Composite video over long distance RJ45

Discussion in 'The Projects Forum' started by yoannwyffels, Mar 23, 2016.

  1. yoannwyffels

    Thread Starter New Member

    Mar 23, 2016
    16
    1
    Hello,

    I'm trying to accomplish sending a composite video signal over long RJ45 cable (> 100 meters).
    For now, I succeed to run it over a 40m RJ45 cable with just a simple video buffer like this one:

    [​IMG]
    VCC=+5V
    C7=470uf

    It gives me a better video quality this way.
    But, if I increase cable distance (> 40m) I'm starting having some white strips over video :/
    So I'm looking (and searching since 4 days) an IC or a circuit capable of repeating or amplifing video signal with just a +5V power supply.

    MAX4030EESA
    MAX4090

    seems to fit the need, but I'm not sure.

    What do you think about ? Does someone succeed transmit composite video over long RJ45 cable ?

    Thank you
     
  2. yoannwyffels

    Thread Starter New Member

    Mar 23, 2016
    16
    1
    It seems AD8131 transmitter and AD8130 receivers will be a solution too.
    Does anyone already have experiments in them ?
     
  3. dl324

    Distinguished Member

    Mar 30, 2015
    3,246
    622
  4. yoannwyffels

    Thread Starter New Member

    Mar 23, 2016
    16
    1
    I already saw this kind of thing. But I'm thinking they are just "passive" adaptater, nothing more (so they will not perform any amplification/correction/filtering...). Am I right ?
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,542
    1,251
    Your circuit has an asymmetrical output impedance, and the effects of that increase as the cable capacitance increases with length.

    Generally speaking, Maxim, Analog Devices, Linear Technology, and Intersil make excellent video driver chips. I remember reading about a single 5V video driver, but I don't remember who makes it.

    ak
     
  6. dl324

    Distinguished Member

    Mar 30, 2015
    3,246
    622
    Do more research. They match the impedance of the video source to the cable. You need to use them at both ends of the CAT5 cable.
     
  7. yoannwyffels

    Thread Starter New Member

    Mar 23, 2016
    16
    1
    MAX4030EESA seems acting as a video driver (If I well understand what's a "video driver" :p)
    Since I started searching for analog video solutions...I have to say, this is over complicated !
     
  8. yoannwyffels

    Thread Starter New Member

    Mar 23, 2016
    16
    1
    Thanks dl324, I've just bought a pair of them on ebay...Will try this low cost and passive solution in parallel of others.
    Thank you !
     
  9. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,542
    1,251
    No, it isn't, but composit video is a very complex signal. And, the vast majority of the standard components and circuit designs are for a cable system that is not yours. There is a very big difference between coax and UTP when dealing with high frequencies.

    ak
     
  10. yoannwyffels

    Thread Starter New Member

    Mar 23, 2016
    16
    1
    So, does video baluns (as mentioned by dl324) will be a good solution for at least 100m cable ?
     
  11. yoannwyffels

    Thread Starter New Member

    Mar 23, 2016
    16
    1
    I think I've found what you were talking about "video driver":

    driver MAX4447
    https://www.maximintegrated.com/en/products/analog/amplifiers/MAX4447.html

    receiver MAX4444
    https://www.maximintegrated.com/en/products/analog/amplifiers/MAX4444.html

    is that what you were talking about ?
     
  12. crutschow

    Expert

    Mar 14, 2008
    13,016
    3,235
    Yes, those differential drivers and receivers should do what you want.
    With those you don't need the baluns.
    Note that you need to match the characteristic impedance of the line, which is 100Ω for Cat5 cable.
    (So use 50Ω for the two resistors at the output of the MAX4447 driver and one 100Ω across the line at the receiving end, with a gain of 2V/V for the driver. That will give on overall signal gain of 1).

    As a nit, the cable is Cat5 or Cat6 which typically use RJ45 connectors, so it's more correctly called Cat5/6 cable or ethernet cable , not RJ45 cable. ;)
     
  13. yoannwyffels

    Thread Starter New Member

    Mar 23, 2016
    16
    1
    You're right crutschow, we can also call them twisted pairs ! ;) I will send video signal over Cat5e cable (which is connected on RJ45 connector :p).
    Thank you about resistors details, I ordered them with a MAX1044 to get an inverted voltage (+5 / -5v) as thoses IC needs -5V to run.

    About the 100 ohm resistor at end of the line...There is 2 pins on MAX4444 (IN- and IN+). Where did you put that resistor ?
     
  14. Sensacell

    Well-Known Member

    Jun 19, 2012
    1,131
    267
    Here is a video-over-cat-5 design I did a long time ago.
    It was great for moving up to 3 video signals over loooong cables.
    48 VAC powers each board.
     
  15. crutschow

    Expert

    Mar 14, 2008
    13,016
    3,235
    I stated it should be "across the line" which means you connect it between the IN- and IN+ inputs.
     
  16. yoannwyffels

    Thread Starter New Member

    Mar 23, 2016
    16
    1
    thanks :)
     
Loading...