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Show Image on TV and Color PAL with AD725

Discussion in 'AVR' started by Majid soltani, May 6, 2015.

  1. Majid soltani

    Majid soltani New Member

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    hi ,

    I need to show color image on TV. I use AD725 for generate PAL signale.i need best R2R circuit for send RGB signal to IC.;)

    i use the UZEBOX R2R circuit but show noise on TV. :banghead:

    i thought my oscillator circuit have problem , because when i don't send any color signal , TV show LOW color niose.

    i need to you help. now my question is witch oscillator and R2R circuit is better for use ?
     
  2. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    Why bother converting to composite video when TV's have VGA already?

    Just use syncs & 75 ohm RGB and choose 50/60Hz with matching native resolution or compatible.
     
  3. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Probably because he needs a composite signal (there are many reasons for this), VGA is also a much higher frequency and harder to do in software, but also because VGA has been mostly dropped on modern sets now (sad really :().

    Unfortunately HDMI is the way of the future.
     
  4. dave

    Dave New Member

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  5. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    All TV's here include VGA and the input to AD725 is RGB V,H sync.
    So no AD725 needed... No TV either, just use 28" LCD in 1080p, unless there is a real need for a big screen.

    VGA is far better for laptop to TV since sleep wake mode detects 75 Ohm on external port sends video, then TV detects video and wakes up and turns on. This is not always true for HDMI TV but true for HDMI monitors and thus Video stays on main laptop screen instead of activating TV power on open lid.

    I watch all my TV from PC on 55" screen in 1080p with ethernet tuner for antenna or web TV/movies on RGB or HDMI but prefer VGA as per above reason.
     
  6. Majid soltani

    Majid soltani New Member

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    because i want my hardware can show image on most TV . i show color on tv with ad725. my probelm is " when is send color signal , tv show my color with a low noise ....
    TIP : my circuit now is on breadboard , it's mybe when i build a PCB board and assemble my circuit , remove that noise?
     
  7. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    better phase noise yes, with adequate EMC in design.

    but best is to look at noise on ground, supply and incoming signals on scope with very short leads on all signals and probe. . Add choke and cap on V+ if needed.
     
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  8. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    I know the USA has always been rather outdated with TV's, but if it hasn't all but disappeared on new sets yet, then it's due when you catch up :D

    Have I missed where he said he was using a laptop?.

    If he is?, then it's unlikely he has a suitable signal to feed the encoder chip, as VGA usually doesn't go low enough for TV standards.
     
  9. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    HDMI on state of the art Hitachi 55" screen has every interface you can imagine, but only Analog signals wake up TV as HDMI is not onstandby, unlike LG monitors (not TV).

    Thats why I prefer VGA, the quality is identical on 1080p

    And I can output PAL or NTSC rates on any video card to VGA with the right driver setup.

    We know we are behind thats why I use ATSC digital tuner on router from any PC to bigscreen or free web movies online streaming in HD.

    I only mentioned laptop since wake on signal may be also important to OP
     
  10. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Interesting idea, it's pretty rare that many VGA cards will go low enough, a laptop one is even more unlikely.

    Have you tried reading what forum we're in?.
     
    • Disagree Disagree x 1
  11. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    Ob
    my you are getting witty? Even AVR's can wake up a TV on VGA or composite , but does yours wake up on HDMI?

    Au contraire laptops are often lower resolution than TV but externally support any std resolution
     
  12. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Yes, haven't you heard of HDMI-CEC?, a fairly universal control system over HDMI - developed jointly by Sony/Panasonic, most current items now support it.

    But regardless your bizarre insistence on talking about laptops is completely pointless as it has no bearing whatsoever to this thread.

    Perhaps you have no understanding of television?, we're talking composite video here output from an IC encoder, resolution is far below any laptop - even the pre-Windows ones.
     
  13. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    Perhaps your ability to judge experience is limited by your own.

    I invented the smallest eyeglass TV monitor using Kopin's Microslice AMLCD chip at least 10 years before google started developing iglasses and Motorola's attempts and showed at Comdex to private clients in wearable computing. This started with QVGA and it also worked with VGA and ultrasound medical analog composite video.

    Mainstream lapstops are only 1Megapixel while 1080p TV's are 2 Megapixel and ancient TV's equivalent to QVGA resolution or 77kPix. With PAL being 20% more.

    In any case since the application is vague, any relevent experience may be useful to some.

    No drama please.
     
    Last edited: May 8, 2015
  14. Ian Rogers

    Ian Rogers Super Moderator Most Helpful Member

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    Hi Tony.... For what its worth, Nigel is trying to say ( regardless of you knowledge in TV rastering ).. The forum we are in is for the AVR micro, so this debate is pointless... The OP isn't working with laptop's or super fast computers... The OP is probably working with a tiny 8 bit processor...
     
  15. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    So then why ancient noisy composite video? For ancient analog TV's? When RGB to LCD monitors for video is cheaper and clearer? Perhaps the OP should buy a $10 RF modulator or direct to SCART.
     
    Last edited: May 8, 2015
  16. Ian Rogers

    Ian Rogers Super Moderator Most Helpful Member

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    True.... There is also a cheap TV output used on the Arduino... This could easily be adopted

    Tellymate and Gameduino.... Gameduino uses CPLD to create TV signals.... I think the Tellymate is retired but still available it used an ATMEGA8 to generate the TV signals....
     
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  17. Majid soltani

    Majid soltani New Member

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    i think my problem is for oscillator circuit .... i use crystal 14.318 mhz and 74LS04 and two capacitor (60pf and 47pf) and 1M ohm resistor for generate 14.318 mhz clock for AD725 IC.
    can you say about best and accurate circuit for generate 14.318 mhz frequency?

    tip : i can't find crystal oscillator for generate that frequency.
     
  18. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    That May not work.. try HC04 and 1/2 the capacitance.

    or better buy an oscillator.

    You mean finding this clock is a problem?
    http://www.digikey.com/product-search/en/crystals-and-oscillators/oscillators/852334?k=14.318

    Post schematic and list of problems.
     
    Last edited: May 9, 2015
  19. Majid soltani

    Majid soltani New Member

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    hi...
    nearly resolved my problem... before , i use two gate of 74HC04 for genrate clock and others gat was free, and set VCC to +5v with 100Ohm resistor ... then my image on tv have noise.
    [​IMG]




    then i remove that resistor and connect others input gate of 74HC04 to GND , then nearly remove noise.




    [​IMG]

    but as you can see in the picture,It is still a bit of noise in the above of image...

    be sure i send schematics of my circuit in here, today
     
  20. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    low phase noise or jitter is critical to clean colour.
    How did you verify phase modulation noise?
     
  21. Majid soltani

    Majid soltani New Member

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    I just send RGB value and Sync signals to R,G,B and Sync pins of ad725 IC. ( R , G , B values is like VGA RGB Value ). then AD725 generate composite signal
     

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