AC Soft Start Incandescent Lamp switch (*FINAL EXPERIMENTAL RESULTS*)

[hgg]

Hi,

In my opinion the best artificial lighting available in the 21 century is still the humble incandescent lamp
for many reasons.  The only problem is that apart from the fact that they are slowly becoming extinct,
after the introduction of the toxic "energy saving" bulbs, the lifetime of the incandescent ones for some
strange reason started to decline dramatically.  <-- (conspiracy theory)   

So, you are replacing the lamps more often than before.   They main thing that burns the incandescent
bulbs is inrush current.  When cold they have low resistance and the sudden increase in voltage creates
very large currents which raise the temperature of the filament very fast.  That is why they get burned
only when they are switched on.  I always wanted to build a small circuit that will switch them on slowly. 
I've searched the net and I could not find any circuit. Only thing I found was the strange Russian guy in
youtube advertising a similar circuit and calling it a phase controller.  (don't know why)

Do you think that something like the following will work, or will it explode?..   


AC Soft Start

Any ideas on a circuit that will actually work?
Thank you!

[Rufus]

They main thing that burns the incandescent bulbs is inrush current.

It isn't the main thing. Lamps have a limited life, when they are almost dead they will likely fail at switch on. Reducing the switch on surge still leaves you with an almost dead lamp that will soon fail anyway.

[hgg]

I would have to disagree with you.
The "limited lifetime" is created by the extreme thermal stress upon switching on
and their actual lifetime is greatly reduced when used is such a way.

[Rufus]

I would have to disagree with you.
The "limited lifetime" is created by the extreme thermal stress upon switching on
and their actual lifetime is greatly reduced when used is such a way.

This http://donklipstein.com/bulb1.html provides a quite good explanation of why you would have to be wrong.

[hgg]

From the same reference:

Making bulbs last longer:
  Long-life bulbs
  Reduced Power
  Soft-start devices ...

Anyway, that was not my initial question. 
If you know how to make a simple circuit that will slowly turn on a bulb please share it.
(Or if you think that the one I've posted will work or not.)

Thank you.

[Paul Moir]

That will not work, but it won't explode.  At 50Hz you could replace that capacitor with a wire and it would make no real difference.  Also 1000uF non polarized capacitors are hard to come by.

NTC thermistor seems like the easier way to do it. 

[hgg]

Hello Paul,

Do you mean using an NTC thermistor in series with the bulb?
What about an AC to DC converter which will power a circuit that will switch on slowly the TRIAC?

An even better idea might be to combine a soft start/stop circuit with a current limiting circuit so
that you will be able to use a 100W bulb, that has a thicker filament, light up as a 60W bulb.

[SeanB]

I just use a NTC thermistor ( taken out of a dead PC power supply so likely to be an easy to find part) in series with the lamp. Increases the life from weeks ( frequent switching cycle) to months, often years. green blob on 2 leads in series with the one mains lead, not much simpler than that.

Years ago I built a soft start for a plate exposer, which used 40 40W golf ball lamps as a light source, and which had the unfortunate tendency to trip the 25A breaker at switch on. It used a simple zero cross detector to control the charging of a capacitor which controlled the on time of an unijunction transistor to give a slow ramp up from a low phase angle to max, over a period of around 2 seconds. was very reliable while we had the developer, never had to change a lamp in it after doing this mod to it.

I used the same circuit later on with larger capacitor values to give a 2 minute turn on time to a lamp to gently wake me in winter.

[hgg]

SeanB, too much for me to digest in a single paragraph...   
That sounds exactly what I want, but the unijuction transistor, I hear it for the first time ...
I will look it up.  Do you have any circuit diagram to have a look at?

So the NTC thermistor is a good solution, but if I can make it ramp up in 30 seconds it would
be even better.  What about the slow switching off?  It might not affect the filament as much but
it will make a difference as well. 

Thank you!

[hgg]

What about the following circuit modification?


AC Soft Start 2

If I find a way to slowly power the gate of the TRIAC, wouldn't that cause the bulb to light up slowly;
Maybe the capacitor needs to be in series with the gate of the TRIAC. (?)

[Zero999]

Just buy a dimmer switch. The amount of time for you to turn the it on should be sufficient to act as a soft start to lengthen the life of the bulb.

[hgg]

Hero999,

Indeed I can buy the dimmer, or even the soft starter circuit already assembled, (if I can find it),
but I also want to learn a thing or two by building it myself.

[Kjelt]

If you insist using incandescent lamps why not switch to 12V Halogen. If you run them with a modern SMPS at 11,7V they have a very long lifetime and the SMPS does the softstart for you. Cheap, long lifetime, no problem but also no project.

[SeanB]

Unijunction transistors are now pretty much unobtanium devices, so building it will be difficult. NTc is cheap and simple, so I use it.

[hgg]

Kjelt the 12V halogen lamps would need transformers and would be difficult to use them on ceiling
lighting.

SeanB, do you know what the switch on time would be with an NTC thermistor?
Can I change that with different thermistors?

(I've already found one from a faulty power supply I had.   Its an SCK2R58)

[IanB]

The modern world is making it very difficult to have controllable lighting. Every light in my house is on a dimmer switch, and I run all my lights at 1/3 to 1/2 brightness. Putting the lights on full power now results in an "Ow! My eyes!" level of brightness.

Sadly, CFLs are invariably not dimmable (and the light has a horrible colour). LED lamps are sometimes dimmable, mostly not, but are hugely expensive. The halogen replacements for regular incan bulbs are not dimmable either. Halogen lamps need to be run at near full power to work properly. I have read that if you dim them they will have a shorter lifetime.

Fortunately I have found that bulbs run at half brightness last for years, so I can stockpile spare bulbs.

[edavid]

The modern world is making it very difficult to have controllable lighting. Every light in my house is on a dimmer switch, and I run all my lights at 1/3 to 1/2 brightness. Putting the lights on full power now results in an "Ow! My eyes!" level of brightness.

Why don't you buy lower wattage bulbs?

Sadly, CFLs are invariably not dimmable (and the light has a horrible colour). LED lamps are sometimes dimmable, mostly not, but are hugely expensive. The halogen replacements for regular incan bulbs are not dimmable either. Halogen lamps need to be run at near full power to work properly. I have read that if you dim them they will have a shorter lifetime.

This is old data, dimmable CFLs are readily available (although expensive).  Also, you have your choice of color/colour temperature.  Warm white CFLs are very close to incandescent.

[hgg]

IanB that's what I want to do.  Run higher wattage bulbs at lower brightness and also use the
soft on - soft off circuit.  I think that they will last much longer this way.

[edavid]

Anyway, that was not my initial question. 
If you know how to make a simple circuit that will slowly turn on a bulb please share it.
(Or if you think that the one I've posted will work or not.)

Well, it was the premise of your question.  If you start from a faulty premise, you can't expect people to ignore that.

Anyway, your circuit won't work.  You need to PWM the bulb from 0% to 100% over the desired startup time.  Your circuit has no way to do that, it's just a dimmer.

The NTC method is the only simple way to do it, but it has the flaw that if you turn the lamp off and then on again, the thermistor stays hot, so it doesn't do anything.  Maybe that doesn't matter since it's a placebo circuit anyway.

[IanB]

Why don't you buy lower wattage bulbs?

Most are 40 W or 25 W.

This is old data, dimmable CFLs are readily available (although expensive).

Why should I replace inexpensive incandescent bulbs with expensive CFLs?

Also, you have your choice of color/colour temperature.  Warm white CFLs are very close to incandescent.

I have not yet met a fluorescent lamp with a pleasant colour. (Also dimmed incans have a warm yellow glow similar to firelight.)

[edavid]

Why don't you buy lower wattage bulbs?

Most are 40 W or 25 W.

Then 15W bulbs should be perfect.

Why should I replace inexpensive incandescent bulbs with expensive CFLs?

I didn't say you should - just that your statement that CFLs are "invariably not dimmable" is incorrect.

I have not yet met a fluorescent lamp with a pleasant colour. (Also dimmed incans have a warm yellow glow similar to firelight.)

It sounds like the problem is that you don't like 2700K "warm white" light.  You must  really hate daylight.

[IanB]

I have not seen a dimmable CFL on the shelves of any brick and mortar store, ever. Believe me, I look every time I go past the lighting section. Where are the dimmable ones to be found?

[Kjelt]

The modern world is making it very difficult to have controllable lighting.

The modern world is making it extremely easy to have controllable lighting, DALI, DMX, Zigbee, Zwave, Dynet, IP, 0-10V, you name it there are lighting fixtures that support it and controllers that make the entire home controllable in a snap.

LED lamps are sometimes dimmable, mostly not, but are hugely expensive.

What is expensive? It is so relative. People spent fortunes on their interior: tables, closets, couches, paintings but lighting which is equally as important to make those couches and paintings etc. shine and flourish at evening to enjoy, may not cost anything? Weird world.

This is old data, dimmable CFLs are readily available

True, but they are being replaced with leds if quality of lighting is an issue.
CFL's and TL's do have a small dimming problem:
1) The colourtemperature rises when dimming, so in contrary to a lightbulb where the colortemperature lowers when dimming the CFL white gets colder. This is due to the phosphors.
2) When dimming, the current through the tube is lowered, but the temperature must not get under a certain temperature or the current will stop and the light is out. Therefore the current through the filaments is increased when dimmed and in case of extreme dimming (<10%) the lifetime of the lamp decreases rapidly.

Anyway here in northern Europe everyone is already starting to switch to Leds, my new extension of the livingroom was fully led and I built my own RS485 network and drivers to control them.

[hgg]

eDavid,  Where is the faulty premise?

They main thing that burns the incandescent bulbs is inrush current.  When cold they have low
resistance and the sudden increase in voltage creates very large currents which raise the temperature of
the filament very fast.

Do you have any actual data which show that inrush current and thermal stress are not important factors
for the lifetime of incandescent lightbulbs?  If you have, you would save me time trying to build this circuit.

[SeanB]

Around a second, plenty of time for the lamp to warm up to operating temp. You typically have an inrush of around 10x normal, which is a lot better than the typical 50x of a cold lamp. Basically it is a 5R or 10R series resistor to limit current in the initial stages to keep the rate of heating down.

[hgg]

Not bad.  So can I use for example 3 thermistors in series to increase the ramp up time?
Can I also use a capacitor in parallel with the bulb to damp the off time as well?

[edavid]

eDavid,  Where is the faulty premise?

They main thing that burns the incandescent bulbs is inrush current.  When cold they have low
resistance and the sudden increase in voltage creates very large currents which raise the temperature of
the filament very fast.

Do you have any actual data which show that inrush current and thermal stress are not important factors
for the lifetime of incandescent lightbulbs?  If you have, you would save me time trying to build this circuit.

The failure mechanism of incandescent lamps is evaporation of the filament.  Don Klipstein's old page does a good job explaining the positive feedback mechanism.  Soft start doesn't change this.

Let me turn it around and ask if you have any actual data that supports your idea that soft start will significantly extend lamp life.

[Paul Moir]

Just attach the NTC to a big block of something to slow it down?

Circuit #2 won't work either I think; it only accounts for the postive going cycle of the AC waveform.  Imagine what happens when everything flips over.

My thinking is that you're trying to do two things at one time; open up the firing phase angle with an RC like a normal light dimmer (which must be done each half cycle, so fast) and second to do this slowly.  Two ways strike me as being possible.  One is to have two circuits essentially, one for the postive and one for the negative cycle.  Probably would be with two SCRs but maybe not.  Second would be brute-force and ignorance.  Take a bog standard dimmer circuit, change out the pot for a optocoupled LDR (so it works on both cycles) and build a slow R/C charge circuit to power the LED.  Stupid but would work!

PS - calculate your current through R1 and R2.  You've got a lot of power being dissipated there.  Don't forget there's a big difference between US/Canada 110v^2/R and 220v^2/R when looking at generic circuits on the web!  And big Rs mean small Cs which is good.  You just need enough current to turn on your TRIAC/SCR when you want it to.

PPS - I have no idea why everyone is getting all high and mighty on this.  I don't agree with the premise either but that's not the point of this discussion, as was covered some time ago. 
 

[edavid]

I have not seen a dimmable CFL on the shelves of any brick and mortar store, ever. Believe me, I look every time I go past the lighting section. Where are the dimmable ones to be found?

Here's one that's sold by Home Depot: http://www.homedepot.com/p/Feit-Electric-60W-Equivalent-Soft-White-2700K-GU24-Spiral-Dimmable-CFL-Light-Bulb-BPESL13T-GU24-DIM/203450789

[Kjelt]

Here's one that's sold by Home Depot: http://www.homedepot.com/p/Feit-Electric-60W-Equivalent-Soft-White-2700K-GU24-Spiral-Dimmable-CFL-Light-Bulb-BPESL13T-GU24-DIM/203450789 

And be amazed about the "ultra expensive" dimmable Led lamp they also sell: $13.-  that's cheap!

http://www.homedepot.com/p/Philips-13-Watt-65W-BR30-Indoor-Soft-White-2700K-Dimmable-LED-Flood-Light-Bulb-E-423798/203408017#.UpO3mklgWCg

[hgg]

The failure mechanism of incandescent lamps is evaporation of the filament.  Don Klipstein's old page does a good job explaining the positive feedback mechanism.  Soft start doesn't change this.

Don't get me wrong but where are the data? 
Neither you nor Don provide any actual data.

The theory says that evaporation is the cause and indeed it is a major factor,
but does anybody leave their lamps on all the time?  I say that another
major factor is thermal (hot & cold) stress.  Going from cold to extreme hot
and vice versa creates the small cracks on the filament which then will get
much worse with time and will decrease its lifetime considerably more.

Here is an example of an immortal bulb...   
http://sanfrancisco.cbslocal.com/video/8903225-worlds-longest-running-lightbulb-goes-out-in-livermore/

[Zero999]

It sounds like the problem is that you don't like 2700K "warm white" light.  You must  really hate daylight.

The 2700K phosphor doesn't produce exactly the same colour as a filament at 2700K. It's just an approximation and not a very good one at that. Rather than emitting a continuous spectrum, there are spikes and gaps so the colour rendering index is poor.

I like real day light but the yucky greyish blue light emitted from daylight simulation bulbs is nothing like the real thing.

[edavid]

It sounds like the problem is that you don't like 2700K "warm white" light.  You must  really hate daylight.

The 2700K phosphor doesn't produce exactly the same colour as a filament at 2700K. It's just an approximation and not a very good one at that. Rather than emitting a continuous spectrum, there are spikes and gaps so the colour rendering index is poor.

Not relevant since he doesn't like 2700K incandescents either.

[jahonen]

I recently changed most of the fluorescent tubes at home from 2700/3000K (827/830) to 4000K (940), thus ones with 4000K CRI > 90. I used Philips TL-D 90 De Luxe series, but they also have TL-D 90 Graphica which has better still CRI. I think that they make those up to 6500K if one prefers higher color temperature. There is some penalty of lumen output for having that improved CRI but not anything huge. lm/W FOM still competes quite well against LED bulbs, especially with electronic ballast (I did upgrade those too).

I think that those 940 ones look much nicer, almost pure white. Colors look much better with those. Only problem with those that they seem to be almost unobtanium locally, all you can find here is just that "piss" colored 2700K.

Regards,
Janne

[Kjelt]

Hi the 8xx series has a usual color rendering around 85 and the 9xx series has a color rendering around 91.
Difference is small and usually the 900 series are used mainly where printed material has to be checked on colors.
So for 4000K you could also look for the cheaper and more obtainable 840 

[BravoV]

I say that another major factor is thermal (hot & cold) stress.  Going from cold to extreme hot and vice versa creates the small cracks on the filament which then will get much worse with time and will decrease its ....

Just curious, do you have any data to back that up ? 

[hgg]

Just curious, do you have any data to back that up ? 

Maybe the following will convince you:
http://spinoff.nasa.gov/spinoff/spinitem?title=Bulp+Miser+%25281978%2529

At least 300% greater runtime! ...
... and they could have done better if they had taken into account the coolling stress as well...
with more than 300% increase, the filament evaporation becomes a secondary factor now.


wilfred, where did you find them ??   Very rare these days.

[BravoV]

Hmm .. not very convincing, besides that is an "advertisement" archive, not a research paper or report.

[dfmischler]

And be amazed about the "ultra expensive" dimmable Led lamp they also sell: $13.-  that's cheap!
http://www.homedepot.com/p/Philips-13-Watt-65W-BR30-Indoor-Soft-White-2700K-Dimmable-LED-Flood-Light-Bulb-E-423798/203408017#.UpO3mklgWCg

I prefer this one (5000K and 10 year warranty).

[Kjelt]

I prefer this one (5000K and 10 year warranty).

5000K that is very cold light to do a lot of work in and keeps you from sleeping or even sustain from creating sleephormones, naah too cold for me at home, nice for in the shed, garage or your job but that's it.

[hgg]

Hi,

Since I cannot (yet) build an AC ramp up and ramp-down circuit I will try to use an in series
thermistor to protect the bulb from inrush current.  Its a bit tricky to size the correct thermistor,
so maybe you can verify my choice.

A typical OSRAM 60 Watt incandescent lamp has a 61 Ohms resistance when cold and 808 Ohms
when hot, with 220V AC.

So the inrush current will be 3.6A which is 13 times more than its working current of 272mA.

The thermistor that I chose has the following specifications:
Resistance @ 25 degC        = 400R
Resistance @ Max Current  = 9.8R
Max Steady State Current  = 200mA
Thermal Time Constant       = 32 sec
Dissipation Factor               = 11mW/degC

I will use the thermistor in series with the bulb and these are the two states of the circuit:


Thermistor Circuit

So the inrush current during the cold state will be 477mA and the working current when the
thermistor is hot will be 269mA.  There will be no stress on the bulb but the initial current
will be 1.7 times more than the thermistor max value.   Do you know if the thermistor will be able
to handle that?  It will be for a short time.  I don't want to save the bulb and stress the thermistor...

Do you think that the above thermistor choice is correct?
How can you calculate the time it takes for the bulb to light up fully?

There is a way to short the thermistor when it gets hot with a latching relay but I not sure
yet how to do it.

Any help is appreciated.
Thank you!

[IanB]

So the inrush current during the cold state will be 477mA and the working current when the
thermistor is hot will be 269mA.  There will be no stress on the bulb but the initial current
will be 1.7 times more than the thermistor max value.   Do you know if the thermistor will be able
to handle that?  It will be for a short time.  I don't want to save the bulb and stress the thermistor...

I don't follow your logic here. You have indicated "Max Steady State Current  = 200 mA" and yet you have calculated a steady state current when the bulb is operating of 269 mA. Your steady state current exceeds the maximum current by a factor of 269/200 = 35%.

This is not for a short time, this is continuous. Exceeding the maximum current rating will mean the thermistor gets hotter than it is designed to get and I presume its life will be shortened as a result.

(You can do a simple calculation about the thermistor temperature. The power dissipated at maximum current will be I²R = 0.2² x 9.8 = 0.39 W = 390 mW. With a thermal coefficient of 11 mW/C the temperature rise above ambient will be 390 / 11 = 35 C. If ambient temperature is 25 C then the thermistor will heat up to about 60 C.)

It may not hurt to exceed the maximum recommended current by 35%, but it is not likely recommended. You might want to choose a part with a higher current rating.

[hgg]

I will not leave the thermistor in the circuit after the initial surge.  I will short it out with
a relay as I said.  (I did not make it clear).  That is why I need to know how long it will
take for the thermistor to reach its lowest resistance.  Your calculation if for the final
temperature of the thermistor, but I need to calculate the time it will take to reach
its lowest resistance.

[IanB]

The time is not something that can be reliably calculated with the data available. It would be far more accurate to put the device on the bench and measure it.

[hgg]

I thought that the time could be calculated from the specification values.

If I use two similar thermistors in parallel they will be able to handle 400mA continuous current.
I need to short them out afterwards, because now I will dissipate more energy than the bulb itself,
they will be running hot and in case of a sudden blackout the thermistor will not protect the bulb
because they need enough time to cool down.

That's why I need to use a latching relay anyway.
Do you know how to connect it so that when the thermistors reach a low resistance they will trip
the relay?

[IanB]

No, time can only be calculated from parameters that have time in them. There are no parameters with a time dimension in the values you listed.

However, good design is a combination of calculation and experiment. You do calculations to help set up the experiments, and then you do experiments to confirm those things that are hard to predict from calculations. The exact time for a thermistor to heat up is not something you can calculate accurately, but it will in any case only be a few seconds. What is a second or two here or there?

How can you say the thermistor will dissipate more energy than the bulb itself? We already did the calculation: thermistor 0.39 W, bulb 60 W. The thermistor is dissipating only 0.65% of the power in the circuit.

Also, please note you can't put two NTC thermistors in parallel because they have a negative temperature coefficient. One of them will simply take all the current and the other one will stay high resistance.

As for the relay, I'm not sure exactly how to do that without some thought and careful choice of the relay. It it easiest just to use the thermistor.

[hgg]

Also, please note you can't put two NTC thermistors in parallel because they have a negative temperature coefficient. One of them will simply take all the current and the other one will stay high resistance.

I didn't know that...

How can you say the thermistor will dissipate more energy than the bulb itself? We already did the calculation: thermistor 0.39 W, bulb 60 W. The thermistor is dissipating only 0.65% of the power in the circuit.

Yes you are right... my mistake.   When its hot its power dissipation will be very low.
P = I2R = 0.269A * 9.8 Ohms = 0.7 watts.

So if I find a way to short it out afterwards, the specific thermistor is not a bad choice, correct?

[SeanB]

If you are going to short it out anyway why use the thermistor? Just use a regular power resistor and a nonresettable thermal fuse in thermal contact with it in case of anything happening to the bypass circuit.

I did that using a 24V ultra low current relay that only had to handle the running current so wear on the contacts is not a factor. The relay was powered via a resistive dropper that fed a bridge rectifier that fed the relay in parallel with a 1000uf capacitor. Gave a delay of around a second on power up to not nuisance trip the breakers on inrush current, but still would trip on a short circuit. A 130c thermal fuse on the resistors was there for the relay failing open circuit. Resistors were 10W ceramic wire wound units of 10R, 2 in parallel for my application.

For your application using 100R 10W would work.

This setup ran for many years until I upgraded and installed separate NTC thermistors on each power transformer ( 2 300VA units to give 220VAC, 50VAC and 24VAC to run the machine) as well as a separate feed for the new inverter via a mains filter, as it has it's own inrush limiter.

[hgg]

Because the thermistor will give the bulb filament a very nice ramp up current with no abrupt steps.
After the lamp is fully on, I will short out the thermistor.  I am trying to think of a way to use the
property of the thermistor so that when it reaches its very low resistance the relay will short it out.
(I haven't found anything yet...)

Do you have any schematic of the resistor & relay circuit you used?

[Rufus]

I will short out the thermistor.  I am trying to think of a way to use the
property of the thermistor so that when it reaches its very low resistance the relay will short it out.
(I haven't found anything yet...)

The only way soft start circuits extend lamp life by more than a few percent is by leaving something in series with the lamp to reduce its operating voltage. Shorting out a soft start thermistor makes it even more pointless.

[SeanB]

I do have the circuit, drawn in what is now called DaveCAD, but it is at work. Not exactly complex though, using 6 different components and a little bit of well butchered Veroboard. Resistors were really derated to fit my definition of safety margins, and they always ran cool. It was built from parts from the junk box, even the thermal fuse was a spare unit I had around for use in fans.

[hgg]

Shorting out a soft start thermistor makes it even more pointless.

I don't want to save the bulb and stress the thermistor... 
After the thermistor does its job, it is no longer needed.
I am looking for the the most efficient way to protect the
bulb and all the other  components as well, so that the
whole solution will last.

[IanB]

I don't want to save the bulb and stress the thermistor... 
After the thermistor does its job, it is no longer needed.

Several people in this thread have told you that putting a soft start on a light bulb will not extend the life of the bulb.

The life of a bulb varies inversely (and exponentially) with the operating temperature of the filament. The hotter the filament, the shorter the life. All a soft start will do is to delay the inevitable bulb failure by a few extra starts.

Furthermore, all components are stressed somewhat in operation. If you put a relay in there you will be stressing the relay to save the thermistor.

If you really want to extend the life of the bulb the best option is to put it on a dimmer circuit and operate the bulb at lower brightness. Drop the brightness by 10% and the bulb life will probably be doubled.

[hgg]

I have yet to see any actual data that support your rather strong belief.
People from the Apollo space program have a different opinion.
If you have any actual data, you will save me a lot of time.

[IanB]

I have yet to see any actual data that support your rather strong belief.
People from the Apollo space program have a different opinion.
If you have any actual data, you will save me a lot of time.

You could start your researches here:

Why does a light bulb burn out?

[hgg]

I've read it before.
They have not used any kind of soft start circuit in their experiments.

Please read the following more carefully:
http://technology.nasa.gov/?t=open&this=/success_story/larc/9/200669

[Rufus]

I have yet to see any actual data that support your rather strong belief.
People from the Apollo space program have a different opinion.
If you have any actual data, you will save me a lot of time.

Seriously?

"It was originally developed during NASA's Apollo program to protect the Saturn V launch vehicle from electrical current surge"

No mention of lamps at all. NASA develop some kind of thermistor. An shyster claims putting it in series with a lamp will save money. NASA keen to show their government funded work provides commercial spin offs publish one page on the work of this shyster and you claim that counts as approval from the Apollo space program.

I am not surprised data on the effect of soft starting is hard to find. Lamp wear out and failure mechanisms are well understood and the effect of soft stating quite predictable. The only people who could benefit from such data are the shysters trying sell soft starters and if they have any they haven't published it because it doesn't support their claims.

[IanB]

So on the one hand we have a detailed analysis of bulb operation and the physics and metallurgy of the bulb filament, with photos, electron micrographs, experiments and calculations you can perform yourself.

On the other hand we have a short paragraph making a claim with no data, no details, and no experimental evidence to support it.

And you would rather believe the unsupported claim than believe the science?

It seems you need to to the experiment yourself. Here is how you can do it:

In a laboratory, set up 100 light bulbs. Put a thermistor in series with 50 of them, and put an ordinary 10 ohm resistor in series with the other 50. Rig up an automated relay system that turns the bulbs on for an hour, then turns them off for an hour, then turns them on for an hour, 24 hours a day.

Watch the bulbs over a period of months and record the failure rate in each group. See whether one group fails at a faster rate than the other.

When you have done the experiment come back and let us know the results.

[IanB]

Seriously?

"It was originally developed during NASA's Apollo program to protect the Saturn V launch vehicle from electrical current surge"

No mention of lamps at all. NASA develop some kind of thermistor. An shyster claims putting it in series with a lamp will save money. NASA keen to show their government funded work provides commercial spin offs publish one page on the work of this shyster and you claim that counts as approval from the Apollo space program.

Here's the kicker:

Public Release Date: 0000-00-00

The "invention" does not even have an official publication date.

[BravoV]

The direction of this thread's discussion is becoming more and more towards religion rather than an applied science.

.... "I want to believe ..."

Audiophool was born this way. 

[hgg]

It sounds almost as if you are working for the "energy saving" CFL bulb industry.   

Anyway, thank you for your help.

[SeanB]

Lower the voltage a little and the bulb lasts longer, but the light output is redder and lower intensity. I run a lot of 12V 20W dichroic lamps at work, and they have a long life with a reduced voltage, failing only at turn on. Failure while operating is invariably caused by a failing socket that arcs and burns the lead wire. Life is also strongly dependant on manufacturer and plant, a lamp made in the EU, USA or almost any country other than China lasts a lot longer, and the PRC made lamps have a widely varying life depending on the manufacturers QC. Best lamps are made in Poland by Phillips currently, as they are about the only ones still left in EU making lamps.

[hgg]

Best lamps are made in Poland by Phillips currently, as they are about the only ones still left in EU making lamps

Nice to know.  Thanks!

[SeanB]

Youy cannot buy then in EU though, too much mercury in them, which gives the best life. Worst lamps are those low mercury ones, as they always go mercury starved and glow pink.

[hgg]

Reviving an old topic just to show the results of an experiment that lasted many months.

I was trying to find a simple soft start for incandescent lamps and in the end I used in series
thermistors.  I made a simple 555 timer circuit that was turning on and off a relay every
five minutes and switching between two bulbs.  One of them had two thermistors in line.
Its hard to find thermistors with exactly the value you want, that is why I used two in series.
The time interval was chosen in order for the thermistors to return from 90 degrees Celsius,
back to the ambient temperature.   Each 40W bulb was 5 minutes on and 5 minutes off.
All bulbs were from the same batch.  OSRAM 40W / 400 lumen.



(Image has been processed in order to show everything equally exposed. 
The bulb is way brighter from what it looks like in the photo.)

The bulb with the thermistor has a nice soft start and was reaching full brightness after 90 seconds.

The results:
The protected bulb has already outlasted two unprotected ones and it keeps going strong!
Each bulb lasted for exactly 2 months.   (or 720 hours of continuous operation and 17280 switchings.)

So, for the life of the incandescent, inrush current and thermal stress is just as important as filament
evaporation. I will continue the experiment to see how much longer this bulb will last because I think
that inrush current is more important.  Its been already on for at least 1440 hours.  I will report back.

Bulb Miser and NASA were right I think.   

[SeanB]

How about this lamp? Still going strong, and made circa 1939.

[hgg]

Its barely lit but nice.    
Do you know if it was shinning brighter before?

[SeanB]

It was dimmed to show the filament. Otherwise it is a 16 candlepower lamp (40W equivalent) and has a SSR and a small 10R thermistor ( ex PC power supply one) to soft start it. It has been doing faithful work as a wake up alarm now every morning for a few years. I took a clock radio and cut the board in half, removing the radio side, and put a hockey puck size Opto22 SSR in the space now opened up and fed the mains through it to the lamp. I had to replace the radio with a new one because the old one failed after 20 years of use.

I do have a lifetime supply of spare lamps as well, and if I am unhappy with the direct light I just put a inside frosted one in instead.

[hgg]

Excellent!   

[Wim_L]

Hi,

In my opinion the best artificial lighting available in the 21 century is still the humble incandescent lamp
for many reasons.  The only problem is that apart from the fact that they are slowly becoming extinct,
after the introduction of the toxic "energy saving" bulbs, the lifetime of the incandescent ones for some
strange reason started to decline dramatically.  <-- (conspiracy theory)   

Many countries now run slightly higher mains voltages than they used to. This makes the lamps run hotter. There may also be the effect of manufacturers trying to make their bulbs more efficient, and the hotter you run a bulb, the more efficient it gets (but lifetime is much shorter). As mentioned before, colour temperature is affected too.

That's also why dimming dramatically extends lifetime - and lowers efficiency. If you use less power per bulb, but need to use more bulbs to get sufficient light, you could end up spending more on increased electrical power than you save by making bulbs last longer. One exception is for bulbs that are hard or expensive to replace for some reason, in that case running a bulb at low power to dramatically increase its lifetime may be a good idea. Otherwise, select bulbs so they can be run at full rated power.

Dimming a halogen bulb too much isn't always a good idea either... http://www.teklight.com/faq_s.html

[hgg]

That's the thing though.  I've tried to protect the lamp but with minimum dimming.
The protected bulb was emitting 132 lumen lux @ 1m and the unprotected 148 lumen lux.
Very subtle difference in luminosity but a huge reduction of inrush current.

[edavid]

That's the thing though.  I've tried to protect the lamp but with minimum dimming.
The protected bulb was emitting 132 lumen @ 1m and the unprotected 148 lumen.
Very subtle difference in luminosity but a huge reduction of inrush current.

You should add a resistor to the unprotected side to match the hot resistance of the thermistors.

P.S. Very nice test setup!

[hgg]

You should add a resistor to the unprotected side to match the hot resistance of the thermistors.

You are right, that would be more accurate.  I will do it.

[ASowa]

You should also increase the on time.  Right now the protected bulb spends 30% of its on time at reduced wattage which is not isolating the soft start mechanism.

I also believe you meant to say lux rather than lumens.   Lumens is not a distant dependent unit.

[retrolefty]

How about this lamp? Still going strong, and made circa 1939.

And the back story, this firehouse is about 30 miles from me.

http://en.wikipedia.org/wiki/Centennial_Light

[hgg]

You should also increase the on time.  Right now the protected bulb spends 30% of its on time at reduced wattage which is not isolating the soft start mechanism.

I also believe you meant to say lux rather than lumens.   Lumens is not a distant dependent unit.

The turn on time is actually around 30 seconds or less.  It was like a capacitor charging curve.
90s passed when I could not measure any further increase in brightness, so its about 10%
at reduced wattage.  But yes, a longer time would be better.    I indeed meant to say Lux...
I've corrected it.  Thanks.

I will increase the on time to 10 minutes and I will also add a resistor to the unprotected bulb
equal to the hot resistance of the thermistors.  Thank you for your feedback and suggestions!

[SeanB]

True a resistor will drop voltage a little, and drop inrush surge a lot. The 15 minute cycle is close to what is used to stress test lamps, though most manufacturers use a 15min off 2 hours on cycle for life testing purposes, and test a batch of 100 or so each time, stopping at around 50% failure rate for lifetime. Longest lasting lamps will do the 1000 hour rating with under 10% failure, but the cheap ones will have 50% at this point, with probably 10% failing in the first 100 hours from poor manufacturing.

I bought ( not by choice) a batch of Chinese made downlighter MR16 lamps, and they are very poor, having a running life of less than rated ( 2000H) by far, most only lasting a month in service. Ironically other lamps on the same transformer, next to them are probably 2 years in the same service, and are still working perfectly, only the odd random failure. Some have done 5 years or more. The difference between Osram, Phillips as the good ones, and GE and Radiant as the poor ones, in order of lifetime. The supplier blames the fitting for the poor lamp life.....

[hgg]

Now that you mention it I don't really want to use a resistor on the unprotected bulb on start up.
I would have to use a relay and connect the equivalent resistor after the unprotected lamp has
been turned on because I don't want to protect it from inrush current.  I just want it to have the
same dimming with the protected one just in case that even such a small dimming of the protected
bulb increases its life by a large amount.  Alternatively I can use the same relay to disconnect the
thermistors after 30 seconds so that both lamps would glow with exactly the same brightness.

I wish I had your Chinese lamps...   I need them to fail fast so that the experiment will not take so
long to show any results.  The only ones I've found were these Osram 40W bulbs that were failing
faster than others I've used.

[johnwa]

I wish I had your Chinese lamps...   I need them to fail fast so that the experiment will not take so
long to show any results.  The only ones I've found were these Osram 40W bulbs that were failing
faster than others I've used.

Perhaps you could just crank the voltage up a bit, to encourage them to fail a bit sooner?
If you don't have a variac, get a 15V or so transformer, and connect its primary to the supply, and the secondary in series with the lamps. (make sure you get the phasing right).

You would need to oversize the transformer a fair bit though, to make sure its impedance doesn't influence the startup surge.

[hgg]

-- FINAL UPDATE.

Hello everybody,

This has been a very very very long experiment.  Almost boring..  But,
the protected bulb has already outlasted 4 other bulbs from the same batch!
The only sign of deterioration of the protected bulb is a slight lower brightness
than the new bulb.  Barely noticeable though.

And this time the circuit was upgraded to switch off the bulb protection after 30 seconds,
in order for both lamps to work with the same current and intensity.  I have already
installed this very small and simple addition to every lamp in my house.  The only thing you
have to be careful about is to carefully size the thermistors for the specific bulb and  that the
thermistors do not touch anything because you might start a fire...




I will wait for the fifth lamp just to confirm the NASA claims and then I will terminate the experiment.
Clearly filament evaporation is not the main factor for the life of the incandescent bulbs.
The main factor is extreme thermal stress from the initial current surge.

George.

[Zero999]

Why should I replace inexpensive incandescent bulbs with expensive CFLs?

Because you'll save more money on your energy bill in the long run?

I have not yet met a fluorescent lamp with a pleasant colour. (Also dimmed incans have a warm yellow glow similar to firelight.)

Try some of the modern LED lamps which can be found with very low colour temperatures, down to 2100k which mimics candle light very effectively.

http://www.ledplanet.co.uk/52243.html


Running incandescents at much lower than their rated power is even more inefficient because the spectrum shifts even more to the infrared, meaning even less of the energy is converted to visible light than it was run at full power. The temperature of the filament in an incandescent is such that it gives optimum cost per lumen over the lamps life. The lamp may last longer at a lower temperature but it's a false economy, since it results in higher energy bills.

[SeanB]

Funny enough yesterday I changed a failed Phillips R63 lamp, made in Poland. It is the outlier, having lasted at least 3 years in operation 8 hours a day 5 days a week 50 weeks a year as room lighting in a downlighter. I know it is 3 years old as I got the current box of 144 R80 lamps 3 years ago when I ran out of R63 lamps. 60W lamps all, and they do last at least more than double the rated 2000 hours.

Some of the 20W 50mm 12V downlighters also did more than a decade in service, as they were still open lamps, while I changed to fully enclosed lamps a decade ago, after a cheap needed it now Eurolux blew up in a shower of hot glass. The old made in EU or German lamps were well made, lasting longer than the Cheaper USA and Mexican made lamps, and the Chinese ones did not even make 200 hours.

[eetech00]

Hi

The easiest way to make an incandescent bulb last longer is....well...by never turning it off.

The idea is to keep the filament warm by allowing a small amount current to flow in the filament
when not in use. When the bulb is off, the filament is cold, its resistance is lower, so there is a greater amount of inrush current and thermal stress, when powered on. If the filiament is kept warm, resistance is higher and there will be less thermal stress on the filament when full power is applied.

eT

[Rufus]

No point trying to argue with hgg, but, for anyone else reading this thread just know it is a stupid idea, stupid experiment, and stupid conclusion drawn from the results.

[hgg]

@eetech00 this is a very good idea actually, but then it gets complicated.

Hero999:

Running incandescents at much lower than their rated power is even more inefficient because the spectrum shifts even more to the infrared, meaning even less of the energy is converted to visible light than it was run at full power

Indeed, but in my experiment the bulbs were running at full power after the 30 second protection
interval from the thermistors.  The protected bulb was completely disconnected from the the
thermistor and connected directly to mains power.

Rufus:

No point trying to argue with hgg, but, for anyone else reading this thread just know it is a stupid idea, stupid experiment, and stupid conclusion drawn from the results.

Rufus I don't know what arguments you have against this experiment but have a look at the following:

- http://en.wikipedia.org/wiki/Phoebus_cartel
- http://spectrum.ieee.org/geek-life/history/the-great-lightbulb-conspiracy

I don't think that this can be called "ethical science".

George.

[DavidDLC]

No point trying to argue with hgg, but, for anyone else reading this thread just know it is a stupid idea, stupid experiment, and stupid conclusion drawn from the results.

Then why are you in this threat and participating, just get out of here

[IanB]

Hero999:

Running incandescents at much lower than their rated power is even more inefficient because the spectrum shifts even more to the infrared, meaning even less of the energy is converted to visible light than it was run at full power

Indeed, but in my experiment the bulbs were running at full power after the 30 second protection
interval from the thermistors.  The protected bulb was completely disconnected from the the
thermistor and connected directly to mains power.

That comment about running bulbs dimmed was in response to me. However, if I take a given bulb and run it at half power it will cost half as much to run compared to running it at full power. Since the running cost is reduced the loss in efficiency is not relevant to the calculation.

[Rufus]

That comment about running bulbs dimmed was in response to me. However, if I take a given bulb and run it at half power it will cost half as much to run compared to running it at full power. Since the running cost is reduced the loss in efficiency is not relevant to the calculation.

If you run a bulb at zero power it costs nothing at all to run and you don't even have to buy a bulb.

[Zero999]

Running incandescents at much lower than their rated power is even more inefficient because the spectrum shifts even more to the infrared, meaning even less of the energy is converted to visible light than it was run at full power. The temperature of the filament in an incandescent is such that it gives optimum cost per lumen over the lamps life. The lamp may last longer at a lower temperature but it's a false economy, since it results in higher energy bills.

That comment about running bulbs dimmed was in response to me. However, if I take a given bulb and run it at half power it will cost half as much to run compared to running it at full power. Since the running cost is reduced the loss in efficiency is not relevant to the calculation.

The loss of efficiency is very relevant to the calculation because it would be much more efficient to just use a lower wattage bulb, than overrate the bulb and under power it. If you take a 60W bulb and run it at half the power, it won't produce half the light but a less than a quarter, so it would be much cheaper in the long run to just swap it for a 15W bulb run at full power. I understand you dislike white light and prefer yellow which is why I recommended a low colour temperature LED lamp, which uses a tiny fraction of the power: the energy savings pay of the high lamp cost fairly quickly.

[IanB]

But a 15 W bulb also loses the convenience of dimming. With a dimmed bulb I can continuously vary the light according to needs. I can make it brighter for a short while if I want good lighting for a task, and I can make it dimmer to watch television or a movie.

Maybe with a new living space I could design a mix of lighting and controls on separate circuits to do what I wish, but it is not practical to retrofit that to an existing space. Even with a new space it is expensive to change what the builders have previously installed (which is likely a low cost minimum).

This is not even to consider the false claims about efficiency circulated in Europe. The most need for electric lighting occurs during the winter months with long dark evenings (it gets dark at 4pm in the UK). This is also the time when houses have the central heating turned on. Bulbs operated in centrally heated houses are 100% efficient. There is no energy saving to be made by replacing them.

It's quite simple. Home lighting makes almost no contribution to energy demand and global warming and the drive to new lighting technologies like CFL and LED is driven purely by the desire of manufacturers and marketers to have new expensive products to sell (and a captive market forced to buy them). As always, when you see a drive for change, follow the money.

[edavid]

This is not even to consider the false claims about efficiency circulated in Europe. The most need for electric lighting occurs during the winter months with long dark evenings (it gets dark at 4pm in the UK). This is also the time when houses have the central heating turned on. Bulbs operated in centrally heated houses are 100% efficient. There is no energy saving to be made by replacing them.

Do people in Europe really use primarily resistive heating?  If so, you're right, that should be fixed first before worrying about lighting.

It's quite simple. Home lighting makes almost no contribution to energy demand and global warming and the drive to new lighting technologies like CFL and LED is driven purely by the desire of manufacturers and marketers to have new expensive products to sell (and a captive market forced to buy them). As always, when you see a drive for change, follow the money.

http://www.eia.gov/tools/faqs/faq.cfm?id=99&t=3

"EIA estimates that in 2012, ... residential lighting consumption was about 186 billion kWh or about 14% of all residential electricity consumption."

Is 14% the same as "almost no contribution"?

[Zero999]

But a 15 W bulb also loses the convenience of dimming. With a dimmed bulb I can continuously vary the light according to needs. I can make it brighter for a short while if I want good lighting for a task, and I can make it dimmer to watch television or a movie.

Maybe with a new living space I could design a mix of lighting and controls on separate circuits to do what I wish, but it is not practical to retrofit that to an existing space. Even with a new space it is expensive to change what the builders have previously installed (which is likely a low cost minimum).

There are already plenty of solutions to that, such as smart lighting, which enables you to control but the colour and brightness. It is expensive but very easy to retrofit, often just as easy as changing a light bulb and it's still cheaper to run.

This is not even to consider the false claims about efficiency circulated in Europe. The most need for electric lighting occurs during the winter months with long dark evenings (it gets dark at 4pm in the UK).

What about the four or so hours a night when the lights are on in the summer when the extra heat is a nuisance and will increase bills further if you have air conditioning?

This is also the time when houses have the central heating turned on. Bulbs operated in centrally heated houses are 100% efficient. There is no energy saving to be made by replacing them.

That's only the case if your home is heated with electricity which is a very expensive and inefficient form of heating. If the home is heated by natural gas, as it is in most cases in the UK, it's much more efficient to use electricity for lighting.

[PauloTiti]

I have a device that fits into the light socket (B22) and sits between the socket and the bulb that does a soft start.
It is only for a single bulb though. Now that incandescent bulbs are getting less common I don't know how readily available they are. Ebay the source of all things cheap adapter related turned up nothing.

You now have the russian soft starter device mentionned in the first post available on Ebay.

[hgg]

Hi, do you have a link?

[PauloTiti]

Hi, here is the link I found: http://www.ebay.fr/itm/321733084301

[hgg]

Thank you for the link.

From the description here : http://provod-nik.ru/p56333418-blok-zaschity-gal.html it looks like that
it uses an integrated circuit that provides the soft start.  It does not use the simple solution of the
cheap thermistor.  I think there are quite a lot of circuits on the market like that.  I though you
found one like the original.

This is the original product : http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070018922.pdf

George.

[PauloTiti]

I didn't know about this one. But looking at some litterature they say you have to wait about 45 seconds to get the light on... Jesus ! You have to be patient ! 

[PostalPreacher]

Forgive my jumping in here at such a late date. I just purchased a refrigerator for my wife. I got a great price, but it was missing one feature of the higher priced models. The deluxe models have interior lights inside that ramp up over about a second or two. I'd like to be able to have my lights do the same. I'm not concerned about life of the bulb or anything else...I just want to make it do that for my wife. Will a simple (properly chosen) thermistor in line work? The bulbs are pretty standard (appliance) 40W 120V bulbs.

[edavid]

Forgive my jumping in here at such a late date. I just purchased a refrigerator for my wife. I got a great price, but it was missing one feature of the higher priced models. The deluxe models have interior lights inside that ramp up over about a second or two. I'd like to be able to have my lights do the same. I'm not concerned about life of the bulb or anything else...I just want to make it do that for my wife. Will a simple (properly chosen) thermistor in line work? The bulbs are pretty standard (appliance) 40W 120V bulbs.

With all respect, that is a stupid feature... why would you want to have to wait around to see what's in the refrigerator?

If I had a refrigerator like that, I would hate it.

[Audioguru]

I have been using White 3300k and 3500k CFL light bulbs for maybe 5 to 10 years. They are not expensive, about the same per year as hot, power wasting incandescents and I save time because they last such a long time that I do not need to replace them so often. Daylight colored bubs produce Blue light, not white.

My city replaced all the incandescent traffic lights with LED ones and all streetlights are also LEDs with a modem and a little antenna on top.

There was (or maybe it is still operating) an incandescent light bulb in Alaska that has been turned on only one time and it has been shining for well over 100 years. It lasts a long time because it has never been turned off and it has missed many on-surges.

[hgg]

Will a simple (properly chosen) thermistor in line work?

Yes.

[PostalPreacher]

Then buy the cheap one, by all means, but I'd go down to the Lowe's or Home Depot and try one first. It is actually pretty pleasant.

[PostalPreacher]

Will a simple (properly chosen) thermistor in line work?

Yes.

Thank you. Time to find some thermistors and do some experimenting on the bench.

[hgg]

You're welcome.   

[chris_leyson]

I read in an old lighting handbook that if you reduce the voltage by 5% an incandescent will last 2000 hours.

[IanB]

I read in an old lighting handbook that if you reduce the voltage by 5% an incandescent will last 2000 hours.

There's an exponential relationship between filament life and operating voltage. For instance, if you run a 100 W bulb at 60 W it will last essentially forever.