Electronic – How does a PC detect a VGA monitor


Currently I am trying to connect my LCD to my laptop through a VGA connector. The LCD has 6 wires out of it which I am trying to solder to a VGA male connector, But the laptop doesn't detect the LCD. What is wrong?

I noticed that the laptop can detect other screen even if they are turned off (no power cable attached), so I think the trick is in the wiring.

What I want to know is how a PC detects the VGA monitor once its connected.
Does it send a signal that the monitor respond to?

My LCD 6-wires are labled [HOUT – ROUT – GOUT – BOUT – SYN – VC0].
I assumed ROUT, BOUT and GOUT are the RGB signals, SYN is the VSYNC and HOUT to be the HSYNC. (Not sure of that though).

Best Answer

Computers detect screens by something called Display Data Channel

It's a low rate data signal on four pins in the VGA connector that tells the computer about its presence, allowed modes and frequencies, etc.

You can still use a screen without DDC, but you need some pull-up or pull-down resistors to tell the computer there's a screen at all. You'll also have to force the adapter to produce the signal, and you'll have to set up the monitor parameters manually.