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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).

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  • \$\begingroup\$ Do you have more information about the LCD? \$\endgroup\$
    – Samuel
    Commented May 14, 2015 at 19:53
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    \$\begingroup\$ There is a strong possibility that if it is a panel from a device like a DVD player, that it is not VGA at all. Without information on the display it is impossible to say what protocol it uses, and just hooking it up to a VGA connector and hoping is a good way of breaking the display or worse your computer. \$\endgroup\$
    – Tom Carpenter
    Commented May 14, 2015 at 20:55
  • \$\begingroup\$ Related to electronics.stackexchange.com/questions/134674/… \$\endgroup\$
    – Gray
    Commented Nov 13, 2018 at 22:32

2 Answers 2

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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.

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  • \$\begingroup\$ Isn't the LCD supposed to have those resistors built-in? What pins are those resistors connected to? Can you provide some more details?? \$\endgroup\$
    – Abuzaid
    Commented May 14, 2015 at 20:31
  • \$\begingroup\$ Actually it's an LCD I pulled out of a DVD player I had. I don't have much details for it. For the moment, I just need the laptop to detect its presence, even if the image is distorted or no-image at all. one step at a time. \$\endgroup\$
    – Abuzaid
    Commented May 14, 2015 at 20:36
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A simple, easy way that may work is to ground the VGA out pins 4, 11 (DDC 0/2), which will put the display mode to > 1024x768 color. I have a HDMI-VGA converter that uses the DDC pins to detect the presence of the monitor, and turn on/off the audio output (it also extracts audio from HDMI) accordingly.

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  • \$\begingroup\$ I know this is an old thread, but hoping you can help. Using the pinout here, are you saying to connect 4 TO 11, or connect 4 AND 11 to 5? \$\endgroup\$
    – LuckySpoon
    Commented Jul 5, 2016 at 13:19
  • \$\begingroup\$ @LuckySpoon "ground the VGA out pins 4, 11" means connecting both pins 4 and 11 to GND (pin 5). All 3 pins shall be connected together. \$\endgroup\$
    – Dmitry Grigoryev
    Commented Jan 24, 2017 at 14:48

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