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Topic: VGA cable causing ground issues (Read 4233 times) previous topic - next topic

arduinopi

I have a computer monitor and a laptop with a charger connected to teh same lead acid battery. The monitor is glitching heavily though making noises through the speakers and not turning on. I unplug the VGA cable and that fixed it. How can I stop a VGA cable from causing interference with everything.

jroorda

#1
Jun 29, 2013, 04:09 am Last Edit: Jun 29, 2013, 04:11 am by jroorda Reason: 1
I have HAD this problem! 

I used to regularly run sound for my church youth group.  Our setup routed all of the mic wiring and a VGA cable for the projector through the same conduits.  The system always had LOTS of buzzing and we figured it was just ground loops and 60Hz from the power lines.  When I recorded the sound and analysed it I found that it has harmonics of 70Hz not 60.  Later I realized that my framerate was 70Hz and turning off the display stopped the noise. 

Your best easy option is to put a ferrite choke on the VGA cable and see if that helps things.  Otherwise using a digital signal that doesn't cause low frequency interference would be a good idea.  HDMI or something similar would be good if you can arrange it.  The VGA cable does also carry a ground, so if you think this is a ground issue keep that in mind. 

sonnyyu


I have a computer monitor and a laptop with a charger connected to teh same lead acid battery. The monitor is glitching heavily though making noises through the speakers and not turning on. I unplug the VGA cable and that fixed it. How can I stop a VGA cable from causing interference with everything.


If I get you right, You use dc-ac inverter to supply power for monitor and laptop.  First you should test monitor and laptop and VGA cable at AC circuit, and if no problem then it is EMI (Electromagnetic interference ) from inverter.

You need upgrade your inverter to pure sine wave inverter.

Wagan EL2200 Elite 180 Watt Pure Sine Wave Inverter ( select watt model meet your requirement)

180 Watt Pure Sine Wave Inverter, Amazon, $79.00

arduinopi

It is definitely a ground issue. If I have the Ardunio disconnect the ground of the monitor with a MOSFET the monitor tries to power it's self through the VGA's ground through the computer! Even when the monitor is connected to the ground it has to be using the computer's VGA ground too because the computers video card fails to start (A reboot does fix it though). Is there anything I can do to eliminate this issue? I am stuck using VGA since that is all the computer supports. would the visual feed still work If I cut the ground in the VGA cable? Is that even advisable?

How are ground issues eliminated in large systems? for example a plane.

EDIT: I also have the same problems with USB items connected to same ground and through speakers connected through same ground.

arduinopi


You use dc-ac inverter to supply power for monitor and laptop. 


Actually the monitor is running straight of 12 volts through the barrel jack on it. The computer's charging unit takes 12 volts DC and outputs 19 volt DC.
All the devices do run if powered off of their AC supplies. (I see there is no ground issues with AC wiring due to transformers)

sonnyyu


...
How are ground issues eliminated in large systems? for example a plane.
...



One solution is - isolated dc dc converter.

Your case unluckly both charger and monitor are not.

convert them will fix the problem, may be just one will do the trick.

sonnyyu


...
All the devices do run if powered off of their AC supplies. (I see there is no ground issues with AC wiring due to transformers)
...


The pure sine wave inverter could be your Plan Z.

arduinopi

I had an Idea. If I leave the ground of the monitor attached  as well as the ground of the charger and just use relays to control the positive voltage would this eliminate the ground problem? Would electricity still flow through the ground of the VGA cable?

sonnyyu

#8
Jun 29, 2013, 01:21 pm Last Edit: Jun 29, 2013, 01:23 pm by sonnyyu Reason: 1
Worth to try, even you need just jumper wire for test ( by  pass relay). Plan A, Plan B... Plan Z are all the processing.  We do really care the result, do we?

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