Screen Tablet malarky => Tutorials and useful knowledge => Topic started by: DonShole on August 20, 2009, 08:31:28 PM

Title: CCFL Extension Cable
Post by: DonShole on August 20, 2009, 08:31:28 PM
While building my DonTiq II, i found that extending the ccfl cables by manually splicing in new wire caused backlights to dim markedly.  Using actual laptop CCFL extenders did not have this effect:

Title: Re: CCFL Extension Cable
Post by: bernard on August 21, 2009, 02:22:30 AM
That is a cool page of used stuff actually -- quite a few variety.  Actually this site it has quite a few interesting things -- inverters for 7 $  CCFL cables for 4 $ -- and, laptop AC Adaptors for 12$ -- although most of them are 14v to 19V -- did not see something in the 9V -- 12V  range and I am not sure about the type of connectors.

It also has a lot of LCD panels of varying sizes -- the price vary a lot and it is easily over 150 US $  --- 155$ for a UXGA (1600x1200) 15 inch LG screen -- OK -- then you have to buy a full monitor kit -- 60$ minimum + shipping .  That goes over 200$ -- but try to get a high-res non-widescreen 15 inch monitor these days...

Title: Re: CCFL Extension Cable
Post by: Drewid on August 27, 2009, 11:37:25 AM
Excellent find. It's always a bit dodgy lengthening HT cables, especially if you're not a techy type person.

Title: Re: CCFL Extension Cable
Post by: DonShole on August 27, 2009, 06:14:10 PM
The dimming is probably down to the resistance in the type of wire.  I think there's a build log somewhere in which manual extension had no dimming effect.  Using the extender sure looks a lot neater.

Title: Re: CCFL Extension Cable
Post by: bernard on August 27, 2009, 11:54:58 PM
I do not know for sure if an extender will actually work -- since it will create a "break" in the middle -- which Ambidextrose seems to imply that it is something to better avoid. Do not read me wrong, it might work just fine (since the wire gauge and type is made for CCFL) and also because some have extended it (soldering) and it worked with a "break" in the middle.  Nobody I know tried those yet, but if they are cheap it might be worth giving it a try. (at worse it fails and you take out the wires from the extender and do the soldering yourself)

Title: Re: CCFL Extension Cable
Post by: Drewid on August 30, 2009, 02:34:25 PM
Good point, at the worst case you have some decent wire to do the extension with.   ;D

Title: Re: CCFL Extension Cable
Post by: cabraswel on August 26, 2011, 11:01:34 PM
Hello all,

Long time lurker, and I'm finally starting my build!  However, I'm still in the parts acquisition phase, and I need some help.

I'm using the screen out of my old laptop (model Samsung LTN154P3-L05), but I basically need to reverse the direction of the video input, so that it travels the shorter distance to the edge of the panel.  I can't seem to find any FFC cables, or adapters that will do this for me.  Ideally, I'd just need a U-shaped FFC cable (with a female connector at one end?).  Attaching an illustration of what I mean, for clarity.

Has anybody encountered or solved this issue before?

Title: Re: CCFL Extension Cable
Post by: bernard on August 27, 2011, 12:14:49 AM
Welcome lurker cabraswel, :)

AFAIK, there is no such thing as a FFC cables with "female" connectors. (this is why diy-beamer is (was?) selling what they call "PCB" connectors). FFC cable are all "male" (it is just the bare wire with no real connector) -- and the "female" part is always a connector soldered on a PCB.  Well, I already saw in a catalog a free standing FFC connector -- but that was for bigger pitch typically (like 2.0mm) -- but maybe it can be found for 1.0 mm?  -- (because you seem to have 1.0mm pitch FFC). (3cm / 30 pins = 1.0mm per pin)

FFC cable are very rarely angled -- well -- some are but these are custom flex PCB (which looks and behaves like FFC -- and this is what you typically see inside ).   You can always take a straight FFC and fold it "in diagonal" to make a sharp & flat 90 degrees turn (if you understand what I mean).  Watchout: you shall only fold it once else the repetitive folding/unfolding action will break it.

I am not sure I understand what you are trying to achieve here -- is this the same case as everybody? Like you are trying to unfold 2 circuits in the back of the LCD Panel that are already connected by a FFC ? 

If you can, take a picture.

Title: Re: CCFL Extension Cable
Post by: cabraswel on August 27, 2011, 12:56:58 AM
Hi Bernard.  Thanks for the very quick response!

I suspected the gender problems with FFCs, but it never hurts to ask--right?  I think I'll be able to get away with DIY-beamer's PCB connector, once I sort out the bent cable.

I had thought that folding FFCs was never recommended.  Do they typically hold up after a single fold?

I'm attaching another image to try and illustrate what I'm going for.  I am designing a custom case (very rough in this image, btw), with a hinged lid.  This will allow me to remove the Intuos, similar to TabletMod's functionality.  The screen will be attached to my lid, with the wiring running towards the hinged side (hence my dilemma), and with the controller et al housed underneath the Intuos.  I hope this makes sense...  :-/

Anyway, in the image, there's a photo of my screen.  In the photo, the input connection points upwards, but I need to run the cable downwards.  The cable which came with my controller is round, so I'd prefer to accomplish this with an FFC, in order to push the screen right up against the Intuos.


Title: Re: CCFL Extension Cable
Post by: bernard on August 27, 2011, 01:27:01 AM
The cable between the LCD Panel and the laptop (or LVDS driver) -- is not a FFC and cannot be one either.   

But it could be "flat" (actually lot of them are flat).  Flat just means that the wires inside are placed next to each other.

Yours is "round" just because the wires are passing through a shield.  In laptop they often do that to have less stress on the cable. If it was flat the cable would have to bend each time you open/close the laptop.  So what they do is you a round wire and pass in it in an "S" fashion so the wire merely "twist" instead of bending.

You could simply cut out the round shield and flatten the cable with your fingers.  You can use simple "tape" to hold the wires flat. If you use transparent tape (used to pack boxes) you will have to advantage of "seeing" your little wires (if you need to diagnose a problem).

You can even make the wire shape of your dream by cutting and placing the tape in whatever shape you like. (provided you have enough lenght in the wires). 

These are thin wires, so watch out when playing and folding these -- plan before hand.  You can even find other dummy wires and "fake" what you want to do to see if the "design" looks fine. You could take wires off VGA cables, IDE connectors, network patch cables or just plain cotton strings!

Hope that helps.

Title: Re: CCFL Extension Cable
Post by: DaBotz on November 12, 2014, 05:38:59 AM
In my ubiq, I used one extender cable "as is",  and one spliced and soldered to - around - 60 cm of length (24" or 2 feet, for the metrically impaired).

I see no differences in lighting from the two lamps.

The extension cable was copper cable for house electrical grids, with an insulating coat rated for 500 volts (being an engineer, I know it should be safe for at least the triple, or one of my colleagues need to change job; OK, I didn't,t trust it, so I added something, just to stay sure) and a conductive core that was - roughly - the diameter of the whole extender cable, coat comprised (so, even if the extenders cable core was silver, and not aluminum as I think it was, its specific resistence should be less than a quarter  ).

I also had the luck of having some bigger cable, whose core had in turn roughly the same diameter of the extending cable, whose insulating coat I removed to use as a tubular isolator around the junctions.

By practicing a circular incision in it, at about 5 cm of length, and then pulling the core out, without damaging the coat, you can have small isolating tubes. They are a very neat (though a bit laborious) alternative to the tape.

I cut the Extender's cables, one at a quarter of its length, the other at three quarters (or vice-versa;  the important thing is that, this way, the junctions are not phisically near to each other) and unsheathed the extender's cable core, for an eight of its length, on both sides of each cut, by making an incision along the length of the cable (give its meager conductive core, a circular incision would have meant a risk; also, in all it's a couple of cm) and then removing the insulating wheat.

I pulled my copper cable inside the aforementioned coat pieces (the play of diameters was just right... the copper cable slided inside with ease), then provided to practice a similar, longitudinal incision in its coat, slightly longer this time, an only bending the coating backward, without removing it.

I opened the strands of both conductive cores, and meshed them together trying to avoid irregularities. then, I twisted close the junction, and soldered it.

Capillarity sucked the solder tin nicely inside the reconstituted cable, so that the junction seemed just a piece of monolithic cable of a couple of cm of length (4/5th of an inch).

I placed back in position the sheat, and than slided the "isolator tube" on the junction, so that it covers it - as the core has "fatten up", it required a bit of an effort, so it is not going to come loose.

I did the same for the four junctions needed, though with the alteration that I pulled one of the two cables inside the external sheet of a coaxial cable (just to reduce the possibility of parasitic capacitances).

I know that, to reduce possible RF interferences, the antenna loop that the two cable constitute should have area zero (using a twisted pair or a coaxial), but I also read somewhere that stacking the ccfl cables too near to each other may negatively affect their performance (losses through the isolator, or the highest harmonics of the PWM signal sucked into capacitances? that's the question... - OK, it' s official; I'm obsessed by unwanted capacitors).

As I said, I do not see differences in luminosity between the two sides of the screen - one extender vs one extender with 2 soldered intermediate junctions -, so I suppose that the results were good.