Why is startup so slow with HID's

windstrings · Nov 13, 2006

I'm sure everyone who owns an HID has noticed it is very bright the first fragment of a second of startup, and then drops to very low as it builds up to full brightness over the next 20 - 30 seconds.

What is the limitation to correcting slow startup time witn an HID?

I understand what presently happens "I think"
But why can't we fine tune a ballast so that it doesn't drop the voltage so fast and thereby allows the gases to become fully bright "faster'?
Why does the voltage have to drop so far after the initial blast?

I can see it may be heat tolerances verses what amps the batteries can dish out etc, but isn't that a desirable enough feature to be worth pursuing?

Can someone please explain the issues that prevent that from being corrected with our current technology?...

Enquiring minds want to know..... :popcorn:

Ra · Nov 13, 2006

Well,

I can enlighten you a bit about this:

Like every arc-lamp the HID also is a non-conducting lamp, so if you connect it to 90 volts of batteries nothing will happen. First the molecules between the electrodes must be ionised, to form the arc.
A short high-voltage burst ionises the gas inside and almost immidiately the arc forms. The electronics 'feel' the arc forming by the higher power it draws. Instandly after that, the electronics switch down to arc-maintaining-voltage which is not stable untill the temperature and the pressure of the gasses inside are stable.

The high-voltage pulse has enough power to produce quite a bright flash at startup.

And the answer to your question: Higher power at startup would melt the electrodes !!: At startup some ballasts put out up to 60watts (35watt ballast) to shorten the startup time and to generate a decent amount of lumens at startup. But it is unwise to generate more lumens by higher power when the inside pressure and temperature are not at 'operation-level'.

Regards,

Ra.

windstrings · Nov 13, 2006

You keep using the term "inside pressure".. is that physical pressure?
Would forming a ballast that did as I suggest create too much pressure and blow the bulb?

yoiu said:

But it is unwise to generate more lumens by higher power when the inside pressure and temperature are not at 'operation-level'.

So your implying that the pressure is too high during startup to increase it yet furthur in an attempt to get the arc forming faster?

When you say "not yet at operation level", do you mean "not yet" as being it's higher or lower than operation level?

Christexan · Nov 13, 2006

My understanding of all "arc" lamps is that they create a bubble of ionized gas around them in operation (aka "capsule"). Initally the gases are randomly dispersed in the bulb, causing a high resistance which the initial high voltage "arc" has to overcome, once this is done, the gases in the vicinity ionize and begin to reduce the resistance to current flow and a cycle begins that requires lower voltage to maintain. So if you kept the initial high voltage, as the current increased, the power dissipated would increase dramatically and quickly melt the electrodes. So the voltage swings until a maintenance current and voltage is achieved that isn't excessive as the gas encapsulates the arc and the temperatures of the gas and electrodes stabilize.

Imagine a car, trying to achieve maximum acceleration, with an engine built to withstand 5000rpm after warming up, but a design that can go much higher (maybe the materials are the limiting factor, a steel bolt can't handle what a titanium bolt could, for instance on the same engine). Now if you want to get to 30MPH as fast as possible, and the engine hits 25MPH in 1st gear at 5000rpm, you have 2 choices, shift gears (saving the engine), or keep accelerating to say 7000rpm if that hits 30mph... you might get there faster, but you'll blow the engine at some point.
Now let's say you take that same engine, cold, turn the key and stomp the accelerator to 7000... now the engine has no lubrication on it's internals, the part experience huge temperature differentials and expansion rates change violently... it'll blow up much faster (maybe the first try).
That's an HID light... when cold, nothing is at equilibrium, and it has to balance all the parameters to keep from overshooting the specs (running engine below redline to keep from damaging it). Might take a minute or two to full brightness (well 15-30 seconds anyhow). When warm, less temp variations, etc, so faster to get to operating conditions.
You could design a more "instant-on" HID light, but it'd be bigger, heavier, shorter lifespan, more expensive, etc.

AndyTiedye · Nov 13, 2006

I'd like to know too.

I would think this would rule out HID for a lot of uses.

windstrings · Nov 13, 2006

Christexan said:
My understanding of all "arc" lamps is that they create a bubble of ionized gas around them in operation (aka "capsule"). Initally the gases are randomly dispersed in the bulb, causing a high resistance which the initial high voltage "arc" has to overcome, once this is done, the gases in the vicinity ionize and begin to reduce the resistance to current flow and a cycle begins that requires lower voltage to maintain. So if you kept the initial high voltage, as the current increased, the power dissipated would increase dramatically and quickly melt the electrodes. So the voltage swings until a maintenance current and voltage is achieved that isn't excessive as the gas encapsulates the arc and the temperatures of the gas and electrodes stabilize.

Imagine a car, trying to achieve maximum acceleration, with an engine built to withstand 5000rpm after warming up, but a design that can go much higher (maybe the materials are the limiting factor, a steel bolt can't handle what a titanium bolt could, for instance on the same engine). Now if you want to get to 30MPH as fast as possible, and the engine hits 25MPH in 1st gear at 5000rpm, you have 2 choices, shift gears (saving the engine), or keep accelerating to say 7000rpm if that hits 30mph... you might get there faster, but you'll blow the engine at some point.
Now let's say you take that same engine, cold, turn the key and stomp the accelerator to 7000... now the engine has no lubrication on it's internals, the part experience huge temperature differentials and expansion rates change violently... it'll blow up much faster (maybe the first try).
That's an HID light... when cold, nothing is at equilibrium, and it has to balance all the parameters to keep from overshooting the specs (running engine below redline to keep from damaging it). Might take a minute or two to full brightness (well 15-30 seconds anyhow). When warm, less temp variations, etc, so faster to get to operating conditions.
You could design a more "instant-on" HID light, but it'd be bigger, heavier, shorter lifespan, more expensive, etc.

So far, It sounds like the common denominating factor is heat for too long.

It just seems it drops "too" low, but maybe thats to allow a little cooldown from that initial burst before it builds up to full brightness?

Just wondering... it seemed like the ballast could be fine tuned for the bulb they use and cut the time in half.. but maybe not.

The analogy with the car.. I had to expand my conciousness to get that one!.. but I get your point.

"time" is always a factor in how much energy can be dissipated.

It would be very interesting to actually know the heat toleraces of the metals inside the bulb.. namely "the electrodes" and then measure the heat during startup to see if it drops rediculosly low and could be bumped up to shorten startup time.

I wonder if a lasar themometer could read that?.. providing you had one that went that high!

The next question would be, I wonder if they could use diffrent metals for the electrodes to prevent meltdown and how expensive that would be?

Ra · Nov 13, 2006

Hi Windstrings,

With inside pressure I mean gas-pressure inside the bulb..

The ballast you dream of would propably melt the electrodes inside the bulb with a power too high.

The pressure is always low when the bulb is cold, that is the main reason the lumens output is low at startup.

I hope I don't have to tell you that a gas-pressure in a bulb rises when the temperature rises.. With HID its even worse: Here solids are becomming a gas by the increasing temperature.

Example: a xenon arc-lamp (Maxabeam) already has a high internal pressure when cold (approx 8atm). WHY ?? Well because xenon already is a gas at roomtemperature! So at the factory, the lamp must be pressurised to be able to reach the optimal pressure at full operation.

But when the ingedients of the lamp are solids or fluids at roomtemperature, the lamp doesn't need to be pressurized at the factory: From a fluid or solid you can obtain much higher pressures at full operation than with a gas.

The downside is that bulbs with fluids or solids need energy at startup to evaporate the ingedients. Xenon gas-filled short arcs operate at 85% lumens-output directly after startup: they don't need to evaporate anyting.

Another example: Take an icecube and try to evaporate that icecube on a stove in a few seconds, you will see how much energy is needed to do such a thing !! Ofcource it can be done in a few seconds, but you'll need so much energy that propably your house will burn down !! (Beleve me, I know the laws of nature!!)

And now you want the HID bulb to do the same without destroying its electrodes !! Beleve me, if you want to keep the advantages of the HID-bulb, give it time to startup...

With the ingedients not properly evaporated the bulb will have lower lumens-output, if you increase the power at that moment to obtain higher lumens-output, the temperature of the electrodes will reach close to meltingpoint, electrode-tips will evaporate or even melt: Electrode-gap increases, drasticly decreasing bulblife!

EDIT: The best material for electrodes is tungsten: Conducting material with the highest meltingpoint avaiable.

Regards,

Ra.

LITEDISORDER · Nov 13, 2006

Get a HELIOUS. Its HID and it starts up instantly. I also have a AE-24p and it takes about 20 seconds to full light-up. (money= fast start ups)

FILA BRAZILIA · Nov 13, 2006

An excellent exception from the rule is the HELIOS. Have you tried it out? The warm-up time is just a few seconds. I have one myself, and actually, the warm-up time is barely noticeable.

windstrings said:
I'm sure everyone who owns an HID has noticed it is very bright the first fragment of a second of startup, and then drops to very low as it builds up to full brightness over the next 20 - 30 seconds.

FILA BRAZILIA · Nov 13, 2006

Damn, LITEDISORDER, you got me :ohgeez:

:laughing:

XeRay · Nov 13, 2006

FILA BRAZILIA said:
Damn, LITEDISORDER, you got me :laughing:

Anything more than about 100 watts immediately after start-up arc and then ramping down to 35 or 50 watts is very bad for the bulb. Our ballasts at 50 watts send about 95 watts to the bulb right after the initial spark. The rampdown to 50 watts is done based on internal impedance of the arc chamber.

For that fast close to full output you desribe, I am again suspicious that the Helios is using a DC output to a bulb designed for AC. If that is true then bulb life will be less than half. Alternatively, if they are overdriving the warmup period more than say 110 watts and not ramping it down quickly to speed thing up this also will greatly reduce bulb life. There is no free lunch. We operate the bulb within the acceptable range per the bulb manufacturer.

Helios uses an Osram D1S (slightly modified by Polarion)

High quality electrodes are "Thoriated Tungsten"

LITEDISORDER · Nov 13, 2006

Maybe that is why i got the extra bulb. I'll go with the fast startup for the price of another bulb.

Handlobraesing · Nov 13, 2006

windstrings said:
I'm sure everyone who owns an HID has noticed it is very bright the first fragment of a second of startup, and then drops to very low as it builds up to full brightness over the next 20 - 30 seconds.

What is the limitation to correcting slow startup time witn an HID?

The fact it is a metal halide lamp.
http://en.wikipedia.org/wiki/Metal_halide

Even car metal halide headlights takes some 30 seconds to come to FULL brightness. Xenon gas provide enough light to get you by for the short time.

Bulbs without a gas fill that provides "enough light to get you by while starting" takes a long time. Those 175W parking lot metal halides takes 5-10 minutes to reach maximum brightness.

windstrings · Nov 13, 2006

XeRay said:
Anything more than about 100 watts immediately after start-up arc and then ramping down to 35 or 50 watts is very bad for the bulb. Our ballasts at 50 watts send about 95 watts to the bulb right after the initial spark. The rampdown to 50 watts is done based on internal impedance of the arc chamber.

For that fast close to full output you desribe, I am again suspicious that the Helios is using a DC output to a bulb designed for AC. If that is true then bulb life will be less than half. Alternatively, if they are overdriving the warmup period more than say 110 watts and not ramping it down quickly to speed thing up this also will greatly reduce bulb life. There is no free lunch. We operate the bulb within the acceptable range per the bulb manufacturer.

Helios uses an Osram D1S (slightly modified by Polarion)

High quality electrodes are "Thoriated Tungsten"

Thanks Dan..this is all quite interesting.. I did notice that thier bulb life they advertize is less than what I would expect.. only 2500hrs , I always assumed it was because they were using the same bulb as thier older 35 watt polarion and getting 40 watts instead. But 5 more watts shouldn't make that big of a dent in lifetime I suppose.

windstrings · Nov 13, 2006

Handlobraesing said:
The fact it is a metal halide lamp.
http://en.wikipedia.org/wiki/Metal_halide

Even car metal halide headlights takes some 30 seconds to come to FULL brightness. Xenon gas provide enough light to get you by for the short time.

Bulbs without a gas fill that provides "enough light to get you by while starting" takes a long time. Those 175W parking lot metal halides takes 5-10 minutes to reach maximum brightness.

Although the 35watt HID's on my car get up and running in about 15 - 20 seconds.. I sometimes think after several minutes they are even brighter.

windstrings · Nov 13, 2006

Ra said:
Hi Windstrings,

With inside pressure I mean gas-pressure inside the bulb..

The ballast you dream of would propably melt the electrodes inside the bulb with a power too high.

The pressure is always low when the bulb is cold, that is the main reason the lumens output is low at startup.

I hope I don't have to tell you that a gas-pressure in a bulb rises when the temperature rises.. With HID its even worse: Here solids are becomming a gas by the increasing temperature.

Example: a xenon arc-lamp (Maxabeam) already has a high internal pressure when cold (approx 8atm). WHY ?? Well because xenon already is a gas at roomtemperature! So at the factory, the lamp must be pressurised to be able to reach the optimal pressure at full operation.

But when the ingedients of the lamp are solids or fluids at roomtemperature, the lamp doesn't need to be pressurized at the factory: From a fluid or solid you can obtain much higher pressures at full operation than with a gas.

The downside is that bulbs with fluids or solids need energy at startup to evaporate the ingedients. Xenon gas-filled short arcs operate at 85% lumens-output directly after startup: they don't need to evaporate anyting.

Another example: Take an icecube and try to evaporate that icecube on a stove in a few seconds, you will see how much energy is needed to do such a thing !! Ofcource it can be done in a few seconds, but you'll need so much energy that propably your house will burn down !! (Beleve me, I know the laws of nature!!)

And now you want the HID bulb to do the same without destroying its electrodes !! Beleve me, if you want to keep the advantages of the HID-bulb, give it time to startup...

With the ingedients not properly evaporated the bulb will have lower lumens-output, if you increase the power at that moment to obtain higher lumens-output, the temperature of the electrodes will reach close to meltingpoint, electrode-tips will evaporate or even melt: Electrode-gap increases, drasticly decreasing bulblife!

EDIT: The best material for electrodes is tungsten: Conducting material with the highest meltingpoint avaiable.

Regards,

Ra.

Facinating, Mr. Scott.....
Seems Helios manufacters may see that as a viable trade-off....
I guess if your gonna give over a grand for a light, having to buy another bulb after 2500 hrs is not supposed to be an issue?

I personally would like to have both obviously, but If I'm gonna knock that much life off of my bulb, I would rather have more total lumens available when its on rather than quicker startup time. Of course more lumens means a more expensive ballast with higher wattage.

The quicker startup is slick.. I"m just not sure I appreciate the trade off for what it costs me.

Different strokes........ LIke Xeray said... there is no free lunch.. only more expensive ones!

lasercrazy · Nov 13, 2006

XeRay said:
Anything more than about 100 watts immediately after start-up arc and then ramping down to 35 or 50 watts is very bad for the bulb. Our ballasts at 50 watts send about 95 watts to the bulb right after the initial spark. The rampdown to 50 watts is done based on internal impedance of the arc chamber.

For that fast close to full output you desribe, I am again suspicious that the Helios is using a DC output to a bulb designed for AC. If that is true then bulb life will be less than half. Alternatively, if they are overdriving the warmup period more than say 110 watts and not ramping it down quickly to speed thing up this also will greatly reduce bulb life. There is no free lunch. We operate the bulb within the acceptable range per the bulb manufacturer.

Helios uses an Osram D1S (slightly modified by Polarion)

High quality electrodes are "Thoriated Tungsten"

If that's true then you'll most likely be down to about 1500 hours for the helios. Since most Hid bulbs seem to be rated 2-3K hours, that's still a long time and most people will never need to change bulbs.

XeRay · Nov 14, 2006

lasercrazy said:
If that's true then you'll most likely be down to about 1500 hours for the helios. Since most Hid bulbs seem to be rated 2-3K hours, that's still a long time and most people will never need to change bulbs.

One more factor though the brightness will be degraded much more rapidly as well, not just total life. Again, there is a price to pay.

LuxLuthor · Nov 14, 2006

I think it is useful to stop and put 1500 hours into perspective. Let's just imagine that you run one of these bright spotlights 5 hours a week for 50 weeks every year...which is way more than most people are going to use any light this bright. That's 250 hours a year.

1500/250 is 6 years. If you can't break down and buy a new bulb every 6 years, you should not be buying any of these expensive lights. Dan's decrease in brightness argument seems a lot more valid...but I would think that applies to the Philips DL-50 running in the BB's 75W also.

I'm quite frankly, much more worried about the DL-50 bulb that failed after only 60 hours as described by Mr. Ted Bear in this other thread (post #70)...due to arc damage at its base, and which no one has commented on. Did the 75W possibly contribute to that failure?

XeRay · Nov 14, 2006

LuxLuthor said:
I'm quite frankly, much more worried about the DL-50 bulb that failed after only 60 hours as described by Mr. Ted Bear in this other thread (post #70)...due to arc damage at its base, and which no one has commented on. Did the 75W possibly contribute to that failure?

Good point Lux, I have only seen 2 (premature) failure modes on that bulb. Extreem shock dropped on hard surface (broke same location) or frequent install of reflector head. The DL-50 has less stregth at its base than other 35 or 50 watt HID bulbs. If not very careful this will happen if the head if frequently removed. Much stress can easily be applied to the tip of this bulb with failure occuring at the base where the metal support structure is. 75 watts would have nothing to do with that failure mode.

Why is startup so slow with HID's

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