CCFL modification questions

I'm trying to build a light box using a CCFL automotive light kit, originally designed to be light rings for speaker enclosures (Roadmaster RNK100 round "neon" - you know the type). From my research, I know these lamps use very high (200V-600V DC) voltages, and that induction losses from the power supply to the lamps, due to coiled or closely running wires, can lower the lamp's output, and may damage the inverter. I have also read you are supposed to keep the power leads to the lamps at a minimum, also to prevent reduced illumination. This particular product uses extremely long power leads from the inverter to the lamps (over 17' long!). The lamps don't really provide adequate illumination for my intended application, and the extremely long power leads are also a major problem.

My question is, can I safely shorten the leads from the inverter to the lamps (say, to about 12")? Will this safely increase the illumination of the lamps to their maximum, and not cause damage to the inverter? I am assuming so, since this would decrease the voltage losses in the wiring, and allow the lamps to recieve their full "requested" voltage. However, since this product was designed with such long leads, could the inverter be designed to allow for the line losses, i.e. it produces more voltage than required so as to mitigate those losses? Could this cause damage to the lamps? Could they explode? I believe they contain Mercury, so this is definately not something I would want to occur, and is the reason for my reluctance in experimenting.

I know just enough about electronics design to make myself dangerous! :) Any help will be MUCH appreciated. TIA

Reply to
Rondor
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As I've had no response to this post, would it be better posted elsewhere?

TIA

p.s. CCFL is Cold Cathode Fluorescent Lamp

Reply to
Rondor

Not clear how you could have "induction losses" from a DC "signal". Do you have a refrence for this information, or are you just guessing?

OTOH, how do you know it is DC? All mains-powered fluorescent AND neon lamps run on AC that I have ever seen. Even the DC-powered ones run on AC because they use a transformer to boost the voltage.

Seems like general, common sense, advice.

Likely because of the intended use (routing to speaker cabs). And likely DESIGNED to run with such long leads.

That may be a fundamental issue that cannot be addressed by reducing the length of the wiring.

Can't see any electrical issue why you couldn't trim them to whatever length is convienent.

I would be surprised if you saw ANY significant increase in light output even by dramatically shortening the supply leads.

What do the instructions say about trimming the length? My gut feeling would be that the inverter is not in danger.

The voltage losses are likely minimal and inconsequential. Because the current is likely low (only a few milliamps).

Seems unlikely to me.

I wouldn't worry about it if it were me. Of course, I would run some worst-case tests and measurements before buttoning everything up and forgetting about it.

Maybe, maybe not. Did you mean NEON or FLUORESCENT? "Neon" (name used for other types of gas also) is where the internal gas glows directly through a clear tube, while fluorescent is where there is a white (or other color) phosphor coating on the inside of the tube. I seem to recall that neon (or other gas) tubes do NOT have mercury, while fluorescent likely contain slight traces of mercury.

If you are really that worried about "exploding" the lamps, take adequate protection (run the tests with something to protect you and your test setup from flying glass/chemicals.)

If it were me, I would wear safety goggles, but don't think that any further protective gear is warranted.

Reply to
Richard Crowley

Richard, I really appreciate you taking the time for a detailed reply to my post. As I said below, I am a novice/hobbiest when it comes to this stuff. I am currently living off a self designed off-grid solar system, and some of my info comes from that experience. I've read that DC wiring can have large losses if the conductors are run close together, but I may be incorrect by naming such losses "induction". My understanding is that the magnetic fields created in the conductors will create a resistance in the wire if the positive and negative conductors are run adjacent to each other, with each conductor's field negatively affecting the other. This is the loss to which I was trying to refer.

The power source for the controller/inveter is DC - from a lighter plug. The instructions say the device can be powered with AC, but only after using a 12Vdc converer (power brick). Also, due to the warning about running the light with the wires bound together (see below), I assumed it is sending high voltage DC to the lamps. I guess I should hook up my meter to determine if it's sending AC or DC. My meter can read either up to 600v, so that should work. The controllers for CCFls ARE called inverters, so it could very well be using AC.

This info came from a CCFL (Cold Cathode Fluorescent Lamp) manufacturer's design info, which I believe these lamps are.

Exactally one of my questions, that maybe the controller was designed to work with the long leads, and shortening them may cause damage.

Agreed.

OK. Good so far! :)

Understood.

The instructions don't mention shortening the leads, but it does emphatically warn against running them while bundled or tied together. From them: "Do not gather the cables and bind together when the light is in use. Turning on the light with the cables bound together will cause the controller unit to malfunction." My understanding is that this would be because of the wiring losses and resistances that I first spoke about above ("induction?").

Again, I may be showing my ignorance, or lack of experience and training in these matters. It may be the current losses, not the voltage, I should be talking about.

Intelligent advice!

The product is called "Neon" on the package, but I know true neon uses large, noisy controllers, and these lamps do have a whiteish coating, and are incased in clear lexan tubes. They look to me to be CCFLs, with the term "neon" used as a marketing tool aimed at the ignorant masses.

More intelligent advice! Believe me, due to past experiences, I have a great respect for electricity, and the damage it can cause if treated incorrectly! I just have absolutely no experience with these lamps, and there is little info about them out there. Even though this product wasn't expensive, I would hate to ruin it or any surrounding property due to my unknowledgable tinkering! Mercury poisioning would also be a downer! :)

Again, many thanks for trying to help me in this matter. I appologize if my ignorance has lead to any of this discourse being "stupidly obvious and tedious".

Happy Holidays to you and yours!

Reply to
Rondor

I'd like to see a reference for this. By itself, it doesn't make any sense to me. Very large DC currents are commonly run in conduits where the conductors are right next to each other. Can't imagine any electrical/physical reason why there would be "losses" from running DC through adjacent conductors.

Inductance and capacitance have no effect on *steady-state* (continuous) DC current. They are effectively AC phenomenon. They may have brief (fractions of a second), transient effect when turning on or off the DC current.

No offense, but this sounds like 10% physics and 90% baloney. Some of it makes sense if talking about AC (and only in very non-conventional power circuits like high-frequency AC), but it makes no sense at all when talking about DC. At least not to me. Perhaps others reading this could shed different light?

I thought you were talking about the OUTPUT from the inverter (the part with the over-long leads to the lamp.) That is what I would strongly suspect is high-frequency AC.

Of course the INPUT is 12VDC as you already stated and I can't think that the input wiring would be anything but completely ordinary and straightforward.

Do you undestand how an inverter works?

But if you are not "binding together" the wires, this seems like a red herring.

I don't see any way of coming to the conclusion that it is DC. I would be very surprised if it were DC as there is no reason to rectify it when the lamp doesn't care (or more likely even runs better on AC)

NO! NO! NO! D-A-N-G-E-R, WILL ROBINSON! (*) I WOULD *NOT* CONDUCT THIS EXPERIMENT!!!!! (*

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It has a HIGH level of RISK (to both YOU and to your meter) and it will prove nothing useful. If they are warning about "binding together" the wires causing damage, then most certainly connecting a meter carries a high risk. Unless you have a specialty high-voltage probe (which I am assuming you do NOT.)

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I'd wager a nice dinner that they ouput high-frequency AC.

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Since you appear to be planning on puting the inverter inside the enclosure WITH the lamp(s), it would seem like you have an even more ideal opportunity to route the cables as far apart as physically possible, so I wouldn't worry about their "bound together" warning.

My best guess would be that the inverter is putting out high- frequency AC, and the capacitance caused by "binding together" the output wires would cause an extra load on the inverter output (or even cause the marginal circuit design to change frequency outside the design range.)

The lamps likely run on high voltage (hundreds of volts), but very low current. Power = current multiplied by voltage so you can see that for equal power, the current goes down as the voltage increases (and vice-versa).

There is always a trade-off between voltage and current, and that is how the utility power grid works. They boost the voltage very high (10s of thousands of volts) to travel long distances over relatively small wires. Then they use transformers to bring it down to 240/120V to send to individual houses.

I can't believe that it is the RESISTANCE of the wires that would cause any reduction of light output from the lamps. It seems more likely that it is capacitance from "binding together" the wires that could likely cause problems at high AC frequencies.

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Not really. They use ordinary transformers that put out high AC voltages. Some are quite small and completely silent. Large neon signs use proportionally larger transformers. They may be less careful about making the transformers quiet because they know that they will be many yards away from anybody to hear them.

In that case, they are certainly what I would call "fluorescent" (or CCFL = Cold-Cathode Fluorescent)

You didn't mention before that the lamps were enclosed in plastic tubes. In this case, the risk from any possible explosion is so low that I wouldn't give it a second thought.

Merry Christmas (*) and Happy New Year. (* It is only the 2nd day of Christmas. Two turtle-doves, etc.)

Reply to
Richard Crowley

Well, I've searched my bookmarks and saved pages, but can't find that reference. Typical! :) I went back to the site that I thought the info came from, but couldn't find it. (OT and BTW, since sites are constantly changing, I've started to save pages of interest in .mht format so I will always have access to the info) The article was quite technical, and even gave percentage losses occuring from varying distances of the conductors to each other, saying that even 12" apart, the effect was mesurable and significant.

The article was refering to the high current battery to inverter conductors. Maybe because the current carried by these conductors does change, depending on the load required by the inverter, is why the issue was discussed. No way to know for sure, 'cause I can't find the blasted article! :(

No offense taken at all. That's why I'm here asking these questions. If I have inaccurate information flowing in my cranium, I want it OUT! :) In searching for this article, I did come across some info about interference in DC wiring, but they recommended twisting the power leads together the length of the run so as to avoid this interference. Totally opposite from what I had thought was correct!

This was based on my understanding at the time that dc conductors run together caused losses or interference. Bad information leads to incorrect assumptions.

My meter is an AC/DC clamp/probe meter rated up to 600v and 1000A (probes are marked CATIII 600V). I know you can't use the clamp for voltage metering, but you can tell if the current is AC or DC by the readout. (metering constant DC current while on AC setting will cause a fluctuating or 0 readout) However, since it's lowest measurement is 0.1A, and I am most probablly dealing with very low current AC, and with that EXCELLENT warning from you, I will forgo any metering! :)

OK. Thanks for alleviating my experimentation fears. As I stated before, I've seen firsthand the damage electricity can do, so I treat it with respect. Again, many thanks for your taking the time to help me with this, Richard. You have racked up many electric Karma points!

All the best to you and yours in the coming New Year!

Reply to
Rondor

Note that using any electrical/electronic equipment right at the upper limit specification is not advisable. You typically want at least a 100% safety factor, meaning that I would use something rated to 600V only up to

300V. Note further that the output of those DC invertors that run neon/fluorescent tubes may have higher-voltage spikes even than the "nominal" RMS rating.

High-frequency AC is nasty stuff and quite a bit more hazardous than line/mains voltage measurement. Even after 40 years of experimenting with electronics, I wouldn't even attempt to measure it even WITH my HV probe unless there were a REALLY GOOD reason to mess with it.

From what we percieve as your level of experience with electronics, I would STRONGLY ADVISE you to not mess with the HF AC except to route, connect, and insulate it as recommended.

Reply to
Richard Crowley

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