I've been reading again. Actually, I do all this research on my iPhone at my job, which is lifeguarding (don't worry, I'm a very good lifeguard, we do 30 up 30 down).

Turns out LVDS stands for Low Voltage Differential Signalling. Differential signalling means the cables are in pairs, and the voltage goes down on cable and comes back down the next. Low voltage means the voltage going down the cables is tiny, and the signal is made by differences in this voltage-- about 350mV. That's why these cables are so hard to produce, and especially hard to extend-- even minor EMI is enough to change the voltage enough to screw up the signal.

There's two ways to combat this interference. Twisted pairs: the interference hits both the coming and the going cable, and it cancels out. This is what our short LVDS cables between our LCDs and controllers use. It works well, but is not that easy to make by hand-- no good for making long extensions. Shielding: wrap all the cables tightly in a conductive material, which blocks interference.

So, how do we make an extension of an LVDS cable? Why would we? There's plenty out there already, and they can be really long too. USB, Firewire, VGA, DVI, HDMI: All LVDS cables. All have either twisted pairs or shielding. So why not just use one of them? None of them have the right number of pins, but going back a few years, SCSI does. SCSI actually had 17 standards (most weren't used), which is why we don't see it anymore. The most common SCSI cable had 50 pins, and the LVDS cable between my controller and my 10.6" panel has 32 pins.

This will be a very slow moving electronics PLOG, because I'm fitting all my projectorism between a very busy school life, work life, and girlfriend life.

First step: Get a SCSI cable and a connector to match the one at each end (so I don't have to mod the cable itself). I think my step dad has some. He's a mac geek, and graphic designer, and I know he used SCSI a few computers ago.

I have some SCSI cables, but I don't think any of them are very long. I'll check and see what I can come up with if you'd like. Just as a suggestion, (and I know you're looking for a single cable), but a bundle of four network cables would give you 32 wires, each has 4 twisted pairs. I have no idea if it will work for what you want to do, just thought I'd throw it out there.

Good idea, I thought of it too. However, in that case I'd have to strip the insulation off the 4 ethernet cables, bundle them all together, and then apply new insulation. I don't know how to apply insulation, except for heat shrink, which would be pretty difficult over such lengths and make a not to flexible cable.

Thanks, but don't worry about looking for old SCSI cables. I've seen them come and go on ebay for cheap, and lengths up to 26ft, and I know my step-dad has some I can use for the testing phase.

Check the pinned Kontron thread as I linked some technical papers in there regarding LVDS extensions and they'll likely give you some useful info.

I used a 68 wire SCSI cable and ran parallel pairs to minimized resistance loss.
Also the cable has a braided shield around it. I did it the hard way by twisting parallel pairs than re-installing shield.

damn I thought I figured out something new!!

Why didn't you put more info about it in your plog? This mod could open up enormous case design possibilities to the community.

Anyway, since I'm conceding idea ownership to you, I might as well ask, any pointers? Did you try without twisting the pairs and just leaving it shielded?

would have been cool

I didn't think too much about for the plog.

On the 68 wire cable, the pairs were already twisted, unfortunately I made my end adapters first. I recommend finding which wires are pre-twisted then make you ends match.

No, I did not try without twisting.

@MarcoPolo:

Just back from your plog. I forgot about that light engine that looks like a nuke! Nice build. Slow and steady. Great craftsmanship.

@chaos86:

So, I see MarcoPolo extended the LVDS only a relatively small amount. You still gonna have a go at a 10 foot extension? I'll be interested to see how it turns out if you do.

Yep. I figure, if SCSI carries data from hard drives 30 ft, it can carry an LCD signal 10ft. I just hope there isn't some signal boosting tech for longer cables in the SCSI spec that I dont know about, and that our controllers dont have.

The chronicle of the LVDS extension


Step 1: Study the cable, make a diagram. On the MST to 10.6" lcd LVDS cable there are 8 twisted pairs and 4 individual wires, and the twisted pairs have to stay twisted the whole way down the line.

Step 2: Cut the cable in half and start connecting the wires to the extension, keeping pairs from the old cable attached to pairs from the extension.

I got the two ends, twisted them together, and used heat-shrink to cover the connection and hold it together. Anything less than a pretty forceful tug will not disconnect them.

Step 2A (not advised): Allow the end connector to lean on the soldering iron while you're distracted and tired.

Disaster.

Step 2B (for if you followed step 2A): Go to about 7 different electronics parts stores to find a new one of those connectors and follow your diagram to finish up the cable. You need to use the point of an X-acto blade or similarly small tool to lift those tiny tabs slightly to release the cables (careful not to break them if you plan to reuse). To put them in is easy though, you just push them in and the tab snaps down.

Step 3: Test the extended cable with your LCD and controller.

Click to view attachment
Click to view attachment

This image may be a little hard to figure out. It's the LCD sitting on top of my iphone, effectively using the iPhone as a backlight. It's the iPhone screen that's showing Google.com, and the 10.6" screen showing "NO SYNC".

As you can see, there's a problem somewhere in the cable, as the background which should be white, is showing as green, and the edges of the NO SYNC type and the blue box around it have a black displacement to one side. However, there is no static and the problems don't change or move, which tells me that the cable is working well, carrying the signal, and blocking interference as it should, but it's missing some of it's data, probable just one or two wires aren't getting full continuity. Now if only I had a working continuity tester. I guess that's for another day.