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Author Topic: General question about shielding  (Read 4136 times)
doghateburger
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« on: November 23, 2013, 08:29:29 AM »

Hey guys, so my screen finally arrive today and I'm about to start building my DIY Cintiq (base using the K-Jintiq)

I just have some general questions regarding shielding the wires and grounding, etc. I'm not very good with this stuff, and I really dont want any circuits to be burning when I turn this thing on. Soo... yeah, any help would be awesome! Cheesy

Questions!
1) Is there anything placed between the screen and the actually wacom tech board? I was thinking of placing some sheets of paper, will that do?

2) Is shielding general referring to separating the individual wires to prevent interference from one and another? Will using aluminium wrap (typically for food) work? What wires should I be shielding and more careful with.

3) Grounding, if I'm not mistaken is when we make sure the wires and electricity are connected to some sort of non conductive material that is touching the ground? Please clarify if I'm wrong.

I'll probably have more questions as I start working on this, but for now, if anyone could help me clarify these points, I would greatly appreciate it!
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Aerendraca
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« Reply #1 on: November 23, 2013, 01:55:30 PM »

Hi Doghateburger (interesting name by the way),

Let's address your questions one at a time.

1. Yes you should have some kind of electrical insulation between the wacom digitizer and the lcd. This is to stop metal parts of the screen short circuiting the wacom circuit and vice versa. Paper will do the trick, but I would recommend something more hardy for your final build, perhaps a sheet of thin acetate, or even thin rigid card. The reason is that small movements within the build might wear the paper over time and expose the wacom digitizer board, but paper is probably alright for testing.

2. When we talk of shielding we are referring to preventing radio signals which can be generated by some lcd screen and circuits from interfering with the radio frequencies that the wacom digitizer uses to communicate with the pen. This usually involves careful placement of parts and/or placing some electrically conductive material - such as aluminium foil, copper sheet/tape, steel sheet - between the offending part and the digitizer. Without going into too much detail, the material you use for shielding should be a metal of some sort since radio waves are electromagnetic meaning that they are composed of an electrical field and a magnetic field. By using a metal you can absorb/reflect (depending on material chosen) the electrical field part, dulling the effects of the radio noise. Shielding is not always necessary to getting a fully working diy cintiq and it's probably better to address this issue and ask for help if you stumble across such problems.

3. Grounding is where we attempt to stop the system (wacom, lcd, and shielding) from creating additional interference problems related to voltage differences. The idea is to join the ground (DC negative) of the wacom digitizer to the ground (DC negative) of the lcd screen, and join both of these to any electrically conductive shielding material that you use. Doing this brings all the voltages together creating a common ground.
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doghateburger
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« Reply #2 on: November 24, 2013, 09:31:02 AM »

Thanks for answering my questions Aerendraca. I'll work out the shielding as I go.

As for grounding, are there any particular methods or any precaution I should take when building my DIY cintiq? Or rather, is there a more specific example of how to join both the LCD and wacom digitizer to an electrical conductive shielding material?
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Aerendraca
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« Reply #3 on: November 25, 2013, 08:42:47 AM »

There are no set in stone instructions for this really as it depends on what hardware you have, but generally speaking you will be looking to connect an exposed area of the wacom digitizer board (the metal reflector plate on the back of the digitizer should be connected to ground so you could try here), to an exposed part of the the LVDS controller (look around screw holes for exposed copper, this is usually connected to a large area of copper on the circuit board; this is the ground, so connect to any part of this which is exposed.

If you're not sure, take a photo of the areas that you are thinking of connecting together, highlight those parts in paint/photoshop and post them up on the forum, we can then take a look and let you know if those parts are ok to join.
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Belvis
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« Reply #4 on: November 25, 2013, 04:36:01 PM »

I have the same question. Hijacking this thread  with picture of my set up

* IMG_1031.JPG (113.37 KB. 800x534 - viewed 404 times.)


Red circle on left is the wacom board, this copper bit goes underneath it to the metal shield at bottom.
Red circle on right is on the LCD screen board.

Connect these together?

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Aerendraca
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« Reply #5 on: November 25, 2013, 05:23:29 PM »

Hi Belvis,

Yes, these two points are more or less what I was refering to, though the screen part shown is the TCON board not the LVDS, but the TCON and LVDS should be grounded by the LVDS cable anyway so it's practically the same thing. They appear to be good spots to ground together, though the exposed tab on the left hand side of the TCON just next to the wacom ground spot might be more convenient.

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Belvis
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« Reply #6 on: November 25, 2013, 05:37:26 PM »

Hey Aerendraca,

I see the part on the left you are referring to on the TCON board. Very close to the wacom ground spot.
So by connecting those two points i should be grounding the wacom, LVDS and TCON all together?
Hopefully this will reduce my jitters a bit
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Aerendraca
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« Reply #7 on: November 25, 2013, 06:32:24 PM »

I would think so yes. May help with the jitters but probably wont stop them altogether, you need to shield the wacom from the screen TCON, but more about that in your build thread.
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doghateburger
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« Reply #8 on: November 26, 2013, 02:55:49 AM »

Thanks for the advice Aerendraca! I'll post more questions and concern up in my build log for help  C:
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