how to use sync on green from computer to rgb monitor

[italianman1987]

for anyone who has some experience or expertiese on this subject please help. I am trying to tap into my car navigation system screen which is a 7'' rgbs monitory. has rgb and sync. i have a vga or svideo output on my laptop i want to connect. i have a vga to rgb calbe, not rgbs.

from my research i should be able to use sync on green method for the sync.

i have tried this but possibly my wireing is wrong. any ideas.. i dont know if i necessarily need a circuit for this, and dont want to spend $500 on a unit to convert the signal. my diagram is as follows

pc--vga------R------R------------ Monitor
pc--vga------G-----G+S---------- Monitor (i dont know if this is correct??)
pc--vga------B------B------------ Monitor

all i get is black screen with lines..

 

[arhi]

for anyone who has some experience or expertiese on this subject please help. I am trying to tap into my car navigation system screen which is a 7'' rgbs monitory. has rgb and sync. i have a vga or svideo output on my laptop i want to connect. i have a vga to rgb calbe, not rgbs.

I must admit I'm not 100% clear what you want to achieve.

Do you want to get the output of the car nav system and display on "other" monitor or you want to detach the car nav system and only use the nav's display as external screen for your laptop?

from my research i should be able to use sync on green method for the sync.

VGA outputs r+g+b +vsync + hsync

most screens have input that can take
r+g+b + vsync + hsync
and
r+g with sync (both v and h) +b == called sync on green

there are only few graphich cards that will output sync on green (for examply my old silicon graphics indigo2 have that output)

In order to display sync on green signal on regular monitor you usually do not have to do anything (most of them will read the sync on green signal without problem, in general, I have some 5 CRT and 2 TFT screens at home and they all read sync on green without a problem) but to make sync on green signal from regular vga singnal (r+g+b+hsync+vsync) is bit harder. I was doing that for years as I was using SGI CRT monitor that only has sync on green input as a display for regular PC ...

The adapter can be found on the net and cost ~50$

The adapter can be built, but the ones I tried are easy to build but there are issues:
- you have "ghosts" on the screen
- green is "stronger" then other colors

simplified schematic (that works but not perfectly)

g+hsync+vsync

             100 uF
          ! !
Green ----! !---------------------------------
         -! !+                                !
                                              !
                                     680E     !
                     BC548                    !
HSync -------------      __---------/\/\------o---------  CSync on Green
                    \     /!
                     \   /
                   ---------
                       !
               1k      !
VSync ----/\/\----------
			

g+composite sync

             100 uF
          ! !
Green ----! !---------------------------------
         -! !+                                !
                                              !
                                  680 ohms    !
                                              !
HSync/CSync ------------------------/\/\------o---------  CSync on Green

Here is some app note from maxim about combining comp sync that is relevant to the story, but you should try the simple schematic I provided first before you start anything else.
**broken link removed**

have fun and send us how it went

EDIT:
There is also a input on a monitor that is
r+g+b+composit sync

to get there from VGA output you should do:

                                     680 ohms
                     BC548                   
HSync -------------      __---------/\/\----------------  composite sync
                    \     /!
                     \   /
                   ---------
                       !
               1k      !
VSync ----/\/\----------

 

[italianman1987]

thanks for the detailed info, but im not very experiened when it comes to the code...

is that a plan for a circuit? because i kind of understand the ohms which im guessing are resistors.. but the rest no idea.

basically what im trying to do is output laptop vga to the car monitor, thats it. so the monitor has rgb and a blue sync cable, i was under the impression that i could use the green wire and also attatch it to the sync therefore using the green to sync.. i may be way off..

so for your example above do i need to build a circuit of some kind? thanks



vga-----> R
G
B
S

 

[Nigel Goodwin]

basically what im trying to do is output laptop vga to the car monitor, thats it. so the monitor has rgb and a blue sync cable, i was under the impression that i could use the green wire and also attatch it to the sync therefore using the green to sync.. i may be way off..

You're certainly 'way off', but not in the way you think - VGA and TV are completely different standards, and you probably can't connect them together without doing difficult (and expensive) standards conversion.

 

[arhi]

thanks for the detailed info, but im not very experiened when it comes to the code...

is that a plan for a circuit? because i kind of understand the ohms which im guessing are resistors.. but the rest no idea.

first, as the nigel noted, you need to know what is the device you are outputting to.. if it is a TV with rgb/sync input, getting the signal from VGA will not be easy, or to be more clear, forget about making the adapter yourself after asking questions like this.

if the panel is "monitor" with rgb+composit sync input or rgb + sync on green then you need to use one of the 2 schematics I provided.

the rgb+composit sync adapter (the lower schematic) actually merge horizontal sync and vertical sync. You have 1K resistor from VGA vsync output going to base of the BC548 transistor. hsync from the VGA is connected to the collector of the BC548 transistor. On emmiter of the same transistor you connect the 680ohm resistor and on the other end of the resistor you have composit sync output to connect to the composit sync of the display device. you connect r/g/b from vga to r/g/b of the display and you should see the pic

the sync on green is fairly similar (the upper part of the upper schematic) only green output from the VGA is connected to the - end of the 100uF electrolyte. + end of the electrolyte is connected to the output of composite sync (explained on previous paragraph) and that together makes "sync on green" - this you connect to G input on the display and r/b connect directly to r/b on the display.

all this can be clearly seen from the schematic I showed but I will now attach a picture that might make things "more clear"

 

[italianman1987]

ok great im getting there, thanks and bare with me.. seems like the composite sync is the most accurate, since it is a 7'' monitor with rgb plus a spereate sync cable.

and as far as making the adapter myself, its not that im not technically incline, just never put a circuit together, but i do get the concept.

but my last question is, it seems like a simple circuit.. could i purchase these specific resistors and electrolite at radioshack and just sloder them on a board.. that would be the idea correct? thanks

 

[blueroomelectronics]

Do you have the model & make of the 7" monitor?

 

[italianman1987]

well its a stock display for a mazda rx8, its built into the car so not aftermarket, no inputs or anything, i woudl be tapping into the wires for the navigation

 

[italianman1987]

question for arhi.. what is the difference between your circuit and this one.. would they both work cuz yours seems simpler...

**broken link removed**

 

[arhi]

my young italian friend, have no idea what you can by in radio shack, I visited that chain once and only thing I purchased there were some batteries, donno if they sell elco's and transistors and stuff...

as for the different schematic, from what I see here, the new one should mix the two signals pretty much the same way as the first (simple one) with difference that
- old one is simpler
- new one requires additional 5V supply
- new one will make output be more "sharp"
- levels .. not sure what are the output levels on the VGA hsync/vsync, if they are 1.5V as I suspect, the first schematic will keep them at that level only mixed, the second one will get the level higher (the output high of 74LS* is IIRC 2.0 - 3.3V) ... now, this might be the good thing but on another hand, it might be to high...

It would be best if you can attach the oscilloscope to the csync line (the live one that is currently driving the screen) and check the levels before you go and attach anything to it.

Now, I tried the first one, and it used to work (not ideal picture but it was working), I tried some similar to the second one with bit better but still not ideal results, finally I purchased ready made adapter (there was some chip on pcb inside it - so no markings) for 50$ (loooong time ago) and that worked better then any schematic I tried....

for 7" screen I believe any of the schematic's will do the job ... in my not so big experience those displays are pretty resilient bastards, the first one is easy to make, you do not even need to make PCB for it, just solder the two resistors and the transistor together directly (I call that spider web, donno what is the right english term) and test the circuit. The oscilloscope would be helpful for testing and I would check all the levels first before I attach anything to the screen

 

[arhi]

one more thing, check the back side of the panel (if you have access to it), it might have a product number, make / model ... it was not made by mazda, they purchase them in big quantities but that do not mean that the manufacturer is not selling them also to regular customers... if possible make a snapshot of the back of the panel... lots of smart ppl on forum, someone might recognise the panel, or some chips on the panel, and then you will get much more info on how to hack it