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Michael Smith

Electromagnetic Interference (EMI) affecting LCD?

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I've been experiencing scrolling lines across both LCD screens that I use for instruments in FSX. 

 

 

I've tried the following:
 
1. Changing out the VGA cables for new ones. The original cables I used were many years old.
 
2. Setting different resolutions and refresh rates to see which work better. 
 
3. Plugging the USB VGA card into other USB ports while disconnecting USB devices that may have been taking power needed by the screens.
 
4. Enabling the Intel onboard graphics in my computer's BIOS and plugging the screen directly into the onboard VGA port. This is where I currently have the screen (PFD only) plugged in.
 
So, after all of these ideas I'm still getting horizontal flickering that will change in speed and intensity if and only if I change the refresh rates of the screen. Right now at 800 x 600 at 60 Hz refresh rate the flickering is at its slowest speed, of course when I go to 75 Hz refresh the flickering is extremely fast and scattering all over the display.
 
I'd like to think that I've eliminated the possibility of a bad USB VGA card, bad cables, insufficient PC, and now exploring the possibility of something in the room giving off too much electromagnetic interference (EMI) and causing the display problems I'm getting on the small LCDs. 
 
My current PC spec is: Intel Core i7-3770K at 3.4 GHz, 16 GB DDR3 memory, NVidia 650Ti graphics card, onboard Intel HD 4000 graphics (which has the PFD plugged into the VGA port right now), 128 GB SSD, 2 TB HDD, and one PCI USB expansion card... The NVidia card is currently driving one 27 inch LCD via the VGA port, and one LG 32 inch TV via HDMI.
 
Anyone have any experience with testing for EMI and how to effectively find the culprit and shield it from everything else in the cockpit? 
 
Hoping for a permanent solution soon!

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Have you tried using them in different rooms?

I'm asking this to see if it is magnetic interference. What are the screens your using? Model and brand and stuff

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Have you tried using them in different rooms?

 

No I have not - reason being is the LCDs are attached to a large instrument panel and it's not very easy to remove the screens and transport them. However, I will be trying this tonight.

 

Also, even if this test proves that there is interference in the room, I still need to find the source of that interference and shield it. 

 

Moving the entire cockpit/screens/computers/etc is not an option for me or my family at this point. 

 

 

I'm asking this to see if it is magnetic interference. What are the screens your using? Model and brand and stuff

 

The screens I'm using came attached to a kit for avionics/GPS simulation and I do not know the specific brand of LCD screen that was used in this kit. 

 

I would rather not disclose the name of the kit at this time as I don't want to give them any negative publicity. 

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It could be that you have your towers to close to your monitors. It sounds odd but it could be the cause. Another thing it could be is something that's running elsewhere causing it. I know that when my microwave is running it does that and it's in the kitchen. You have to do some testing.

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It could be that you have your towers to close to your monitors. It sounds odd but it could be the cause. Another thing it could be is something that's running elsewhere causing it. I know that when my microwave is running it does that and it's in the kitchen. You have to do some testing.

 

Thanks for this idea. Currently the PC is located approximately 1.5 meters away from one screen and nearly 2 meters away from the other screen. 

 

I have also tried turning off the HDTV that I use for front visual, and the LCD I use for main monitor, the USB Wi-Fi receiver, and then plugged the problem LCDs into their own power socket to see if that had any affect... unfortunately it did not. Same exact problem existed. 

 

Will test other items tonight, perhaps the dining room TV or maybe the wireless mouse I configured as a Push to talk switch. 

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The TVs shouldn't be causing it nor the mouse or wifi receiver. Is anything shaking the screens? What all is in the room?

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The TVs shouldn't be causing it nor the mouse or wifi receiver. Is anything shaking the screens? What all is in the room?

 

In addition to the PC and the avionics LCDs that I'm having trouble with, currently in the room are the following: 

 

1 Samsung SyncMaster 27 inch LCD monitor

1 LG 32 inch HDTV

1 Elite ProPanel II controller

1 Elite Rudder Pedals

1 David Clark headset

1 USB audio jack

1 USB Wi-Fi receiver

1 wireless keyboard 

2 wireless mice (one is plugged into the PC and the other to an external USB hub)

1 USB hub

2 wooden chairs

1 aluminum instrument panel/cockpit 

3 lights mounted on the wall

3 power strips/surge protectors

2 UHF handheld radios (turned off) 

1 bladeless fan (Ikon brand) 

Lots of papers, charts, pencils, pens, etc

 

The room size is approximately 2 meters by 3 meters - it's an under-the-stairs closet so all of my "airplane crap" (as its known to my lovely wife) is out of reach from our dog and 10-month old. 

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Try taking the radios out. Even though their off they could still interfere. I'm just running through stuff in my mind that has helped me

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Try taking the radios out. Even though their off they could still interfere. I'm just running through stuff in my mind that has helped me

OK - I have written that down on my list of things to try tonight when I get home. Thanks!

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Ok keep me updated and I will start researching other alternatives.

Roger - I've also seen a YouTube video where a guy used an AM radio to search for EMI in his house... do you know of any other method that might be a bit more precise?

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No that method is actually pretty good. Plus it's free if you have an AM radio. Give it a try also.

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Alright so for tracking purposes I'm posting this to document the latest development...

 

First thing I did this evening was power everything up to confirm the problem still existed - yep, still flickering.

 

Next, I used my wife's laptop (an old Dell with a VGA port on the back) and connected it direct to the troubled LCD - no flickering at all. None. Nil. Checked it at several resolutions and looked fine as the day I bought the kit.

 

So, perhaps that disproves the theory of random EMI/RFI as the cause... now on to my own computer to try and figure where this problem truly lies... stay tuned Cubs fans...

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Update... I've now tested the USB devices... removing a few and observing the changes... this avionics kit has three USB cables and I've narrowed down one of them that whenever its plugged the two screen start to flicker. You unplug this third cable and the screens appear fine... this is the case no matter which USB port on the computer I try... now I'm going to run this one problem cable to an external USB (powered) hub...

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Update... The USB hub idea did not work... I also tried swapping the cable for a different one and that didn't fix it either. I'm now removing the component to bench check it...

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Turns out we have a culprit... the audio panel is causing the interference every time it makes metal-to-metal contact with the instrument panel brackets... I've wrapped the housing of the audio panel in electrical tape, reinstalled, and flickering is gone! B)

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Thanks for your help! Had it not been for your posts I probably would have procrastinated in frustration!

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