Monitor Power up through a breadboard.

Thread Starter

sciengart

Joined Mar 25, 2020
36
UPDATED

Hey Guys, I have a monitor that works and am trying to probe it out of standby.

So far through my research I can make it come out of standby for a moment, and then says no signal, and turns off.
I want to get it to stay on so I can screw around with it.

So I have the 6 standard connections setup on my breadboard, GND, R, G, B, VSYNC and HSYNC.

I have RGB connected to .6v, which should kick out an off white color if I understand. I can adjust my voltage to vary the color.
I have Hsync on a timer at around 60hz and vsync on that same timer.

Any ideas how I can use a voltage to generate a color?
 
Last edited:

Thread Starter

sciengart

Joined Mar 25, 2020
36
I will post my findings here:
I have connected a astable timer, at
Using a 555timer, I connected VSync and HSync to the output at about 100khz ,
With 1,2,and 3 at .6v, and pin 10 at ground, the monitor comes out of standby.
 

kubeek

Joined Sep 20, 2005
5,724
I would start with something like 4060 cmos oscillator with divider and some crystal, and look at the options and try to get a combination of some reasonable line frequency for the hsync and and some other vsync frequency, possibly out of one divider. Then drive the RGB lines to get your color.
If your monitor is lcd and not crt, you might have a hard time finding a combination that is agreeable to that lcd and looks okayish. I am not sure two standalone freerunning oscillators for vsync and hsync could do the trick for an lcd, maybe that would be the first try if you have the resources.

But anyway, for a 1080p@60Hz you need the horizontal sync freq to be at 115200Hz and the vertical at 60Hz. So setting up a 115200 clock for hsync and dividing by 1920 to get vsync should not be too complicated. However, I am not really sure how back and front porch, blanking interval etc. have to be accounted for, and what is the band for the monitor to accept those correctly, and probably you have to add some to get the monitor to accept the signal.
 

wayneh

Joined Sep 9, 2010
16,390
... its a 22" asus monitor lol.
So if you succeed in fixing it, it’s worth all of $5?

It’s always hard to “give up”. Pack rats and fixers like you and me don’t give up easily but it’s often the prudent choice. Just something to think about.
 

DickCappels

Joined Aug 21, 2008
6,392
UPDATED

Hey Guys, I have a monitor that works and am trying to probe it out of standby.

So far through my research I can make it come out of standby for a moment, and then says no signal, and turns off.
I want to get it to stay on so I can screw around with it.

So I have the 6 standard connections setup on my breadboard, GND, R, G, B, VSYNC and HSYNC.

I have RGB connected to .6v, which should kick out an off white color if I understand. I can adjust my voltage to vary the color.
I have Hsync on a timer at around 60hz and vsync on that same timer.

Any ideas how I can use a voltage to generate a color?
Is this a CRT display or a flat panel display?

Assuming it is a CRT display, the horizontal should be much faster than the vertical. For the 640 x 480 VGA mode horizontal sync is 31.4685 kH and the vertical sync is 60 Hz. You will need to supply both of these signals to keep the monitor from going into standby or sleep mode.

The signals are 5V logic signals, 0V to +5V positive going. Horizontal pulse width is 3.8 microseconds and the vertical pulse width is 64 microseconds.

The video inputs are AC coupled, so putting a DC voltage on those inputs doesn't do anything other than to heat up the 75 Ω termination resistors. Instead of DC you can make a 0.8 volt P-P pulse, positive-going centered between horizontal sync pulses to get a vertical stripe. Make the pulse about 5 microseconds to start with.

The video signal can range from 0V P-P to 08.V P-P to obtain the desired luminance and hue.
To get white, have equal amounts of R, G, and B.
To get a primary, use R, G OR B.

You can get an idea of how the colors mix from the Venn diagram below.

1587959126138.png

One other thing, Vertical blanking might be desirable to prevent "funny squiggly lines" in the background on a CRT display. To get vertical blanking AND the R,G, and B pulses with the vertical blanking signal to keep the video at zero volts a few hundred microseconds prior to and after the vertical sync pulse -these are referred to the vertical front porch and back porch respectiively

There is more detail at this link (below):
https://en.wikipedia.org/wiki/Video_Graphics_Array#Circuitry_design
 

MisterBill2

Joined Jan 23, 2018
6,112
To work on an LCD monitor you can use the video output of any old computer, if it has a functional VGA port. The benefit is that there is no risk of damaging the monitor.
BUT if it comes up and states "no signal" when there is no signal then the most likely failure is the backlight. OTHERS will be happy to tell you ALL about fixing that problem.
 

Thread Starter

sciengart

Joined Mar 25, 2020
36
So if you succeed in fixing it, it’s worth all of $5?

It’s always hard to “give up”. Pack rats and fixers like you and me don’t give up easily but it’s often the prudent choice. Just something to think about.
The monitor is perfectly good, I am just trying to learn about vga timing. I would love to be able to indivually address a single pixel on the screen using just voltage. But from what I have learned its all about timing. In a thousandth of a second, an entire image is transferred to the screen by having the timing perfectly aligned.

https://hackaday.com/2019/07/17/pushing-pixels-to-a-display-with-vga-without-a-pc/
this dude blew my mind, and so I basically understand how to do it now.

Not something easily explained in a post. But pretty cool.
 

MisterBill2

Joined Jan 23, 2018
6,112
OK, so you have discovered that it is not just voltage, but more important, it is TIMING. Of course, that is how CGA worked, and NTSC video, PAL, and SECOM video all work. Of course the last 3 also use different voltage levels to delver synchronizing signals as well. Those 1-wire video schemes are remarkable feats of engineering indeed. But modern digital video with that HDMI connector is really cheating by having it all be digital. Doing it with ananlog signals was a far greater achievement.
AND STILL, with your monitor, you did not tell us if it is a CRT or a flat screen device. And still, a flat screen device may have a backlight problem, either with the illumination tube drivers or with the LED power circuit.
 
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