Lights Again

Dave said:

Anyway I am looking at very basic lights in case I happen to be out in the
dark but wondered what the difference in brightness is if any between
kryptonite and halogen bulbs.

"Kryptonite" will be some sort of trade name, I'd think, it's not a
generic type AFAICT.

Quoted message said:

Both appear to claim to be brighter than "ordinary/standard" bulbs
(forgetting any discussion about LEDS) - not sure what they are either.

Quite so: halogen bulbs /are/ brighter than "normal" bulbs, but consume
more power.

However, LED lamps are probably a better way forward these days. They
run for longer and they're more robust (no bulbs to blow). Not all are
created equal, of course, but the good ones are very good, and there are
some nifty lightweight clip-ons that will see you home.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

Dave said:

I know there is a lot of talk at the moment about lights - perhaps the time
of year.

Anyway I am looking at very basic lights in case I happen to be out in the
dark but wondered what the difference in brightness is if any between
kryptonite and halogen bulbs.

Both appear to claim to be brighter than "ordinary/standard" bulbs
(forgetting any discussion about LEDS) - not sure what they are either.

Any ideas.

Thanks
DaveB

Halogen lamps can be more efficient than standard lamps because a
reaction between the tungsten filament and the halogen gas allows the
filament to burn hotter.
This is because without that reaction the tungsten evaporates at
hot-spots and becomes thinner. This thinning makes the hot-spot hotter
since it increases the resistance there, and so the process continues
until the bulb fails. With the Halogen (Chlorine or bromine) in the bulb
the evaporated tungsten forms compunds that acually deposit tungsten on
those hot-spots instead of condensing it on the glass.
Since the element is hotter, more of the radiation emmitted is in the
visible region and it is this that increases the efficiency.
I'm less sure about what happens in the krypton bulb. I think that the
job of the low pressure inert gas is to inhibit conduction to the
envelope, allowing smaller bulbs to be made, with hotter filaments. My
guess is that this might be connected to the mean free path of gas
molecules leaving the surface of the filament.

Both of these efficiency improvements are marginal compared to the
difference between incandescent bulbs and LEDs

--
Roger Thorpe

My email address is spamtrapped. You can work it out!

Roger Thorpe said the following on 29/09/2006 14:10:

Quoted message said:

Halogen lamps can be more efficient than standard lamps because a
reaction between the tungsten filament and the halogen gas allows the
filament to burn hotter.
This is because without that reaction the tungsten evaporates at
hot-spots and becomes thinner. This thinning makes the hot-spot hotter
since it increases the resistance there, and so the process continues
until the bulb fails. With the Halogen (Chlorine or bromine) in the bulb
the evaporated tungsten forms compunds that acually deposit tungsten on
those hot-spots instead of condensing it on the glass.
Since the element is hotter, more of the radiation emmitted is in the
visible region and it is this that increases the efficiency.
I'm less sure about what happens in the krypton bulb. I think that the
job of the low pressure inert gas is to inhibit conduction to the
envelope, allowing smaller bulbs to be made, with hotter filaments. My
guess is that this might be connected to the mean free path of gas
molecules leaving the surface of the filament.

I think that means that if you turn it on, it lights up :-)

--
Paul Boyd
http://www.paul-boyd.co.uk/

Paul Boyd said:

Roger Thorpe said the following on 29/09/2006 14:10:

Quoted message said:

Halogen lamps can be more efficient than standard lamps because a
reaction between the tungsten filament and the halogen gas allows the
filament to burn hotter.
This is because without that reaction the tungsten evaporates at
hot-spots and becomes thinner. This thinning makes the hot-spot hotter
since it increases the resistance there, and so the process continues
until the bulb fails. With the Halogen (Chlorine or bromine) in the
bulb the evaporated tungsten forms compunds that acually deposit
tungsten on those hot-spots instead of condensing it on the glass.
Since the element is hotter, more of the radiation emmitted is in the
visible region and it is this that increases the efficiency.
I'm less sure about what happens in the krypton bulb. I think that the
job of the low pressure inert gas is to inhibit conduction to the
envelope, allowing smaller bulbs to be made, with hotter filaments. My
guess is that this might be connected to the mean free path of gas
molecules leaving the surface of the filament.

I think that means that if you turn it on, it lights up :-)

I can't believe that I wrote such an incomprehensible answer. It made
sense when it left my head!

--
Roger Thorpe

My email address is spamtrapped. You can work it out!

Quoted message said:

Halogen lamps can be more efficient than standard lamps because a
reaction between the tungsten filament and the halogen gas allows the
filament to burn hotter.

Both of these efficiency improvements are marginal compared to the
difference between incandescent bulbs and LEDs

I used to think that LEDs were much more efficient than halogen, but
reading around a bit I'm not so sure. Sure, you can make very low
power LEDs, but to get the same light output as a halogen bulb I
believe the power input required is similar.
One big advantages of LEDs is that they last virtually forever,
especially compared to a filament bulb that's being bumped around on a
bike.
Another is that they can be made to flash rapidly, and when they're in
the "off" part of the flashing cycle they obviously don't consume power.

POHB said:

Quoted message said:

Halogen lamps can be more efficient than standard lamps because a
reaction between the tungsten filament and the halogen gas allows the
filament to burn hotter.

Both of these efficiency improvements are marginal compared to the
difference between incandescent bulbs and LEDs

I used to think that LEDs were much more efficient than halogen, but
reading around a bit I'm not so sure. Sure, you can make very low
power LEDs, but to get the same light output as a halogen bulb I
believe the power input required is similar.
One big advantages of LEDs is that they last virtually forever,
especially compared to a filament bulb that's being bumped around on a
bike.
Another is that they can be made to flash rapidly, and when they're in
the "off" part of the flashing cycle they obviously don't consume power.

My take on the LEDs vs 'standard' bulbs:

Bulbs so *you* can see where you're going. LEDs so *everyone else* can
see where you're going.

Wheelist

On 2006-09-29, Wheelist <[email hidden]> wrote:

*snip*

Quoted message said:

My take on the LEDs vs 'standard' bulbs:

Bulbs so *you* can see where you're going. LEDs so *everyone else* can
see where you're going.

Roughly, yes but it's worth noting that bulbs tend to leak light in all
directions (despite optics) whereas LEDs are quite directional. So to be
seen from "suboptimal" angles a bulb light is probably best. Obviously there
are some nifty LED lights that have their LEDs pointing in various different
ways which are good for visibility.

I do like LED flashing modes as a supplement to a steady lamp though. What'd
be really nice would be dynamo-powered head/tail lights that would flash the
standlight LED when the main bulb was illuminated, and switch it to steady
when the bike stopped (as normal).

Regards,

-david

Wheelist said:

My take on the LEDs vs 'standard' bulbs:

Bulbs so *you* can see where you're going. LEDs so *everyone else* can
see where you're going.

That used to be the case a couple of years ago, but things have moved on
with the best LEDs competing with halogen bulbs.

In a test in a recent copy of VeloVision Peter Eland tested the old,
tried and trusted halogen B&M Lumotec Oval against its new LED
stablemate, and found the LED version considerably better in most
respects (it is more expensive, mind).

If you want really, /really/ serious lighting (I'm thinking of high
power sets designed for night-time MTB work with 3 figure price tags)
then LEDs aren't there yet, but they're now certainly good enough for
road use at anything other than mad velocities on unlit roads.

I've just changed my Lumotec Oval for the LED version, but have only
ridden it down the lane and back to make sure I'd plumbed it in
properly, not enough for a proper test. But on that showing I was quite
impressed.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

Peter Clinch said:

If you want really, /really/ serious lighting (I'm thinking of high
power sets designed for night-time MTB work with 3 figure price tags)
then LEDs aren't there yet, but they're now certainly good enough for
road use at anything other than mad velocities on unlit roads.

I think even that isn't true any more:

http://www.use1.com/exposure/products/exp_enduro/index.php

That 300 pounds worth of light mind.

Arthur

--
Arthur Clune

Wheelist said:

Bulbs so *you* can see where you're going. LEDs so *everyone else* can
see where you're going.

I suspect you're thinking of traditional 5mm LEDs. These generally don't run
at more than ~0.1 watt each because it's difficult to dissipate the excess
heat. Modern high power LEDs can run at up to 5 watts per LED, but require
careful heatsinking and power regulation. They are not much more efficient
than halogen bulbs that are driven hard, but have other significant
advantages such as longer lifetime and dimming without loosing efficiency.
I suspect halogen bike lights will be difficult to find within a few years.

Anthony

"Dave" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I know there is a lot of talk at the moment about lights - perhaps the

time

Quoted message said:

of year.

Anyway I am looking at very basic lights in case I happen to be out in the
dark but wondered what the difference in brightness is if any between
kryptonite and halogen bulbs.

Both appear to claim to be brighter than "ordinary/standard" bulbs
(forgetting any discussion about LEDS) - not sure what they are either.

Any ideas.

Thanks
DaveB

Not sure that Superman would be too keen on Kryptonite bulbs.
(OK - I`ll get me coat)

Colin N.

Peter Clinch said:

If you want really, /really/ serious lighting (I'm thinking of high
power sets designed for night-time MTB work with 3 figure price tags)
then LEDs aren't there yet,

Indeed, you want halide (gas-discharge) bulbs for that...

regards, Ian SMith
--
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