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Electronics => Repair => Topic started by: luis garcia on May 29, 2023, 10:32:48 pm

Title: VGA monitor detection, simple way
Post by: luis garcia on May 29, 2023, 10:32:48 pm

Hi,
in order to detect a monitor on VGA connector in a way as simple as possible, i have used the old method of setting to ground pins 4 and 11.
Apparently these should be enough to detect a monitor 1024x768 capable. Or at least it was many years ago.
I have also to ground pins 6,7,8 and 10. Pin 5 is Gnd.

However, when I connect this VGA connector to my PC VGA out, it detects no monitor.
The graphics card is an old Nvidia with HDMI and VGA outputs. It is not the latest graphics card but it is not too old either.

Do these relatively new graphics cards, detect 1024x768 monitors using this pin configuration, as old VGA cards did?

Title: Re: VGA monitor detection, simple way
Post by: fzabkar on May 29, 2023, 11:28:12 pm

You need to install 75-ohm resistors between the RGB pins and their respective grounds. The graphics card looks for these terminations.

Title: Re: VGA monitor detection, simple way
Post by: luis garcia on May 30, 2023, 06:56:18 am

It works! Thanks fzabkar!  :-+

Title: Re: VGA monitor detection, simple way
Post by: spostma on May 30, 2023, 08:38:22 pm

old monitors have 3 ID pins (4, 11, 12), one of which is grounded inside the monitor (see very end of linked page)

Newer monitors ground ID0/pin 11, and have an I2C DDC on pins 12 and 15 for plug-and-play and monitor control functions.

details see https://pinoutguide.com/Video/VGA15_pinout.shtml