Computer Hope

Thanks for the link geek-9pm, I will definitely check   the interference my machine will cause once finished and engineer a fix if it is not complient. I'm guessing that there is probably a metalic spray paint of some sort out there that I could coat the inside with to create a Faraday cage. I'll check into it in the morning and read that article too

Yes,Apple had to spray the inside of the case with a conductive paint.
More links...
https://www.youtube.com/watch?v=CeRHtGSVyb4
http://hollandshielding.com/106-EMI%20Shielding%20Applications

Quote from: minigrowl on May 24, 2016, 08:17:58 PM
...and engineer a fix if it is not complient. ...

And for more advice on this, visit amateur radio forums on the web.  This is something that these technically minded people deal with.  Their receivers are very sensitive.  Further, they tend to come up with creative solutions that while effective are still economical.   In other words, if there is a cheap way to do it, they will know.   

Long see no time Willy....

Hope all is well.

Quote from: patio on May 25, 2016, 09:05:54 AM
Long see no time Willy....

Yep.   
I skim and read often though.  My desire to post here was pretty much squelched by the terrible and uncaring attitude of the management.
For this person though, I doubted anybody else would come up with the same idea that I had - and know that would be a good source of tested info.

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Hope all is well.

Hanging in. 
Thanks.
Same to you.

I did find some conductive coating spray on amazon that should work perfectly. It is designed to be sprayed inside of electronics housed in plastic to reduce emi/rfi. I'll plan to get that after this weekend of frame building. I'll also put some rubber spray coating over it to minimize the risk of actual electrical conductivity. Does that sound about right WillyW?

Quote from: minigrowl on May 25, 2016, 09:26:17 AM
I did find some conductive coating spray on amazon that should work perfectly. It is designed to be sprayed inside of electronics housed in plastic to reduce emi/rfi.

Then what?

Off the top of my head - ( I haven't ask advice or researched it) -  I would then want to make a very good electrical connection to that conductive layer, and connect it to a very good ground.   I might even want to use coaxial cable as that ground lead - thus being able to shield the lead to ground all the way.

You might be able to simply jumper a lead from the conductive layer, to the metal case (whatever is grounded) of the computer's power supply, instead.   That might do it.  Not sure....

I still suggest that you ask people that actually do this sort of thing, all the time.  That is: deal with sensitive receivers, in close proximity to computers that generate all sorts of rf interference.    While in the non-commercial, home-brew type envirorment (meaning: figure out how to do it yourself, without unlimited funding by the employer. )

Go here:  http://www.eham.net/ehamforum/smf/index.php/board,7.0.html
That's an example.
That section of their forum is dedicated to computer stuff.
You could sign up and post there.

On the flip side, THEY might like to have patio sign up there, and advise THEM from time to time.   

For general info:
If a enclosure in a full enclosure, with no openings larger than centimeter,  massive grounding is not needed to prevent radiation from escaping the enclosure.

To prove this to yourself, put a battery powered RF oscillator inside a complete overlapped  metal box and try to find it on a shareware radio. Any remission has to come from an opening. The attenuation of the box is beyond  -90 DB.

What I have been gathering from radio forums is to be FCC compliant in emi/rfi emissions all that needs to be done is have a conductive cage around my components, either individually or the whole and if necessary a line conditioner. A lot of people are saying radiation comes more from peripherals than from the actual computer but it is debated. Now if I wanted to protect my equipment from an electro-magnetic pulse that's when I would need to ground my Faraday cage so the absorbed voltage has a route to ground and not destroy my components. All of that being said I still want to coat the entire inside of the case with conductive spray but before doing that I'll secure a threaded grounding post (bolt/washer) to the case then spray the nickel shielding over it, and lastly plastidip for insulation from my hardware and to look nice. I'll nut down a grounding cable from the ground post to the frame that will be grounded to the PSU that when plugged in will be grounded to earth. All of that may not be necessary but I don't want to half build this, besides it will be neat to show it off and tell people what I did.

Quote from: minigrowl on May 26, 2016, 06:13:53 AM
What I have been gathering from radio forums is to be FCC compliant ...

But I doubt that this is your first concern.... all the minuscule details.   I think you just want something that works and doesn't make a mess, in a practical everyday environment.

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... A lot of people are saying radiation comes more from peripherals than from the actual computer but it is debated.

Sure.  Think of them as antennas.  If they are connected to something that is 'hot', then whatever connects them can carry the signal and radiate it.

The trick is to minimize this as much as reasonably possible.

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... Now if I wanted to protect my equipment from an electro-magnetic pulse that's when I would need to ground my Faraday cage so the absorbed voltage has a route to ground and not destroy my components. ...

Different thing.  Digression....

But think of your 'cage' this way.  If IT becomes 'hot' with signal, what's to keep IT from radiating it?
Again, the trick is to minimize this....  kill the signal...  take it to ground.

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...  I'll nut down a grounding cable from the ground post to the frame that will be grounded to the PSU that when plugged in will be grounded to earth.

To me - off the top of my head - this sounds like a good thing.    I still suggest that you ask somebody else - that might have already actually done exactly what you are about to do.

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".. All of that may not be necessary but I don't want to half build this, besides it will be neat to show it off and tell people what I did.

Have fun.
Congrats.

The real issue si not about theoretical radiation. It is about real interference.
As I said earlier, have a TV set in your house with an indoor antenna. If the interference is slight, you are OK to go.

Yes, things connected to the PC may also have some small amount of radiation.

Will somebody please look up 'Faraday Shield'. It is not a EMI shield.
The term 'Faraday Cage' is not the same thing in formal reports.
The shield blocks one component.

The cage blocks both components. 
 

Quote from: Geek-9pm on May 26, 2016, 10:01:01 AM

The real issue si not about theoretical radiation. It is about real interference.
...

Yep.
That's what I said.

I think we all agree on this and that's why I agreed on shielding the machine properly the way I described earlier whether it needs it or not. I would test it the way you suggest but I do not have an indoor tv antenna, and most people around me just use cable or satellite, I personally stream through the interwebz. What do you guys think about the hardware layout? Should I try to get the psu above the motherboard or keep it to the side?

The shielding on this project to me is as if you were going to market it. I have had computers outside the case components connected together with only shielding being the power supply case enclosure and no problems with TV interference etc. When it comes to Radio though you hear lots of noise on even a brand new computer off the shelf that is highly shielded if the Radio is too close to the computer box. The only time I use FM Radio anymore is in my car on the rare occasion as for I have a distaste for so many commercials and the play it to death blocks of music the local stations play.

If it was back in the days of CRT's and you were building a computer you might have to shield more. Back when I had a TRS-80 it caused all sorts of interference because Radio Shack didnt have adequate shielding. It was a cheap computer designed to be cheap and it worked, but it was a garage computer project turned into a product line sort of.

These days with flat screen displays that are shielded well and digital vs analog video signals, the picture problems with noise is just about gone.

There was a project I read up on a couple years back about some people paranoid that an EMP would blow out their home computer and they took a steel ammo box and installed computer guts to that and then had added wire mesh at the seam of the lid so that it would cage and protect the electronics inside. If an EMP happened you will have bigger problems than worrying about a home computer being fried, and the electrical grid to power it would also likely be blown out and not operational for some time given the massive transformers at substations are usually special order and can take months to have them made and shipped in which the last place I knew of that made substation transformers was a company in Japan, although there may be cheaper companies out there closer like in Mexico etc.

Its awesome that you want to go all out and do it up proper as if it was going to be made for sale and to comply with FCC, but I wouldnt worry about the shielding for this. Its kind of overkill.

The only concern I would have with this is making sure that the Chassis Ground is joined between the ground of the motherboard, power supply case, and external to the motherboard ports such as USB ports etc. I have seen floating USB ground/shield cause issues before as well as a user had a spark jump from their finger to the USB port when getting ready to plug in a flash stick and blow their USB port out because instead of the discharge going to ground, it went to the USB Chip on the main board killing the USB.

If it were my build I wouldnt worry about the shielding as for its almost unnecessary unless needed to comply with a installation environment that requires it to be properly shielded. BUT I would definitely make sure the chassis ground is all tied adequately together to have all components not floating on different ground potentials as well as to channel a static discharge to ground through ground vs it taking an alternate path through for example a USB Chip on the main board.

Quote from: DaveLembke on May 27, 2016, 11:44:31 AM
...
There was a project I read up on a couple years back about some people paranoid that an EMP would blow out their home computer and they took a steel ammo box and installed computer guts to that and then had added wire mesh at the seam of the lid so that it would cage and protect the electronics inside.

http://mygaming.co.za/news/wp-content/uploads/2012/04/tinfoil-hat-guy.jpg

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... unless needed to comply with a installation environment that requires it to be properly shielded.

Agree.

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BUT I would definitely make sure the chassis ground is all tied adequately together to have all components not floating on different ground potentials as well as to channel a static discharge to ground through ground ...

Agree.