Cold cathodes - do they have polarity?

Jeff7

Lifer
Jan 4, 2001
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I've got an extra CC bulb and an inverter I bought elsewhere. There is a Ground and a High connector; I connected both of these to the bulb and it lit, so those are the ones. Question is, do CC bulbs have polarity? I'm selling off 4 extra kits I didn't need, and the plugs on them are keyed.
I just don't want to damage either the bulb or inverter here, as it'll be custom wired.
 

corkyg

Elite Member | Peripherals
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Mar 4, 2000
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I believe they run offf of an inverter - that means they are actually AC, not DC - therefore they would not be polarized.
 

Jeff7

Lifer
Jan 4, 2001
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Originally posted by: corky-g
I believe they run off of an inverter - that means they are actually AC, not DC - therefore they would not be polarized.

Ok; though I have always wondered why AC outlets around the house are now polarized. Something to do with hot and neutral, but that never made sense either because of AC having no polarity.
 
Aug 16, 2001
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If you mean the 'glow electrode' inside that generates electrons?

Well, they can actually be both AC or DC driven. In high-end audio amplifiers you do not want to use AC since it can be heard (low frequency humming).

Was this what you were asking?
 

Jeff7

Lifer
Jan 4, 2001
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Huh? I'm talking about cold cathode lights for inside computers; is that what you mean too?
The one I'm using uses an inverter to convert 12VDC to high voltage AC.
 

Bovinicus

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Aug 8, 2001
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I believe it depends on the CC. For example, the various switches and lights that connect to the motherboard can either have polarity or not. I don't know if this applies to CCs, but a test is the best way to find out. =)
 
Aug 16, 2001
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Originally posted by: Jeff7
Huh? I'm talking about cold cathode lights for inside computers; is that what you mean too?
The one I'm using uses an inverter to convert 12VDC to high voltage AC.

No, I misunderstood you. Thought you were talking about vacuum tubes, as in pre-transistor technology. They have a cathode.
 

dszd0g

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Jun 14, 2000
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No, a test is not the best way to find out polarity with electronics -- but I am pretty sure you were being sarcastic. Some things will litteraly blow up if you give them the wrong polarity.

If there is a part number on the bulb you can try doing a search for a datasheet on google. If you can find the datasheet for it that should have plenty of information.
 

Jeff7

Lifer
Jan 4, 2001
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Originally posted by: dszd0g
No, a test is not the best way to find out polarity with electronics -- but I am pretty sure you were being sarcastic. Some things will literaly blow up if you give them the wrong polarity.

If there is a part number on the bulb you can try doing a search for a datasheet on google. If you can find the datasheet for it that should have plenty of information.

The bulb is in a sealed tube; I do know that it is from Sunbeamtech; I just sent them an e-mail. I was a bit wary of doing so because I've dealt with them before - their English interpretation and responses are lacking in just a few areas.;)
 

Jeff7

Lifer
Jan 4, 2001
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Originally posted by: dszd0g
This seems like it should provide you with some information:

Cold Cathode Information

Most CCFL tubes do have polarity, one would hope that it would be marked on your tube.


Cool; thanks for the link. The only thing I really see there though concerning polarity is the input which makes perfect sense, as that's DC. Not sure about the output yet though.

From the article:
"Generally speaking, voltage (not amperage) kills."
I disagree with that. My Tesla Coil on my website generates around 100,000 volts at very low amperage. It's safe enough to let the current run right through your body - metal bolt in one hand, flourescent light in the other, then let the sparks hit the bolt, and the power goes through you, and lights the bulb. You can't even feel a thing when it does that.
Though technically, voltage AND amperage kill. You can't have electrical flow with only one and not the other. ;)
12VDC at high amperage can easily shut down someone's heart.
His analogy:
"A bullet can easily kill you. Now think of amperage as a slow moving but comparatively heavy object, like a car moving at less than 1 MPH. The physical act of the contact of a car moving at less than 1 MPH won't kill or probably even hurt you."

A large bullet (more 'amperage') will do far more damage. As for the car moving at 1mph, you can get out of the way of it. If you're getting shocked with a lot of amperage, you can't move - your muscles lock up.
A better analogy:
You are against a brick wall. A motorcycle (low amperage) hits you at 1mph. You might hurt a little, but it stopped easily. Now a truck comes at you at 1mph. Speed doesn't matter here - it's going to take a lot of resistance to stop that truck. By the time it does stop after making initial contact with you, you'll be squished.
 

Bleep

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Oct 9, 1999
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My Tesla Coil on my website generates around 100,000 volts at very low amperage

This is really not the entire reason that the things that you say happen do happen.
This also has to do with the frequency of the tesla coil, high frequencies tend to flow on the surface of the conductor, this is the reason that wave guides work . DC uses the entire center of the conductor whereas ac does not and the higher the frequency the less of the inside of the conductor is used. In this case it is a combination of low current and high frequency that the Tesla coil generates.

Bleep
 

Jeff7

Lifer
Jan 4, 2001
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Originally posted by: Bleep
My Tesla Coil on my website generates around 100,000 volts at very low amperage

This is really not the entire reason that the things that you say happen do happen.
This also has to do with the frequency of the tesla coil, high frequencies tend to flow on the surface of the conductor, this is the reason that wave guides work . DC uses the entire center of the conductor whereas ac does not and the higher the frequency the less of the inside of the conductor is used. In this case it is a combination of low current and high frequency that the Tesla coil generates.

Bleep

Oh, duh, forgot about that. :p
Yeah, high frequency AC can be safe, the lower the frequency, the more dangerous it becomes - DC can be very dangerous - 0HZ.
 

dszd0g

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Jun 14, 2000
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Originally posted by: Bleep

This is really not the entire reason that the things that you say happen do happen.
This also has to do with the frequency of the tesla coil, high frequencies tend to flow on the surface of the conductor, this is the reason that wave guides work . DC uses the entire center of the conductor whereas ac does not and the higher the frequency the less of the inside of the conductor is used. In this case it is a combination of low current and high frequency that the Tesla coil generates.

This is generally referred to as the "skin effect."

As far as voltage or current killing, it depends. Electronics voltage causes dielectric breakdown and static (high voltage, low current) can kill electronics. High current heats up components and can melt or fry components. But really it is the wattage that matters there (Voltage * Amps).

I think for people they both matter (wattage) but current plays a larger role. If someone asked me if I would rather be hit by 10V and 1A or 1V and 10A (both 10W), I would definitely chose the 10V and 1A as that won't kill me and the other might (probably not). I have actually played around quite about with around 10V and 1A and zapped myself once or twice. I haven't zapped myself with the other and I hope I never do.

I guess I get to find out if it is 1001 posts that one gets Golden member, it wasn't 1000. [Edit: Yep!]
 

KF

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Dec 3, 1999
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>The only thing I really see there though concerning polarity is the input which
>makes perfect sense, as that's DC. Not sure about the output yet though.

According to what I read on that site, the bare lamp operates on about 1000V AC. What you are calling the input is the input (power) to the DC to AC converter (inverter). The output is AC and so has no polarity. Since the bare bulb operates on AC, it has no polarity. There is nothing in the way it is made that would require one end to be grounded over the other.


Why does house AC have a polarized plug? AC in itself has no polarity. The purpose of the polarized plug is mainly to reduce the hazard of shock. House AC has one side of the power line connected to the earth, literally. Therefore if you accidently touch that side of the line and another part of your body is contact with the ground, the shock hazard is generally less because there should only be a low or zero voltage between the two. In addition the big round prong on the plug is directly connected to the earth and carries no current, unlike the "neutral" side of the power wire which does. Exposed parts in modem equipment are connected to the round ground prong. Therefore the most likely kind of electrical fault (faulty insulation) will likely only put that wire in contact with a grounded part and there will not be a shock hazard. The neutral wire, although grounded, carries current, and therefore developes a voltage above ground due to the resistance of the wire. In some instances the resistance, due to corroded or poor contacts, can be high enough to result in a hazard. Therefore a third prong, not carrying current was added to the original system.

In the older system (which is still in place), the neutral wire was connected to the electrical contact which was most likely to be touched. For instance in a light socket the outer ring, the part that contacts the light bulbs thread, is connected to the neutral. The center contact is the hot side, the side not connected to the earth. In order for this to make any sense, a two pronged plug has to have one wide prong, which is the neutral side.
 

Jeff7

Lifer
Jan 4, 2001
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Ok, thank you KF. Thanks for the explanation too; I never knew that the neutral was grounded as well. I had heard of some kind of ground fault being a shock hazard, but never understood why, as the "ground plug" carried no current; guess if one does, that's why. Thanks for the info. :)
 

KF

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Dec 3, 1999
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Does current or voltage or current kill? Since from an electrical point of view a person is just a resistance, current is proportional to voltage. If subject to a particular voltage, a particular current will flow. The resistance of the skin can vary a lot, and in turn cause higher or lower total resistance. In the practical world, we generally deal with constant voltage sources, so the voltage is the identifying feature.

Although people can be burned to death, the usual problem is heart fibrilation. The heart stops beating effectively, like a heart attack. It does not require a lot of current/voltage. It depends on the path the current takes how much goes through the heart.

People can be knocked on conscious due to a jolt. Presumably it is electricity affecting the brain. Being knocked out, or just losing your balance can get you killed if, say, it happens on the roof.

As people have pointed out, when you deal with radio frequency voltages, little current flows in a conductor except at the surface. But consider this: as a piece of the circuit you may disrupt the RF oscillator for a moment, which could get you killed.

As dangerous as it can be, few people that have dealt with electicity have not gotten a shock, and the usual result is harmless. I have. You might bash your fingers jerking away. I also have a couple of screwdrivers and some alligator clips pieces of which are gone due to being instantly vaporized in a blinding flash. Those circuit breakers take a finite amount of time to open.
 

dszd0g

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Jun 14, 2000
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Originally posted by: KF
I also have a couple of screwdrivers and some alligator clips pieces of which are gone due to being instantly vaporized in a blinding flash.

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