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'[EE]: Bulb Life (x:Modulating headlight)'
2001\07\02@140140 by Barry Gershenfeld

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>An update - it's been around 5 months since I added 47R 10W
>resistors to my 240VAC wall lights, and so far not one has blown.

Two light bulb preserving ideas:

1. I used to see, in those gift catalogues, a small disc-shaped
device that you put into the base under bulb.  It was a
thermistor, such that the cold resistance was high, and
once the lamp was on it would heat up, drop resistance and
give you full brightness.

2. I have always thought that the one place that X-10 "blew it"
was that you cannot start a dimmer up from zero.  If the things
would turn the lights on using a slow ramp up from "dim", I
think the life of any bulb would be extended.  Maybe the bulb
manufacturers "influenced" the design.

Barry

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2001\07\02@144737 by Jeff DeMaagd

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----- Original Message -----
From: Barry Gershenfeld <spam_OUTbarryTakeThisOuTspamZMICRO.COM>

> 2. I have always thought that the one place that X-10 "blew it"
> was that you cannot start a dimmer up from zero.  If the things
> would turn the lights on using a slow ramp up from "dim", I
> think the life of any bulb would be extended.  Maybe the bulb
> manufacturers "influenced" the design.

I don't think there's any need to suggest outside influences other than
pricing.  IMO X-10 simply plays it cheap, note the lack of 5 cent screws to
attach the serial dongle to the computer.  One is needed in order to use it
competently as a pass-through device, or jiggling the computer would cause
it to fall under the weight of the attached cable.

Jeff

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2001\07\02@152543 by Robert E. Griffith

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>> I don't think there's any need to suggest outside influences
>> other than pricing.  IMO X-10 simply plays it cheap,

That, and general ineptitude.  A few years ago a letter to the editor to
Home Automation magazine complained that most X10 products did not provide a
way to query the device as to its status.  Someone from X10 responded in a
letter to the editor (I think it may have been the founder/president)
something like "What we are doing is home control, not home feedback".  The
concept that feedback is an important part of control systems was apparently
foreign to him.

X10 is the poster boy for the worst what our patent system promotes.

OTOH, every once in a while, they do come up with an interesting,
inexpensive gadget.

--BobG


{Original Message removed}

2001\07\02@162024 by Michael C. Reid

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Regarding those small disc shaped devices, I understood that some brands
were diodes, dropping the voltage in half to save on bulb life, if you like
the idea of DC being introduced into the power grid of your home.

In the lighting control industry, we have information from Lutron that if
you decrease the voltage into a light bulb by 10% you double the life of the
bulb, 20%, quadruple the life, etc.

A big advantage of a control system is in the fading on of a load.  You do
not stress the filament with a 3 or 4 second fade time, like happens with a
mechanical switch, when the filament gets hit with the full voltage.  We
have clients who rarely replace light bulbs.

A word of warning for halogen light users, though.  In a normal incandcent
bulb, the tungsten filament slowly evaporates until it breaks.  The dark
spot on the bulb is the tungsten from the filament.  Halogen bulb need to be
run at full voltage about once a week for at least 10 minutes.  This process
redeposits the tungsten back onto the filament.  Doing this with halogen
bulbs increases their life expectancy considerably.

Also, if you ever decide to get into dimmable fluorescent lighting, it is
critical that the fluorescent bulbs or tubes be run 100 hours at full
intensity, without any dimming, before you start to dim them.

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2001\07\02@162811 by Spehro Pefhany
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At 03:22 PM 7/2/01 -0600, you wrote:
>Regarding those small disc shaped devices, I understood that some brands
>were diodes, dropping the voltage in half to save on bulb life, if you like
>the idea of DC being introduced into the power grid of your home.

It doesn't drop the voltage in half, it decreases it by about 30%.

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2001\07\02@183801 by Dale Botkin

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On Mon, 2 Jul 2001, Michael C. Reid wrote:

> Regarding those small disc shaped devices, I understood that some brands
> were diodes, dropping the voltage in half to save on bulb life, if you like
> the idea of DC being introduced into the power grid of your home.

Ummm...  no more than my bench power supply does.

Dale
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2001\07\02@184427 by Michael C. Reid

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your bench power supply has this thing called a transformer that isolates it
from the main power input!

{Original Message removed}

2001\07\02@185303 by Dale Botkin

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One does...  the other is a switcher.

On Mon, 2 Jul 2001, Michael C. Reid wrote:

> your bench power supply has this thing called a transformer that isolates it
> from the main power input!
>
> {Original Message removed}

2001\07\02@190341 by David VanHorn

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At 05:58 PM 7/2/01 -0500, Dale Botkin wrote:
>One does...  the other is a switcher.

Your switcher is either a flyback, providing it's own isolation, or
hideously dangerous.

Besides, what DC are we talking about here?
In reality, we're saying that the average current in one half cycle will be
higher than the other.
This is nothing new to the power company, they've dealt with a lot worse in
the past.

Your switchers will draw current on both cycles, BTW, as will your bench
supply, unless it's half wave rectified, which is a lousy design for a
bench supply.
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2001\07\02@190553 by michael brown

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> One does...  the other is a switcher.
>
> On Mon, 2 Jul 2001, Michael C. Reid wrote:
>
> > your bench power supply has this thing called a transformer that
isolates it
> > from the main power input!
> >

<SNIP>
>>>if you like the idea of DC being introduced into the power grid of your
home.
> >
> > Ummm...  no more than my bench power supply does.
> >
> > Dale

Seriously, could this "pulsed DC" load on the line really cause any ill
effects with other equipment?  I have never heard of this and am extremely
curious.  What about equipment that, say, contains a bridge rectifier for
example with no isolation transformer?  Wouldn't this be a "DC injector"
load on the line also?  Would there be a difference between full wave and
half wave rectifiers?  I am trying to imagine the flow of the DC current.
IOW, How does this work?

michael

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2001\07\02@190745 by Bob Ammerman

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An 'off-line' switcher (like in a computer), which is driven directly off
the AC line will still have a higher frequency transformer in it, and will
almost always contain a full wave rectifier on the incoming A/C power. This
removes any DC component from the load the switcher presents to the house
mains.

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

----- Original Message -----
From: "Dale Botkin" <dalespamKILLspamBOTKIN.ORG>
To: <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
Sent: Monday, July 02, 2001 6:58 PM
Subject: Re: [EE]: Bulb Life (x:Modulating headlight)


> One does...  the other is a switcher.
>
> On Mon, 2 Jul 2001, Michael C. Reid wrote:
>
> > your bench power supply has this thing called a transformer that
isolates it
> > from the main power input!
> >
> > {Original Message removed}

2001\07\02@193904 by Michael C. Reid

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I rarely contribute to this forum but I love the winding road that comes out
of the various topics discussed.  Although an engineer by schooling I have
not been doing much engineering in my career.  As my skills get rusty it is
fun to read the stuff on this site.  As for the injected DC with a diode on
a light bulb, I just remember reading about it in an electronics magazine
one time.

It is interested to not how many products now days are using the reactance
of a capacitor to drop AC down and then rectify it.  Most motion sensor
lights use this circuit.  In school we were always taught that you always
had to use a transformer for isolation and safety.  I guess with the
pressure on price now this is not always to rule of thumb.  BTW, are there
any ramifications with a diode on the AC mains.  When you look at all the
other sources of dirt on the AC mains, is this really of importance?


An 'off-line' switcher (like in a computer), which is driven directly off
the AC line will still have a higher frequency transformer in it, and will
almost always contain a full wave rectifier on the incoming A/C power. This
removes any DC component from the load the switcher presents to the house
mains.

Bo
>

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2001\07\02@194523 by David VanHorn

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>
>Seriously, could this "pulsed DC" load on the line really cause any ill
>effects with other equipment?

Only in extreme cases, and I'm not sure you would notice.

>  I have never heard of this and am extremely
>curious.  What about equipment that, say, contains a bridge rectifier for
>example with no isolation transformer?

Draws current on both halves, that's what bridges are for!


>  Wouldn't this be a "DC injector" load on the line also?

No, it't just that it only draws current during one half-cycle.

>Would there be a difference between full wave and
>half wave rectifiers?

Yes, half wave draws current during half the wave.
Full wave draws current during the full wave..


>  I am trying to imagine the flow of the DC current.
>IOW, How does this work?

Pretty well, usually.
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2001\07\02@200408 by michael brown

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> >
> >Seriously, could this "pulsed DC" load on the line really cause any ill
> >effects with other equipment?
>
> Only in extreme cases, and I'm not sure you would notice.
>
> >  I have never heard of this and am extremely
> >curious.  What about equipment that, say, contains a bridge rectifier for
> >example with no isolation transformer?
>
> Draws current on both halves, that's what bridges are for!

I know that, but I 'ass-u-me'd that a full wave rectifier was used just
because it gave a smother dc supply, that was easier to filter, not that it
was there to present a "balanced" load to the line.  Plus it makes more
"power" available at a higher voltage.

{Quote hidden}

Not exactly what I was looking for there.

>
>
> >  I am trying to imagine the flow of the DC current.
> >IOW, How does this work?
>
> Pretty well, usually.

OK.  I am trying to imagine the flow of the DC current within the big
picture involving the "offending" light bulb, a neutral and a hot wire.
What "unwanted" effect on the AC mains is obtained from the diode inline
with the bulb?  I hope I have been specific enough here.

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2001\07\02@201436 by Alexandre Domingos F. Souza

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>your bench power supply has this thing called a transformer that isolates it
>from the main power input!

       Maybe a switcher one?


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2001\07\02@201656 by David VanHorn

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At 07:01 PM 7/2/01 -0500, michael brown wrote:
> > >
> > >Seriously, could this "pulsed DC" load on the line really cause any ill
> > >effects with other equipment?
> >
> > Only in extreme cases, and I'm not sure you would notice.
> >
> > >  I have never heard of this and am extremely
> > >curious.  What about equipment that, say, contains a bridge rectifier for
> > >example with no isolation transformer?
> >
> > Draws current on both halves, that's what bridges are for!
>
>I know that, but I 'ass-u-me'd that a full wave rectifier was used just
>because it gave a smother dc supply, that was easier to filter, not that it
>was there to present a "balanced" load to the line.  Plus it makes more
>"power" available at a higher voltage.

Full wave is relevant to a center tapped transformer, and only uses half
the windings at a time.
Bridge works without the center tap, and uses all the windings all the time.
In a bridge, you dissipate for two diode drops in series, in a full wave,
only one.
Otherwise they are the same.



> > >Would there be a difference between full wave and
> > >half wave rectifiers?
> >
> > Yes, half wave draws current during half the wave.
> > Full wave draws current during the full wave..
>
>Not exactly what I was looking for there.

That is the only difference that I'm aware of.


>OK.  I am trying to imagine the flow of the DC current within the big
>picture involving the "offending" light bulb, a neutral and a hot wire.
>What "unwanted" effect on the AC mains is obtained from the diode inline
>with the bulb?  I hope I have been specific enough here.

None.. The pole transformer sees more load on one half of the cycle than
the other.
If EVERYBODY used diodes on EVERYTHING, and they were ALL installed the
same way, it would likely be a problem.  Odds of happening, near zero.


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2001\07\02@201854 by David VanHorn

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Sorry, correction:

Odds of happening:  1 - (the sum of the infinite series, 0.9999....)

(ducks, and runs for cover)
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2001\07\02@210635 by michael brown

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> >OK.  I am trying to imagine the flow of the DC current within the big
> >picture involving the "offending" light bulb, a neutral and a hot wire.
> >What "unwanted" effect on the AC mains is obtained from the diode inline
> >with the bulb?  I hope I have been specific enough here.
>
> None.. The pole transformer sees more load on one half of the cycle than
> the other.
> If EVERYBODY used diodes on EVERYTHING, and they were ALL installed the
> same way, it would likely be a problem.  Odds of happening, near zero.

Ok, I understand.  But originally, there was talk of a DC component being
placed onto the line because of the diode.  Would the effect of the
diode/bulb be comparable to an impedance mismatch in feed lines along with
the associated consequences?

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2001\07\02@213612 by David VanHorn

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>
>Ok, I understand.  But originally, there was talk of a DC component being
>placed onto the line because of the diode.  Would the effect of the
>diode/bulb be comparable to an impedance mismatch in feed lines along with
>the associated consequences?

I don't think so.

I don't know where this DC component came from. It's a simple circuit, on
the secondary of a transformer.
Remove the primary current, and you'll find no DC remainder.
The only effect that I can see, is more current in one half or the other of
the cycle.
Given that each individual load is small, and the fact that any large
number of them will average twoard a 50/50 distribution of polarity, I
don't see any problems.

This sounds like the sort of troubles you get into when you chrome-plate
your roll center.

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2001\07\03@075941 by Olin Lathrop

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> > Regarding those small disc shaped devices, I understood that some brands
> > were diodes, dropping the voltage in half to save on bulb life, if you
like
> > the idea of DC being introduced into the power grid of your home.
>
> Ummm...  no more than my bench power supply does.

A bench power supply would have a full wave bridge, which draws current on
both halves of the AC cycle.  A single series diode only conducts for one of
the halves, thereby drawing an average DC current.


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2001\07\03@075953 by Olin Lathrop

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> your bench power supply has this thing called a transformer that isolates
it
> from the main power input!

Unless its a "plain old" linear supply, it more likely full wave rectifies
the AC to make DC, then chops it thru a transformer at much higher than
60Hz.


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2001\07\03@075958 by Olin Lathrop

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> What about equipment that, say, contains a bridge rectifier for
> example with no isolation transformer?  Wouldn't this be a "DC injector"
> load on the line also?

No.

> Would there be a difference between full wave and
> half wave rectifiers?

Yes.


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2001\07\03@084224 by Dale Botkin

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On Mon, 2 Jul 2001, David VanHorn wrote:

> At 05:58 PM 7/2/01 -0500, Dale Botkin wrote:
> >One does...  the other is a switcher.
>
> Your switcher is either a flyback, providing it's own isolation, or
> hideously dangerous.

Yes, but the rectifcation is done before the isolation, which is what the
original poster was complaining about -- recifying AC directly.

> Besides, what DC are we talking about here?
> In reality, we're saying that the average current in one half cycle will be
> higher than the other.
> This is nothing new to the power company, they've dealt with a lot worse in
> the past.

Yes, that was my point.

> Your switchers will draw current on both cycles, BTW, as will your bench
> supply, unless it's half wave rectified, which is a lousy design for a
> bench supply.

I know.  They're both excellent power supplies, actually.

Dale
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2001\07\03@133227 by Douglas Butler

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Note that your house is fed by a transformer from the utility.  That
transformer won't allow any DC to accumulate on the power lines.  You
may provide an asymetrical load to the generator, but other appliances
in you house in parallel with the rectified ligh bulb will not know the
difference.  In theory you electric meter could detect the difference,
but I doubt it cares.

Sherpa Doug

> {Original Message removed}

2001\07\04@140755 by Peter L. Peres

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> dc in mains: ill effects

Let me put this in perspective: If you have one nightlight running
continuously at 20W and put a diode in series with it, nothing will
happen.

If your 4kW electric heater has a burned out thermostat and you wisely
decide to wire a 20A diode across the dead thermostat so you can have it
run at 2.2kW overnight, then you may or may not cause a utility
transformer on a pole outside your house to catch fire after a long enough
time (and assuming some higher load cooperation from other loads, like the
washing machine, a fridge or two and a couple more heaters). If the
electricity company catches you doing this you might be the guy paying for
all the burned out utility transformers in the past centuries.

The technical explanation has to do with transformer saturation which can
cause overheating followed by thermal runaway or a parted wire or
insulation -> flash, boom.

Peter

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