Could anyboby explain why the 12v 50w halogen lamps I have in my kitchen
appear brighter than the 240v 50w halogen Par 20 lamps I have fitted in the
lounge?

"Trevor Smith" wrote in message
...
Could anyboby explain why the 12v 50w halogen lamps I have in my kitchen
appear brighter than the 240v 50w halogen Par 20 lamps I have fitted in
the
lounge?

Higher colour value. Whiter light. Dichrioc prismatic diffusion.

"BigWallop" wrote in message
om...

"Trevor Smith" wrote in message
...
Could anyboby explain why the 12v 50w halogen lamps I have in my kitchen
appear brighter than the 240v 50w halogen Par 20 lamps I have fitted in
the
lounge?

Higher colour value. Whiter light. Dichrioc prismatic diffusion.



********

Its all to do with the filament size. On a 12V lamp the filament guage is
much lower and the filament winding diameter is larger, and there are fewer
turns so:-

1) More exposed surface area so more light can escape from the confines of
the filament and

2) A 12V filament is far more robust and will last longer

Richard Head wrote:
"BigWallop" wrote in message
om...
"Trevor Smith" wrote in message
...
Could anyboby explain why the 12v 50w halogen lamps I have in my kitchen
appear brighter than the 240v 50w halogen Par 20 lamps I have fitted in
the
lounge?

Higher colour value. Whiter light. Dichrioc prismatic diffusion.



********

Its all to do with the filament size. On a 12V lamp the filament guage is
much lower and the filament winding diameter is larger, and there are fewer
turns so:-

1) More exposed surface area so more light can escape from the confines of
the filament and

2) A 12V filament is far more robust and will last longer


I don't get that.

In both cases 50W of heat and light is being emitted by the lamp.

So the issues are surely:

o The proportions of heat to light;

o The colour.

The colour depends largely on temperature, and at a higher temperature
there will be more light/less heat - so not wholly independent.

(I have not even tried to work it out, but while the 12V is a thicker
filament, isn't the 240V one longer? So which really does have the
larger surface area? Or effective surface area?)

Of course, if they are not running at exactly the specified voltage,
then all bets are off!

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

Richard Head wrote:

"BigWallop" wrote in message
om...
"Trevor Smith" wrote in message
...
Could anyboby explain why the 12v 50w halogen lamps I have in my kitchen
appear brighter than the 240v 50w halogen Par 20 lamps I have fitted in
the
lounge?

Higher colour value. Whiter light. Dichrioc prismatic diffusion.



********

Ah, a charm school graduate I see...

I expect by "colour value" BW probably meant CRI, which is indeed higher
for a 12V halogen, and the light is certainly whiter. Many 12V lamps
also have dichroic reflectors that also enhances the whiteness of the
light by allowing some of the redder end of the spectra to escape out of
the back of the bulb...

So I don't think you can really say "********" unless it was of course a
prelude to what you were about to follow it with.

Its all to do with the filament size. On a 12V lamp the filament guage is
much lower and the filament winding diameter is larger, and there are fewer
turns so:-

1) More exposed surface area so more light can escape from the confines of
the filament and

Not that convincing really, also missing the more relevant point that
the more robust filament can be run at a higher temperature which yields
the aforementioned whiter light, and an increase in efficiency (i.e.
more lumens per watt) which is why it not only appears brighter for the
same power consumption, but in reality *is* brighter.

2) A 12V filament is far more robust and will last longer

true, but not relevant to the question

--
Cheers,

John.

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\================================================= ================/

"John Rumm" wrote in message
et...
Richard Head wrote:

"BigWallop" wrote in message
om...
"Trevor Smith" wrote in message
...
Could anyboby explain why the 12v 50w halogen lamps I have in my
kitchen
appear brighter than the 240v 50w halogen Par 20 lamps I have fitted in
the
lounge?

Higher colour value. Whiter light. Dichrioc prismatic diffusion.



********

Ah, a charm school graduate I see...

I expect by "colour value" BW probably meant CRI, which is indeed higher
for a 12V halogen, and the light is certainly whiter. Many 12V lamps also
have dichroic reflectors that also enhances the whiteness of the light by
allowing some of the redder end of the spectra to escape out of the back
of the bulb...

So I don't think you can really say "********" unless it was of course a
prelude to what you were about to follow it with.

Its all to do with the filament size. On a 12V lamp the filament guage is
much lower and the filament winding diameter is larger, and there are
fewer turns so:-

1) More exposed surface area so more light can escape from the confines
of the filament and

Not that convincing really, also missing the more relevant point that the
more robust filament can be run at a higher temperature which yields the
aforementioned whiter light, and an increase in efficiency (i.e. more
lumens per watt) which is why it not only appears brighter for the same
power consumption, but in reality *is* brighter.

2) A 12V filament is far more robust and will last longer

true, but not relevant to the question

--
Cheers,

John.

/================================================== ===============\
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|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Thankyou for the replies, I didn't think the dichrioc reflector had much to
do with it as both lamps have them but when you look at the capsual the 12v
one is a lot brighter. I just done a bit of quick maths and the 12v 50w lamp
draws 4.16 amps and the 240v 50w lamp draws 0.208 amps so I gather more amps
= more light.

Trevor Smith wrote:
Thankyou for the replies, I didn't think the dichrioc reflector had much to
do with it as both lamps have them but when you look at the capsual the 12v
one is a lot brighter. I just done a bit of quick maths and the 12v 50w lamp
draws 4.16 amps and the 240v 50w lamp draws 0.208 amps so I gather more amps
= more light.



I don't know the correct answer, but that definitely isn't it. (I'd
_guess_ the 12v is running at a higher temperature, which gives better
efficiency but shorter life)

Andy

Trevor Smith wrote:

Thankyou for the replies, I didn't think the dichrioc reflector had much to
do with it as both lamps have them but when you look at the capsual the 12v

The mains halogens typically don't have dichroic reflectors and use
ordinary opaque aluminium "silvering". That is also why they project
more heat forwards.

one is a lot brighter. I just done a bit of quick maths and the 12v 50w lamp
draws 4.16 amps and the 240v 50w lamp draws 0.208 amps so I gather more amps
= more light.

Partly, more amps in this case translate to a higher filament
temperature which gives more light.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm brought next idea :
Partly, more amps in this case translate to a higher filament temperature
which gives more light.

Plus the fact that lower voltage means a shorter and more compact
filament, which enables a better focus of the beam.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

BigWallop wrote:
"Trevor Smith" wrote in message
...
Could anyboby explain why the 12v 50w halogen lamps I have in my kitchen
appear brighter than the 240v 50w halogen Par 20 lamps I have fitted in
the
lounge?

Higher colour value. Whiter light. Dichrioc prismatic diffusion.



Actually its simpler:

Bigger filament=runs hotter without melting = higher colour temperature=
whiter light.

Andy Champ wrote:
Trevor Smith wrote:
Thankyou for the replies, I didn't think the dichrioc reflector had
much to do with it as both lamps have them but when you look at the
capsual the 12v one is a lot brighter. I just done a bit of quick
maths and the 12v 50w lamp draws 4.16 amps and the 240v 50w lamp draws
0.208 amps so I gather more amps = more light.


I don't know the correct answer, but that definitely isn't it. (I'd
_guess_ the 12v is running at a higher temperature, which gives better
efficiency but shorter life)

Andy
half right. More efficiency, but longer life. I suppose the element,
being thicker, abardes away more slowly.

But its a fact. 12v lamps outlast 240v ones by about 10:1

In article ,
The Natural Philosopher wrote:
But its a fact. 12v lamps outlast 240v ones by about 10:1

Far too broad a statement. Lamps last according to design and use. The
most common 12 volts bulbs we see are in cars - and they certainly don't
last 10 times longer than 240v. Nor do normal LV domestic ones.

--
*He who laughs last has just realised the joke.

Dave Plowman London SW
To e-mail, change noise into sound.

On Nov 17, 6:03*pm, John Rumm wrote:
Richard Head wrote:
"BigWallop" wrote in message
. com...
"Trevor Smith" wrote in message
...
Could anyboby explain why the 12v 50w halogen lamps I have in my kitchen
appear brighter than the 240v 50w halogen Par 20 lamps I have fitted in
the
lounge?

Higher colour value. *Whiter light. *Dichrioc prismatic diffusion.

********

Ah, a charm school graduate I see...

Well, with a name like Dick Head...


MBQ

Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
But its a fact. 12v lamps outlast 240v ones by about 10:1

Far too broad a statement. Lamps last according to design and use. The
most common 12 volts bulbs we see are in cars - and they certainly don't
last 10 times longer than 240v. Nor do normal LV domestic ones.

My LVs do.

I assumed we were talking halogens.
12v 50W halogen replacement frequency is about 10% of 240v 50W halogen.

In article ,
The Natural Philosopher wrote:
Far too broad a statement. Lamps last according to design and use. The
most common 12 volts bulbs we see are in cars - and they certainly
don't last 10 times longer than 240v. Nor do normal LV domestic ones.

My LVs do.

I assumed we were talking halogens.
12v 50W halogen replacement frequency is about 10% of 240v 50W halogen.

Not so here. By far the longest lived lamps out of all I have are PAR 38s.
The halogen R80s seem pretty good too.

--
*We have enough youth, how about a fountain of Smart?

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ,
The Natural Philosopher wrote:
But its a fact. 12v lamps outlast 240v ones by about 10:1

Far too broad a statement. Lamps last according to design and use. The
most common 12 volts bulbs we see are in cars - and they certainly don't
last 10 times longer than 240v. Nor do normal LV domestic ones.

They probably last longer due to the electronic transformer having soft
start.

On 18 Nov, 15:29, "dennis@home" wrote:
"Dave Plowman (News)" wrote in ...

In article ,
* The Natural Philosopher wrote:
But its a fact. 12v lamps outlast 240v ones by about 10:1

Far too broad a statement. Lamps last according to design and use. The
most common 12 volts bulbs we see are in cars - and they certainly don't
last 10 times longer than 240v. Nor do normal LV domestic ones.

They probably last longer due to the electronic transformer having soft
start.

I`ve got some good quality Osram LV MR16s run off a Mode ,soft start,
electronic trafo gone past their 12th Birthday in a frequently used
bathroom.

Adam

In article ,
dennis@home wrote:


"Dave Plowman (News)" wrote in message
...
In article ,
The Natural Philosopher wrote:
But its a fact. 12v lamps outlast 240v ones by about 10:1

Far too broad a statement. Lamps last according to design and use. The
most common 12 volts bulbs we see are in cars - and they certainly
don't last 10 times longer than 240v. Nor do normal LV domestic ones.

They probably last longer due to the electronic transformer having soft
start.

You can get soft start dimmers for 240v too.

--
*If tennis elbow is painful, imagine suffering with tennis balls *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) coughed up some electrons that declared:

In article ,
dennis@home wrote:


"Dave Plowman (News)" wrote in message
...
In article ,
The Natural Philosopher wrote:
But its a fact. 12v lamps outlast 240v ones by about 10:1

Far too broad a statement. Lamps last according to design and use. The
most common 12 volts bulbs we see are in cars - and they certainly
don't last 10 times longer than 240v. Nor do normal LV domestic ones.

They probably last longer due to the electronic transformer having soft
start.

You can get soft start dimmers for 240v too.


GET Ultimate touch dimmers are soft start, because I've just tried one

Cheers

Tim

Tim S wrote:
Dave Plowman (News) coughed up some electrons that declared:

In article ,
dennis@home wrote:


"Dave Plowman (News)" wrote in message
...
In article ,
The Natural Philosopher wrote:
But its a fact. 12v lamps outlast 240v ones by about 10:1
Far too broad a statement. Lamps last according to design and use. The
most common 12 volts bulbs we see are in cars - and they certainly
don't last 10 times longer than 240v. Nor do normal LV domestic ones.
They probably last longer due to the electronic transformer having soft
start.
You can get soft start dimmers for 240v too.


GET Ultimate touch dimmers are soft start, because I've just tried one

Same for the master / slave jobbies (varilight IIRC) that TLC do.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
"Trevor Smith" writes:
Could anyboby explain why the 12v 50w halogen lamps I have in my kitchen
appear brighter than the 240v 50w halogen Par 20 lamps I have fitted in the
lounge?

"Brighter" could mean many things (gives off more light,
illuminates the target object better, illuminates the room
better, has a higher intensity beam centre, etc). You
weren't specific.

A 12V filament lamp of that power is significantly more efficient
than a 240V filament of that power. If you want to design the
most efficient filament to operate at 100W, it turns out to be
one designed to run on about 55V. (It's not going to be very
different for 50W.) 12V is nearer to this peak efficiency than
240V. That's also the reason a US 100W 120V lamp gives off more
light than a UK 100W 240V lamp.

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

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "Trevor Smith"
saying something like:

Could anyboby explain why the 12v 50w halogen lamps I have in my kitchen
appear brighter than the 240v 50w halogen Par 20 lamps I have fitted in the
lounge?

The packets didn't mention Xenon filling by any chance?