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Author Topic: Shielding enclosure, Steel or Aluminum?  (Read 3549 times)
ThrowingChicken
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« on: September 11, 2013, 09:18:51 PM »

So I am going to be following eqsOne's build converting an Intuos 3 into a Cintiq.  I have tracked down the same RF boxes he uses, which are tin-plated steel, but they are a bit costly and it will take nearly a month before they would ship to me.  As an alternative, I can purchase a aluminum rectangular tube with 1/8" (~3mm) thick walls, for a fraction of the price, and convert it into a box fairly easily, and it would ship in a day or two.  My question is, are the Teko boxes worth the added expense and wait?  Will one block interference better than the other? 

I can also get the rectangular tube in steel, it actually cost less than the aluminum, but I may not be able to cut it with the tools I already have. 
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Aerendraca
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« Reply #1 on: September 14, 2013, 07:36:54 AM »

The reason for tin plating steel is to stop it rusting, one of the reasons they use tin cans for food packages. Any steel enclosure will do the job (apart from stainless and reinforced), aluminium should also be fine as long as the material is thick enough to be rigid. You can buy electrical steel boxes in diy stores for electrical wall fitting - UK mains - for very cheap, they would work i should think. I don't think that there is much point going for exotic materials when mild steel (like that found in a pc case) is cheap and easily workable, you might even get away with modifying a dvd drive or power supply.

Please note that this is in terms of shielding as an enclosure, ie as a container preventing RFI getting out. There are other issues involved with trying to shield noise using a single layer for example, which are to do with material and design but that get complicated and is not what you asked about, plus I think I've covered part of that somewhere on the forum.
« Last Edit: September 14, 2013, 07:45:10 AM by Aerendraca » Logged
TheIdeaCan
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« Reply #2 on: September 14, 2013, 11:06:43 AM »

You could try my solution as an alternative to the Teko boxes. I haven't tested it yet as I just placed my order yesterday and I'm waiting on my new LCD controller to arrive, but I found out that Mouser carries a steel 10" x 6" x 1" box built by Hammond that should easily house the LCD controller board, the inverter, and the keypad. With FedEx shipping to Ohio, it cost about $28 total (can't remember what the Teko boxes cost, but I seem to remember it was around $30-40 before shipping). In theory, the box should work for shielding a fair bit of the RFI noise. To get rid of the rest and block the EMI, I plan to cover the bottom and sides and maybe the top with copper tape (like you'd use to shield an electric guitar) to turn it into sort of a Faraday Cage. Also, since the backlight inverter is the largest culprit for producing RFI and EMI noise, I was going to try wrapping the plastic shield around it in a layer of electrical tape followed by a layer of copper tape connected to the copper tape on the large box to create a mini-Faraday Cage within the larger Faraday Cage. Another bonus to using such a large box is that I should be able to mount it up and down on the back of the Intuos in such a way as to have almost all (though possibly all) of the backlight cable and LVDS cable routed internally to give it a cleaner look. Of course, it could be mounted horizontally as well if you don't plan to use a stand or VESA arm though the LVDS cable would end up running along the back of the Intuos like the Cintriq.

Like I said, it's mostly theory and hasn't been tested yet. Once DHL is able to ship my new RM5451 LCD controller to me from China (it may be a week or two), I should be able to try it out and see how well it works. I bought the last black finished box that Mouser had, but I think they have a few of the unfinished steel version available to ship immediately.
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ThrowingChicken
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« Reply #3 on: September 14, 2013, 05:36:31 PM »

Thanks for the suggestions!  TheIdeaCan, did you happen to get the dimensions of the controller board from the seller?  I've asked mine twice now and yet to get them. 

Here is what I think I am going to do.  I am going to pick up an aluminum rectangular tube with 1/8" thick walls.  To this tube I will cut the top off, bend back the sides to form a box and use the removed top as a lid.  I went to the hardware store and had a look at the steel enclosures they sell but they were too large, BUT I did see they sell these flat steel plates for like 60 cents, so I am going to get a couple of those and place them between my aluminum box and the Intuos back.  I have some copper tape too, I may put some of that down for good measure (or maybe a layer of pennies; inch for inch I think the pennies are cheaper).  I will ground all of that to my LCD controller.  I am also thinking I might strip a cable and ground it to the LCD controller, then run it next to all the copper tape I shield the wires and LCD circuits with.  The tape is only conductive on the outside, so it would probably be good to have a dedicated ground wire wrapped around the tape to make sure it gets contact the whole way. 

I've also considered stripping the mesh off of a coax cable and trying to fit the LCD cables into it, so it would be a wire < shrink tube/tape < copper tape <ground wire < coax cable mesh < shrink tube/tape sandwich.  Think that would help or is it overkill? 
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bernard
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« Reply #4 on: September 15, 2013, 03:58:07 PM »

Layer of pennies?   Stripping off a Coax-cable shield mesh?  Wow, that's crazy!  Tongue

I do not want to kill your fun, but I would recommend checking if you actually have a problem before hyper-shielding everything. Some builds work without *any* shielding!

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ThrowingChicken
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« Reply #5 on: September 15, 2013, 05:30:27 PM »

Fair enough! 
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bernard
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« Reply #6 on: September 15, 2013, 08:53:41 PM »

Your name "ThrowingChicken" always remind me of the famous test whereby they would throw a frozen chicken in an airplane's motor.
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