turning hid on above water

[Meng_Tze]

It's ok that we are divers but not engineers, the society needs different types
of professions, each serve for it's purpose:
Conductance instead of "negative resistance", which is 1/Resistance (in Ohms)
Power (in Watts) instead of wattage.

This is exactly why I used these words, to make it pallatable to the general audience.....

 

[Meng_Tze]

Hi,

o.k. I agree, but then you should write that it is just example with fictional voltages, otherwise you make the systems more harmless as they are. Also you write about a negative resistance characteristics of the bulb?????? what do you mean by that??? When there is an arc then the arc has nearly no resistance.
I can not follow what you mean by that.


Greetings, Michael

If you read carefully I do mention .. (say 85v) which is indicative of picking a number. But okay, I guess explicit comments would have served it better.

The arc having negative resistance is the fact that the arc heats the gas, this in return increases conductance (if I may call it that) and this in return would allow for increase in current demand (even lower resistance in the arc), which increases heat in gas, etc, etc.... this is why there is a control to prevent the arc 'running away' from set operating parameters. The fact that the resistance get smaller and smaller based based on input is equal to conductance.....the reverse of resistance

One way to experiment with this is to cancel out the control of the current and monitor the demand at the supply... you will see an increase demand (non linear) for current based on the fact that the arc runs away. Well at least it did when I last looked at this...many, many moons ago.

 

[bradshsi]

One way to experiment with this is to cancel out the control of the current and monitor the demand at the supply... you will see an increase demand (non linear) for current based on the fact that the arc runs away. Well at least it did when I last looked at this...many, many moons ago.

I think your intent is clear even if there are differences between posters over the language. If I can summarise thus:

A filament type light is inherently self limiting in that as the filament gets hotter, it's resistance increases, thus there is only one possible current flow for any given voltage.

The HID resistance is not self limiting hence the need to regulate (using electronics), the current flow through it to prevent very rapid failure.

 

[alo100]

Hi alo100

I think there is a misunderstanding. These devices are not our devices!!
I have just tested them deeply and I sell them in Germany.
The WA products are not controlled at all. The resistance is fixed and so the current decreases when the input battery voltage is decreasing. This will result in a light that is getting more and more blue.



Greetings, Michael

I thought there are always kind of regulator being used to optimize the use of the battery, and to keep the bulb in operating range (fixed voltage)...
Referring to the products of your company, is that true?

Or is your company using WA for some of the products without any controlling device?

 

[alo100]

I think your intent is clear even if there are differences between posters over the language. If I can summarise thus:

A filament type light is inherently self limiting in that as the filament gets hotter, it's resistance increases, thus there is only one possible current flow for any given voltage.

The HID resistance is not self limiting hence the need to regulate (using electronics), the current flow through it to prevent very rapid failure.

In some of the HID bulb (head light for automobile), I saw a wire within the bulb just like the filament, does it exist in all HID bulb? Or some are just chemical (without wire) inside?
Do you notice?

For filament, I knew that the resistance goes up with the current gets through, I know know too much about the HID light, but I though in general... it's hard to have a bulb that is of constant resistance... what do you think?

 

[alo100]

Thanks for all the info, especially for the data sheet for the light reliability.
Other technical question, I think after reading the DIY section, many of the questions are answered...

 

[Jason B]

The arc having negative resistance is the fact that the arc heats the gas, this in return increases conductance (if I may call it that) and this in return would allow for increase in current demand (even lower resistance in the arc), which increases heat in gas, etc, etc.... this is why there is a control to prevent the arc 'running away' from set operating parameters. The fact that the resistance get smaller and smaller based based on input is equal to conductance.....the reverse of resistance

First off, as for conductance, negative and reciprocal are two different things. Conductance is the reciprocal of resistance. A negative temperature coefficient I can handle.

Another thing, arcs don't have resistance (or negative resistance), they are created by a lack of resistance (in a nut shell).

 

[Meng_Tze]

First off, as for conductance, negative and reciprocal are two different things. Conductance is the reciprocal of resistance. A negative temperature coefficient I can handle.

Another thing, arcs don't have resistance (or negative resistance), they are created by a lack of resistance (in a nut shell).

I beg to differ.

Mathematically resistance and conductance are reciprocal, yes. Arcs do have conductance however (in your assessment reciprocal to resistance) and this keeps growing if not controlled... hence negative conductance.

I have attached a PDF for a simulation (simulation being the operative word, which is a approximation of what catually happens) of HID lamps, the first section explains the science behind HID lamps, the other half goes into how the SPICE model was set up.

But we are now getting to a point in the thread where we are discussing applied electronics and background math to assess how long to leave between striking....

 

[alo100]

First off, as for conductance, negative and reciprocal are two different things. Conductance is the reciprocal of resistance. A negative temperature coefficient I can handle.

Another thing, arcs don't have resistance (or negative resistance), they are created by a lack of resistance (in a nut shell).

Wait... conductance = 1/resistance, we can find in any text book,
e.g. http://en.wikipedia.org/wiki/Electrical_resistance
but the way you're saying is that the negative resistance does really mean some negative values in Ohms... what does it mean? I think most people have heard super conductor in lab, but having a negative values in Ohm, what does it mean? If we look at the wikipedia page for the physical meaning, it's only a measurement of how good the material can conduct electrically.

 

[alo100]

I beg to differ.

Mathematically resistance and conductance are reciprocal, yes. Arcs do have conductance however (in your assessment reciprocal to resistance) and this keeps growing if not controlled... hence negative conductance.

I have attached a PDF for a simulation (simulation being the operative word, which is a approximation of what catually happens) of HID lamps, the first section explains the science behind HID lamps, the other half goes into how the SPICE model was set up.

But we are now getting to a point in the thread where we are discussing applied electronics and background math to assess how long to leave between striking....

Same here, if you look at how the passage talked about the conductance of the HID lamp, delta(t) = deltak f(P, T) exp(E,T) it can only give you a positive number.
Besides, you don't need to use a spice model in order to get the meaning of conductance. Spice model is for calculating the physical behavior of the device for the the given physical conditions e.g. applied voltage, temperature, pressure etc.

Meng, you know what? My bad, some how I have also gone too far away from the topic. Sorry for hijacking the thread.