S-video analog?

Discussion in 'General Electronics Chat' started by Mathematics!, Jan 22, 2010.

  1. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    Ok I want to make this cord that converts S-video to RCA composite
    Both are analog video signals
    The directions look pretty simple
    Here is the page
    http://www.tkk.fi/Misc/Electronics/circuits/svideo2cvideo.html

    However I don't know what wire I should use would a regular 22gage copper wire be ok?

    And I don't know how long I can make it so it will still work.
    I can figure out how much voltage dropped a wire will have by looking up the ohms per foot for the specfic gage wire.

    However I don't know what the exceptable min signal voltage that a TV or other standard device needs it to be at?

    Also I am curious what type of wire is under the black insulation of an S-video or RCA cord... ? Is it just copper wire with a specific gage or is it bradded like telephone wire is to reduce crosstalk...etc

    Would a cat5 ,or telephone wire be ok to use for the cord???

    Thanks for any help
     
  2. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    well I found this
    http://www.datapro.net/products/s-video-to-rca-composite.html

    and apparently they use 75ohm coaxial cable for the wire.
    And it can be used up to 200ft which is more then enough.

    However
    I don't know how to rig it.
    Because in the picture they have 4 wires tied to 2 wires.
    So I would think I would need to coaxial cables ???

    Unless,...where is the ground on a coaxial cable ?
     
  3. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    If you use the circuit you posted and want to make a cable like the one in your second post, it shouldn't b that hard to use coax, since they are taking both Y & C grounds anyway and both Y & C are also tied together, so use the coax shield as the ground wire, and use the center conductor for the C & Y.

    My .02
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,646
    2,345
    Hello,

    I have tried to draw the connections:

    [​IMG]

    When you solder the capacitor right in the plug, you can go out with the coax.

    Greetings,
    Bertus
     
  5. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    Ok , perfect thanks

    Anyway now that I got all the supplies and am ready to rig it up I have a few last minute questions.

    First attached is a picture of a phono-plug (RCA)
    Question 1)
    I am wondering what metal leg is the ground and which is the signal source???

    Question 2)
    I am have a problem soldering to the aluminum sheath of the coaxial cable. (i.e the ground of the coaxial cable )
    Solder just doesn't hold to this material. I am just wondering how I should go about professional hooking it in... what would the typical way be to make connections to the sheath... I am thinking some copper crimp on coax ring that I can solder on and then crimp on to the sheath....
    Just would like to know the best way to go about this with out causeing any interference...????

    Question 3)
    Attached is a picture of the inside of an S-video connector.
    The circled part is the part you crimp on to the coax cable.
    Wondering from the pin out their is 2 ground wires and to signal source wires in this S-video connector. But is the crimp part also some kind third ground that needs to be crimped on the the ground sheath of the coax or does it not matter because it is not ground?

    What I was think is I may just solder the 2 ground connections into the crimp part and then all I would have to do is make the crimp part attach to the sheath. Maybe that is the way to go ?

    Also it just a double check when I look at the 4 pins of the S-video their are 2 bigger pin holes then the other 2. Going by the pinout it looks like the 2 ground connections are the bigger to which is odd to me I thought that the signal would be on the bigger ones. But I am just posting this as a double check let me know if I got it right and the bigger pins are the ground pins.

    Thanks Thats about
     
  6. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    forgot to attach pictures
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,646
    2,345
    Hello,

    The middle pin is the signal on a RCA plug.
    The outer side is the ground (shield) connection.

    Are there copper strands with the aluminium foil of the coax cable?
    You can use the strands to solder it to the outer ring of the RCA connection.

    Greetings,
    Bertus
     
  8. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    Ok , got that. Thought that was the case just making sure before a start soldering

    Well they don't look like copper (goldish strands) but their are some silverish tiny wire strands. Wondering if those will hold on with solder?
    Eitherway if they do are they don't it looks like an easy way to make the cable not as durable and easylly breakable using that method.

    Do you know if I get some of those coaxial rings you can crimp on do those hold solder? I am basically looking for a really good way of makeing the connection last long under harsh conditions (kids ....etc)

    Thanks
     
  9. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    at radio shack they have some coax connectors you can get that do not require soldering, the connector just screws onto the cable ends. Usually the aluminum foil is just a shield the small gauge silver wires around the center core is usually the ground. Most crimp on connectors do not require solder, you would just fold the outer shield and ground shield over the outside of the coax and crimp the connector onto it.
     
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