Cord Length on Cold Cathode?

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-zax-

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Mods... not sure where this is supposed to go, but if I placed wrongfully, can you please move it for me? :D

Here's my dilemma. I'm running dual cold cathodes in a system, and I know for fact that both of them worked before I started modding them.

What I am doing is making the cables longer on them so I can hide the cables in the case. The standard cable is about 6" in length, and I made the first one just over 12"... works great! The second one is where I'm having the problem. In order for me to have this one placed where I want it, I had to make the cable pretty long. Its just over 30". This cathode doen't provide half the light that the other does, and seems to be making weird noise.

Can the cable length be my problem?
 
If you lengthen the cable from the inverter to the tube, you will lose lighting power. There's nothing you can do about it, it's rooted in how CCFL's work. You can lengthen the wire from the PSU to the inverter all day long, but changing the length of the wire between the inverter and the tube itself will change the light output and can make it produce funny noises.
 
if you use a lower gage wire to extend the length of the wire you shouldnt have a problem, but make sure its insalated properly because i did the same, and whenever you touch the wires it can give u a little "poke" of electricity :D
 
I'm using the same gauge of cable as what was originally on the cold cathode fo this project.

I'm gonna try cutting it back again to see if it fixes it.. hopefully it does..

I'm just wondering if I fubared the light when soldering the wires together or something. :confused:
 
as was already said, if you use the same guage wire and lengthen it a lot, the lighting suffers. You can try a lower (thicker) guage wire. The longer the wire, the more resistance, the more the voltage will drop.

And it'll give you a "poke" because the inverter changes 12v to 600-700v (usually). And the higher the voltage, the easier it penetrates insulation/skin/whatever.
 
w00t.. thats what it was... too long of cable. I'm going to try some heavier gauge cable to see if I can make the distance with that.

Thanks guys!
 
If this isn't the weirdest thing.. I'm not sure what is... lol

I lengthend the wire with the thicker gauge and ran both cathodes... both were bright as hell. At that time... my original one was still sleeved, and the new one was not. As soon as I sleeved the 2nd one... it went dim again.

I was like wtf. So I de-sleeved it and checked some odds and ends, and then just plugged it back into the inverter without being sleeved. When the sleeve was off of it ... was bright as hell again. So... I thought was maybe just a coincidence... and resleeved it. As soon as I finished it, and plugged it in... it was dim.

I de-sleeved it again, and just plugged it in this time without checking any of my solder joints.. and it was bright again.

Why in the hell would sleeving cause this problem? This is beyond me... and I'm no electrician.. :rolleyes:
 
You're getting too much capacitance between the wires. Separate the wires as far apart from each other as you can. If you have the tube turned on while you do this, you will notice the tube going on and off and the brightness changing as you move the wires around. If you put each wire in it's own aquarium tube, and route them seperately, trying to keep them 3 inches apart, you'll be able to use significantly longer wires than normal.

CCFT work on oscillating power at high voltage, and putting a capacitor on the wires would buffer the oscillations, lowering the voltage peaks below what is needed to create the light. By putting wires close together, you are in effect making a simple capacitor, and by making the wires too long, the capacitance of that capacitor is increased until it is problematic.

I believe the capacitance problem is also exacerbated by routing the wires close to a metal plate, especially when the metal is connected to metal close to the other wire, such as if you routed the wires along the metal insides of your case. Put lots of air around them. Note that even trying to minimise capacitance like there, there will be a length limit, it's just greater than what you could get away with otherwise.
 
I'm assuming the sleeving made the difference because you were putting both cables in the same sleeve and thus raising the capacitance. If you were putting each cable in a different sleeve, then there are some other possibilities.
 
Ah.. I suppose that makes sense. Thanks for the info. :D

I don't have the one sleeved right now, and the wires are separated by between 1/8 and 3/4 inch. (just hanging for a test)... and now its brighter than the other one that looked bright before.. lol


Harlequin - No metal... just plastic sleeving like what you sleeve a PSU with.
 
Thx again for everyone's help. Got my cold cathodes up and runnin' with no dimness... w00t

Now I gotta consentrate on re-tubing my H2O setup in this case... will just about be done after that.
 
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