help with s-video 4x4 video matrix switcher

Discussion in 'The Projects Forum' started by p4ntb0y, Apr 20, 2011.

  1. p4ntb0y

    Thread Starter Member

    Apr 19, 2011
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    hi guys,

    I am trying to make a s-video matrix selector switch

    I make an unpowered version but I get bad picture qauilty when I have them all on the same setting.

    So I decieded to build a powered version using a MAX452 video booster.

    link herehttp://datasheets.maxim-ic.com/en/ds/MAX452-MAX455.pdf

    now I am new to all of this :(

    I have 4 inputs s-video RCA
    dvd
    tv
    Sky perfect
    PC

    and I have 4 out puts going to 4 different TVs

    I have 4x rotary switches which i can choose which channel to output on the 4 tvs

    my questions are....

    I am going from 100V ac to DC 5v for the chip is that right?
    how do I wire in the chip?
    how can i reduce noise?
    can I integrate an remote?

    I would ask at the shop where i bought it but I am in japan and do not speak much Japanese.

    I will also make my own board which I am reading up now.

    regards

    Dan
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Welcome to AAC!

    You are talking a simple S-video switch box? A schematic is going to be absolutely necessary for any real help. Guessing, you are using a chip to do the actual switching, with the rotary switch selecting the channel the chip lets through?

    The main issues is RF, video signals qualify. Isolation is likely to be the biggest issues. You will get ghosting from other inputs on the channel you have selected, which is pretty bad. The isolation will have to be substantial, better than -60db. I don't do it much anymore, but I went through a phase where I worked on video and RF projects pretty heavily. I suspect -80db isolation is pretty much a minimum spec.

    This means you will need to pay very special attention to the impedance of your lines, and the ground plane (it is going to be required). A PCB is pretty much required.

    You can do less. I did, and lived with the crappy results. :D Just something to be aware of.
     
  3. p4ntb0y

    Thread Starter Member

    Apr 19, 2011
    33
    0
    I was going to let the rotary switch select the channel and then use the max452 to boost the signal.

    I have a feeling now that this is wrong?

    the ground is required to isolate the noise I take it?

    I will knock up a quick schematic in visio later

    many thanks for the prompt reply
     
  4. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    You can try it and see if it works. The problem is the high frequencies, they need precision lines to maintain a flat frequency response. My advice, try it your way without all the bells and whistles and see how it works. I suspect it will appear smeared, but try it and see.

    There will be others folks with other ideas, some will be pretty good. How are you amplifying the signal.
     
  5. p4ntb0y

    Thread Starter Member

    Apr 19, 2011
    33
    0
    the max452 should take care of that but i am a little stuck on the wiring

    v - voltage input -5dc
    v + voltage input 5dc
    -in ground in on cable
    +in cable in center core 75 ohms? is that right?
    v out output on s video cable center core?


    sorry if this is a lame question, but i am learning quick, I know this may be simple so I wanted to say thank you for your time bill.

    i looked on the internet but could not find anything like i want to do it took me a week to find the chip to amp my s video.
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Have you looked at MAX4456? You should be able to use this to route 4 channels of luma and chroma. You will still need an audio routing switcher.
    Note that you must use a computer or microcontroller to control this crosspoint matrix. this
     
  7. p4ntb0y

    Thread Starter Member

    Apr 19, 2011
    33
    0
    Hi Ron thanks for the suggestion.

    I do not need audio just video.

    I just need to drive four sources but able to switch the four to any or the four tvs.

    for example...

    tv 1 tv2 tv3 tv4
    dvd player tv pc sat

    or

    tv 1 tv2 tv3 tv4
    tv tv tv tv

    I did have a look for that chip but I cant buy it in my region (Osaka, Japan)

    as I am just starting out I am trying to work out how to wire the max452 into my setup picture attached....

    I have an un-powered version that works but I do get a bit of ghosting and when all four are set to the same channel I lose picture quality and the color changes.

    I know know this may be because I do not have a ground plane as I just wired all the connectors and switches and just joined all the grounds together.

    This has now officially become a hobby ;)
     
  8. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    MAX452 is just a video amplifier. This is the easy part. The crosspoint matrix is the tricky part, as Bill pointed out. I spent about 25 years of my career designing analog (and some digital) video studio equipment. Ten of those years were spent designing video routing switchers. I know of whence I speak.:D
     
  9. p4ntb0y

    Thread Starter Member

    Apr 19, 2011
    33
    0
    Hi Ron thanks for the quick reply!

    ok I think I need to do this in steps

    1. power supply ok done this I am going from 100v to 5v DC for the video amps.
    this bit I have done. (after much reading)

    2. work out what the -in +in etc actually mean on the max452 picture need help on this.

    3. switching system should I get rid of the rotary switch? is there a better way?

    4. design pcb board with suitable plane and sort the impedance on my s-video out. I will worry about this later ;)

    Regards
     
  10. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    You probably know what a 4x4 crosspoint switch matrix looks like.
    Here is a block diagram. Each switch, in order to maintain adequate isolation, should be a T switch, as shown in the detail. There are numerous ways of implementing a T switch. You might consider 74HC(T)4066 analog switch ICs, on a GOOD ground plane. Trace layout is also critical to maintain isolation.
     
  11. p4ntb0y

    Thread Starter Member

    Apr 19, 2011
    33
    0
    thanks Ron!

    I did not know what a crosspoint matrix switch looked like so many thanks as a it helps my project and b I learnt something.

    I am reading up now as I am a little lost but I understand it a little.

    I am looking for the t switches now thanks.

    so once I work out the matrix switch i just need to add the amp on the end for the video out.

    so glad its just video and not audio as well.

    reading up on making my own pcbs.
     
  12. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    DG540 is a quad video T switch.
     
  13. p4ntb0y

    Thread Starter Member

    Apr 19, 2011
    33
    0
    thanks Ron!!

    Ok I have been reading up and I think I do not need the video booster.

    My problems with my current setup is ground plane and isolation issues causing ghosting and picture problems.

    Thank you for the guidence.

    so basically I just need to get 16x DG540 where my 4 click rotary switch can select the the right channel for my output via the DG540?

    saw the part "Use extensive ground plane"

    I have to change my power input but thats ok good pratice
     
  14. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    If you have to drive coaxial cable, you will need video amplifiers. You may also need input buffers.
     
  15. p4ntb0y

    Thread Starter Member

    Apr 19, 2011
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    ok I will start with the matrix switch first.

    how many do I need?
     
  16. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Why don't you do the math and tell us. You won't learn much if we spoon-feed you.
     
  17. p4ntb0y

    Thread Starter Member

    Apr 19, 2011
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    ok reading the datasheets.

    the DG540 has 4 video ins if I supply 5v to D1 will open the matrix switch and output IN1 to S1.

    so I can wire up my 4x4 slot rotary switch to each Dx output.

    this in turn will then go the MAX452 to the -IN which will amplify the signal to 2v and out put to V out.

    I want to learn but I need to start somewhere. I did not know the difference between AC and DC until a few months ago.
     
  18. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Don't try to run video through rotary switches. You will get crosstalk. Make each 4x4 matrix out of DG540's. Control the matrix with the switches.
     
  19. p4ntb0y

    Thread Starter Member

    Apr 19, 2011
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    ahhhh got you thanks !

    Hopefully they have these switches in den den town Osaka!!
     
  20. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Don't buy all your DG540's before you design the matrices. Post a schematic here.
     
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