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'[PICLIST] [EE] Phase control dimming on a cheap pi'
2001\01\04@043538 by Jinx

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Twice this week I've had my work spotlight bulb blow when I turned
it on. Other spotlights in the house seem to fail more often than
ordinary bulbs, and quite regularly. And I'm sick of it. The other day
I said I thought that cold filaments are more likely to burn out if
power was applied at the peak of the mains cycle. Is this true ?

Is there a simple non-PIC solution to reduce this stress or reduce the
230V down by 10% (which would significantly increases bulb life) for
a 60W bulb. A series resistor sounds like it should work, but are there
any real safety concerns with a few watts of heat and/or regulations
that prohibit this

I'm peed off enough, if all else fails, to make a PIC circuit that will
allow initial power to the bulb only at 0V (and I don't care if I don't
break even in the long run. The satisfaction of almost never replacing
a bulb is quite appealing right at this moment)

Any comments or experiences ? One other thought was to replace
filament bulbs with the more expensive fluorescent bulbs, although
I've always felt they're "a bit cold"

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2001\01\04@044406 by Alan B. Pearce

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>Is there a simple non-PIC solution to reduce this stress or reduce the
>230V down by 10% (which would significantly increases bulb life) for
>a 60W bulb. A series resistor sounds like it should work, but are there
>any real safety concerns with a few watts of heat and/or regulations
>that prohibit this

use a high efficiency bulb. They provide more light, last longer and produce
less heat. Because of this you can usually use the highest wattage one you can
obtain in any desk lamp. The worst things about them is the shape and price.

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2001\01\04@045439 by Michael Rigby-Jones

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{Quote hidden}

How about an NTC thermistor? High resistance to begin with so switch on
surge current to the lamp will be low.  As the thermistor heats up it's
resistance decreases and applies more power to the lamp.  I think the
concept is ok, but wether you could find a suitable thermistor is another
matter all together...

Alternatively you can get an opto isolators with built in zero crossing
detection and relatively high power triac outputs.  Might be able to rig one
of these up to ensure your lamps always get switched on at the zero crossing
point.

Mike

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2001\01\04@050515 by Jinx

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> use a high efficiency bulb. They provide more light, last longer and
> produce less heat. Because of this you can usually use the highest
> wattage one you can obtain in any desk lamp. The worst things
> about them is the shape and price

But would they still blow on turn-on ? Quite happy with a 60W spot
and it's not too hot. Just fed up replacing the damn things

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2001\01\04@051335 by Michael Rigby-Jones

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> -----Original Message-----
> From: Jinx [SMTP:joecolquittspamKILLspamCLEAR.NET.NZ]
> Sent: Thursday, January 04, 2001 10:07 AM
> To:   .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
> Subject:      Re: [EE] Phase control dimming on a cheap pic
>
> > use a high efficiency bulb. They provide more light, last longer and
> > produce less heat. Because of this you can usually use the highest
> > wattage one you can obtain in any desk lamp. The worst things
> > about them is the shape and price
>
> But would they still blow on turn-on ? Quite happy with a 60W spot
> and it's not too hot. Just fed up replacing the damn things
>
Not, at least not in my experience.  They do seem to last a very long time,
but they are just compact flourescents so you have to put up with the "cold"
light, although they do seem to be better than standard tubes.  Those spot
lights don't last long at all, I was forever replacing the ones I had in my
bedroom, and they aren't cheap.

Mike

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2001\01\04@051532 by Michael Rigby-Jones

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> -----Original Message-----
> From: Jinx [SMTP:EraseMEjoecolquittspam_OUTspamTakeThisOuTCLEAR.NET.NZ]
> Sent: Thursday, January 04, 2001 9:37 AM
> To:   PICLISTspamspam_OUTMITVMA.MIT.EDU
> Subject:      Re: [EE] Phase control dimming on a cheap pic
>
> Is there a simple non-PIC solution to reduce this stress or reduce the
> 230V down by 10% (which would significantly increases bulb life) for
> a 60W bulb. A series resistor sounds like it should work, but are there
> any real safety concerns with a few watts of heat and/or regulations
> that prohibit this
>
You could just use a series cap for (relatively) lossless current limiting.
Hmm..a quick bash on my calculator says you'll need something in the region
of a 33 uF cap.  That's gonna be pretty large (and pricey) for a 230v mains
rated device.  Maybe not.

Mike

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2001\01\04@051747 by Jinx

face picon face
> How about an NTC thermistor
> whether you could find a suitable thermistor

Aye. The bulb still needs around 60W

> Alternatively you can get an opto isolators with built in zero crossing
> detection and relatively high power triac outputs.  Might be able to
> rig one of these up to ensure your lamps always get switched on at
> the zero crossing point.

Got some MOC3041's left over from a job. That would be the non-
s/w solution to zero crossing - but zero crossing needs to be done
only once, at turn-on. After that the bulb can shine on unimpeded like
a good'un. Ideally start at the zero-cross and ramp up to a V slightly
lower than full mains

There's a technique used in display matrices of pre-heating filaments
by giving them a quick flick of power for bits of a few cycles. I wonder
if this would extend bulb life by alleviating any thermal shock or is this
getting too geeky ?

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2001\01\04@051757 by Alan B. Pearce

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>But would they still blow on turn-on ? Quite happy with a 60W spot
>and it's not too hot. Just fed up replacing the damn things

The high efficiency bulbs are actually a fluorescent lamp of some sort with
either a small choke or electronic ballast. The latter are the higher efficiency
units. As I understand it the electronic ballast is done as a switch mode power
supply, so the lamp is driven with high frequency and you do not get the flicker
sometimes associated with fluorescent lamps.

The ones with a choke in them are a lower efficiency then the electronic ones as
the ballast generates some heat.

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2001\01\04@052449 by Jinx

face picon face
> > But would they still blow on turn-on ? Quite happy with a 60W spot
> > and it's not too hot. Just fed up replacing the damn things
> >
> Not, at least not in my experience.  They do seem to last a very long
> time, but they are just compact flourescents

Aahh fluorescents - thought ABP was talking about filament bulbs. Yes,
that's my thinking. False economy to keep buying these filament things.
I assume these were wall-mounted Edison screw ?

And another thing - filament bulbs are designed to work best in a
certain orientation - true ? True at one time ?

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2001\01\04@052846 by Jinx

face picon face
> You could just use a series cap for (relatively) lossless current
limiting.
> Hmm..a quick bash on my calculator says you'll need something in the
> region of a 33 uF cap.  That's gonna be pretty large (and pricey) for a
> 230v mains rated device.  Maybe not.
>
> Mike

You sure about the 33uF ? If 1uF can pass 70mA then wouldn't 4u7 be
enough for 60W ?

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2001\01\04@053509 by Michael Rigby-Jones

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> -----Original Message-----
> From: Jinx [SMTP:@spam@joecolquittKILLspamspamCLEAR.NET.NZ]
> Sent: Thursday, January 04, 2001 10:25 AM
> To:   KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU
> Subject:      Re: [EE] Phase control dimming on a cheap pic
>
> > > But would they still blow on turn-on ? Quite happy with a 60W spot
> > > and it's not too hot. Just fed up replacing the damn things
> > >
> > Not, at least not in my experience.  They do seem to last a very long
> > time, but they are just compact flourescents
>
> Aahh fluorescents - thought ABP was talking about filament bulbs. Yes,
> that's my thinking. False economy to keep buying these filament things.
> I assume these were wall-mounted Edison screw ?
>
The hi efficiency light or the spots?  The spotlights that were forever
failing were indeed wall mounted ES types.  The hi efficiency lamps I have
now are standard bayonet fitting.  At only 12 watts or so, I don't feel bad
about leaving my hallway light on all day so I can see to get into my house
after work.

> And another thing - filament bulbs are designed to work best in a
> certain orientation - true ? True at one time ?
>
Never heard this one.  Perhaps a spot would run hotter pointing down ( as
the mostly are) because the silvered side would be uppermost and hindering
the convenction cooling of the gas in the lamp??  Just a guess though.

Mike

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2001\01\04@054540 by Alan B. Pearce

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> And another thing - filament bulbs are designed to work best in a
> certain orientation - true ? True at one time ?

I believe the problem comes if you change the orientation after they have been
operating for some time. The filament can get a sag in it from being heated for
long periods of time, and if you move the bulb the filament can shake and touch
other points, resulting in a shorter electrical path which results in higher
current which results in brighter but shorter life.... which is why you can get
ruggedised bulbs for use in items like trouble lamps. These are reputed to have
stronger filaments and more filament supports so they can withstand movement
while powered on.

Another possible failure at switch on is reputed to be the filament moving due
to magnetic effects resulting in the filament touching where it shouldn't. This
is often seen by the bulb giving a bright flash at switch on.

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2001\01\04@055004 by Michael Rigby-Jones

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> -----Original Message-----
> From: Jinx [SMTP:RemoveMEjoecolquittTakeThisOuTspamCLEAR.NET.NZ]
> Sent: Thursday, January 04, 2001 10:31 AM
> To:   spamBeGonePICLISTspamBeGonespamMITVMA.MIT.EDU
> Subject:      Re: [EE] Phase control dimming on a cheap pic
>
> > You could just use a series cap for (relatively) lossless current
> limiting.
> > Hmm..a quick bash on my calculator says you'll need something in the
> > region of a 33 uF cap.  That's gonna be pretty large (and pricey) for a
> > 230v mains rated device.  Maybe not.
> >
> > Mike
>
> You sure about the 33uF ? If 1uF can pass 70mA then wouldn't 4u7 be
> enough for 60W ?
>
>
       Hmmm..880 ohms for a 60 watt lamp @ 230 volts.  For 10% less current
you would need 968 ohms total impedance.

       (968 * 968) - (880 * 880) all square rooted gives Xc=403 ohms.
1/(2pi*50*403) = 7.9 uF.

       OK, so my quick estimate was a little out....oops.  I should really
stop trying to do this electricity thing, university was such a long time
ago :o)

       Cheers

       Mike

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2001\01\04@060432 by Jinx

face picon face
> 1/(2pi*50*403) = 7.9 uF.
>
>         OK, so my quick estimate was a little out....oops.  I should
really
> stop trying to do this electricity thing, university was such a long time
> ago :o)
>
>         Cheers
>
>         Mike

I'm sure that big Christmas :oO~~##@@# has put you out of sorts for
a while. Wasn't _your_ carpet btw ?

I guess 8u2 would be the preferred value. Might have a shop around
tomorrow and get a price for an X2 if I can find one. Got this feeling
though........

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2001\01\04@061449 by Roman Black

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Jinx wrote:
{Quote hidden}

Yes. Spots are notorious for blowing often when turned
on, low life and low vibration tolerance. We had them
on the awning for one of our shops and they blew every
few weeks. Try to keep them cool if possible.

For startup, just use a resistor? Why didn't anyone
mention this? I thought it was common knowledge. The
cold filament has a very low resistance, and startups
kill bulbs. A resistor that drops 5% volts at running
will give a very soft start.
230v/60w=261mA, drop 5%=11.5v=44ohms@3w (use 10w or
2x5w). Remember a 5w resistor run at 1.5w will get
quite hot. Keep them away from the bulb.

You will get *huge* bulb life improvement from this.

-Roman

PS. We had the high efficiency bulbs in a shop, they
blew all the time too. The light fittings were recessed
into the roof, and they got hot. Don't use these
electronic ballast things anywhere they don't have
enough cooling airflow.

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2001\01\04@062120 by Michael Rigby-Jones

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{Quote hidden}

This should quite possibly be moving OT anytime now....but here goes:

Do the low voltage halogens have good life (assuming you don;t touch the
lamp and it has good airflow etc)?  Been thinking about putting some into my
workshop/spare room to provide better desk illumination.

Mike

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2001\01\04@063603 by Roman Black

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Michael Rigby-Jones wrote:

> Do the low voltage halogens have good life (assuming you don;t touch the
> lamp and it has good airflow etc)?  Been thinking about putting some into my
> workshop/spare room to provide better desk illumination.

I believe they do. Maybe the step down transformer
does a lot to reduce turn on current at phase peak
due to it's inductance, and probably reduces startup
current quite a bit due to saturation limits of its
core and windings. I've never used them, but friends
have and I have never heard mention of short bulb
life. :o)
-Roman

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2001\01\04@064019 by Jinx

face picon face
> For startup, just use a resistor? Why didn't anyone
> mention this? I thought it was common knowledge. The
> cold filament has a very low resistance, and startups
> kill bulbs. A resistor that drops 5% volts at running
> will give a very soft start.
> 230v/60w=261mA, drop 5%=11.5v=44ohms@3w (use 10w or
> 2x5w). Remember a 5w resistor run at 1.5w will get
> quite hot. Keep them away from the bulb.

Thanks. I did think a resistor was feasible, if there weren't any
serious gotchas

> You will get *huge* bulb life improvement from this

And conversely at (if you reckon with the odd voltage surge
from time to time) or over the rated bulb voltage will drastically
reduce bulb life. On a smaller scale I picked up a new 3V torch
a few months ago and the bulb lasted about a minute. Only rated
for 2.4V, thanks very much Mr Manufacturer. Nice and bright it
was though ;-)  Put 3 white LEDs in, almost as good

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2001\01\04@064844 by Jinx

face picon face
> I believe they do. Maybe the step down transformer
> does a lot to reduce turn on current at phase peak
> due to it's inductance, and probably reduces startup
> current quite a bit due to saturation limits of its
> core and windings. I've never used them, but friends
> have and I have never heard mention of short bulb
> life. :o)
> -Roman

Halogens came up last time there was a long talk about dimming.
Don't recall anything said about life-time as such, but I have this
vague recollection of if you run them too cold for the evaporate-
condense cycle to work properly it can affect long-term operation.
And dimming is off the menu because of the temperature drop

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2001\01\04@065259 by David Duffy

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Jinx wrote:
>Twice this week I've had my work spotlight bulb blow when I turned
>it on. Other spotlights in the house seem to fail more often than
>ordinary bulbs, and quite regularly. And I'm sick of it. The other day
>I said I thought that cold filaments are more likely to burn out if
>power was applied at the peak of the mains cycle. Is this true ?

Clipsal make a range of soft start switches. (~ AU$20 each) They just
replace the normal light switch mech. Just starting at 0V is not enough.
You need to limit (inrush) current for the first few hundred milliseconds.
Some of the Clipsal ones have time-out functions in them too.

{Quote hidden}

I have one of the timer (36 mins) ones on my outside light. It even warns
you (blinks off-on) 1 minute before the timer expires. You can also over-
ride them the same way as PIR light sensors. The timer circuit is very
small - looks like a TO-126 transistor sized package hanging off the back.

>Any comments or experiences ? One other thought was to replace
>filament bulbs with the more expensive fluorescent bulbs, although
>I've always felt they're "a bit cold"

Regards...

___________________________________________
David Duffy        Audio Visual Devices P/L
U8, 9-11 Trade St, Cleveland 4163 Australia
Ph: +61 7 38210362   Fax: +61 7 38210281
New Web: http://www.audiovisualdevices.com.au
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2001\01\04@070304 by Jinx

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> Clipsal make a range of soft start switches. (~ AU$20 each)

Thanks, I'll have a look into those. AU$20 is  ~ NZ$30 so it may
yet be worth having a go at my own

"Belt and braces" would be a voltage-dropping component plus
a PIC that would gradually increase the length of the portion of
the cycles

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2001\01\04@070513 by mike

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On Thu, 4 Jan 2001 22:37:27 +1300, you wrote:

{Quote hidden}

Switchmode PSUs often include thermistor-type devices to limit inrush
current - you may be able to use one of these.

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2001\01\04@070721 by David Duffy

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Jinx wrote:
>Halogens came up last time there was a long talk about dimming.
>Don't recall anything said about life-time as such, but I have this
>vague recollection of if you run them too cold for the evaporate-
>condense cycle to work properly it can affect long-term operation.
>And dimming is off the menu because of the temperature drop

I followed this thread too. Had a good talk to a friend in the lighting
control business & he said that although running halogens at low
levels for extended periods does upset the cycle, they will recover
quite OK if you run them up at 100% every so often. Some of the
lighting control systems are programmed to do this by themselves
during out-of-business hours. He also said that the cycle problem
is mainly confined to lamps where the glass envelope is far away
(in relative terms) from the filament. Dicroic lamps don't seem to be
in this category. So the upshot is that dimming is OK for them. One
thing he did mention is running electronic transformers from standard
phase control dimmers. They don't always behave correctly. Seems
that the iron-cored transformer types work best with those dimmers.
Sorry to ramble on, but it may clear things up for a lot of people.
Regards...

___________________________________________
David Duffy        Audio Visual Devices P/L
U8, 9-11 Trade St, Cleveland 4163 Australia
Ph: +61 7 38210362   Fax: +61 7 38210281
New Web: http://www.audiovisualdevices.com.au
New email: RemoveMEavdspamTakeThisOuTaudiovisualdevices.com.au
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2001\01\04@070935 by Roman Black

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Jinx wrote:
> On a smaller scale I picked up a new 3V torch
> a few months ago and the bulb lasted about a minute. Only rated
> for 2.4V, thanks very much Mr Manufacturer. Nice and bright it
> was though ;-)  Put 3 white LEDs in, almost as good

Aren't those white leds great? We use the 6000mcd
ones, mount on a stick (piece of stiff bendable
wire) and a NiCd battery. We have two in the
workshops, great for poking down in the guts
of something and putting a *lot* of light on
a tiny part. Good for reading tiny part numbers
without removing the part, and inspecting solder
connections in places the 30x micrscope won't fit.
Darn, now I'm giving away all our secrets! ;o)
-Roman

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2001\01\04@072007 by Jinx

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> Aren't those white leds great?

I've just made a 1/2 dozen 3mm torches for members of
a black powder club (that's guns, y'know, muskets, bang
bang) to poke down the barrels for inspecting wear'n'tear.
Pitting and erosion is a problem and something to look
out for if you're buying a musket

I was lucky to get those - guy the same day bought the whole
lot they had in stock to make helmet lamps for cavers and
visitors to the glow-worm grottos

But we digress......

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2001\01\04@075034 by Alan B. Pearce

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>I was lucky to get those - guy the same day bought the whole
>lot they had in stock to make helmet lamps for cavers and
>visitors to the glow-worm grottos

One of my work colleagues here in the UK does this as well, though only for
himself. He also uses them on his pushbike - provides enough light around dark
English country lanes to stop you from running into a hedge or off the road. He
tends to use little switch mode regulators from Maxim to up the voltage so he
can run them of a single AA battery. He has a small flashlight that he has
mounted 3 LEDs in instead of the single bulb. The light is brighter than the
bulb, and the battery draw lower!

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2001\01\04@075837 by Roman Black

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Alan B. Pearce wrote:
>
> >I was lucky to get those - guy the same day bought the whole
> >lot they had in stock to make helmet lamps for cavers and
> >visitors to the glow-worm grottos
>
> One of my work colleagues here in the UK does this as well, though only for
> himself. He also uses them on his pushbike - provides enough light around dark
> English country lanes to stop you from running into a hedge or off the road. He
> tends to use little switch mode regulators from Maxim to up the voltage so he
> can run them of a single AA battery. He has a small flashlight that he has
> mounted 3 LEDs in instead of the single bulb. The light is brighter than the
> bulb, and the battery draw lower!

Yep, the amount of light is amazing, especially
considering power usage. Perfect home lights,
when the price drops. I can imagine different
"warm" color options, in super-energy efficient
lights that last forever. Uncle Roman's future
prediction. ;o)

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2001\01\04@105420 by Bill Westfield

face picon face
How about replacing the switch with a dimmer, and turning them on by
turning up the dimmer, rather than a sudden "on"?  Since dimmers that
replace switches are quite common and cheap (at least here in 115VAC land),
this may be easiest and cheapest.  Beware if you have track lighting or
something though - those 60W bulbs add together pretty quick to get total
wattage beyond the usual dimmer's capabilities.

If you want to involve a PIC, it should be "easy" to create a pseudo-dimmer
circuit that does the ramp up based on a simple on/off switch...

BillW

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2001\01\04@152610 by Chris Carr

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This is the little I do know with regards Halogen Lamps

1.     The voltage of operation is critical. 12volt Halogens are designed to
operate at 11.8 volts. Anything above this voltage dramatically reduces the
life of the bulb.

2. Electronic Regulators tend to be better than transformers for maintaining
the voltage output. But there are poor electronic Regulators and good
transformers.
I should say that in the UK we now operate at the nominal European Voltage
of 230 volts but our voltage continues to be held at the upper end of the
voltage range i.e. 240 volts so a transformer with a 11.8 volt output with
an input of 230 volts is actually running the bulbs at 12.3 volts. I would
need to hunt for the graphs but trust me this significantly reduces the life
of the bulb.

3. If you have to use a transformer (easier to dim) Do not put multiple
bulbs on one transformer, One Transformer - One Bulb. Why? With Multiple
bulbs on one transformer, when one bulb blows, the output voltage of the
transformer rises, accelerating the demise of of the next weakest bulb,
which causes the voltage to rise further.........

4. All incandescent lamps last longer if soft started. The main failure mode
is the high inrush current causing a weakened element to fuse.

Regards

Chris

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2001\01\04@155403 by Jinx

face picon face
> Yep, the amount of light is amazing, especially
> considering power usage. Perfect home lights,
> Roman

I know that least one mftr is making LED traffic lights. Proper
grown-up ones, not train set dinkies

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2001\01\04@155408 by Jinx

face picon face
> Switchmode PSUs often include thermistor-type devices to limit
> inrush current - you may be able to use one of these.

Don't monitors also have one ? A little black wotsit down by the
power switch?

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2001\01\04@161254 by M. Adam Davis

flavicon
face
We have red LED stop lights in several places around Ann Arbor (MI, USA,
EARTH, SOL, uh...  The Universe...)

They are bright enough, and easy to see.  No green or yellow LED lights
(or if they are then the lens is obscuring them, the individual red leds
are easy to see)

-Adam

Jinx wrote:
{Quote hidden}

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2001\01\05@045505 by Alan B. Pearce

face picon face
>Don't monitors also have one ? A little black wotsit down by the
>power switch?

Normally in series with the degaussing coil.

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2001\01\05@082316 by Roman Black

flavicon
face
Alan B. Pearce wrote:
>
> >Don't monitors also have one ? A little black wotsit down by the
> >power switch?
>
> Normally in series with the degaussing coil.

DONT DONT use the degauss thermistor!!!!
This gives a HUGE current surge when cold,
then allows almost zero current through
when hot. The exact opposite of a lamp
soft starter!!

Just use the series resistor at about 5%
volt drop when the lamp is running. This
will give a very soft lamp start. That was
the topic?? :o)
-Roman

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2001\01\05@085434 by Bob Ammerman

picon face
----- Original Message -----
From: Alan B. Pearce <RemoveMEA.B.PearceEraseMEspamEraseMERL.AC.UK>
To: <RemoveMEPICLISTspam_OUTspamKILLspamMITVMA.MIT.EDU>
Sent: Friday, January 05, 2001 4:55 AM
Subject: Re: [EE] Phase control dimming on a cheap pic


> >Don't monitors also have one ? A little black wotsit down by the
> >power switch?
>
> Normally in series with the degaussing coil.

Yeah, and I'm guessing the final current when connected to the rather
low-impedence degaussing coil is on the very low side.

Probably too high an "Rhot" to use in series with much of a light bulb.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2001\01\05@091119 by Michael Rigby-Jones

flavicon
face
{Quote hidden}

In fact a positor has exactly the opposite characteristic that you would
want for a lamp soft start.  It has a low resistance when cold which causes
a large current to flow through the degaussing coils.  The current heats the
positor which rapidly increases it's resistance.  Would be good for making a
device to ensure a large inrush current maybe :o)

Mike

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2001\01\05@091534 by Bob Ammerman

picon face
> In fact a positor has exactly the opposite characteristic that you would
> want for a lamp soft start.  It has a low resistance when cold which
causes
> a large current to flow through the degaussing coils.  The current heats
the
> positor which rapidly increases it's resistance.  Would be good for making
a
> device to ensure a large inrush current maybe :o)
>
> Mike

yep (oh boy do I feel dumb...)
Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2001\01\05@093001 by Michael Rigby-Jones

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{Quote hidden}

Hey, happens to me every Friday.  And Monday.  Come to think of it, Tuesday
to Thursday ain't so hot either.

Mike

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2001\01\06@080147 by Peter L. Peres

picon face
>>Don't monitors also have one ? A little black wotsit down by the
>>power switch?
>
>Normally in series with the degaussing coil.

That's a PTC, not NTC. You don't want a PTC for lamps (they will light
very briefly <g>). However, looking at a dead fridge compressor might
bring luck because some of these use a NTC for the main coil to limit
inrush (remember the thread about squirrel cage AC motors and their inrush
current). They also sometimes use a PTC to drive the starting winding
instead of a capacitor (but these are rare).

Peter

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2001\01\14@194322 by Gennette, Bruce

flavicon
face
{Quote hidden}

       Uhm, don't most LEDs dim down by about 40% as they age?  You'd have
to accommodate the deteriation into any 'long-life' lighting device (slowly
increase max operating current at each switch on?).

       Bye.

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'[PICLIST] [EE] Phase control dimming on a cheap pi'
2001\03\03@191103 by Jinx
face picon face
A couple of months ago I had a big b*tch about my spotlights
regularly blowing. I've done some testing with series resistors.
Very happy with the results

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

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2001\03\04@043708 by Chris Carr

flavicon
face
First I apologise if I am repeating what has already been covered by this
thread

Jinx wrote

> A couple of months ago I had a big b*tch about my spotlights
> regularly blowing. I've done some testing with series resistors.
> Very happy with the results
>
> http://home.clear.net.nz/pages/joecolquitt/0bulblife.html
>
I've been looking for graphs like that for some time now, particularly with
regards to low voltage halogen lamps. Do you have any reference you can
point me to ? I know I have the information somewhere but I cannot find it
and all references on the web result in broken links.

If it is the switch on surge that is the predominant failure mechanism, then
instead of a resistor have you considered using a NTC (Negative Temperature
Coefficient) Thermistor. Some (considerable) time ago these used to be
marketed, for insertion in the bottom of an ES type lampholder before you
screwed in the lamp bulb.

The following deals with the subject of using NTC Thermistors for In-Rush
Current Limiting
http://www.epcos.com/inf/50/ap/ntc.pdf

Regards

Chris

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2001\03\04@050857 by Jinx

face picon face
> Do you have any reference you can point me to ?

Unfortunately no. The graph is just in a parts catalogue, don't
know where they got it from. I would expect any bulb mftr has
something similar, I didn't need to look after I found that one

> If it is the switch on surge that is the predominant failure
> mechanism, then instead of a resistor have you considered
> using a NTC (Negative Temperature Coefficient) Thermistor.

Yes I have considered a thermistor, and will try them. It happened
that I conveniently had enough Rs in the spares box to do a test.
Although it works I'm not over the moon about having a hot resistor,
but 63C isn't an excessive difficult temperature to insulate other
materials from. From what I (think I) can deduce from the pattern
of bulb failures around the house, it's that those that are on for
most of the time are the ones that fail most often at turn-on. This
would be because the filaments are weakened by working hours ?

Is it not necessarily the number of times a bulb is turned on/off (if
you ignore the chance of a peak hitting the cold filament at turn-on)
but rather the degradation of the filament that makes it more likely
to fail ?

> The following deals with the subject of using NTC Thermistors
> for In-Rush Current Limiting

> http://www.epcos.com/inf/50/ap/ntc.pdf

That is very helpful thank you. I don't like fiddling with mains and
every little helps. Cheers

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2001\03\04@065232 by Roman Black

flavicon
face
Chris Carr wrote:
>
> Jinx wrote
> > A couple of months ago I had a big b*tch about my spotlights
> > regularly blowing. I've done some testing with series resistors.
> > Very happy with the results
> >
> > home.clear.net.nz/pages/joecolquitt/0bulblife.html
> >

> If it is the switch on surge that is the predominant failure mechanism, then
> instead of a resistor have you considered using a NTC (Negative Temperature
> Coefficient) Thermistor. Some (considerable) time ago these used to be
> marketed, for insertion in the bottom of an ES type lampholder before you
> screwed in the lamp bulb.

Generally it is. After long hours of use the filament
gets metal fatigue, then the "russian roulette" factor
of turning it on cold and not knowing how many volts
exists on the mains at that part of the AC cycle causes
the filament to break.

If the mains is near full value (about a 50% chance)
there is a HUGE current into the cold filament limited
only by it's cold resistance. With a 60w globe this is
about 60 ohms. 340v into 60 ohms = 1900w. Ouch!

Adding a 50 ohm resistor in series with the bulb
only loses about 5% of total running volts, which loses
5-10% of light output. No big deal. BUT it can give
many times the running life of the bulb due to greatly
reduced cold turn-on surge current. When there is a
5% volts drop series resistor the bulbs usually run
for many years before blowing.

The resistor gives about half the cold turn on current
and half volts, so reduces cold turn on power to
about 1/4.

I learned this from an old electrician when I was an
apprentice, they used this 5% resistor trick for some
ceiling bulbs that were a real pain to get to. :o)

As for the NTC thermistor, my experience with
thermistors in the repair industry tells me they
are a LOT less reliable long term than a large
resistor is. I suppose a series thermistor + resistor
might give the best of both worlds?
-Roman

PS. The chart on Jinx' web page is great, but I would
really like to know if the "life" of the bulbs was
measured continuous or under what on/off cycling.
And does 110v/240v mains make a difference too??

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2001\03\04@082631 by Jinx

face picon face
> And does 110v/240v mains make a difference too??

One suggestion in the text with the graph is that you use
2 x 120V bulbs in series, as they have thicker filaments
to take more current at the lower voltage

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2001\03\05@030503 by Nick Taylor

picon face
Jinx wrote:
>
> A couple of months ago I had a big b*tch about my spotlights
> regularly blowing. I've done some testing with series resistors.
> Very happy with the results
>
> http://home.clear.net.nz/pages/joecolquitt/0bulblife.html

Reducing the operating voltage will most certainly extended the
bulb life, but it doesn't answer the question as to why they have
such a short operational life.  Assuming that the bulb are rated
for 240V operation they should last a lot longer unless there is
a problem.  What IS the problem?  Inadequate ventilation, allowing
excessive heat build up?  Large spikes on the power line?  Multiple
hard on/off cycles?  Excessive vibration?  Seems to me that it
would be far better to correct the problem than to waste 5% or
11% of the electricity you are buying.

  -Nick T.

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2001\03\05@035736 by Jinx

face picon face
> Inadequate ventilation, allowing excessive heat build up?

Open metal housings

> Large spikes on the power line?

Horrible coincidence if there's one always EXACTLY at turn on

> Multiple hard on/off cycles?

Once on at sunset, once off at bedtime. That's about as kind as
you could be

> Excessive vibration?

Fixed firmly to walls and ceilings

> Seems to me that it would be far better to correct the problem
> than to waste 5% or 11% of the electricity you are buying

I agree, if there was an identifiable cause other than the obvious
wear and tear through under-rated manufacturing. I betcha bulb
mftrs could make bulbs last a damn sight longer if they wanted
to. Resistors are an acceptable $10 one-off alternative to spending
$50 a year on replacement bulbs. Besides, as the brightness
hardly changes, what's the diff ?

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2001\03\05@062121 by Alan B. Pearce

face picon face
>Adding a 50 ohm resistor in series with the bulb
>only loses about 5% of total running volts, which loses
>5-10% of light output. No big deal. BUT it can give
>many times the running life of the bulb due to greatly
>reduced cold turn-on surge current. When there is a
>5% volts drop series resistor the bulbs usually run
>for many years before blowing.

One of the chain stores used to sell "long life" bulbs. These were actually 250V
bulbs, and because they were being run on 230V supply did give very long life.
The only problem was that there colour temperature was rather low, so they gave
a rather more orange colour than was really nice.

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2001\03\05@092326 by Roman Black

flavicon
face
Jinx wrote:
{Quote hidden}

I side with Jinx here, it is not always the users
fault when they get bad bulb life. Here in Australia
we have 240vac power, but it varies street to street.
I have had 220v, 260v!!, and lots of amounts in between
depending on where I lived and the current load at that
time of day. And I do measure it! :o)

People with a 110v mains may not understand what it
is like to have a cupboard full of light bulbs and put
them on regular shopping list!

I showed the calcs in a post before, the cold resistance
of a 240v 60w bulb I measured at 60 ohms. Let's assume
a 110v 60w bulb is 30 ohms cold.

At worst case (50% chance, turn-on near peak AC volts):
240v 60 ohm, = 340v peak = 1900w cold
110v 30 ohm, = 155v peak = 800w cold

So even though the bulbs are both 60w, the US
bulb has less than half the turn-on surge power
AND has a filament about twice as thick (strong).

We had 3x 100w sealed spotlights on the awning of
one of our TV repair shops, and we were replacing a
bulb just about every week. If we still owned that
shop I would have 5% loss resistors in there now!
:o)
-Roman

PS. Jinx, you spent $10 on a 10w resistor??????
I can get 5w resistors here in any shop for about
60c each!

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2001\03\05@130256 by Peter L. Peres

picon face
Well, since this is the piclist, why not make an automatic lamp saver
dimmer using a 12C508 and a triac ;-)

Peter

(It's a dimmer that has zero crossing switching and starts from 0% and
goes up to 100% in a few cycles - full brightness is attained in 1-2
seconds -- its big brothers save theatre and other big expensive lights
every day).

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2001\03\05@135301 by hard Prosser

flavicon
face
Jinx
What about using "rough service" bulbs. We use them on out garage door
opener as the vibration kills std. bulbs in a matter of weeks. The "RS"
bulbs last > 1 year. I generally get them from a repair outlet here in Chch
so I imagine a similar place in Auckland would be available to you.
The ones I use are ES fitting but I'm sure I've seen bayonet versions as
well.

Richard P




> Inadequate ventilation, allowing excessive heat build up?

Open metal housings

> Large spikes on the power line?

Horrible coincidence if there's one always EXACTLY at turn on

> Multiple hard on/off cycles?

Once on at sunset, once off at bedtime. That's about as kind as
you could be

> Excessive vibration?

Fixed firmly to walls and ceilings

> Seems to me that it would be far better to correct the problem
> than to waste 5% or 11% of the electricity you are buying

I agree, if there was an identifiable cause other than the obvious
wear and tear through under-rated manufacturing. I betcha bulb
mftrs could make bulbs last a damn sight longer if they wanted
to. Resistors are an acceptable $10 one-off alternative to spending
$50 a year on replacement bulbs. Besides, as the brightness
hardly changes, what's the diff ?

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2001\03\05@171945 by Jinx

face picon face
> Well, since this is the piclist, why not make an automatic lamp saver
> dimmer using a 12C508 and a triac ;-)

I'm working on it, trust me :)

> PS. Jinx, you spent $10 on a 10w resistor??????
> I can get 5w resistors here in any shop for about
> 60c each!

$10/10

> What about using "rough service" bulbs
> The ones I use are ES fitting

I'll look into it, ES is OK

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2001\03\06@024401 by Vasile Surducan

flavicon
face
>
> PS. Jinx, you spent $10 on a 10w resistor??????
> I can get 5w resistors here in any shop for about
> 60c each!
>
 here 5W resistors are for free...
Vasile

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2001\03\06@042100 by Jinx

face picon face
>   here 5W resistors are for free...
> Vasile

How does that work ? Have you got state resistor mines
or something ?

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2001\03\07@095128 by NDuckworth

flavicon
face
> What IS the problem?

The problem is light bulb manufacturers like to sell light bulbs!

A few years ago I was buying solenoid valves from a company that was also
supplying a light bulb manufacturer. The rep got talking to their technical
people and asked why they couldn't make a light bulb last longer. He was told
it was very easy to make a long lasting bulb, the trick was to make one that
only lasted a few thousand hours before failing!

I think we're being had!

Nigel


On Monday, March 05, 2001 5:27 AM, Nick Taylor [SMTP:TakeThisOuTntaylorspamspamINAME.COM] wrote:
{Quote hidden}

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2001\03\07@113437 by Bob Blick

face
flavicon
face
> people and asked why they couldn't make a light bulb last longer. He was told
> it was very easy to make a long lasting bulb, the trick was to make one that
> only lasted a few thousand hours before failing!

Just get some of those compact fluorescents, they always fail due to bad
electrolytic caps and then other components failing as a result. What an
incredible ripoff. Advertised as having a 5 year life, but they don't have
components that will survive 5 years.

-Bob

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2001\03\07@123453 by Bill Westfield

face picon face
   Just get some of those compact fluorescents, they always fail due to bad
   electrolytic caps and then other components failing as a result.

Yep, although I suspect that it has as much to do with poor thermal design
leading to overheating of the caps, especially when used in any orientation
other than "base straight down."  Very annoying.

BillW

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'[PICLIST] [EE] Phase control dimming on a cheap pi'
2002\06\06@182446 by Jinx
face picon face
>Twice this week I've had my work spotlight bulb blow when I turned
> it on.

> Is there a simple non-PIC solution to reduce this stress or reduce the
> 230V down by 10% (which would significantly increases bulb life) for
> a 60W bulb. A series resistor sounds like it should work, but are there
> any real safety concerns with a few watts of heat and/or regulations
> that prohibit this

It's been 18 months since this original post. Results here

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

Ditto for bulbs at my brother's house

Unqualified success

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2002\06\06@184741 by Jim

flavicon
face
Congrats!

I've got what must be five years (and more!) on a hall
lamp used a number of times (and and off) daily - but
it's *only* switched/controlled by a BSR lamp module ...

... I wonder how one of those would work in your test?

Jim

{Original Message removed}

2002\06\06@191049 by Jinx

face picon face
> I've got what must be five years (and more!) on a hall
> lamp used a number of times (and and off) daily - but
> it's *only* switched/controlled by a BSR lamp module ...
>
> ... I wonder how one of those would work in your test?

As the resistor is a completely passive device (maybe a little
inductance, but nothing compared to a filament's double coil)
I'd expect it to work just fine. To a dimmer or switcher the bulb
would look pretty normal. The control in a BSR/x10 is a triac
or relay ? Do they soft-start ? If the resistor idea had been
a flop, I'd have considered making a soft-starter with a 508
that also did zero-crossing detection. That would eliminate
possibly any occurence of turn-on pop and subsequent
cursing

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2002\06\07@091055 by Peter L. Peres

picon face
On Fri, 7 Jun 2002, Jinx wrote:

>> I've got what must be five years (and more!) on a hall
>> lamp used a number of times (and and off) daily - but
>> it's *only* switched/controlled by a BSR lamp module ...
>>
>> ... I wonder how one of those would work in your test?
>
>As the resistor is a completely passive device (maybe a little
>inductance, but nothing compared to a filament's double coil)
>I'd expect it to work just fine. To a dimmer or switcher the bulb
>would look pretty normal. The control in a BSR/x10 is a triac
>or relay ? Do they soft-start ? If the resistor idea had been
>a flop, I'd have considered making a soft-starter with a 508
>that also did zero-crossing detection. That would eliminate
>possibly any occurence of turn-on pop and subsequent
>cursing

Of course you know that there are disc type NTCs that fit in the bottom of
a screw-in E27 bulb (and others), and that they are sold in bulk (12 or 24
pieces per set) for something like $20 or less last time I looked. Just
don't use these in plastic fixtures (the heat has to go somewhere - even
if it's 5W).

Peter

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2002\06\08@160753 by Jim

flavicon
face
What I'm *really* interested in is a head-to-
head test against a "resistored" bulb ... (already
*knowing* all the factors involved ...)

I think it's common knowledge around these parts
that it's the high in-rush current to a cold
filament that does all these bulbs in with such
sudden efect (in conjuction with a thinned-filament
over time).

Now the contest comes down to zero-crosing start for
a bulb as opposed to simple 'ballasting' with a
fixed resistor - although the resistor, by lowering
the operating temp of the filament, will also work
to lengthen the life of the bulb ...

Jim


{Original Message removed}

2002\06\08@195346 by Jinx

face picon face
> What I'm *really* interested in is a head-to-
> head test against a "resistored" bulb ... (already
> *knowing* all the factors involved ...)

I'm sure the bulb manufacturers have that data. Whether
you can get it is another matter. A reasonably small test
sample might do, maybe a dozen bulbs and a PIC to run
the switching. My guess is that a combination of resistor
+soft-start (electronic or using an in-rush suppressor)
would extend the life-time of a bulb 10's of times for very
little outlay. If the bulbs I've got resistored popped today
I wouldn't care - made my money back many times already

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2002\06\09@002626 by Jim

flavicon
face
Again, I'm not interested in the hypothetical (been
there, already performed *limited* tests myself in this
area) -

- but I'm interested in *the* head-to-head _test result_
numbers (the WHOLE reason I keep responding to this thread!) ...

Maybe I can get a gov't grant to perform this head-to-head
test myself of resistored bulb versus zero-crossing turn-on
(and variation threreof) since this is an area that touches
MANY MANY people in the US (not to mention th erest of the
world) -

- but then gain the 'bulb lobby' would propbably put a kabash
on that idea (a 'study') seeing as how they make out better
business-wise with people 'in the dark' on this issue!

Jim

{Original Message removed}

2002\06\09@012100 by Jinx

face picon face
> Again, I'm not interested in the hypothetical (been
> there, already performed *limited* tests myself in this
> area) -
>
> - but I'm interested in *the* head-to-head _test result_
> numbers (the WHOLE reason I keep responding to this thread!) ...

Sorry, I don't quite understand the distinction

> Maybe I can get a gov't grant to perform this head-to-head

If one can get money for this

http://home.clear.net.nz/pages/joecolquitt/spiders.html

then I don't see a problem. (the NASA researchers had
the added bonus of taking home what the spiders didn't
use up). From a piece on ABC News the other night, I know
there is much advice available on how to get your hands
on US govt money

> test myself of resistored bulb versus zero-crossing turn-on
> (and variation threreof) since this is an area that touches
> MANY MANY people in the US (not to mention th erest of the
> world) -

Absolutely - bulb sales world-wide must gi-normous

You've heard of the world's longest-running light bulb in
Livermore, California ? 101 years old

http://www.centennialbulb.org/

> - but then gain the 'bulb lobby' would probably put a kabash
> on that idea (a 'study') seeing as how they make out better
> business-wise with people 'in the dark' on this issue!

You'll end up on a slab next to the guys who push water as an
alternative to gasoline

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2002\06\10@114511 by Harold M Hallikainen

picon face
       I kind of like the light dimmers that look like a regular wall switch.
The relatively slow fade up (when compared to filament warm up time) of
bringing the control up to full should limit inrush current, increasing
lamp life.

Harold


On Thu, 6 Jun 2002 20:07:26 -0500 Jim <@spam@jvpollspam_OUTspam.....DALLAS.NET> writes:
{Quote hidden}

> {Original Message removed}

2002\06\11@080528 by Roman Black

flavicon
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Jim wrote:

> Now the contest comes down to zero-crosing start for
> a bulb as opposed to simple 'ballasting' with a
> fixed resistor - although the resistor, by lowering
> the operating temp of the filament, will also work
> to lengthen the life of the bulb ...


Hi Jim, the resistor will WIN this contest. :o)
60w 240vac bulb filament is about 60 ohms cold,
which will dissipate close to 2kW at cold turn on.
The filament does not heat fully in one half-cycle
and even with a zero-crossing turn on device the
filament will get almost 2kW the first half-cycle,
reducing for each half cycle over the first 10 to
20. But yes, that will be SLIGHTLY gentler than
turn on at wave peak.

The resistor will give longer life than just using
zero-cross turn on. But won't compare to proper
soft-starting like many dimmers that slowly ramp the
average voltage to the bulb over 1 second etc.

I also don't like the soft-start thermistors, power
thermistors undergo significant mechanical and thermal
stresses everytime they start up (heat up) and are
one of the least reliable devices i've come across.
Yes the bulbs may last longer but the thermistors
will self destruct.

I have a incubator using a 100w light globe and a
resistor dropping 7% average volts, even with the
nasty 240vac supply we have here (often sees 255v)
the thing has gone for many months switching on/off
every few seconds. :o)
-Roman

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2002\06\11@080748 by Roman Black

flavicon
face
Jinx wrote:
>
> > What I'm *really* interested in is a head-to-
> > head test against a "resistored" bulb ... (already
> > *knowing* all the factors involved ...)
>
> I'm sure the bulb manufacturers have that data. Whether
> you can get it is another matter. A reasonably small test
> sample might do, maybe a dozen bulbs and a PIC to run
> the switching. My guess is that a combination of resistor
> +soft-start (electronic or using an in-rush suppressor)
> would extend the life-time of a bulb 10's of times for very
> little outlay. If the bulbs I've got resistored popped today
> I wouldn't care - made my money back many times already


Hi Jinx, hey I wonder if you could put something
in the switchboard on the lighting circuit, most
houses here have one or two lighting-only circuits.
Maybe a decent inductor after the "lights" fuse
would work for all lights on the circuit, as the
inrush currents will generally occur at separate
times... :o)
-Roman

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2002\06\11@084513 by Jinx

face picon face
> Hi Jinx,

Hi dude. We must catch up off-list soon - how about
your boy Bayliss then ? Doesn't he make it look easy ?

> hey I wonder if you could put something
> in the switchboard on the lighting circuit, most
> houses here have one or two lighting-only circuits.
> Maybe a decent inductor after the "lights" fuse
> would work for all lights on the circuit, as the
> inrush currents will generally occur at separate
> times... :o)
> -Roman

Do you think that would work ? For example, we've got
4 spots in the kitchen. Filaments are obviously very
different from LEDs, but I wonder if there's a chance
that one bulb might somehow reap the benefit, leaving
the others as vulnerable as they were. I just don't know

If those 4 spots are already drawing 400W through an
inductor, would a 25W or 60W then turned on benefit
from the surge-suppressing qualities of the inductor ?

I did briefly think about a single resistor in the fuse box
but I'm not a registered electrician and don't want to
monkey about with house wiring. The power rating of
such a resistor had me a little concerned, and I feel more
comfortable with each bulb having its own resistor or
whatever

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2002\06\11@091458 by Roman Black

flavicon
face
Jinx wrote:
>
> > Hi Jinx,
>
> Hi dude. We must catch up off-list soon - how about
> your boy Bayliss then ? Doesn't he make it look easy ?

Ha ha! Yeah we all ride like that here y'know. ;o)
Will email you soon!

{Quote hidden}

Yep it might not be a perfect solution but maybe
bears thinking about. The worst case scenario is when
bulb is turned on and AC volts are at peak, which
is quite a sharp waveform. An inductor would make
quite a bit of difference in that instance, and
obviously with power surges etc. I just wonder how
much difference it would make? Sick of changing
bulbs here as always.

How about this for a whacko idea, rectify lighting
circuit to DC in the switchboard, then use a PIC
controlled circuit to only allow current to rise
at a set (and gentle) delta, so the one simple device
would work for all bulbs in the house, giving soft
turn-on for any and all bulbs. You get additional
bulb life gains from running on DC too. Obviously
only good for incandescents and limited applications,
but may have some commercial value for particular
installations? :o)
-Roman

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2002\06\11@093712 by M. Adam Davis

flavicon
face
Another idea is to take advantage of fixtures that have more than one
bulb.  A pic and a few SCRs (or replace the pic with some discrete
components) in the fiture.  It turns the bulbs on in series, let's then
warm up for half a second, then switches them to parallel.

-Adam

Roman Black wrote:

{Quote hidden}

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2002\06\11@093915 by Jinx

face picon face
> How about this for a whacko idea, rectify lighting
> circuit to DC in the switchboard, then use a PIC

I'll reply to this later but here's something I just thought of -

Probably the most common users of high wattage DC
bulbs would be vehicles. Are there any comparable stats
for car lights blowing in same way that we seem to
have experience for mains bulbs ? As I ride around it
appears to me that almost all cars have a full set of lights
yet I know plenty of people that are forever changing
house bulbs

Don't know if that's just a "so what ?" question. So what
if it is ? ;-)

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2002\06\11@094303 by Jinx

face picon face
> Another idea is to take advantage of fixtures that have more
> than one bulb.  A pic and a few SCRs (or replace the pic with
> some discrete components) in the fiture.  It turns the bulbs on
> in series, let's then warm up for half a second, then switches
> them to parallel.

> >>Do you think that would work ? For example, we've got
> >>4 spots in the kitchen. Filaments are obviously very

I should have mentioned that these four spots, probably like
a lot of kitchens, hallways, lounge, etc are on the one switch.
That's not a half-bad idea changing from S to P

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2002\06\11@094736 by M. Adam Davis

flavicon
face
If you paid for a regular light bulb as much as you pay for a car light
bulb and use it as little then you should expect similar life from it.
Even in cars with daytime running lights the lights are not on for more
than an hour or two every day (on average).  1,000 hours is a long time
if you only use one per day.

-Adam

Jinx wrote:

{Quote hidden}

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2002\06\11@101119 by Doug Butler

picon face
Here in 110VAC USA we don't seem to have the problems you are having in
220VACland.  Vehicle bulbs are even lower voltage, which may explain fewer
blown bulbs.

An identical bulb designed for a lower voltage will have a shorted thicker
filament, which gives it more mechanical strength.

Doug Butler
Sherpa Engineering


> {Original Message removed}

2002\06\11@111528 by Rex Byrns

flavicon
face
I live in rural USA and DO have the same problem with bulbs blowing.  I have
learned several things.

1. Light bulbs are available with different voltage ratings - 110v,115v,120v
or even 125v
       If I use the over 110 rated, they last for a long time.
2. Long life bulbs are usually the higher voltage -- Sylvania's work best
3. Sometimes the higher voltage are called "Commercial"
4. A dimmer switch makes them last for years, even when turned up high most
of the time
5.  Flouresent bulbs replacements last very well too and are getting cheaper
all the time.

Normal bulbs - might not last one month at my house, particularly in the
kitchen or bathroom.

There is an organization, I am guessing "Tha American Society for the
Blind", they sell a higher voltage bulb for fund raising that has a built in
resistor, they last for a very long time but the output is much dimmer than
a comparable bulb.
(they also sell the best plastic wrap (Saran Wrap type) you can get)

Take note of your regrigerator at 2 in the morning.  I will probably
indicate that your freq increases markedly in the wee hours if you are on a
bulb blower line.




> {Original Message removed}

2002\06\11@115948 by Jim

flavicon
face
Rex wrote:

    "Take note of your regrigerator at 2 in the
     morning.  I will probably indicate that
     your freq increases markedly in the wee
     hours if you are on a bulb blower line."

That means *most* of us in the US would see this - as
we are all (*) tied to the same 'grid'.

I suspect it that it seems to be running faster because of
the higher line voltage at that time of night.


(*) There are a few exceptions, such as Texas - who once upon a
time was on it's own isolated grid and I think still is even
now.

Jim

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2002\06\11@122804 by M. Adam Davis

flavicon
face
They also vary the line frequency so that  in any 24 hour period there
are as close to 5184000 cycles as they can get (in the US on 60Hz AC
lines).  This is for the many clocks that still base their time on the
frequency of the line, and that loading during the day changes the
frequency slightly.

I suppose the matter is more complex than that, since they have to
synchronize the AC on many grids, but it's easier to adjust the
frequency when the load is lighter.

-Adam

Jim wrote:

{Quote hidden}

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2002\06\11@125044 by Jim

flavicon
face
My past experiments in watching line frequency (actually,
watching 1/f or the period of a cycle with a Time-Interval
Counter) showed that line frequency varied only ever so
slightly - and fractionally (small fraction) at that.

Of course, that was monitoring our grid under normal
conditions here in 'Tejas' ...

I also once upon a time programmed up a BRG (Baud Rate
Generator) set for 60 Hz rate and applied this to a
dual-trace scope -

- allowing me to watch the 'phase' of the commercial
AC mains bounce around a little in relation to the
crystal-controlled BRG reference oscillator.

Jim

{Original Message removed}

2002\06\11@165952 by Micro Eng

picon face
sounds like a good science fair project for jr high....if they started soon
enough? Rather than the month the project was due..

{Quote hidden}

>{Original Message removed}

2002\06\11@174315 by Peter L. Peres

picon face
On Wed, 12 Jun 2002, Jinx wrote:

>> How about this for a whacko idea, rectify lighting
>> circuit to DC in the switchboard, then use a PIC
>
>I'll reply to this later but here's something I just thought of -
>
>Probably the most common users of high wattage DC
>bulbs would be vehicles. Are there any comparable stats
>for car lights blowing in same way that we seem to
>have experience for mains bulbs ? As I ride around it
>appears to me that almost all cars have a full set of lights
>yet I know plenty of people that are forever changing
>house bulbs
>
>Don't know if that's just a "so what ?" question. So what
>if it is ? ;-)

Car bulbs blow just fine, thank you. Especially if the voltage regulator
is not so healthy. But they take some time to do that, because the
filament is MUCH thicker.

Peter

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2002\06\11@174319 by Peter L. Peres

picon face
On Tue, 11 Jun 2002, M. Adam Davis wrote:

>Another idea is to take advantage of fixtures that have more than one
>bulb.  A pic and a few SCRs (or replace the pic with some discrete
>components) in the fiture.  It turns the bulbs on in series, let's then
>warm up for half a second, then switches them to parallel.

And the weakest in the chain will fail first thereafter having all the
bulbs switched on 'dead cold' when paralleling.

Cheap cheap cheap places that run lots of bulbs use thermistors in each
bulb. Less cheap places can afford controlled turn-on dimmers. They use
this to save manpower, not to save bulbs. It costs more to keep spare
bulbs and janitors than to lose power on thermistors.

And Roman, thermistors are much more reliable than anything that has more
than two pins and contains a dumb blob of metal and semiconductor oxides
sintered in a press. Do not confuse these with the PTCs in TVs. They do
not come from the same mother.

Peter

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2002\06\11@174322 by Peter L. Peres

picon face
On Tue, 11 Jun 2002, Doug Butler wrote:

>Here in 110VAC USA we don't seem to have the problems you are having in
>220VACland.  Vehicle bulbs are even lower voltage, which may explain fewer
>blown bulbs.
>
>An identical bulb designed for a lower voltage will have a shorted thicker
>filament, which gives it more mechanical strength.

True, the main failure mechanism is a thinned filament spot that overheats
at startup. With a thick filament the unevenness of the surface correponds
to a much lower difference in area plus there is a lot more thermal
conductivity to neighboring cold areas. I think that the pitting effect
increases with some power of the ratio between surface evenness and
filament diameter.

Peter

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2002\06\11@215338 by Michael Rigby-Jones

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face
{Quote hidden}

Low voltage lamps are far more robust than high voltage ones, simply because
the filament in high voltage lamps has to be made very thin and long to get
the required resistance.

Cheers

Mike

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2002\06\11@215348 by Michael Rigby-Jones

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{Quote hidden}

One downside being that all lamps on the circuit would briefly dim everytime
you switched a light on.

Regards

Mike

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2002\06\12@015305 by Brendan Moran

picon face
I've been reading this thread for quite a while, and I'm beginning to think
that there are several options that aren't being considered.  Of course, it
could be that everyone considered them and decided they were useless, but
in any case, here we go:

To achieve a slow turn-on for a bulb, the best solution I can think of is
not, in fact a PIC.  It seems to me that what is needed is an analog
control circuit.  Something that regulates AC current the way that any FET
can be used to regulate DC current. (I don't know enough about TRIACs to be
able to say if they would be the answer) One possibility would be to use a
charging capacitor as one input of an analog multiplication circuit.  That
way the voltage could be slowly increased without the requirement of a
complicated digital control based circuit.

One way to simplify the idea would be to rectify to DC, then use MOSFETs as
current regulators.  Though the power consumption would be  a bit high, but
then it would be expected that that would be unusual.

I am having a similar problem at work at the moment, though the bulb life
has another factor that is not present in this discussion.  The situation
is that the light bulbs are having very short life spans.  Like 2
weeks.  They are the lighting for a shielding room for a permanent magnet
MRI.  Thus there is a very large magnetic field on them all the time, so
that when a current is passed through them, a force is created that
alternates direction 120 times a second.  In other words, being in that
room, causes the filaments to shake themselves apart.  When I was asked
about the problem, my answer to them was to rectify to DC, but no steps
have been taken on that count, so I'm not certain that it will make a very
big difference.

But I do think that using an analog circuit based on rectifying and
filtering the AC, then passing it through a MOSFET that is governed by a
charging capacitor is something that might work.  The details would need to
be hammered out, but it's still a possible solution.

As to voltage control, I was thinking that using a flyback switching
converter would be pretty easy to implement on a PIC, so if hte voltage
were too high, that could be dropped.

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2002\06\12@042731 by Roman Black

flavicon
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Brendan Moran wrote:

> I am having a similar problem at work at the moment, though the bulb life
> has another factor that is not present in this discussion.  The situation
> is that the light bulbs are having very short life spans.  Like 2
> weeks.  They are the lighting for a shielding room for a permanent magnet
> MRI.  Thus there is a very large magnetic field on them all the time, so
> that when a current is passed through them, a force is created that
> alternates direction 120 times a second.  In other words, being in that
> room, causes the filaments to shake themselves apart.  When I was asked
> about the problem, my answer to them was to rectify to DC, but no steps
> have been taken on that count, so I'm not certain that it will make a very
> big difference.

The easiest way to fix this is to switch to 12v bulbs,
with large filaments etc. Preferably automotive bulbs
which are better suited for vibration than the trendy
12v lights for home use.
-Roman

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2002\06\12@104851 by Micro Eng

picon face
deleting text about resistor in the load center...

Don't think this is a good idea, because if you ever add a plug onto the
circuit (I can't think of anything that only has lights on a circuit,
typically its the entire room) and then depending on the load will affect
the heat/power the resistor will be subject too.

I might be better to put in the switch box...better access, and the load can
be controlled (from all lights on to only one...if the bulbs burn out)



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2002\06\12@202018 by Michael Rigby-Jones

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{Quote hidden}

One downside being that all lamps on the circuit would briefly dim everytime
you switched a light on.

Regards

Mike

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