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Acrylic Case Static/Grounding Issues

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February 21, 2006 11:28:23 AM

I'm going to be building a system in an acrylic case soon, and I was wondering if anyone knew of any static or grounding issues I should be careful of (more than normal, that is).

I know that the components will be grounded once they're plugged into the power supply, but I'm used to being able to grab the case to ground myself when working inside a system, and without that available I was wondering what the most effective alternative was (i.e. where should I connect a wrist strap thingy)?

I've also heard that systems in acrylic much more susceptible to electromagnetic interference from nearby radio transmitters and such. Is the effect enough that I should worry?

I've never caused static damage to any of the hundreds of systems I've built, but this is my first with a non-conductive case. And I'm just a bit paranoid considering it's the prime time of year for static build-up.
Anonymous
a b ) Power supply
February 22, 2006 10:21:29 PM

I would recomend using any and all static control mechanisms/procedures you have available to you. It's just good practice no matter what electronics you are working with. I would say this anyway but yeah acrylic is going to be a static problem if you let it be. At work I use wrist straps, ankle straps, conductive workstations, conductive clothing, and air ionizers among many procedures to deal with the ESD problems that are a real hit to my companies bottom line, but we deal with solid state lasers which can be extremely sensitive.

You will get zero shielding from EMI with the acrylic but this is only a problem when there are strong fields in the vicinity to worry about (or if the PC is generating it's own fields which are interfering with other nearby and sensitive equipment) or of course if you are planning to sell this creation as a product. Of course by the time you realized you had the problem there would be pretty much nothing you could do other than putting in a case material which shields better.

I think about the best you could do to improve grounding and decrease EMI concerns is a nice RF braid tying all the gear to all the other gear, ie mb, hdd, etc, and finally tying the braid into a solid earth connection.
February 23, 2006 11:15:23 AM

Verify that the power supply case is connected to its black ground wires. If they aren't, then run separate ground wires from each component to the power supply case because a failure in the supply's high voltage isolation can create a dangerous electric shock situation even though the supply is grounded to an outlet. Oddly, this is far more likely to occur with high quality supplies because they are almost the only ones where earth and equipment grounds are kept separate, but this is no problem as long as the compute case is metal.

On the bright side, regular acrylic plastic burns much worse than plastic used for TVs sold in the U.S. This may be one reason why a maker of acrylic computer cases warned that they were to be used only for demonstration purposes and never unattended.
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Anonymous
a b ) Power supply
February 23, 2006 8:33:57 PM

mmm good point about the isolated supplies. I am wondering if it wouldn't be as effective in many cases to just short the black wire to the supply chassis, it's not like this thing will need to pass emissions testing.
February 23, 2006 8:53:44 PM

That is a pretty good point but for the answer I don't know. I used aluminum case for my rig. But I don't think theres any danger of static to worry about otherwise they won't be selling acrylic clear cases in the first place. right? :?
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