Main > Monitor/Video Forum
How to use SCART for our hobby
Zebidee:
--- Quote from: Dodonpachinko on August 07, 2024, 09:42:12 am ---We don't really know how good the connections are on those passive DVI to VGA adapters. They're often cheaply made and can become a point of failure in the line.
--- End quote ---
A good point and fair enough.
--- Quote ---The C5 pin on DVI is analog GND. It's connected to the shields of each RGB wires. I don't know if TV need these but there is RGB return on pins 13-9-5 of the SCART and it correspond to DVI-I C5 pin(Analog GND).
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Those RGB "shields" double as RGB grounds, or "RGB returns".
Yes, those SCART "RGB return" pins are same as "analog GND". They must be connected to DVI C5 pin (analog GND). This is exactly what I was talking about when I said:
--- Quote ---- Run all your VGA RGB+sync grounds (5,6,7,8,10) together to one wire and a single SCART ground (choose whichever is convenient). For DVI-I end they're already joined [at C5] .
--- End quote ---
Your latest diagram looks right. I think it'll work as-is, but I'd be tempted to separate the "analog GND" and "Blanking ground":
* Run "Analog GND" (DVI C5) to a separate SCART ground pin (like one of those "RGB return" SCART pins 13-9-5), to keep it away from the RGB blanking ground. Like you did in your original USB/MOLEX diagrams, except you don't need to split it out three ways. You don't need to connect C5 to all the "RGB returns", just one of them.
* Run DVI 15 ("ground") to SCART 18 ("blanking ground"), like in your diagram. This will give your blanking voltage a more direct and dedicated ground path
For the practical purposes of these diagrams "RGB return" = "RGB shield" = GND = video ground = analog ground = audio ground = ground. These grounds have different names but are most likely all connected together at the video card end, and again at the TV end. You can check this with a multimeter.
However, and this can be confusing: Don't connect anything to "Shield ground", the mesh stuff that goes around the entire cable - this is bulk cable shielding, used for trapping signal interference, so you don't want your video grounds connected to it.
Dodonpachinko:
--- Quote ---
--- Quote ---The C5 pin on DVI is analog GND. It's connected to the shields of each RGB wires. I don't know if TV need these but there is RGB return on pins 13-9-5 of the SCART and it correspond to DVI-I C5 pin(Analog GND).
--- End quote ---
Those RGB "shields" double as RGB grounds, or "RGB returns".
Yes, those SCART "RGB return" pins are same as "analog GND". They must be connected to DVI C5 pin (analog GND). This is exactly what I was talking about when I said:
--- Quote ---- Run all your VGA RGB+sync grounds (5,6,7,8,10) together to one wire and a single SCART ground (choose whichever is convenient). For DVI-I end they're already joined [at C5] .
--- End quote ---
--- End quote ---
Indeed, sorry for missing this.
--- Quote ---Your latest diagram looks right. I think it'll work as-is, but I'd be tempted to separate the "analog GND" and "Blanking ground":
Run "Analog GND" (DVI C5) to a separate SCART ground pin (like one of those "RGB return" SCART pins 13-9-5), to keep it away from the RGB blanking ground. Like you did in your original USB/MOLEX diagrams, except you don't need to split it out three ways. You don't need to connect C5 to all the "RGB returns", just one of them.
Run DVI 15 ("ground") to SCART 18 ("blanking ground"), like in your diagram. This will give your blanking voltage a more direct and dedicated ground path
--- End quote ---
I know the grounds are utlimately the same on each side but i was wondering if the TV needed these 13-9-5 ground pins connected on the SCART side.
Anyway, it should look like that with analog ground separated from blanking ground: https://imgur.com/a/7AmlwQ6
I'll try to build it and will come back with feedbacks.
Thanks a lot Zebidee!
Zebidee:
--- Quote from: Dodonpachinko on August 07, 2024, 05:06:42 pm ---
--- Quote --- Run "Analog GND" (DVI C5) to a separate SCART ground pin (like one of those "RGB return" SCART pins 13-9-5), to keep it away from the RGB blanking ground. Like you did in your original USB/MOLEX diagrams, except you don't need to split it out three ways. You don't need to connect C5 to all the "RGB returns", just one of them.
Run DVI 15 ("ground") to SCART 18 ("blanking ground"), like in your diagram. This will give your blanking voltage a more direct and dedicated ground path
--- End quote ---
I know the grounds are utlimately the same on each side but i was wondering if the TV needed these 13-9-5 ground pins connected on the SCART side.
--- End quote ---
You really don't need all those RGB ground pins connected - that would be overkill. In practice manufacturers know/knew it too and designed to common industry standards. Those grounds are always closely connected on the device-side, and commercial cables almost never connect all those grounds individually. Makes more sense and makes things easier for us.
Even separating the analog ground from the blanking ground might be reasoned unnecessary, it'll probably work OK anyway. They are ultimately connected at each end. However while it might look great in a theoretical SPICE model, pathways/proximity/wire resistance etc. also matter when it comes to signal interference and electronic design. Connected a metre or two down a cable is different to connected 1cm away on a PCB.
--- Quote ---Anyway, it should look like that with analog ground separated from blanking ground: https://imgur.com/a/7AmlwQ6
I'll try to build it and will come back with feedbacks.
Thanks a lot Zebidee!
--- End quote ---
Cheers and no worries 8) :cheers:
That design looks perfect! Looking forward to build pics!? ::)
Dodonpachinko:
I think we could integrate a micro switch in the SCART shell for enabling Composite SYNC: https://imgur.com/a/nonxeSr
I probably can make it accessible from the outside with some precise cuts and superglue on the SCART plastic shell...
I'll try to post build pics for the cable.
Thanks again!
Zebidee:
--- Quote from: Dodonpachinko on August 08, 2024, 11:24:38 am ---I think we could integrate a micro switch in the SCART shell for enabling Composite SYNC: https://imgur.com/a/nonxeSr
I probably can make it accessible from the outside with some precise cuts and superglue on the SCART plastic shell...
--- End quote ---
Fancy!
Last time I went very basic. I have a bunch of small wires with Dupont connectors (Often used for breadboard or "arduino"-type builds, similar to mainboard headers connectors for front USB ports, audio LEDs, etc), so I chopped ends off a couple (one male, one female) and soldered them into the V sync line. For the SCART end I just included the wire end in the crimp (described above). Have to open the SCART housing to change it, but that is not too difficult and doesn't happen often.
For example: https://www.aliexpress.com/i/1005004062991289.html
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