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'[OT] 240-volt Power'
2005\02\07@165937 by Martin McCormick

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       My parents recently visited some friends who live on an island
in the Caribbean which is near Granada.  I'd happily mention the name,
but I don't remember how it is spelled.  The island's electricity is
50 HZ and 240 volts reflecting its British experience, but it got me
to wondering.

       Are fluorescent tubes made for either the 120-volt or 240-volt
markets or is all that taken care of in the ballast?

       Actually my father didn't see much fluorescent lighting where
they were but he did notice that incandescent reading lamps in the
house seemed to die like flies.  I would imagine that good 240-volt
bulbs running at the proper voltage probably don't burn out any faster
than 120-volt bulbs.  The voltage there does fluctuate quite a bit and
the bulbs may not be the best money can buy.  They do not have any
voltage or wattage rating on their base or the glass.

       It seems like my wife and I bought some bargain-basement
120-volt bulbs for general use and they generally had much shorter
life-spans than do the only slightly-more-expensive bulbs with actual
names on them.:-)

Martin McCormick WB5AGZ  Stillwater, OK
OSU Information Technology Division Network Operations Group

2005\02\07@172338 by Bob Blick

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> Are fluorescent tubes made for either the 120-volt or 240-volt
> markets or is all that taken care of in the ballast?

Although there are some socket differences, basically the difference is in
the ballast. Fluorescent bulbs are current devices. And since the
operating voltage increases with age, fluorescents will run continuously
almost forever at 240 volts. The same bulb at 120 volts will start
flickering much earlier.

> they were but he did notice that incandescent reading lamps in the
> house seemed to die like flies.

The thin filaments make 240 volt incandescent bulbs very fragile.

Cheerful regards,

Bob


2005\02\07@182757 by Jinx

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> I would imagine that good 240-volt bulbs running at the proper
> voltage probably don't burn out any faster than 120-volt bulbs

First you have to define and find a "good" 240V bulb !

They don't last as long as 120V bulbs. The filament is thinner.
Someone did say here once that they used 2 x 120V in series
and got pretty good economy. Also, adding a series resistor
can increase bulb life significantly

http://home.clear.net.nz./pages/joecolquitt/0bulblife.html

You'll probably find that most bulbs blow at turn on, because
the filament is cold and takes an inrush of current greater than
its normal operating current. Particularly if you happen to turn
it on at the peak of the mains cycle and the filament is getting
old and depleted. So the more often a light is switched on the
greater the chance of it blowing

As colour degrades with decreasing voltage, this approach
might suit some positions better than others ; reading lamp,
no - porch light, yes

A more sophisticated approach would be soft-start. A zero-
cross detecting micro and triac for example to apply power
in a controlled fashion rather than a random wallop

I'm pleased to report that no bulbs have blown since the
last update to that page (June 2002), so that's around 4
years now. Previously, as mentioned, they would blow
with annoying regularity

2005\02\07@215604 by Martin McCormick

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Jinx writes:
>First you have to define and find a "good" 240V bulb !
>
>They don't last as long as 120V bulbs. The filament is thinner.
>Someone did say here once that they used 2 x 120V in series
>and got pretty good economy. Also, adding a series resistor
>can increase bulb life significantly

       Well, I had to think a bit about why the manufacturer couldn't
simply roll in more tungston wire of the same gauge as the 120-volt
bulbs, but it really wouldn't work unless someone figured out how to
formulate a higher-resistance tungston wire that was the same gauge as
that used in the 120-volt bulbs.

       A resistor causes the bulb to light more gently because
it initially takes the in-rush of the filament current when it is
cold.  If you put two bulbs in series, they will reach operating
temperature faster since they at least theoretically will always have
half the supply voltage across them.

Martin McCormick

2005\02\07@221117 by Matt Pobursky

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On Tue, 08 Feb 2005 12:27:09 +1300, Jinx wrote:
> I'm pleased to report that no bulbs have blown since the
> last update to that page (June 2002), so that's around 4
> years now.

I hope you bill your clients by the hour (and they don't check your
math)!

;-)

Matt

2005\02\07@222209 by John J. McDonough

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----- Original Message -----
From: "Matt Pobursky" <spam_OUTpiclistTakeThisOuTspammps-design.com>
Subject: Re: [OT] 240-volt Power


> I hope you bill your clients by the hour (and they don't check your
> math)!

I think he's on the other side of the international date line.  They've
claimed "It's tomorrow here" enough times they must be at least a year ahead
by now.

--McD



2005\02\08@000336 by Jinx

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> > I hope you bill your clients by the hour (and they don't check
> > your math)!

Hmmm, let's see. Where are those countin' fingers...........

18 months before June Ought Two is 01/01. We're now in
01/05. I make that (double-checks on toes) - 4 years ?

> I think he's on the other side of the international date line.  They've
> claimed "It's tomorrow here" enough times they must be at least a
> year ahead by now

Light-years ahead. Actually

Sit Ubu, sit. Good dog

2005\02\08@005513 by Hopkins

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Have not tried this but someone once said by putting a diode in series
with the lamp but as this would be half wave rectification I would think
a full diode bridge would be better.

But would this help with the turn on burn out problem?

Maybe a full wave bridge and a capacitor on the DC side would help to
slow down the turn on pulse to the bulb while the capacitor is charging.

_______________________________________
Roy
Tauranga
New Zealand
_______________________________________



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2005\02\08@022505 by Russell McMahon

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> Have not tried this but someone once said by putting a diode in
> series
> with the lamp but as this would be half wave rectification I would
> think
> a full diode bridge would be better.
>
> But would this help with the turn on burn out problem?
>
> Maybe a full wave bridge and a capacitor on the DC side would help
> to
> slow down the turn on pulse to the bulb while the capacitor is
> charging.

A slow turn on device could be  achieved with 2 MOSFETS,  a diode, a
resistor, a capacitor and a zener. Given the fact that energy saving
fluorescent bulbs are selling here for as little as $US2 and they have
2 suitable FETs inside, the cost of such a device in zillions should
be able to be well under $US2. Whether it is worth doing is debateable
unless you greatly favour incandescent bulbs over fluorescent power
savers. If you have a very expensive incandescent bulb (projector etc)
then it may well be worthwhile.

Two MOSFETS connected Gate to Gate. Source to Source. Drains are input
/ output. Wire in series with bulb.
Capacitor gate to source.
Diode in series with R drain to gate.
Zener gate to source , cathode to source.
Add a second resistor gate to ground for turnoff control

A single MOSFET would start up in half wave and switch to full AC -
this MAY be enough.



       RM

2005\02\08@035847 by Alan B. Pearce

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>A slow turn on device could be  achieved with 2 MOSFETS,  a diode, a
>resistor, a capacitor and a zener. Given the fact that energy saving
>fluorescent bulbs are selling here for as little as $US2

Gee, you are doing well, in Rip Off Britain the best is still several pounds
(but they are down into the single digit pounds mostly).

I do have one that died, and I believe the semi-conductors have gone the way
it took out the circuit breaker. Seems to use standard IRF devices inside,
so hopefully will get round to doing something with it one day, or use the
tube on another one when its tube dies (currently the more likely with the
other projects I have).

2005\02\08@041803 by Michael Rigby-Jones

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{Quote hidden}

Alan,

If you have an Ikea store nearby they sell "own brand" CF's for around £1.50.  I have a few in my house, they seem to work fine although they seem to take longer to reach full brightness than some of the brand names ones I have.

Regards

Mike

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2005\02\08@043114 by Russell McMahon

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> >A slow turn on device could be  achieved with 2 MOSFETS,  a diode,
> >a
>>resistor, a capacitor and a zener. Given the fact that energy saving
>>fluorescent bulbs are selling here for as little as $US2
>
> Gee, you are doing well, in Rip Off Britain the best is still
> several pounds
> (but they are down into the single digit pounds mostly).

I have a box of variously dead ones. I pulled a range apart a while
ago to see how they vary and the increasing econonmies acheived as
they get cheaper is quite educational. Quality of build in some is
very poor. I could not build one here for many times the price.

       RM


2005\02\08@053039 by Alan B. Pearce

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>If you have an Ikea store nearby they sell "own brand" CF's for around
£1.50.

I think the nearest are Bristol or London

>I have a few in my house, they seem to work fine although they seem to

>take longer to reach full brightness than some of the brand names ones I
have.

I have some GE ones like that which I bought recently at B&Q. Real pain they
are, especially as other GE ones I had bought some time previously come up
pretty bright real quick.



thanks for the pointer though.

2005\02\08@093548 by John Ferrell

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The "life extenders" that are sold commercially (a button that is inserted
in the lamp socket) are diodes. They cause a soft yellow light that is OK
for outside lighting and they do work. Unfortunately most are poorly made.

If you rectify the AC to DC and put a Capacitor across it you will produce a
higher voltage, not a lower one!

John Ferrell
http://DixieNC.US

{Original Message removed}

2005\02\08@094026 by John Ferrell

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In another life I had a customer (Ohio University) that included a 70 volt
system in their new Science Building (1970?) for florescent lights. As I
recall, it eliminated the need for ballasts all together.

I have not looked on Google...

John Ferrell
http://DixieNC.US

{Original Message removed}

2005\02\08@101930 by michael brown

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----- Original Message -----
From: "John Ferrell" <.....johnferrellKILLspamspam.....earthlink.net>
To: "Microcontroller discussion list - Public." <EraseMEpiclistspam_OUTspamTakeThisOuTmit.edu>
Sent: Tuesday, February 08, 2005 8:43 AM
Subject: Re: [OT] 240-volt Power


> In another life I had a customer (Ohio University) that included a 70
volt
> system in their new Science Building (1970?) for florescent lights. As
I
> recall, it eliminated the need for ballasts all together.
>
> I have not looked on Google...

Could it have been 377V?  I see that allot in office buildings.  70V
sounds like a PA system.

2005\02\08@125802 by Hopkins

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The point was to slow down the inrush current to the lamp.

_______________________________________
Roy
Tauranga
New Zealand
_______________________________________

If you rectify the AC to DC and put a Capacitor across it you will
produce a
higher voltage, not a lower one!



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2005\02\08@131317 by Michael Rigby-Jones

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>-----Original Message-----
>From: piclist-bouncesspamspam_OUTmit.edu [@spam@piclist-bouncesKILLspamspammit.edu]
>Sent: 08 February 2005 17:57
>To: 'Microcontroller discussion list - Public.'
>Subject: RE: [OT] 240-volt Power
>
>
>The point was to slow down the inrush current to the lamp.

With just a full bridge and a capacitor, the only thing restricting the
inrush current would be the impedance of the rectifiers and mains
wiring.  You need some kind of resistive element to reduce inrush
current.  An NTC thermistor would be ideal as it has a high initial
resistance to reduce inrush, and as it heats up it's resistance reduces
so the lamp gets brighter.  However, getting hold of a suitably rated
thermistor might be a problem.

Regards

Mike

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2005\02\08@140013 by Richard.Prosser

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Russell,

I found some at Bunnings - ~NZ $2.75  IIRC. But ES fitting only.
RP





>... Given the fact that energy saving
fluorescent bulbs are selling here for as little as $US2 and they have
2 suitable FETs inside, ....



       RM





2005\02\08@143923 by Mike Hawkshaw

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----- Original Message -----
From: "Jinx"
Subject: Re: [OT] 240-volt Power
> Also, adding a series resistor can increase bulb life significantly
> http://home.clear.net.nz./pages/joecolquitt/0bulblife.html

Jinx, that is brilliant, thanks for sharing. I have been thinking along
similar lines but using an auto transformer to drop the supply to the whole
lighting circuit by a similar amount. The series resistor is such a simple
low cost idea that it would be almost daft to not try it.

Can I ask you - where did you get the graph at the bottom of the page?
Google brings up very little that looks like data sheets, and I would be
interested in a copy.

Mike.



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2005\02\08@153316 by Jinx

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> Can I ask you - where did you get the graph at the bottom of the page?

Honestly don't remember. It must have been off the web because it's
so crookedly scanned, which I wouldn't have done. I have made a
small attempt to make it readable

Here's a graph showing CFL vs filament

http://www.susdesign.com/cfl/cfl-spreadsheet-1.xls

And an opinion piece by the editor of Silicon Chip

"Compact fluorescent lights are not economic"

http://www.siliconchip.com.au/cms/A_102164/article.html

2005\02\08@155647 by Bob Blick

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> And an opinion piece by the editor of Silicon Chip
>
> "Compact fluorescent lights are not economic"

Here in California I typically pay US$1 for a compact fluorescent. 20
percent of them die in about a year or so, the rest usually last about 4
years. Then you can salvage them for some nice UL-listed caps and a couple
of sweet inductors, and usually a bridge rectifier.

Also, electricity sometimes hits US$0.25 per kilowatt-hour, so any savings
is welcome.

Cheerful regards,

Bob


2005\02\08@170938 by Jinx

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> Then you can salvage them for some nice UL-listed caps and a couple
> of sweet inductors, and usually a bridge rectifier.

Well, get them where you can eh ?

Savings aside, CFLs, especially at this time of year (hot 'n' humid), are
preferable because they don't generate so much heat. A 15W CFL as
a desk lamp is much more comfortable than a 100W filament bulb in
your face

2005\02\08@180913 by Russell McMahon

face
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> I found some at Bunnings - ~NZ $2.75  IIRC. But ES fitting only.

Mitre 10 (NZ hardware franchise chain store) were selling 2 for $4,50
AFAIR. Both ES and bayonet. 20 W rated which gives a bit less light
than 100 W incandescent.


       RM

2005\02\08@181029 by Russell McMahon

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> And an opinion piece by the editor of Silicon Chip
> "Compact fluorescent lights are not economic"
>
> http://www.siliconchip.com.au/cms/A_102164/article.html

That was written in 2004. I'm surprised. He's wrong.
Or, at least, my overwhelming experience of CFLs is quite different
from his. I can categorically state that I have had some versions last
well over the rated 8000 hours as I have a lamp my electrical workshop
and another in my front path light that are always on, and the bulbs
last typically well over a year. I write the date that I put CFL bulbs
into service on their base. I have had some fail long before expected,
but overall the results are acceptable, if not as good as some claim.
Given the current low cost of CFLs and the substantial savings in
energy use, it doesn't take long to justify their cost on energy
savings alone. Note that CFLs save money on energy ONLY if you do not
have thermostat controlled heating. Any time you use a
thermostatically controlled heater energy sources such as light bulbs
contribute to the heating and reduce heating power costs
proportionately.

Simple example of savings. Compare an incandescent 100W bulb and a 25W
CFL. (usually 20W are sold as 100w replacements but they don't quite
meet 100W equivalent light output so lets be fair). Electricity costs
about $NZ1 per watt per years continuous operation. That varies with
area, and the price is rising, but it's an OK approximation. If an IB
(incandescent bulb) and CFL are assumed to cost equal amounts of
capital per hour run then power savings are all that needs to be
compared. Even factoring in bulb costs does not make much difference.
Energy savings per year run 24/7 are 100-25 = $75 per year. Run a bulb
10% of the time = 2.4 hours per day and the saving is $7.50. As CFL
bulbs now often cost under $3 and IBs are down to say $0.50 there MAY
be a slight extra bulb cost for the CFLs. But its far less than
$7.50/year.

I run an often or always on CFL in several locations. Front porch,
path light, workshop. There are a few other areas where they are often
on. At $1/year/watt and with a small wattage CFL the costs are
acceptable. I would not consider doing this with IBs.

I just went and checked the ALWAYS on front path light. It was
installed on 22 September 2003. That's about 11.700 continuous running
hours so far. It's an 8 watt bulb so running costs so far are about
$11. ($11.22 at 12 cents per unit.)

My workshop bulb was installed in 15 October 2003 after having been
moved there from some other (unspecified) location so total hours are
unknown but at least as long as the path light. .

A significant failure mode is mechanical damage due to careless
handling. It's far easier to crack the bulb seal on a CFL than on an
IB. Due care is required,


There are few places where I would recommend an IB these days.




       RM

2005\02\08@183746 by Peter Johansson

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Mike Hawkshaw writes:

> ----- Original Message -----
> From: "Jinx"
> Subject: Re: [OT] 240-volt Power
> > Also, adding a series resistor can increase bulb life significantly
> > home.clear.net.nz./pages/joecolquitt/0bulblife.html
>
> Jinx, that is brilliant, thanks for sharing. I have been thinking along
> similar lines but using an auto transformer to drop the supply to the whole
> lighting circuit by a similar amount. The series resistor is such a simple
> low cost idea that it would be almost daft to not try it.

Unfortunately, this is not without it's downside.  Not only does it
reduce the brightness of hte bulb, but it reduces the *efficiency* of
the bulb as well -- the filaments are more efficient at converting
electricity into visible light at higher temperatures.

While this may be a penny-wise solution in terms of bulb cost, it
could very well be pound-foolish in terms of electricity cost.

-p.

2005\02\08@190019 by Peter Johansson

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Russell McMahon writes:

> >And an opinion piece by the editor of Silicon Chip
> >"Compact fluorescent lights are not economic"
> >
> >www.siliconchip.com.au/cms/A_102164/article.html
>
> That was written in 2004. I'm surprised. He's wrong.
> Or, at least, my overwhelming experience of CFLs is quite different
> from his.

My results have been much more mixed.  Some of the first CF bulbs I
purchased are still working great.  Based on my initial good
experiences, a bought a six-pack of bulbs "on special sale" to use
throughout the house.  Two died within the first month.  A third
started emitting a nasty odor.  A fourth only operates at half
brightness.  I don't know what has happened to the other two.

There isn't anything wrong with the technology; there is just a lot of
crap out there.  If you see a deal of CFs that looks too good to be
true, it very well may be...

-p.

2005\02\08@192619 by Harold Hallikainen

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How about using an NTC thermistor, just like the inrush current limiter in
low cost switching supplies? These low cost switchers have a problem when
you get a power interruption for less than a second, as the filter
capacitor discharges but the thermistor does not cool off. When the power
comes back, there is no inrush current limiter. I've had a bunch of
rectifiers blow out due to that. In those cases, I just stuck a resistor
in series with the input to the supply, as has been suggested here in
series with an incandescent lamp. However, the lack of inrush current
limiting with the incandescent is not as serious as it is for the
switching power supply (we're back to the way the lamp has always been
run).

Another approach to limiting inrush current on incandescent lamps is to
use a consumer type triac dimmer that looks like a normal wall switch.
These dimmers are off when the handle is down, on when the handle is up,
and 50% when the handle is horizontal. If you just "flip the switch on,"
the lamp has a little time to warm up as the handle is brought up,
limiting the inrush current. You also get the benefit of having a dimmer!

Several years ago I did current measurements on flashing broadcast tower
lights and captured the current waveform. These flashing beacons have a
pair of 620 watt lamps in each beacon. The inrush current is amazing! I
just measured the cold filament resistance on one of the lamps. I get
about 1.8 ohms. So, at 120VAC, the inrush would be 67 amps. Once warmed
up, the current is 5.2 amps. When flashing on a tower, the lamps do not
cool off all the way between flashes, so there is inrush current, but it's
not as bad as it could be.

Harold


--
FCC Rules Updated Daily at http://www.hallikainen.com

2005\02\08@194010 by Russell McMahon

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>> > http://www.siliconchip.com.au/cms/A_102164/article.html

>>... my overwhelming experience of CFLs is quite different
>> from his.

> My results have been much more mixed.  Some of the first CF bulbs I
> purchased are still working great.  Based on my initial good
> experiences, a bought a six-pack of bulbs "on special sale" to use
> throughout the house.  Two died within the first month.  A third
> started emitting a nasty odor.  A fourth only operates at half
> brightness.  I don't know what has happened to the other two.
>
> There isn't anything wrong with the technology; there is just a lot
> of
> crap out there.  If you see a deal of CFs that looks too good to be
> true, it very well may be...

Even the el cheapo ones have mostly worked OK for me.
When prices are about the same I try to buy name brand ones. I find
Philips & Osram have been OK. They may all come out of the same
factories but name brand sellers have a reputation to protect and are
perhaps more likely to keep quality reasonable. Comparison with older
and newer ones shows a reduction in parts count and general complexity
and cutting corners. eg power devices seem to be of smaller physical
size with about no attention to heat dissipation.


       RM


2005\02\08@213744 by Lee Jones

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>>>> http://www.siliconchip.com.au/cms/A_102164/article.html

>>> ... my overwhelming experience of CFLs is quite different from his.

>> My results have been much more mixed.
>>
>> There isn't anything wrong with the technology; there is just a lot
>> of crap out there.

> Even the el cheapo ones have mostly worked OK for me.
> When prices are about the same I try to buy name brand ones.

I've had very mixed results.  The commercial grade CFLs ($8-10
each) have run without a problem.  The cheapos (4 pack for $15)
have dropped like flies (4 dead out of 5 in less than a year).
However, we don't run any lighting 24 x 7.  Maximum continuous
on time for any location is ~8 hours per day.  Switching events
seem to take a toll.

Since I switch lighting off to conserve energy (can't beat 0KWh),
I'm not very enamored of the slow light output ramp-up (instant on
bulb is well under half the rated light output at first and takes
1-2 minutes to reach full brightness (I've measured it) ).

One dead one was an inexpensive 3-way CFL.  I haven't been able
to find a replacement.  While looking for same, I did find a
recall notice for the 3-way CFL units due to dangerous failure
mode (fire hazard, I think).  So the corner cutting has been
very tight -- some might say, too tight.

Here in southwest US, I haven't seen name brands at anywhere
near the same price as cheap ones.

By my estimates, price break-even point due to energy saving is
only a few months.  A couple weeks ago, I was looking for a pair
of CFLs to put in some roof fixtures.  Access is via ladder with
a long stretch out to get to the bulbs.  Old 75W reflector flood
incandescents would last for years.  New CFLs saved energy.  But
I do not want to change them every 6 months.  Previous unit was
cheapo CFL.  I went with better commercial grade units this time.

I did compare in the store.  Mechanical construction of more
expensive units (rivits) was better than cheapos (crimped metal).
Only time will tell how reliable the new units are.

Short CFL lifetimes may be giving them a bad reputation with the
general public.  I doubt that most people do power consumption
calculations.  All they see is the more expensive CFL dying at
the same rate (or faster) than the older incandescent bulbs.

                                               Lee

2005\02\09@013453 by William Chops Westfield

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On Feb 8, 2005, at 2:08 PM, Jinx wrote:

> CFLs ... are preferable because they don't generate so much heat.

Yeah.  The computer room here used to be a lawyer's office, and
had 1200 W of candelabra based filament bulbs in fancy glass globes.
Now it has maybe 150W or less of CFLs in chinese tissue spheres;
Much nicer, especially in the summer...

A fair number of the early failures in my CFLs seem to be due
to ruptured electrolytics; not quite up to the heat, I guess.

BillW

2005\02\09@031344 by Wouter van Ooijen

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> Any time you use a
> thermostatically controlled heater energy sources such as light bulbs
> contribute to the heating and reduce heating power costs
> proportionately.

But you'd still have to figure into account the efficiency of generating
electricity, compared to the efficiency of generating house heating. In
my country the latter is ~ 90% using high-efficiency gas heaters. The
former is much lower.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\02\09@040104 by Russell McMahon

face
flavicon
face
>> Any time you use a
>> thermostatically controlled heater energy sources such as light
>> bulbs
>> contribute to the heating and reduce heating power costs
>> proportionately.

> But you'd still have to figure into account the efficiency of
> generating
> electricity, compared to the efficiency of generating house heating.
> In
> my country the latter is ~ 90% using high-efficiency gas heaters.
> The
> former is much lower.

True. This will vary with country and, as far as the consumer is
concerned, the cost of the energy sources. In NZ a large amount of our
domestic heating is by mains electricity. A large proportion of our
electricity is from hydroelectric sources. A limited number of coal
and oil fired stations exist.  Reticulated LPG gas (mainly from gas
fields off the west coast of our North Island) is substantially
cheaper than electricity but not available in all areas. Bottled LPG
gas is available nationwide but is dearer per energy content than
mains electricity.

Then, there's always gas lights ... :-)



       RM

2005\02\09@050557 by Michael Rigby-Jones

picon face


>-----Original Message-----
>From: KILLspampiclist-bouncesKILLspamspammit.edu [RemoveMEpiclist-bouncesTakeThisOuTspammit.edu]
>Sent: 08 February 2005 23:38
>To: Microcontroller discussion list - Public.
>Subject: Re: [OT] 240-volt Power
>
>Unfortunately, this is not without it's downside.  Not only
>does it reduce the brightness of hte bulb, but it reduces the
>*efficiency* of the bulb as well -- the filaments are more
>efficient at converting electricity into visible light at
>higher temperatures.
>
>While this may be a penny-wise solution in terms of bulb cost,
>it could very well be pound-foolish in terms of electricity cost.

Only if you add more lamps to compensate for the decreased brightness,
which wasn't the idea of the scheme.  As Joes web page shows, dropping
the voltage by ~5% significantly increases lamp life whilst still giving
acceptable light output.

Regards

Mike

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2005\02\09@083603 by Howard Winter

face
flavicon
picon face
Russell,

On Wed, 09 Feb 2005 12:10:17 +1300, Russell McMahon wrote:

>...<
> Note that CFLs save money on energy ONLY if you do not
> have thermostat controlled heating. Any time you use a
> thermostatically controlled heater energy sources such as light bulbs
> contribute to the heating and reduce heating power costs
> proportionately.

You're making some hefty assumptions here:

1. That heating is electrical, so costs the same regardless of the device supplying the heat.  Mains-fed gas heating is usually much cheaper (ironic, since electrical heating is 100% efficient in itself - all of the energy turns to heat, which is what you want! :-)
2. That heating is always used (whenever there are lights on), ignoring the time when the temperature is fine without heating, and that air-conditioning isn't used.  As soon as you add air-con to the equation it turns round dramatically, because you are paying for the electricity to create the heat, then paying again to extract it from the building.

I realise you're from a similar climate to me so heating is what you think of, but if you look at somewhere like Southern California the time of maximum electrical demand is high summer due to air-con.

> Electricity costs about $NZ1 per watt per years continuous operation.
Good grief, that's cheap!  Can you send some to me and we'll split the difference?  :-)

I'm on a split meter, 7 hours overnight "cheap" at 3.09p/kWh, 17 hours at 12.84p/kWh.  That comes to 7.895p + 79.67p = UK£0.876 per watt per year or NZ$2.32 or US$1.63 at today's exchange rates (this is without tax, and without volume discounts).  If I was on a single rate meter it would be dearer, at UK£0.95 (NZ$2.53, US$1.77).

I hadn't realised we were being fleeced quite so much!

As for the CFL discussion, I don't have any lights on 24/7, but several on for 8 to 12 hours a day, depending on the time of year.  I've been doing this for some years, since the original Philips units came out, that had a tough glass cover over the tubes (and they weighed a lot!).  Those lasted for about 4-5 years.  Being in a cold environment (garage, unheated room) seemed to cause them problems, with failure to strike being a common failure mode (flicking the switch repeatedly would usually get them going) .  The more modern ones with exposed tubes, and some with a decorative globe cover, seem to last at least as long.  I must start recording when I start using each one, so I'll know for sure!

Prices of CFLs vary dramatically here, from about 2.5 watt-years' cost to about 4 times that, with no obvious reason for the difference.

Cheers,



Howard Winter
St.Albans, England

2005\02\09@104401 by Mike Hawkshaw

flavicon
face
From: "Peter Johansson"
Subject: Re: [OT] 240-volt Power


> Unfortunately, this is not without it's downside.  Not only does it
> reduce the brightness of hte bulb, but it reduces the *efficiency* of
> the bulb as well -- the filaments are more efficient at converting
> electricity into visible light at higher temperatures.
>
> While this may be a penny-wise solution in terms of bulb cost, it
> could very well be pound-foolish in terms of electricity cost.

True, but the problem lights at our house are for mood lighting, and have
25W bulbs in them. These things are wall mounted and have small bayonet type
holders - the fittings are rated for 40W bulbs. The fittings are mounted
such that the lamp is connector side down, yet the bulbs typically last 4
months. I wouldn't want to use CFLs in these lights as the quality of the
light is too harsh and the lamps would stick out from the top of the
fitting, so reducing the voltage to the bulbs is really the only way to go,
and will not impact on electricity useage at all.

Interestingly, another direction this thread took was CFL life span. We use
about 8 of these where I work, to provide just enough light to navigate
round the building at night with the normal office lights off. We find that
they typically last between 18 and 24 months (13,000 -> 18,000 hrs) however
they are never ever switched off. The lamps end up very black just before
they fail though! This probably saves money in the long run, as it causes
less wear and tear on the office lights when ever someone gets called in to
a fault.

Mike.



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2005\02\09@105712 by Mike Hawkshaw

flavicon
face
From: "Jinx"
Subject: Re: [OT] 240-volt Power


> Honestly don't remember.
Not to worry it gives the right idea!

> Here's a graph showing CFL vs filament
> http://www.susdesign.com/cfl/cfl-spreadsheet-1.xls
>
> And an opinion piece by the editor of Silicon Chip
>
> "Compact fluorescent lights are not economic"
> http://www.siliconchip.com.au/cms/A_102164/article.html

Both these are very interesting. We have a mixture of CFLs and fillaments at
home for reasons of mood / convienience / efficiency.

I posted another reply with my experiences of CFLs at work. We get the
cheepest we can find, and get about 2 years continuous life (24/7). From
this, I suggest that the electronics probably fails long before the tubes if
the second article is correct.

Cheers....Mike.



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2005\02\09@123533 by Mike Hawkshaw

flavicon
face
I've just found this software on GE's web site. It plots graphs and
calculates life etc given lamp and socket voltage.
http://www.gelighting.com/apo/specoem/hicalc.html

Their FAQ has its moments as well....
http://www.gelighting.com/apo/contactus/faq.html

Cheers....Mike.



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2005\02\09@130708 by Josh Koffman

face picon face
Thanks for the link...I'm playing around in HiCalc...and on the
efficiency graph, it seems that if I supply my lamp with more than
100% of it's rated voltage...it becomes more than 100% efficient? The
only think I can think of is that they are referencing it back to the
rated output...so with higher voltage, you get a higher than rated
output, so they say it's more efficient? That's a bit confusing...I
can't think of a better way to describe what I'm thinking though.

Ideas?

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
       -Douglas Adams

On Wed, 9 Feb 2005 17:35:32 -0000, Mike Hawkshaw <spamBeGonemikespamBeGonespamspikey-mike.com> wrote:
> I've just found this software on GE's web site. It plots graphs and
> calculates life etc given lamp and socket voltage.
> www.gelighting.com/apo/specoem/hicalc.html

2005\02\09@134625 by Peter Johansson

flavicon
face
I wrote:

> >Unfortunately, this is not without it's downside.  Not only
> >does it reduce the brightness of hte bulb, but it reduces the
> >*efficiency* of the bulb as well -- the filaments are more
> >efficient at converting electricity into visible light at
> >higher temperatures.
> >
> >While this may be a penny-wise solution in terms of bulb cost,
> >it could very well be pound-foolish in terms of electricity cost.

Michael Rigby-Jones writes:

> Only if you add more lamps to compensate for the decreased brightness,
> which wasn't the idea of the scheme.  As Joes web page shows, dropping
> the voltage by ~5% significantly increases lamp life whilst still giving
> acceptable light output.

If you need less light, it then becomes more cost effective to simply
purchase a lower-wattage bulb.  Sure, you'll need to replace the bulb
more frequently, buy you will save money in the long run.

-p.

2005\02\09@140750 by Bob Ammerman

picon face
They are expressing a relative efficiency using lumens per watt. When you
raise the voltage the lumens go up faster than the watts, and thus the
efficiency goes up.

Bob Ammerman
RAm Systems

{Original Message removed}

2005\02\09@144234 by Mike Hawkshaw

flavicon
face
> >From: "Josh Koffman"
> > Thanks for the link...I'm playing around in HiCalc...and on the
> > efficiency graph, it seems that if I supply my lamp with more than
> > 100% of it's rated voltage...it becomes more than 100% efficient?

From: "Bob Ammerman"
> They are expressing a relative efficiency using lumens per watt. When you
> raise the voltage the lumens go up faster than the watts, and thus the
> efficiency goes up.

Definately confusing....but correct, I think, in Lumens / Watt. It must be
the devils own work to design these things...no wonder they are so
expensive.

Cheers....Mike.



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2005\02\09@150501 by Josh Koffman

face picon face
Ok, good explanation. Now how about the "Graph Voltage" part? You end
up with a graph that has Percent Rated Lamp Voltage on the X
axis...and Percent Rated Lamp Voltage on the Y axis. At least the X
values are equal to the Y values :)

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
       -Douglas Adams

On Wed, 9 Feb 2005 19:42:33 -0000, Mike Hawkshaw <TakeThisOuTmikeEraseMEspamspam_OUTspikey-mike.com> wrote:
> From: "Bob Ammerman"
> > They are expressing a relative efficiency using lumens per watt. When you
> > raise the voltage the lumens go up faster than the watts, and thus the
> > efficiency goes up.
>
> Definately confusing....but correct, I think, in Lumens / Watt. It must be
> the devils own work to design these things...no wonder they are so
> expensive.

2005\02\09@153154 by Martin K

flavicon
face


Jinx wrote:
>>Can I ask you - where did you get the graph at the bottom of the page?
>
>
> Honestly don't remember. It must have been off the web because it's
> so crookedly scanned, which I wouldn't have done. I have made a
> small attempt to make it readable
>
> Here's a graph showing CFL vs filament
>
> www.susdesign.com/cfl/cfl-spreadsheet-1.xls
>
> And an opinion piece by the editor of Silicon Chip
>
> "Compact fluorescent lights are not economic"
>
> www.siliconchip.com.au/cms/A_102164/article.html
>

They must not have CFLs that are as good as the kind I get here in the
states for a few US$ a piece that have been used for several years. I
don't think I've seen one fail in my house.

--
Martin K
http://wwia.org/sgroup/biofuel/

2005\02\09@153507 by gacrowell

flavicon
face
My own experience with CFL's for the past couple of years at home has
been good, with one exception.  I have had up to four at a time in a
(poorly vented) bathroom, where they only last a few months.  I suspect
the humidity kills them, so I've went back to incandescent there.  I
have also started writing the install date on the base of the CFL bulbs.

Very useful spreadsheet.  Gives me the urge to purge any other
incandescents I can find.

GC



{Quote hidden}

> --

2005\02\09@181650 by Russell McMahon

face
flavicon
face
>> >While this may be a penny-wise solution in terms of bulb cost,
>> >it could very well be pound-foolish in terms of electricity cost.

>> Only if you add more lamps to compensate for the decreased
>> brightness,
>> which wasn't the idea of the scheme.  As Joes web page shows,
>> dropping
>> the voltage by ~5% significantly increases lamp life whilst still
>> giving
>> acceptable light output.

> If you need less light, it then becomes more cost effective to
> simply
> purchase a lower-wattage bulb.  Sure, you'll need to replace the
> bulb
> more frequently, buy you will save money in the long run.

Bulb costs, especially of fancy ones, are liable to be an average of
$NZ2. (Std bulb $0.50 - $1. Fancy bulbs $2 - $5).  Bulb lifetimes in
some applications can occur within months and are liable to normally
be 1 to 2 years. Adding a series resistor can, according to Joe's
experience, extend lifetime indefinitely - say 4 years. Savings for a
6 months to 4 year life extension are $2 x (2 - 0.25) = $3.50 per
year. I can imagine that a suitably constructed resistor base or
inline add in (terminal block and resistor mounted in junction box)
would meet that cost. Labour cost of installation is very well offset
by bulb changing labour. In fact, based on labour costs alone, the
resistor solution wins hands down.



       RM

2005\02\09@182753 by Robert Rolf

picon face
gacrowell@micron.com wrote:

> My own experience with CFL's for the past couple of years at home has
> been good, with one exception.  I have had up to four at a time in a
> (poorly vented) bathroom, where they only last a few months.  I suspect

I've had mine working just fine since 4/98. My wife and Kid take
mega long showers without a vent fan (they like the sauna effect)
so it's isn't the humidity.
I have GE 23W straight tubes that do not appear to have any
special sealing at the tube/case junction.

> the humidity kills them, so I've went back to incandescent there.  I
> have also started writing the install date on the base of the CFL bulbs.

Ditto. And the warrantee expire date so I know whether to dig
out the receipt from the 'warrantee' files. Unfortunately the
shipping cost is more than the cost of replacements. Nice scam.

> Very useful spreadsheet.  Gives me the urge to purge any other
> incandescents I can find.

I went completely CFL over a period of a year or so. Payback was
only a few years since the other bodies in the house don't seem to
understand the concept of 'lights off when not in use'.

R


2005\02\09@183805 by Mark Jordan

flavicon
face
On 10 Feb 2005 at 12:16, Russell McMahon wrote:

> Bulb costs, especially of fancy ones, are liable to be an average of
> $NZ2. (Std bulb $0.50 - $1. Fancy bulbs $2 - $5).  Bulb lifetimes in
> some applications can occur within months and are liable to normally
> be 1 to 2 years. Adding a series resistor can, according to Joe's
> experience, extend lifetime indefinitely - say 4 years. Savings for a
> 6 months to 4 year life extension are $2 x (2 - 0.25) = $3.50 per
> year. I can imagine that a suitably constructed resistor base or
> inline add in (terminal block and resistor mounted in junction box)
> would meet that cost. Labour cost of installation is very well offset
> by bulb changing labour. In fact, based on labour costs alone, the
> resistor solution wins hands down.
>

       I guess the electricity cost can be reduced changing that resistor
by an AC capacitor. The power meters don't care about reactive power.

       Mark Jordan


2005\02\09@183815 by Robert Rolf

picon face
Russell McMahon wrote:

{Quote hidden}

There used to be a US product called "WattSaver" which did EXACTLY
that. It was a 1" diameter disk that you stuck in the base of the
Edison socket to drop the voltage and hence 'save watts'. Of course
it killed efficiency.

> experience, extend lifetime indefinitely - say 4 years. Savings for a
> 6 months to 4 year life extension are $2 x (2 - 0.25) = $3.50 per
> year. I can imagine that a suitably constructed resistor base or
> inline add in (terminal block and resistor mounted in junction box)
> would meet that cost. Labour cost of installation is very well offset
> by bulb changing labour. In fact, based on labour costs alone, the
> resistor solution wins hands down.

In which case you just install 240V bulbs in 120V sockets
as is often done here on campus in the fire exit signs.
They're a bit dimmer, but they don't need replacement, EVER.
(and much cheaper that switching to LED lights).

I believe you can also get 384V bulbs for commercial lighting
circuits, so those of you in 240V countries may have that option.

R

2005\02\09@224707 by Bob Ammerman

picon face
Just a silliness in the program IMHO.

Bob Ammerman
RAm Systems

----- Original Message -----
From: "Josh Koffman" <RemoveMEjoshybearspamTakeThisOuTgmail.com>
To: "Microcontroller discussion list - Public." <piclistEraseMEspam.....mit.edu>
Sent: Wednesday, February 09, 2005 3:05 PM
Subject: Re: [OT] 240-volt Power


{Quote hidden}

> --

2005\02\10@042313 by Alan B. Pearce

face picon face
>In which case you just install 240V bulbs in 120V sockets
>as is often done here on campus in the fire exit signs.
>They're a bit dimmer, but they don't need replacement, EVER.
>(and much cheaper that switching to LED lights).

>I believe you can also get 384V bulbs for commercial lighting
>circuits, so those of you in 240V countries may have that option.

You don't even need that voltage bulb. When I was a small lad in NZ,
Woolworth's used to sell 250V bulbs for running on the 230V supply, and
although they were a touch orange in the light output, they did last for
ages. Essentially you do not need to drop the bulb voltage much (about 5% or
so) to get a drastic increase in life.

2005\02\10@110408 by gacrowell

flavicon
face


> -----Original Message-----
> From: RemoveMEpiclist-bouncesEraseMEspamEraseMEmit.edu
> [RemoveMEpiclist-bouncesspam_OUTspamKILLspammit.edu] On Behalf Of Robert Rolf
> I went completely CFL over a period of a year or so. Payback was
> only a few years since the other bodies in the house don't seem to
> understand the concept of 'lights off when not in use'.

I'm sure an investigator would find only my fingerprints on the top of
all the light switches in the house; wife/kids prints would only be on
the bottom.

GC

2005\02\14@162304 by Martin McCormick

flavicon
face
       I didn't realize I had started such an active thread.:-)  A
couple of comments:  Someone in N.Z. suggested putting a diode in
series with a lamp and a couple of others described the diode buttons
that fit in the lamp socket.  In one of my past lives, I was an
electronics technician with the Audio Visual Department at Oklahoma
State University and one of our staple fix-it jobs was to revive a
certain name brand of overhead projector that, for some reason, was
designed with a diode in series with the projection lamp.  I think
they even called it an 85-volt bulb but it's been 15 years so some of
my memory may have been dimmed by the sands of time.

       Anyway, the diode sometimes burned out to a short and put the
full mains voltage across the bulb.  The energy of a half-wave
rectifier is .7 the energy of full-wave sinusoidal AC so the bulb ran
somewhat brighter but not for long.  Those bulbs were usually in the
$20-$30 range so the customers used to get pretty peeved when they
replace the first bulb, thinking its time had run out only to find the
next bulb's time ran out a few minutes later.

       We'd plug in a new diode and sell them yet another $20 bulb
and the projector was whole once again until that diode overheated and
fused in to a fancy jumper once again.  I never understood the value
of that useless bit of over-engineering at all.  Plenty of models of
overhead projectors ran on similar bulbs except they were optimized
for 120-volt service so no diode was needed.  It would have made sense
if they were 120-volt bulbs and one could throw a switch to un-short a
diode in series with it for slightly dimmer (= longer bulb life)
operation.

       The Kodak Slide projectors did have a Dim position on their
power switch, but it was a ceramic tubular wire-wound resistor in
series with the bulb, not a diode.

       Someone on this list also suggested putting a full-wave bridge
ahead of the lamp and a filter capacitor across the output.  Another
lister responded that it would make the lamp brighter which is quite
true.  Just as a half-wave rectifier supplies .7 of the energy of the
full sine-wave AC, the filtered bridge will supply the peak, not RMS
voltage of the AC wave.  This is the square root of 2 or about ~1.4
times the RMS voltage.  On a 240-volt lamp, this will be hitting it
with a steady 340 volts assuming that the filter capacitor is large
enough  to fully charge.

       The bulb will run brighter, whiter and die much
sooner just like those ill-fated projector bulbs did.

       A bit of useless trivia is in order.  A lot of projector bulbs
have what is known as an iodized quartz filament.  They actually must
run at a certain range of voltage for optimum bulb life.  I don't
totally understand what is happening, but these type bulbs have a
process at which the filament vaporizes when run at low voltage but
recovers somewhat at the optimum temperature.  The lamps even have a
collection grid in them which is not an electrical component, but a
chemical one that is involved with this process.

       No matter how one cuts it, those bulbs are like rase cars.
They run extremely hot and die young with expected lives of a few tens
of hours at best.

       It's not uncommon for 16-millimeter movie projectors to use a
30-volt lamp since the filament can be made smaller which makes the
optics a little easier to produce.  Those systems have a monster
transformer and a few of them even have a Dim option on the lamp
switch which selects a slightly lower-voltage tap on the transformer.

Martin McCormick WB5AGZ  Stillwater, OK
OSU Information Technology Division Network Operations Group

2005\02\14@165446 by Wouter van Ooijen

face picon face
> The energy of a half-wave
> rectifier is .7 the energy of full-wave sinusoidal AC

The suggestion was to put a diode in series with the lamp. No capacitors
(or inductors or other storage elements). You want to say that this
istuation the energy in half the sine (say positive halve only) is 0.7
times the energy in the full sine? So the energy in the positive + the
negative halves must be 1.4 the energy in the full sine ???? I think you
should apply for a patent immediately!

Wouter van Ooijen

-- -------------------------------------------
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consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\02\14@171655 by Mark Jordan

flavicon
face
On 14 Feb 2005 at 22:54, Wouter van Ooijen wrote:

> > The energy of a half-wave
> > rectifier is .7 the energy of full-wave sinusoidal AC
>
> The suggestion was to put a diode in series with the lamp. No capacitors
> (or inductors or other storage elements). You want to say that this
> istuation the energy in half the sine (say positive halve only) is 0.7
> times the energy in the full sine? So the energy in the positive + the
> negative halves must be 1.4 the energy in the full sine ???? I think you
> should apply for a patent immediately!
>
> Wouter van Ooijen
>

       Watch your power meter because some of them can run faster
with a half-wave load!

       Mark Jordan


2005\02\14@181204 by Martin McCormick

flavicon
face
"Wouter van Ooijen" writes:
>The suggestion was to put a diode in series with the lamp. No capacitors
>(or inductors or other storage elements). You want to say that this
>istuation the energy in half the sine (say positive halve only) is 0.7
>times the energy in the full sine? So the energy in the positive + the
>negative halves must be 1.4 the energy in the full sine ???? I think you
>should apply for a patent immediately!

       I get an Email from time to time offering an incredible
number of good Email addresses I can use to spam people with for an
amazingly low price of $99.95 or other such nonsense
so maybe I should.

       One person did suggest both a diode bridge and capacitor and
that's what I referred to.

       With a capacitor, you get the peak voltage and if the cap has
enough Joules in it, that will supply the load with a steady DC
voltage that is about 1.414 times the RMS value of the sine wave.

       If I wasn't clear, that is what I meant.

       A resistive load like a light bulb should burn almost the same
brightness when placed at the output of an unfiltered bridge as it
does when it is directly across the line.

Martin McCormick WB5AGZ  Stillwater, OK
OSU Information Technology Division Network Operations Group

2005\02\14@200913 by Russell McMahon

face
flavicon
face
> "Wouter van Ooijen" writes:
>>The suggestion was to put a diode in series with the lamp. No
>>capacitors
>>(or inductors or other storage elements). You want to say that this
>>istuation the energy in half the sine (say positive halve only) is
>>0.7
>>times the energy in the full sine? So the energy in the positive +
>>the
>>negative halves must be 1.4 the energy in the full sine ???? I think
>>you
>>should apply for a patent immediately!

> A resistive load like a light bulb should burn almost the same
> brightness when placed at the output of an unfiltered bridge as it
> does when it is directly across the line.

A single diode supplying half wave will give the filament time to cool
for substantially longer. Bulb filaments have time constants which are
roughly in the order of a half cycle - ie they do give mains hum when
a photodetector is used with them but do not give deep flickering on
the half cycles. So you would expect a reasonably greater degree of
cooling when left off for a whole half-cycle.

A warm filament has a higher on resistance than a colder filament so
MAYBE one might expect half cycle AC to give MORE than half the watts
of full cycle AC :-)




       RM

2005\02\15@032357 by Wouter van Ooijen

face picon face
>        One person did suggest both a diode bridge and capacitor and
> that's what I referred to.
>
>        With a capacitor, you get the peak voltage and if the cap has
> enough Joules in it, that will supply the load with a steady DC
> voltage that is about 1.414 times the RMS value of the sine wave.

So where does that factor 0.7 come from? Rectifying (half or full) with
sufficient capacity yields sqrt(2) times the voltage, hence 2 times the
power (neglecting non-linearity of the lamp).

>        A resistive load like a light bulb should burn almost the same
> brightness when placed at the output of an unfiltered bridge as it
> does when it is directly across the line.

Now we agree. And roughly half the brightness with a single diode if the
characteristics of the lamp were linear. But as they are not, a single
diode will reduce the brightness much more. Plus (in my experience)
introduce and irritating flickering.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\02\15@032417 by Wouter van Ooijen

face picon face
>        Watch your power meter because some of them can run faster
> with a half-wave load!

But even faster than that with the full wave, because it is 1.4 times
the -eh- full wave!

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\02\15@045959 by Russell McMahon

face
flavicon
face
> Now we agree. And roughly half the brightness with a single diode if
> the
> characteristics of the lamp were linear. But as they are not, a
> single
> diode will reduce the brightness much more.

Intuitively I would expect brightness to go down below 50% of full.

But what did you think of my argument that power consumption should be
ABOVE 50% of full due to the colder than average filament?


       RM

2005\02\15@060330 by Brent Brown

picon face
> > Now we agree. And roughly half the brightness with a single diode if
> > the
> > characteristics of the lamp were linear. But as they are not, a
> > single
> > diode will reduce the brightness much more.
>
> Intuitively I would expect brightness to go down below 50% of full.
>
> But what did you think of my argument that power consumption should be
> ABOVE 50% of full due to the colder than average filament?

Yeah I follow, but looking from another angle... if the power consumption
were above 50%, how could the filament remain colder than average?!!

(PS, don't listen to me - I'm not even thinking about it) :-)

--
Brent Brown, Electronic Design Solutions
16 English Street, Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/txt: 025 334 069
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2005\02\15@071951 by Russell McMahon

face
flavicon
face
>> Intuitively I would expect brightness to go down below 50% of full.
>> But what did you think of my argument that power consumption should
>> be
>> ABOVE 50% of full due to the colder than average filament?

> Yeah I follow, but looking from another angle... if the power
> consumption
> were above 50%, how could the filament remain colder than average?!!

It doesn't seem intuitive initially, but it's possible.
A bulb is probably more efficient in terms of watts per lumen (or
watt-ever) as the filament gets hotter. The practical limit for
hotness is a tradeoff between temperature and lifetime. Also, as
temperature rises emission moves to shorter wavelengths and moves more
out of the invisible infrared into the visible wavelengths.

So a bulb run at low temperature will draw more power than the same
bulb at a higher temperature but MAY radiate less of its energy in the
visible spectrum and also may be less efficient. I can feel a simple
experiment coming on. Defining and measuring "power" here may be
trickier than is at first apparent.


       RM

2005\02\15@075946 by Howard Winter
face
flavicon
picon face
Russell,

On Wed, 16 Feb 2005 01:19:14 +1300, Russell McMahon wrote:

> So a bulb run at low temperature will draw more power than the same
> bulb at a higher temperature

Indeed, a bulb that's severely under-run may emit heat but no light whatsoever.

> but MAY radiate less of its energy in the visible spectrum and also may be less efficient.

But hang on - surely efficiency of a lightbulb is the ratio of electrical power used to useful light emitted?  
So emitting less of its energy in the visible spectrum is a definition of lower efficiency!  All of the power
it uses is emitted (unless it creates matter per E=MC^2, and we won't get into that :-) but a lot of it is
heat (and IR) which is no good to us for the purpose of seeing.  That's why fluorescents are more efficient,
because more of their output is light rather than heat.

> I can feel a simple experiment coming on. Defining and measuring "power" here may be
> trickier than is at first apparent.

Well input power is dead easy: P = IV !  Measuring the power of the light emitted is tricky because it's
spread all round, and collecting it to measure it will involve losses.  It's actually easier to measure its
heating effect and subtract that from the input - what remains is (almost) the light that we wanted in the
first place.

I've always thought it ironic that electric heating is (in the UK at least) very expensive, when an electric
heater in a house is 100% efficient - all of the energy it is fed is emitted as heat, which is what you want!

Cheers,


Howard Winter
St.Albans, England


2005\02\15@081334 by Michael Rigby-Jones

picon face


{Quote hidden}

Whilst the conversion into heat is pretty well 100% efficient,
converting it from coal/oil etc. in the first place is not!  The you
have the transmission losses to take into account.  Whilst gas costs
some money to pump around, at least you get out of one end what you put
in the other (more or less).

Regards

Mike

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2005\02\15@082226 by Hulatt, Jon

picon face

>> I've always thought it ironic that electric heating is (in the UK at
least) very expensive, when an electric heater
>> in a house is 100% efficient - all of the energy it is fed is emitted
as heat, which is what you want!

The high cost of electricity is due to it's less that 100% efficient
generation process, as well as market conditions meaning that the
electricity companies can get away with their price.

I always find it amusing that Argos, etc, advertise "high efficiency"
etc electric heaters. I'd be impressed if they managed one less that
100% efficient.

-----Original Message-----
From: piclist-bouncesSTOPspamspamspam_OUTmit.edu [spamBeGonepiclist-bouncesSTOPspamspamEraseMEmit.edu] On Behalf
Of Howard Winter
Sent: 15 February 2005 13:00
To: Microcontroller discussion list - Public.
Subject: Re: [OT] 240-volt Power

I've always thought it ironic that electric heating is (in the UK at
least) very expensive, when an electric heater in a house is 100%
efficient - all of the energy it is fed is emitted as heat, which is
what you want!

Cheers,


Howard Winter
St.Albans, England


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