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Guest

On Oct 7, 5:00 pm, z <gzuck...@snail-mail.net> wrote:
[quote]On Sep 11, 1:44 pm, cabraha...@msn.com wrote:

On Sep 1, 12:41 pm, exxos...@yahoo.co.uk wrote:

Hi all,

While messing with buck/boost circuits I had some thoughts which don>t
hold up in real tests....

A simple example (aside from losses) is that if transfer energy from
say 10V 10uF into 1uF the voltage will increase to preserve the
charge.

Now, in my circuit, I charge 25V 1,000uF capacitor and charge a 10uH
inductor. When the switch turns off, all the energy should be in the
10uH inductance. So if I have a 100pF capacitor, then the voltage
should be like 100,000volts according to my workings out.

Now I ran a computer simulation on this, at best I can only obtain
12KV on the 100pF. So most of the energy is lost in switching losses I
assume.

In realworld tests, I end up with less voltage than I started out
with, So I am trying to find out why ?

I know charging 22uH inductor at 100khz can be used as a buck/boost
supply, I built a simple 12V to 30V inverter, can switch 10amps
easily. Though I am not running at 100khz, only 100hz. Though the
current pulse rises to something like 500amps over 500uS.

I am not sure I follow all this exactly, Or even if it will work ?
AFAIK, The longer a inductor has current pumped across it the more
charge it obtains over time. So at turn off, all the energy given to a
coil is recovered. It works well, even with my simple buck/boost
circuit.

So I am slightly confused as to why pushing 500A into a coil has no
effect. I can only assume I have a huge loss somewhere, Or I do not
follow the idea correctly ?

Cheers,
Chris

You need to aquaint yourself with the buck-boost topology and theory
of its operation. If you go to TI>s web site and download their buck-
boost app note no. SLVA059, studying this thoroughly, you will
understand why.

In a nutshell, the 1000 uf input capacitor did not transfer ALL of its
energy to the inductor. The output voltage is related to the input
voltage and the duty cycle as follows:

Vout = Vin * (D/(1-D)) not accounting for losses.

The energy transferred to the inductor is half the inductance times
the difference between the square of the final current and square of
the original current. This is determined by the voltage across said
inductor multiplied by the on time. During the power switch off time,
the volt-seconds must equal that of the on time. The app note covers
this. The value of the input capacitor does not determine the output
voltage. The same goes for the output cap value. The values of both
caps, however, are important regarding ripple. noise, and transient
response.

Did I help? BR.- Hide quoted text -

- Show quoted text -

i haven>t gotten the whole detail, but you seem to start with a bit of
a misunderstanding which i will now endeavor to correct:

you charge a capacitor by loading a voltage into it, then open
circuiting it; but, an inductor being essentially the opposite, you
charge it by loading a current into it and shortcircuiting it; whereas
a charged capacitor holds its energy in the electric field with zero
current, a charged inductor holds its energy in the magnetic field,
with zero voltage. If you short circuit a capacitor it loses its
charge, if you open circuit an inductor it loses its current. In real
life, the series resistance in the inductor windings decays the
charged current a lot more quickly than the leakage resistance in the
capacitor decays the charged voltage.- Hide quoted text -

- Show quoted text -
[/quote]
So where is my misunderstanding? What have you "corrected"? I know
the operation of inductors and capacitors. I looked over my previous
post and found nothing in need of correction. What specific point
have I made that you take issue with?

I>ve been developing buck-boost converters and SMPS for more than 2
decades, and have 2 published papers on SMPS in world wide peer
reviewed magazines. I>ve been a regular attendee at the Unitrode/TI
power seminars since the mid-1980>s. I know my power supplies. I
referred you to a TI app note so that you can acquaint yourself with
the basics of buck-boost operation. Reading it is my advice to you.

Are you really looking for help. or someone to argue with? I offer
you free expert advice, and then I get a lecture on L and C basics?
Best regards.

Claude

Eeyore · Guest

cabraham01@msn.com wrote:

[quote]Are you really looking for help. or someone to argue with? I offer
you free expert advice, and then I get a lecture on L and C basics?
[/quote]
This group is full of loonies.

I>m considering doing a bulk abuse report to keep them out of the sci or energy
groups.

Graham

Gaetan Mailloux · Guest

Gaetan Mailloux (ba221@FreeNet.Carleton.CA) writes:
[quote]Hello

Anybody have those cds photoresistors; NSL-7540 and NSL7550 ?

Thank

Gaetan
[/quote]

Hello

It can also be those two other CDS photoresistors who can perfectly do the
job;

NSL-5160 , and , NSL-5170

Thank

Bye

Gaetan

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Wim Lewis · Guest

In article <gdnpfa$cpk$1@registered.motzarella.org>,
Don Bruder <dakidd@sonic.net> wrote:
[quote]I can>t see a halogen bulb being anything but a purely physical danger
due to the sharp edges typically found on broken glass. I can think of
no chemical hazard at all.
[/quote]
The halogen itself is probably bad for you. But there>s not much of
it, it>ll have escaped once the bulb is broken, and it>s not an
accumulating poison like mercury or lead. I have a hard time coming
up with a scenario in which it would be an actual danger.

I assume the warnings about the dangers of broken bulbs have to do with
the use of mercury and beryllium (both pretty toxic) in fluorescents.

Thing is, the OP mentions the marking "5 mg Hg" on the broken bulb.
Maybe it isn>t actually a halogen?

--
Wim Lewis <wiml@hhhh.org>, Seattle, WA, USA. PGP keyID 27F772C1
"We learn from history that we do not learn from history." -Hegel

Don Klipstein · Guest

In article <4901be75$0$15857$e4fe514c@dreader26.news.xs4all.nl>, petrus
bitbyter wrote:
[quote]
"Sjouke Burry" <burrynulnulfour@ppllaanneett.nnlll> schreef in bericht
news:4901a05b$0$27235$ba620dc5@text.nova.planet.nl...
Jeff Layman wrote:
Switches intended for use with lighting (timers, PIR, photocells) warn
against use with CFLs, and state that filament lamps should be used.
Why? It shouldn>t make any difference whether a relay or triac (with ZCD
circuitry) is used to switch the lamp on/off the lamp. I>ve used a couple
of timers with a CFL for years without any apparent problem.

And if there is a problem I am unaware of, what will we be able to use
when the filament lamps are taken off the market in the EU in a few years
time?

A CFL starts with a huge current pulse charging the main
supply cap inside.
Not all switches like that.

Maybe but I doubt it. Cold filament lamps start with a high inrush peak
current too.
[/quote]
Cold filaments draw peak current something like 20 times their RMS
current, depending on when in an AC half-cycle they are switched on. CFLs
often draw much more than that, with peak current limited by line
impedance and the impedance of the bridge rectifier, filter capacitor, and
a small RF choke. Sounds to me like an ohm or two.

[quote]For all I can imagine switching off a CFL with a classic
ballast may cause problems. Switching on/off modern "energy saving" CFLs
should not do worse then filament bulbs. Dimmers are different and I think
the warning not to use CFLs in timers and the like comes from that dimmers.
The manufacturers simply stay on the safe side to avoid claims.
[/quote]
Probably a good idea for consumers also. I would not like to have to
explain to a fire insurance company why I was using electrical equipment
other than as directed, even if the fire started for a reason other than
the fact that the equipment was being used in a way that was warned
against.

- Don Klipstein (don@misty.com)

IanM · Guest

Don Klipstein wrote:
[quote]petrus bitbyter wrote:

"Sjouke Burry" wrote:

Jeff Layman wrote:

Switches intended for use with lighting (timers, PIR, photocells) warn
against use with CFLs, and state that filament lamps should be used.
Why? It shouldn>t make any difference whether a relay or triac (with ZCD
circuitry) is used to switch the lamp on/off the lamp. I>ve used a couple
of timers with a CFL for years without any apparent problem.

And if there is a problem I am unaware of, what will we be able to use
when the filament lamps are taken off the market in the EU in a few years
time?

A CFL starts with a huge current pulse charging the main
supply cap inside.
Not all switches like that.

Maybe but I doubt it. Cold filament lamps start with a high inrush peak
current too.

Cold filaments draw peak current something like 20 times their RMS
current, depending on when in an AC half-cycle they are switched on. CFLs
often draw much more than that, with peak current limited by line
impedance and the impedance of the bridge rectifier, filter capacitor, and
a small RF choke. Sounds to me like an ohm or two.

For all I can imagine switching off a CFL with a classic
ballast may cause problems. Switching on/off modern "energy saving" CFLs
should not do worse then filament bulbs. Dimmers are different and I think
the warning not to use CFLs in timers and the like comes from that dimmers.
The manufacturers simply stay on the safe side to avoid claims.

Probably a good idea for consumers also. I would not like to have to
explain to a fire insurance company why I was using electrical equipment
other than as directed, even if the fire started for a reason other than
the fact that the equipment was being used in a way that was warned
against.

[/quote]
There is also the observed fact that for many CFLs, any small leakage
current through or across the switch will cause the CFL>s reservoir
capacitor to charge until there is enough voltage for the inverter
circuit to start, thus the lamp tends to flash. I have seen this happen
with just the capacitance between two parallel wires (in the same cable)
in stairway lighting circuits. I wonder what effect on the safety and
reliability of the lamp many thousands of repeated starts a day has?

Failure modes for a normal lightbulb tend to be short (often with a
momentary arc) - usually protected by an integral fuse, open, and
envelope rupture. In a normal operating environment, none are
particularly hazardous. Perhaps CFLs have a failure mode that involves
dangerous overheating on startup so require a human present to check
they have turned on safely?

Jeff Layman · Guest

IanM wrote:
[quote]Don Klipstein wrote:
petrus bitbyter wrote:

"Sjouke Burry" wrote:

Jeff Layman wrote:

Switches intended for use with lighting (timers, PIR, photocells)
warn against use with CFLs, and state that filament lamps should
be used. Why? It shouldn>t make any difference whether a relay or
triac (with ZCD circuitry) is used to switch the lamp on/off the
lamp. I>ve used a couple of timers with a CFL for years without
any apparent problem. And if there is a problem I am unaware of, what
will we be able
to use when the filament lamps are taken off the market in the EU
in a few years time?

A CFL starts with a huge current pulse charging the main
supply cap inside.
Not all switches like that.

Maybe but I doubt it. Cold filament lamps start with a high inrush
peak current too.

Cold filaments draw peak current something like 20 times their RMS
current, depending on when in an AC half-cycle they are switched on.
CFLs often draw much more than that, with peak current limited by
line impedance and the impedance of the bridge rectifier, filter
capacitor, and a small RF choke. Sounds to me like an ohm or two.

For all I can imagine switching off a CFL with a classic
ballast may cause problems. Switching on/off modern "energy saving"
CFLs should not do worse then filament bulbs. Dimmers are different
and I think the warning not to use CFLs in timers and the like
comes from that dimmers. The manufacturers simply stay on the safe
side to avoid claims.

Probably a good idea for consumers also. I would not like to have
to explain to a fire insurance company why I was using electrical
equipment other than as directed, even if the fire started for a
reason other than the fact that the equipment was being used in a
way that was warned against.

There is also the observed fact that for many CFLs, any small leakage
current through or across the switch will cause the CFL>s reservoir
capacitor to charge until there is enough voltage for the inverter
circuit to start, thus the lamp tends to flash. I have seen this
happen with just the capacitance between two parallel wires (in the
same cable) in stairway lighting circuits. I wonder what effect on
the safety and reliability of the lamp many thousands of repeated
starts a day has?
Failure modes for a normal lightbulb tend to be short (often with a
momentary arc) - usually protected by an integral fuse, open, and
envelope rupture. In a normal operating environment, none are
particularly hazardous. Perhaps CFLs have a failure mode that involves
dangerous overheating on startup so require a human present to check
they have turned on safely?
[/quote]
Some interesting comments.

I>m not sure about the peak current taken by a CFL at switch-on, but
according to the circuits at
http://www.pavouk.org/hw/lamp/en_index.html#sinecan5, it can>t be more than
a 1N4007 can take - 30A. Looking at various triac specs, the peak current
allowed is around 5 - 10 times the average (for an 8A triac, it seems to be
around 65A). Most electronic timers claim to be able to work with 13A
loads, so they should be able to take a peak of around 100A.

Out of interest once I connected a CFL up to a standard light dimmer. Waste
of time - the CFL was basically on or off, and flickered badly at any
intermediate setting.

--
Jeff

Peter Hucker · Guest

On Tue, 28 Oct 2008 10:27:53 -0000, Jeff Layman <jmlayman@invalid.invalid> wrote:

[quote]IanM wrote:
Don Klipstein wrote:
petrus bitbyter wrote:

"Sjouke Burry" wrote:

Jeff Layman wrote:

Switches intended for use with lighting (timers, PIR, photocells)
warn against use with CFLs, and state that filament lamps should
be used. Why? It shouldn>t make any difference whether a relay or
triac (with ZCD circuitry) is used to switch the lamp on/off the
lamp. I>ve used a couple of timers with a CFL for years without
any apparent problem. And if there is a problem I am unaware of, what
will we be able
to use when the filament lamps are taken off the market in the EU
in a few years time?

A CFL starts with a huge current pulse charging the main
supply cap inside.
Not all switches like that.

Maybe but I doubt it. Cold filament lamps start with a high inrush
peak current too.

Cold filaments draw peak current something like 20 times their RMS
current, depending on when in an AC half-cycle they are switched on.
CFLs often draw much more than that, with peak current limited by
line impedance and the impedance of the bridge rectifier, filter
capacitor, and a small RF choke. Sounds to me like an ohm or two.

For all I can imagine switching off a CFL with a classic
ballast may cause problems. Switching on/off modern "energy saving"
CFLs should not do worse then filament bulbs. Dimmers are different
and I think the warning not to use CFLs in timers and the like
comes from that dimmers. The manufacturers simply stay on the safe
side to avoid claims.

Probably a good idea for consumers also. I would not like to have
to explain to a fire insurance company why I was using electrical
equipment other than as directed, even if the fire started for a
reason other than the fact that the equipment was being used in a
way that was warned against.

There is also the observed fact that for many CFLs, any small leakage
current through or across the switch will cause the CFL>s reservoir
capacitor to charge until there is enough voltage for the inverter
circuit to start, thus the lamp tends to flash. I have seen this
happen with just the capacitance between two parallel wires (in the
same cable) in stairway lighting circuits. I wonder what effect on
the safety and reliability of the lamp many thousands of repeated
starts a day has?
Failure modes for a normal lightbulb tend to be short (often with a
momentary arc) - usually protected by an integral fuse, open, and
envelope rupture. In a normal operating environment, none are
particularly hazardous. Perhaps CFLs have a failure mode that involves
dangerous overheating on startup so require a human present to check
they have turned on safely?

Some interesting comments.

I>m not sure about the peak current taken by a CFL at switch-on, but
according to the circuits at
http://www.pavouk.org/hw/lamp/en_index.html#sinecan5, it can>t be more than
a 1N4007 can take - 30A. Looking at various triac specs, the peak current
allowed is around 5 - 10 times the average (for an 8A triac, it seems to be
around 65A). Most electronic timers claim to be able to work with 13A
loads, so they should be able to take a peak of around 100A.

Out of interest once I connected a CFL up to a standard light dimmer. Waste
of time - the CFL was basically on or off, and flickered badly at any
intermediate setting.
[/quote]
Mine made a gentle pop, and ceased to function thereafter. Can>t remember what type of dimmer switch it was.

--
http://www.petersparrots.com http://www.insanevideoclips.com http://www.petersphotos.com

A construction worker goes to the doctor and says, "Doc, I>m constipated."
The doctor examines him for a minute and then says, "Lean over the table."
The construction worker leans over the table, the doctor whacks him on the ass with a baseball bat, and then sends him into the bathroom.
He comes out a few minutes later and says, "Doc, I feel great. What should I do?"
The doctor says, "Stop wiping with cement bags."

PhattyMo · Guest

Peter Hucker wrote:
[quote]On Tue, 28 Oct 2008 10:27:53 -0000, Jeff Layman <jmlayman@invalid.invalid> wrote:

IanM wrote:
Don Klipstein wrote:
petrus bitbyter wrote:

"Sjouke Burry" wrote:

Jeff Layman wrote:

Switches intended for use with lighting (timers, PIR, photocells)
warn against use with CFLs, and state that filament lamps should
be used. Why? It shouldn>t make any difference whether a relay or
triac (with ZCD circuitry) is used to switch the lamp on/off the
lamp. I>ve used a couple of timers with a CFL for years without
any apparent problem. And if there is a problem I am unaware of, what
will we be able
to use when the filament lamps are taken off the market in the EU
in a few years time?

A CFL starts with a huge current pulse charging the main
supply cap inside.
Not all switches like that.
Maybe but I doubt it. Cold filament lamps start with a high inrush
peak current too.

Cold filaments draw peak current something like 20 times their RMS
current, depending on when in an AC half-cycle they are switched on.
CFLs often draw much more than that, with peak current limited by
line impedance and the impedance of the bridge rectifier, filter
capacitor, and a small RF choke. Sounds to me like an ohm or two.

For all I can imagine switching off a CFL with a classic
ballast may cause problems. Switching on/off modern "energy saving"
CFLs should not do worse then filament bulbs. Dimmers are different
and I think the warning not to use CFLs in timers and the like
comes from that dimmers. The manufacturers simply stay on the safe
side to avoid claims.

Probably a good idea for consumers also. I would not like to have
to explain to a fire insurance company why I was using electrical
equipment other than as directed, even if the fire started for a
reason other than the fact that the equipment was being used in a
way that was warned against.

There is also the observed fact that for many CFLs, any small leakage
current through or across the switch will cause the CFL>s reservoir
capacitor to charge until there is enough voltage for the inverter
circuit to start, thus the lamp tends to flash. I have seen this
happen with just the capacitance between two parallel wires (in the
same cable) in stairway lighting circuits. I wonder what effect on
the safety and reliability of the lamp many thousands of repeated
starts a day has?
Failure modes for a normal lightbulb tend to be short (often with a
momentary arc) - usually protected by an integral fuse, open, and
envelope rupture. In a normal operating environment, none are
particularly hazardous. Perhaps CFLs have a failure mode that involves
dangerous overheating on startup so require a human present to check
they have turned on safely?
Some interesting comments.

I>m not sure about the peak current taken by a CFL at switch-on, but
according to the circuits at
http://www.pavouk.org/hw/lamp/en_index.html#sinecan5, it can>t be more than
a 1N4007 can take - 30A. Looking at various triac specs, the peak current
allowed is around 5 - 10 times the average (for an 8A triac, it seems to be
around 65A). Most electronic timers claim to be able to work with 13A
loads, so they should be able to take a peak of around 100A.

Out of interest once I connected a CFL up to a standard light dimmer. Waste
of time - the CFL was basically on or off, and flickered badly at any
intermediate setting.

Mine made a gentle pop, and ceased to function thereafter. Can>t remember what type of dimmer switch it was.

[/quote]

There is/was some good info on flouro lights,and CFL>s here:
http://sound.westhost.com/lamps/index.html
I can>t seem to find the article I>m thinking of,however.

Don Klipstein · Guest

In article <4909b7cf$0$89393$815e3792@news.qwest.net>, PhattyMo wrote:

[quote]There is/was some good info on flouro lights,and CFL>s here:
http://sound.westhost.com/lamps/index.html
I can>t seem to find the article I>m thinking of,however.
[/quote]
I am finding some flawed measurements, such as in:

http://sound.westhost.com/lamps/fluorescent.html

That page claims that an LED tube light produces more than twice as much
light per watt than fluorescents that it replaces, on basis of power
consumption and lux on a benchtop under the light.
However, the LED tube light is probably illuminating a smaller area than
the fluorescents did.

If you find benefit from making a light source directional, there is
such a thing as reflectors. With a suitable reflector, a decent fluorescent
will have the same directional pattern as the LED tube light and provide
similar (more likely greater) lux per watt than the LED tube light.

I am also finding some flawed data, as in:

http://sound.westhost.com/articles/incandescent.htm

That page has a table showing supposed overall luminous efficacies of
various light sources.

It shows 17.5 lumens/watt for 100 watt incandescent - that is top end
for 100W non-halogen 120V incandescent. And top end 230V 100W ones do not
achieve that, due to economies of scale on the thinner filament.

A few paragraphs later that page says a 100 watt incandescent produces
1800 lumens but clams CFL manufacturers are claiming 1246 lumens as
equivalent to 100W. In what country? Many European and Australian 100W
incandescents do only produce 1200-1400 lumens. 100W incandescents that
get referred to as GLS lamps (a term used on that page and where
household voltage is 230V) do not produce 1750-1800 lumens, and even USA
ones don>t produce 1800 lumens.

Same story for the 40 watt incandescent.

It also shows 93 lumens/watt as "max, typical" for 36 watt T8
fluorescent. Keep in mind a couple things:

1. Most countries where most household incandescents are designed for
120V have T8 4-foot fluorescents mainly being 32 watt ones, and where
36 watts if the wattage of most T8 fluorescents most incandescents are
rated for 230V.

2. Catalog watt and lumen figures for T8 fluorescents are with line
frequency magnetic ballasts, while catalog figures for modern T5
fluorescents is with high frequency electronic ballasts. But most 32 watt
T8 fluorescents are used with high frequency electronic ballasts, which
largely eliminates one loss of most fluorescent lamps and reduces another.
I suspect that in new fixtures in Europe with 36 watt lamps, the ballasts
are probably mostly electronic.

The same table says 24 lumens/watt for halogen. Most rated at least
2,000 hours and drawing 2.5 amps or less achieve 21 or less.

That page also mentions some fixtures to not use any CFLs in. However,
some CFLs, such as Philips "triple arch" 15, 20 and 23 watt non-dimmable,
are specifically rated to be OK in recessed ceiling fixtures.

That page claims that CFLs emit significantly more UV than
incandescents. I have found that to hardly be true. And that page claims
that the UV increases risk of *breast* cancer?

That page also mentions problems from CFLs taking 5 minutes to warm up.
Ones without outer bulbs generally take more like 1 minute to be most of
the way warmed up.

I sense anti-fluorescent bias.

- Don Klipstein (don@misty.com)

Peter Hucker · Guest

On Fri, 31 Oct 2008 00:10:49 -0000, Don Klipstein <don@manx.misty.com> wrote:

[quote]In article <4909b7cf$0$89393$815e3792@news.qwest.net>, PhattyMo wrote:

There is/was some good info on flouro lights,and CFL>s here:
http://sound.westhost.com/lamps/index.html
I can>t seem to find the article I>m thinking of,however.

I am finding some flawed measurements, such as in:

http://sound.westhost.com/lamps/fluorescent.html

That page claims that an LED tube light produces more than twice as much
light per watt than fluorescents that it replaces, on basis of power
consumption and lux on a benchtop under the light.
However, the LED tube light is probably illuminating a smaller area than
the fluorescents did.

If you find benefit from making a light source directional, there is
such a thing as reflectors. With a suitable reflector, a decent fluorescent
will have the same directional pattern as the LED tube light and provide
similar (more likely greater) lux per watt than the LED tube light.

I am also finding some flawed data, as in:

http://sound.westhost.com/articles/incandescent.htm

That page has a table showing supposed overall luminous efficacies of
various light sources.

It shows 17.5 lumens/watt for 100 watt incandescent - that is top end
for 100W non-halogen 120V incandescent. And top end 230V 100W ones do not
achieve that, due to economies of scale on the thinner filament.

A few paragraphs later that page says a 100 watt incandescent produces
1800 lumens but clams CFL manufacturers are claiming 1246 lumens as
equivalent to 100W. In what country? Many European and Australian 100W
incandescents do only produce 1200-1400 lumens. 100W incandescents that
get referred to as GLS lamps (a term used on that page and where
household voltage is 230V) do not produce 1750-1800 lumens, and even USA
ones don>t produce 1800 lumens.

Same story for the 40 watt incandescent.

It also shows 93 lumens/watt as "max, typical" for 36 watt T8
fluorescent. Keep in mind a couple things:

1. Most countries where most household incandescents are designed for
120V have T8 4-foot fluorescents mainly being 32 watt ones, and where
36 watts if the wattage of most T8 fluorescents most incandescents are
rated for 230V.

2. Catalog watt and lumen figures for T8 fluorescents are with line
frequency magnetic ballasts, while catalog figures for modern T5
fluorescents is with high frequency electronic ballasts. But most 32 watt
T8 fluorescents are used with high frequency electronic ballasts, which
largely eliminates one loss of most fluorescent lamps and reduces another.
I suspect that in new fixtures in Europe with 36 watt lamps, the ballasts
are probably mostly electronic.

The same table says 24 lumens/watt for halogen. Most rated at least
2,000 hours and drawing 2.5 amps or less achieve 21 or less.

That page also mentions some fixtures to not use any CFLs in. However,
some CFLs, such as Philips "triple arch" 15, 20 and 23 watt non-dimmable,
are specifically rated to be OK in recessed ceiling fixtures.

That page claims that CFLs emit significantly more UV than
incandescents. I have found that to hardly be true. And that page claims
that the UV increases risk of *breast* cancer?

That page also mentions problems from CFLs taking 5 minutes to warm up.
Ones without outer bulbs generally take more like 1 minute to be most of
the way warmed up.

I sense anti-fluorescent bias.
[/quote]
Or just confusion. There are far too many ways to measure light.

LEDs WILL take over our lighting. They may need to get more efficient first though. They already have advantages in things like traffic light5s and cars, as they don>t need changing so often, and are instant on/off.

--
http://www.petersparrots.com http://www.insanevideoclips.com http://www.petersphotos.com

Never dive into deep concrete.

Jeff Layman · Guest

Peter Hucker wrote:
(snip)
[quote]
LEDs WILL take over our lighting. They may need to get more
efficient first though. They already have advantages in things like
traffic light5s and cars, as they don>t need changing so often, and
are instant on/off.
[/quote]
I am sure that they will. But I>m not so sure about their predicted life
(compare what is still being said about CFLs with real-life experience).
The high-power LEDs do run really hot, and need a good-sized heatsink to
deal with the waste heat. No good adding fans to cool them, as they aren>t
reliable enough for really long-term usage.

Of course it may be that semiconductor LEDs will be superseded by OLEDs.
Not for every use, perhaps, but where one needs diffuse lighting they will
be OK. I can foresee the time when we don>t have luminaires as such - the
whole ceiling (and perhaps walls) will be a light emitter.

--
Jeff

Peter Hucker · Guest

On Sat, 01 Nov 2008 13:03:22 -0000, Jeff Layman <jmlayman@invalid.invalid> wrote:

[quote]Peter Hucker wrote:
(snip)

LEDs WILL take over our lighting. They may need to get more
efficient first though. They already have advantages in things like
traffic light5s and cars, as they don>t need changing so often, and
are instant on/off.

I am sure that they will. But I>m not so sure about their predicted life
(compare what is still being said about CFLs with real-life experience).
The high-power LEDs do run really hot, and need a good-sized heatsink to
deal with the waste heat. No good adding fans to cool them, as they aren>t
reliable enough for really long-term usage.
[/quote]
When they become more efficient, there will be less heat output.

What about a heat pipe like thy use in computers?

[quote]Of course it may be that semiconductor LEDs will be superseded by OLEDs.
Not for every use, perhaps, but where one needs diffuse lighting they will
be OK. I can foresee the time when we don>t have luminaires as such - the
whole ceiling (and perhaps walls) will be a light emitter.
[/quote]
From wikipedia: "The biggest technical problem for OLEDs is the limited lifetime of the organic materials. In particular, blue OLEDs historically have had a lifetime of around 14,000 hours"

--
http://www.petersparrots.com http://www.insanevideoclips.com http://www.petersphotos.com

What do you call a dwarf who throws the discus?
A compact disc player.

Jeff Layman · Guest

Peter Hucker wrote:
[quote]On Sat, 01 Nov 2008 13:03:22 -0000, Jeff Layman
jmlayman@invalid.invalid> wrote:

Peter Hucker wrote:
(snip)

LEDs WILL take over our lighting. They may need to get more
efficient first though. They already have advantages in things like
traffic light5s and cars, as they don>t need changing so often, and
are instant on/off.

I am sure that they will. But I>m not so sure about their predicted
life (compare what is still being said about CFLs with real-life
experience). The high-power LEDs do run really hot, and need a
good-sized heatsink to deal with the waste heat. No good adding
fans to cool them, as they aren>t reliable enough for really
long-term usage.

When they become more efficient, there will be less heat output.

What about a heat pipe like thy use in computers?
[/quote]
Too expensive.

[quote]
Of course it may be that semiconductor LEDs will be superseded by
OLEDs. Not for every use, perhaps, but where one needs diffuse
lighting they will be OK. I can foresee the time when we don>t have
luminaires as such - the whole ceiling (and perhaps walls) will be a
light emitter.

From wikipedia: "The biggest technical problem for OLEDs is the
limited lifetime of the organic materials. In particular, blue OLEDs
historically have had a lifetime of around 14,000 hours"
[/quote]
But see
http://www.osram-os.com/osram_os/EN/Press/Press_Releases/Organic_LED/Press-release-OPAL-research-project.jsp

True, the life isn>t that good yet (although 5000+ hours isn>t bad), but
look at the lm/W figure, and what is projected for next March. ISTM that
OLEDs are in the stage of development that LEDs were in a couple of years
ago, but are catching up fast.

--
Jeff


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