Main > Monitor/Video Forum
How to use SCART for our hobby
SailorSat:
--- Quote from: lettuce on April 08, 2012, 03:46:29 am ---Great find my friend!, one thing that bugs the hell out of me though is it requires a external power supply. He could of drawn the power from pin 9 on the VGA side if the user was using an ATI card :-(
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Any and i repeat, any, VGA card made after 1995 (and calling itself VESA compatible) is required to deliver the 5V on Pin9. I've encountered like 2 or 3 card till today that don't supply 5v. (ironically ATI Rage 2c :))
Sadly the output on the VGA is too low to power both the 5v-to-12v and the XOR gate.
--- Quote from: Zebidee on April 07, 2012, 11:41:17 pm ---I wonder what it does exactly ... And what it might do to the sync signals.
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Nothing with the sync. Actually everything is straight through except for the DDC Pins (12 and 15 iirc) and supply (9 and 14).
The dongle provides a "valid" EDID signature required by GeForce 8 and newer nvidia cards.
ATI cards don't require a valid EDID
Zebidee:
--- Quote from: apfelanni on April 08, 2012, 04:39:53 am ---ps. chinese power supply , vga and scart cable is what usually everyone has laying around somewhere. u may combine vga and scart cable fitting to ur purpose , i took a 50 cm vga and a 1 m scart for example and kept the cables as short as possible. the idea was to leave it to the customer to pick cable length and quality he prefers. a chinese external power supply may cost 3 dollar and can be found anywhere.
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VGA and 5v PSU might be cheap, but expect to pay $5 each for these unless you have spares lying around. Which I probably do, but then I'd have to eventually buy new ones to replace the spares I use. There is a cost to everything, even if it is hidden (BTW, in my day job I am an economist & policy analyst ...).
You would need the right type of plug for your PSU as well, although you could just solder the wires to the board (a somewhat barbaric approach).
It is the male-male Scart cable which would be the biggest add-on cost. I've never found them cheap, although there might be something reasonable on eBay I guess.
Edit: found a 3m male-male Scart cable for $4.59 + $4.59 postage so $9 for that.
Zebidee:
--- Quote from: SailorSat on April 08, 2012, 04:56:34 am ---
--- Quote from: Zebidee on April 07, 2012, 11:41:17 pm ---I wonder what it does exactly ... And what it might do to the sync signals.
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Nothing with the sync. Actually everything is straight through except for the DDC Pins (12 and 15 iirc) and supply (9 and 14).
The dongle provides a "valid" EDID signature required by GeForce 8 and newer nvidia cards.
ATI cards don't require a valid EDID
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Ahh, now that is interesting.
VGA pin 14 is vertical sync. But on looking at the pinout i see that it is also a "data clock", so I guess that it has something to do with the valid EDID signature?
Sailor, I wasn't aware that 5v availability on pin 9 was so prevalent. Such a shame that many VGA cables don't bother to include pin 9.
joecontra:
lettuce
So if i did bridge pins 20 and 16 then i dont need wire in Pin 9 on the VGA ti pin 16 on the scart?
Yeah, as you say.
Zebidee
what is bc548b again?
It's a transistor which merges the horizontal and vertical sync signals. It's in the schematic I linked before. This solution only works if both sync signals are negative.
That's why I put the "the" in there.
You're right, I misunderstood you. :)
When I used the powerstrip software, it always gave an option to adjust sync polarity regardless of the card.
That's right. The option is there but in some cases it just doesn't let change to negative, no matter how many times I push the "-" button.
Still, pretty good to be able to do it.
Thanks. It isn't that hard to build as it looks. It's good in cases where not even with PowerStrip the sync polarity changable is.
I tested it with my integrated GeForce 6150, changed both sync polarities to positive and there still was a nice picture on the TV.
I also tried it with a card GeForce 8600 GT, that even in PowerStrip didn't let change sync polarities. The circuit worked fine. There was a good image on the TV. It just had to be positioned.
lettuce:
--- Quote from: apfelanni on April 08, 2012, 04:39:53 am ---taking the voltage of pin 9 has several disadvantages. u need a card delivering 5 volt , a fully wired cable and after all u dont have 12 volt for correct av switch. so it features an external power supply or molex if u prefer taking 5-12 volt from ur pc .
im currently runnig a first test sample in my ok baby cab with the 25 inch sony tv . the auto power on tv-pc works great . guess i ll replace the second selfbuild cable in the other philips ok baby in the future . i kept the jpac for keyboard encoding , video and audio are running through the umsa device to the scart in of the tv chassis .
ps. chinese power supply , vga and scart cable is what usually everyone has laying around somewhere. u may combine vga and scart cable fitting to ur purpose , i took a 50 cm vga and a 1 m scart for example and kept the cables as short as possible. the idea was to leave it to the customer to pick cable length and quality he prefers. a chinese external power supply may cost 3 dollar and can be found anywhere.
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So what advantages does this device have over say building your own VGA to Scart cable then?. It will obviously be cheaper to build you won cable?, as the extra parts your need to buy in order to use the UMSA (VGA 2 VGA and Scart 2 scart cable) you can make your won cable from?
A really neat idea would be if the creator of the UMSA could have an option so it has a brack attached to it like a GFX card, so you could actuall fit it inside your MAME PC!?