truth about HID

shift6 · 04-08-2004, 01:15 PM

Can someone please explain how HID's work? And can they burn out?

Halo · 04-09-2004, 10:20 AM

short answer: HIDs are just fluorescent lights.

Long answer:
An incandescent light bulb works by heating a filament with electricity until it glows. The filament would burn out quickly but the light bulb is in a vacuum (usually) or has inert gases (so-called halogen bulbs) to prevent this. This is what is in most cars.

A high intensity discharge (HID) light has no filament. Instead, it has two electrodes that are separate in space. A very high voltage is applied to these electrodes and arcs (creates a spark) between them. However, there is again an inert gas in the bulb which glows from this spark. The standard fluorescent bulb has two electrodes at either end of a long tube (look up at your ceiling at work/school) with gas in between. A car bulb has them next to each other. The voltages are very high so, in order for your car's 12V electrical system to get there, there is a component called a "ballast" which is basically just a transformer to step up the voltage from 12V to several thousand.

Honestly, a car HID is slightly more 'fancy' than just a plain fluo bulb because it needs to be able to come on instantly on demand, and is cycled many more times during its life than a room light. (Some of this technology is borrowed from stadium lighting) But there is nothing 'magical' about the technology despite what the marketing people at BMW, MB, Porsche, Honda want you to believe.

As to burning out. Yes they can, but in genereal they last longer than incandescent. The ballasts can fail independent of the bulbs but can be replaced separately. The lifetime depends on various factors, but things like flashing them on and off definitely reduce the life.

Incidentally, the same technology is used in digital LCD projectors for the bulb and each element in a plasma TV (each pixel) is also a little fluorescent bulb. In fact, they could have called HID's 'plasma lights' and it would have been just as correct. Funny how marketing can make things that are basically 50 year old technology seem sexy and expensive by giving it a new name.

shift6 · 04-09-2004, 11:03 AM

Thanks Halo, much appreciated

tekniq · 04-11-2004, 06:14 PM

Good answer Halo. I learned more about HIDs. Thank you.

S2KOOL · 04-11-2004, 08:48 PM

Wow halo...you seem to know a lot of HIDs...are you sure you didn't invent them...anyways that was a lot of great information....now I actually know about HIds instead of them been "pretty" light...thx

04-08-2004, 01:15 PM	#1 (permalink)
shift6 Junior Member Join Date: Apr 2004 Posts: 3	truth about HID Can someone please explain how HID's work? And can they burn out?

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04-09-2004, 10:20 AM	#2 (permalink)
Halo Senior Member Join Date: Mar 2004 Posts: 600	short answer: HIDs are just fluorescent lights. Long answer: An incandescent light bulb works by heating a filament with electricity until it glows. The filament would burn out quickly but the light bulb is in a vacuum (usually) or has inert gases (so-called halogen bulbs) to prevent this. This is what is in most cars. A high intensity discharge (HID) light has no filament. Instead, it has two electrodes that are separate in space. A very high voltage is applied to these electrodes and arcs (creates a spark) between them. However, there is again an inert gas in the bulb which glows from this spark. The standard fluorescent bulb has two electrodes at either end of a long tube (look up at your ceiling at work/school) with gas in between. A car bulb has them next to each other. The voltages are very high so, in order for your car's 12V electrical system to get there, there is a component called a "ballast" which is basically just a transformer to step up the voltage from 12V to several thousand. Honestly, a car HID is slightly more 'fancy' than just a plain fluo bulb because it needs to be able to come on instantly on demand, and is cycled many more times during its life than a room light. (Some of this technology is borrowed from stadium lighting) But there is nothing 'magical' about the technology despite what the marketing people at BMW, MB, Porsche, Honda want you to believe. As to burning out. Yes they can, but in genereal they last longer than incandescent. The ballasts can fail independent of the bulbs but can be replaced separately. The lifetime depends on various factors, but things like flashing them on and off definitely reduce the life. Incidentally, the same technology is used in digital LCD projectors for the bulb and each element in a plasma TV (each pixel) is also a little fluorescent bulb. In fact, they could have called HID's 'plasma lights' and it would have been just as correct. Funny how marketing can make things that are basically 50 year old technology seem sexy and expensive by giving it a new name.

04-09-2004, 11:03 AM	#3 (permalink)
shift6 Junior Member Join Date: Apr 2004 Posts: 3	Thanks Halo, much appreciated

04-11-2004, 06:14 PM	#4 (permalink)
tekniq Junior Member Join Date: Oct 2003 Posts: 13	Good answer Halo. I learned more about HIDs. Thank you.

04-11-2004, 08:48 PM	#5 (permalink)
S2KOOL Junior Member Join Date: Jul 2003 Posts: 9	Wow halo...you seem to know a lot of HIDs...are you sure you didn't invent them...anyways that was a lot of great information....now I actually know about HIds instead of them been "pretty" light...thx