VGA Over Cat-5 Cable

7/29/2019 VGA Over Cat-5 Cable

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VGA over Cat-5 cable

VGA over Cat-5 ethernet cable

It's possible to send a VGA "video" signal down an ordinary Cat-5

ethernet cable. This is possible for two reasons: firstly, although

VGA connectors have 15 (or 13) pins, only about 8 wires are actually

necessary to send the VGA signal; and secondly, ethernet cable is

twisted pair, and we can use the magic oftwisted pair to push theanalog VGA signal further than spec.

http://www.geocities.com/dougburbidge/vgaovercat5.html (1 of 4)16/02/2009 08:32:30 a.m.
http://en.wikipedia.org/wiki/Twisted_pairhttp://geocities.yahoo.com/http://en.wikipedia.org/wiki/Twisted_pair


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The diagram above shows conversion from HD15 (VGA) to RJ45

(an ethernet socket). A similar adapter is used to convert back again.

Connectors are shown from the solder side. This diagram assumes

your Cat-5 cable is crimped in the standard way (not as a cross-over

cable).

This is nifty because:

q Cat-5 is cheaper than a VGA cable (whether you're buyingpre-made Ethernet cables or crimping your own off a roll),

q you can run Cat-5 easily through conduits,

q electricians understand what Cat-5 is and how they should run

it,

q you may already have Cat-5 in your walls

q compared to other VGA-over-something solutions, it's cheap,

compact, and does not require its own power

Standard VGA extension cables come in lengths of 1.8 metres (6

feet), and if you need to go a bit further you can daisy-chain several

of these, with a little signal loss. You can also get a super-special low-

loss 30 metre (100 foot) VGA extension cable, but they're very

expensive and very hard to find. Additionally, their fat VGA plug

ends won't run through conduit smaller than about 50mm.

I've run VGA over Cat-5 for distances of about 15 metres (50 feet).

At this range, the 800x600 screen looked fine when it was displaying

a coloured background; although when it was displaying black, a

lighter gray region was visible, probably due to interference from the

synch signals. Your mileage will vary depending on screen res and

refresh rate (lower will go further), contrast and brightness in the

image (high contrast and brightness will go further), and interference

from other sources (running the cable in its own metal conduit is

best; if you're not in conduit, running parallel to other cables is bad).

This trick will work equally well with Cat-5e and Cat-6; possibly

even a little better.

There are two easy ways to implement the above diagram:

q Etch circuit boards,

q Use an RJ45-to-DB9 adapter, but replace the DB9 with anHD15.



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Etch circuit boards

Above is artwork for two adapters, on single-sided PCB. On the right

is a male HD15 to RJ45, to plug into the back of your computer.

There are three "components" on the board: the HD15 connector, the

RJ45 connector, and a wire link.

For the monitor end, you can use the board on the left, which has an

RJ45, a female HD15, and five wire links. Or you can simply use two

of the male HD15-to-RJ45, plus a female-female VGA gender

changer.

Print at 300 dpi. The artwork is shown here from the component side

-- print it onto transparency film, and then flip the transparency over

so that the text runs the correct way. There are nice wide tracks with

wide gaps between to allow easy etching; and nice big solder pads to

allow easy drilling and soldering. The very thin "solder pads" are

merely drill guides.



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Use an RJ45-to-DB9 adapter

Buy an RJ45-to-DB9 adapter likethis. Throw away the DB9. Cut off

the nifty little pins that insert into the DB9. Buy a "solder cup" HD15

connector of the appropriate gender. Strip back a little of the wires

leading from the RJ45 socket, and solder them onto the HD15. Then

do all this again, for the other gender. You now have a matched pair.

Index

http://www.altronics.com.au/index.asp?area=item&id=P1690http://www.altronics.com.au/index.asp?area=item&id=P1692http://www.geocities.com/dougburbidge/index.htmlhttp://www.geocities.com/dougburbidge/index.htmlhttp://www.altronics.com.au/index.asp?area=item&id=P1692http://www.altronics.com.au/index.asp?area=item&id=P1690

VGA Over Cat-5 Cable

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