A bang or a whimper?

[Bill Stock]

CF bulb expiry that is.

I was just wondering if Compact Fluorescent bulbs generally fade out of
existence or go out with a pop? I was watching the TV on the computer when
the speakers started making snapping sounds. Great, the computer has a
problem. Then about 30 minutes later, the light on the aquarium went out. I
was thinking the ballast must be fried, with all that noise on the power
line. But switching the bulbs around proved it was just a dead bulb.

I was surprised that the bulb didn't just fade away (although it probably
has somewhat) and also by the amount of noise these things put out. What's
your experience been? Do you let your CF bulbs die or replace them at
regular intervals?

[Richard Sexton]

In article >, Bill Stock > wrote:
>CF bulb expiry that is.
>
>I was just wondering if Compact Fluorescent bulbs generally fade out of
>existence or go out with a pop?

I've seen them do both. We had a nasty recall here in Canada of some cheap
Asian screw in ones than "leaked out" smoke and caught fire. Terrifying.

--
Need Mercedes parts ? - http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
1970 280SE, 72 280SE | Home page: http://rs79.vrx.net
633CSi 250SE/C 300SD | http://aquaria.net http://killi.net

[George Pontis]

Bill Stock wrote:

> CF bulb expiry that is.
>
> I was just wondering if Compact Fluorescent bulbs generally fade out
> of existence or go out with a pop? I was watching the TV on the
> computer when the speakers started making snapping sounds. Great, the
> computer has a problem. Then about 30 minutes later, the light on the
> aquarium went out. I was thinking the ballast must be fried, with all
> that noise on the power line. But switching the bulbs around proved
> it was just a dead bulb.
>
> I was surprised that the bulb didn't just fade away (although it
> probably has somewhat) and also by the amount of noise these things
> put out. What's your experience been? Do you let your CF bulbs die or
> replace them at regular intervals?


The light output for the lamp goes down with old age, and for that
reason it is often recommended to replace CF once a year.

Also, as the lamp gets older the voltage drop across it increases. With
an electronic ballast, that means that the power dissipated in the bulb
goes up. So now the ballast is putting out more power and getting
hotter, and the lamp is running hotter too. Sometimes things break
badly due to the extra stress of temperature and power. The best
electronic ballasts have circuitry to prevent this runaway condition,
and it is usually implemented by not starting the lamp or shutting it
down when the power goes up too much.

The economical and generally troublefree Fulham Workhorse ballasts do
not have this protection. A 2x55W JBJ fixture (that I had to repair)
also did not have this protection. I don't know if any of the usual
aquarium lighting vendors do provide it, but it is a worthwhile safety
if you have a choice. It is sometimes called "End of Life" protection.

George

--

[NetMax]

"George Pontis" > wrote in message
...
> Bill Stock wrote:
>
>> CF bulb expiry that is.
>>
>> I was just wondering if Compact Fluorescent bulbs generally fade out
>> of existence or go out with a pop? I was watching the TV on the
>> computer when the speakers started making snapping sounds. Great, the
>> computer has a problem. Then about 30 minutes later, the light on the
>> aquarium went out. I was thinking the ballast must be fried, with all
>> that noise on the power line. But switching the bulbs around proved
>> it was just a dead bulb.
>>
>> I was surprised that the bulb didn't just fade away (although it
>> probably has somewhat) and also by the amount of noise these things
>> put out. What's your experience been? Do you let your CF bulbs die or
>> replace them at regular intervals?
>
>
> The light output for the lamp goes down with old age, and for that
> reason it is often recommended to replace CF once a year.
>
> Also, as the lamp gets older the voltage drop across it increases. With
> an electronic ballast, that means that the power dissipated in the bulb
> goes up. So now the ballast is putting out more power and getting
> hotter, and the lamp is running hotter too. Sometimes things break
> badly due to the extra stress of temperature and power. The best
> electronic ballasts have circuitry to prevent this runaway condition,
> and it is usually implemented by not starting the lamp or shutting it
> down when the power goes up too much.
>
> The economical and generally troublefree Fulham Workhorse ballasts do
> not have this protection. A 2x55W JBJ fixture (that I had to repair)
> also did not have this protection. I don't know if any of the usual
> aquarium lighting vendors do provide it, but it is a worthwhile safety
> if you have a choice. It is sometimes called "End of Life" protection.
>
> George


OT, and at the risk of sounding like I know what I'm talking about (cause
I'm not familiar with electronic ballasts), I don't see the power
increasing because the voltage dropped (P=E^2/R, less voltage = less
power). If the resistance increased, then the voltage might increase
from the lower current, but that would also decrease the power (P=I^2R).
If the resistance decreased, then the current would increase, and the
power would increase, but the voltage would have dropped (or remained the
same, not increased). So not I'm just curious, what is the non-critical
failure mode direction (change in resistance?).

Along the same lines (and perhaps the real source of my curiosity) is
that I was always taught that conventional fluorescent bulbs should be
changed at between 6 and 12 months of operation, but the higher cost CFs
lasted years. It was never apparent why this should be so. Sorry for
all the questions and going a bit OT.
--
www.NetMax.tk

[George Pontis]

NetMax wrote:

> "George Pontis" > wrote in message
> ...
> > Bill Stock wrote:
> >
> > > CF bulb expiry that is.
> > >
> > > I was just wondering if Compact Fluorescent bulbs generally fade
> > > out of existence or go out with a pop? I was watching the TV on
> > > the computer when the speakers started making snapping sounds.
> > > Great, the computer has a problem. Then about 30 minutes later,
> > > the light on the aquarium went out. I was thinking the ballast
> > > must be fried, with all that noise on the power line. But
> > > switching the bulbs around proved it was just a dead bulb.
> > >
> > > I was surprised that the bulb didn't just fade away (although it
> > > probably has somewhat) and also by the amount of noise these
> > > things put out. What's your experience been? Do you let your CF
> > > bulbs die or replace them at regular intervals?
> >
> >
> > The light output for the lamp goes down with old age, and for that
> > reason it is often recommended to replace CF once a year.
> >
> > Also, as the lamp gets older the voltage drop across it increases.
> > With an electronic ballast, that means that the power dissipated in
> > the bulb goes up. So now the ballast is putting out more power and
> > getting hotter, and the lamp is running hotter too. Sometimes
> > things break badly due to the extra stress of temperature and
> > power. The best electronic ballasts have circuitry to prevent this
> > runaway condition, and it is usually implemented by not starting
> > the lamp or shutting it down when the power goes up too much.
> >
> > The economical and generally troublefree Fulham Workhorse ballasts
> > do not have this protection. A 2x55W JBJ fixture (that I had to
> > repair) also did not have this protection. I don't know if any of
> > the usual aquarium lighting vendors do provide it, but it is a
> > worthwhile safety if you have a choice. It is sometimes called "End
> > of Life" protection.
> >
> > George
>
>
> OT, and at the risk of sounding like I know what I'm talking about
> (cause I'm not familiar with electronic ballasts), I don't see the
> power increasing because the voltage dropped (P=E^2/R, less voltage =
> less power). If the resistance increased, then the voltage might
> increase from the lower current, but that would also decrease the
> power (P=I^2R). If the resistance decreased, then the current would
> increase, and the power would increase, but the voltage would have
> dropped (or remained the same, not increased). So not I'm just
> curious, what is the non-critical failure mode direction (change in
> resistance?).
>
> Along the same lines (and perhaps the real source of my curiosity) is
> that I was always taught that conventional fluorescent bulbs should
> be changed at between 6 and 12 months of operation, but the higher
> cost CFs lasted years. It was never apparent why this should be so.
> Sorry for all the questions and going a bit OT.


The voltage _increases_ as the lamp ages. The electronic ballast
maintains a fairly constant current even as the voltage increases, so
power (V * I) goes up.

The older magnetic ballasts were not able to maintain the current as
the lamp aged, so they were not prone to the same type of failure.
Intead, they would have trouble starting the lamp because of the
increased voltage requirement. If it started then the current would be
lower than nominal, and the brightness would drop off more quickly with
age. In addition, the current through a magnetic ballast follows the AC
line which means that the peaks are higher than the average. This wears
out the electrodes faster than the steady current of a good electronic
ballast.

The best T8 fluorescent lamps specify a lifetime of 20000 hours. That
would be reached with a good ballast and few starts, as in a modern
office with good fixtures. But power compact lamps (and T5) that we use
for aquaria operate at a higher power density and probably will not
last quite as long. Cheap knockoffs and some common lamps may be closer
to 5000 hours. So with a good ballast, operating 12 hours a day, the
one year figure seems reasonable and conservative. When they become
hard to start, or have a lot of blackening around the tube ends, then
that would be a good time to replace.

Geo.

--

[NetMax]

"George Pontis" > wrote in message
...
> NetMax wrote:
>
>> "George Pontis" > wrote in message
>> ...
>> > Bill Stock wrote:
>> >
>> > > CF bulb expiry that is.
>> > >
>> > > I was just wondering if Compact Fluorescent bulbs generally fade
>> > > out of existence or go out with a pop? I was watching the TV on
>> > > the computer when the speakers started making snapping sounds.
>> > > Great, the computer has a problem. Then about 30 minutes later,
>> > > the light on the aquarium went out. I was thinking the ballast
>> > > must be fried, with all that noise on the power line. But
>> > > switching the bulbs around proved it was just a dead bulb.
>> > >
>> > > I was surprised that the bulb didn't just fade away (although it
>> > > probably has somewhat) and also by the amount of noise these
>> > > things put out. What's your experience been? Do you let your CF
>> > > bulbs die or replace them at regular intervals?
>> >
>> >
>> > The light output for the lamp goes down with old age, and for that
>> > reason it is often recommended to replace CF once a year.
>> >
>> > Also, as the lamp gets older the voltage drop across it increases.
>> > With an electronic ballast, that means that the power dissipated in
>> > the bulb goes up. So now the ballast is putting out more power and
>> > getting hotter, and the lamp is running hotter too. Sometimes
>> > things break badly due to the extra stress of temperature and
>> > power. The best electronic ballasts have circuitry to prevent this
>> > runaway condition, and it is usually implemented by not starting
>> > the lamp or shutting it down when the power goes up too much.
>> >
>> > The economical and generally troublefree Fulham Workhorse ballasts
>> > do not have this protection. A 2x55W JBJ fixture (that I had to
>> > repair) also did not have this protection. I don't know if any of
>> > the usual aquarium lighting vendors do provide it, but it is a
>> > worthwhile safety if you have a choice. It is sometimes called "End
>> > of Life" protection.
>> >
>> > George
>>
>>
>> OT, and at the risk of sounding like I know what I'm talking about
>> (cause I'm not familiar with electronic ballasts), I don't see the
>> power increasing because the voltage dropped (P=E^2/R, less voltage =
>> less power). If the resistance increased, then the voltage might
>> increase from the lower current, but that would also decrease the
>> power (P=I^2R). If the resistance decreased, then the current would
>> increase, and the power would increase, but the voltage would have
>> dropped (or remained the same, not increased). So not I'm just
>> curious, what is the non-critical failure mode direction (change in
>> resistance?).
>>
>> Along the same lines (and perhaps the real source of my curiosity) is
>> that I was always taught that conventional fluorescent bulbs should
>> be changed at between 6 and 12 months of operation, but the higher
>> cost CFs lasted years. It was never apparent why this should be so.
>> Sorry for all the questions and going a bit OT.
>
>
> The voltage _increases_ as the lamp ages. The electronic ballast
> maintains a fairly constant current even as the voltage increases, so
> power (V * I) goes up.

Ahh ...'constant current source' *lights went on* excuse the pun ;~). So
the tube's resistance must be *increasing* with age, but with a constant
current source (I) and an increasing R, the voltage would go up (V=IR) and
the power too (P=I^2R or IV). Thanks for that George.

This end of life circuit might just be a shunt circuit (zener diode and a
resistor) to bleed off some current when the voltage gets too high, causing
the lamp to dim (perhaps even noticeably). Without the end of life circuit,
the ballast's components would be under thermal stress from operating at
higher voltages under constant current. Regrettable that a manufacturer
can't add the few cents of circuitry (40 cents?) to save it from failure.
Built in obsolesence?
--
www.NetMax.tk

> The older magnetic ballasts were not able to maintain the current as
> the lamp aged, so they were not prone to the same type of failure.
> Intead, they would have trouble starting the lamp because of the
> increased voltage requirement. If it started then the current would be
> lower than nominal, and the brightness would drop off more quickly with
> age. In addition, the current through a magnetic ballast follows the AC
> line which means that the peaks are higher than the average. This wears
> out the electrodes faster than the steady current of a good electronic
> ballast.
>
> The best T8 fluorescent lamps specify a lifetime of 20000 hours. That
> would be reached with a good ballast and few starts, as in a modern
> office with good fixtures. But power compact lamps (and T5) that we use
> for aquaria operate at a higher power density and probably will not
> last quite as long. Cheap knockoffs and some common lamps may be closer
> to 5000 hours. So with a good ballast, operating 12 hours a day, the
> one year figure seems reasonable and conservative. When they become
> hard to start, or have a lot of blackening around the tube ends, then
> that would be a good time to replace.
>
> Geo.
>
> --
>

[Bill Stock]

"George Pontis" > wrote in message
...
> Bill Stock wrote:
>
>> CF bulb expiry that is.
>>
>> I was just wondering if Compact Fluorescent bulbs generally fade out
>> of existence or go out with a pop? I was watching the TV on the
>> computer when the speakers started making snapping sounds. Great, the
>> computer has a problem. Then about 30 minutes later, the light on the
>> aquarium went out. I was thinking the ballast must be fried, with all
>> that noise on the power line. But switching the bulbs around proved
>> it was just a dead bulb.
>>
>> I was surprised that the bulb didn't just fade away (although it
>> probably has somewhat) and also by the amount of noise these things
>> put out. What's your experience been? Do you let your CF bulbs die or
>> replace them at regular intervals?
>
>
> The light output for the lamp goes down with old age, and for that
> reason it is often recommended to replace CF once a year.
>
> Also, as the lamp gets older the voltage drop across it increases. With
> an electronic ballast, that means that the power dissipated in the bulb
> goes up. So now the ballast is putting out more power and getting
> hotter, and the lamp is running hotter too. Sometimes things break
> badly due to the extra stress of temperature and power. The best
> electronic ballasts have circuitry to prevent this runaway condition,
> and it is usually implemented by not starting the lamp or shutting it
> down when the power goes up too much.
>
> The economical and generally troublefree Fulham Workhorse ballasts do
> not have this protection. A 2x55W JBJ fixture (that I had to repair)
> also did not have this protection. I don't know if any of the usual
> aquarium lighting vendors do provide it, but it is a worthwhile safety
> if you have a choice. It is sometimes called "End of Life" protection.
>
> George
>
> --

Thanks George. It's a Workhorse5.