Chris Charles
wrote:

The filament is overwhelmingly resitive so the current and votage must
be in phase.

Even if the current is not switched on until it's 90 degrees out of
phase ?

I think you are getting a little confused here. Sketch the voltage
waveform produced by a dimmer. Now sketch the current waveform you
would expect if that voltage waveform went into a purely resistive
load. Hint: I(t) = V(t)/R.

Ian