I have a plastic enclosure that will be coated with conductive paint on the inside. I would like to make a good RF ground to the machine enclosure from the conductive painted interior of the plastic enclosure. I think that copper tape, which is conductive on both sides, would perfectly make this RF ground. Anyone ever have any experience with this?
RF Ground Using Copper Tape
- Thread starter fifty60
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petersonra
Senior Member
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- Northern illinois
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- Semi-retired engineer
It is not clear to me what you mean by "RF ground".
If what you are attempting amounts to a Faraday cage it probably won't work all that well. You are better off just buying an EMI style enclosure with the EMI gasketing and such built in rather than trying to tack it on after the fact.
The comment about conductive paint is curious. That suggests the concern is more about static than RF.
If what you are attempting amounts to a Faraday cage it probably won't work all that well. You are better off just buying an EMI style enclosure with the EMI gasketing and such built in rather than trying to tack it on after the fact.
The comment about conductive paint is curious. That suggests the concern is more about static than RF.
I have a component that is radiating 600MHz. It is housed inside a fabricated urethane enclosure. I would like to use conductive paint to coat the inside of the enclosure, which will effectively create a five-sided shielded enclosure. Since the noise is at 600MHz, the thin paint should be very effective.
The five sided enclosure mounts to a metal enclosure, but the enclosure is coated in non-conductive powder coat. I would like to use the copper tape since it meets the 5 to 1 length to width ratio that I need for an effective RF ground from the painted enclosure to the metal machine surface. Its not for static or lightning protection, but for 600MHz protection..
The five sided enclosure mounts to a metal enclosure, but the enclosure is coated in non-conductive powder coat. I would like to use the copper tape since it meets the 5 to 1 length to width ratio that I need for an effective RF ground from the painted enclosure to the metal machine surface. Its not for static or lightning protection, but for 600MHz protection..
ghostbuster
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- Great White North
Note: at the frequency the wevelength is extremely small and any tiny crack or gap will nullify all these RF paint jobs.
The wavelength for 600MHz is approximately 20 inches. I will need to keep any openings to less than 1/20th of that, so less than 1 inch..
I am worried about the seams where the 5 sides plastic enclosure (with conducted paint interior) meet the metal equipment. How do I seal that?
Outside of a metal enclosure, how else to attenuate 600MHz by a few dBuV? Can a DC-DC converter inside the equipment cause that high of frequency to be radiated? It surely would only be coming from the 1GHz processor right? If it is from the processor, then external ferrites will not be of much help, right?
I am worried about the seams where the 5 sides plastic enclosure (with conducted paint interior) meet the metal equipment. How do I seal that?
Outside of a metal enclosure, how else to attenuate 600MHz by a few dBuV? Can a DC-DC converter inside the equipment cause that high of frequency to be radiated? It surely would only be coming from the 1GHz processor right? If it is from the processor, then external ferrites will not be of much help, right?
junkhound
Senior Member
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- Renton, WA
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- EE, power electronics specialty
have used copper (and aluminum) tape for EMI mitigation in lab work successfully for over 40 years.
Have even popped over to the grocery store for a roll of wide aluminum foil to connect equipment chassis that had voltage differential (hence coupled noise onto digital com lines).
Have even popped over to the grocery store for a roll of wide aluminum foil to connect equipment chassis that had voltage differential (hence coupled noise onto digital com lines).
rlundsrud
Senior Member
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- chicago, il, USA
If it needs to be flexible you could use copper screen and attach it with conductive epoxy or any mechanical means that you prefer.
Why does connecting the shield to ground matter? Lets say I have a piece of stainless steel that is 1 foot by 1 foot, and I apply a 600mHz RF signal across it. Will more reflect off of the stainless steel if it is not grounded, or will more reflect off of the stainless steel if it is grounded? Does grounding increase attenuation of a shield?
gadfly56
Senior Member
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- New Jersey
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- Professional Engineer, Fire & Life Safety
Lap the copper tape over the edge and fold it accordion-style to create a gasket. Make sure the paint is removed from equipment and secure enclosure "A" to equipment "B". I'm assuming that the enclosure has some kind of flange secured via screws or bolts to the equipment.
fmtjfw
Senior Member
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- Fairmont, WV, USA
If you don't ground the plate (and maybe even if you d)o, it could become an antenna.
Why only five sided, what is the 6th side?
gadfly56
Senior Member
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- New Jersey
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The surface of the equipment is the sixth side of the box.
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- Placerville, CA, USA
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- Retired PV System Designer
And therefore the box needs to be bonded to the surface of the equipment to complete the Faraday cage / shield.
It is not specifically important that it be grounded, but if the equipment surface is grounded, that comes along for the ride.
Also, as long as the RF source is entirely inside the continuous surface, no RF will escape, but as mentioned earlier, if the box surface is allowed to be excited by the RF inside and change its absolute potential, it becomes an antenna.
Yes, the surface of the equipment is the 6th side. An HMI touchscreen, for example, mounted inside of a urethane enclosure that is then mounted on a stainless steel piece of machinery. In this instance, only 1 side is shielded and the other five sides are urethane and touchscreen.
The urethane is certainly no obstacle to the radiated emissions from the screen, but the stainless steel of the machinery is. If iremove the safety ground from the equipment, then the equipment is floating relative to ground. Above 500MHz, does this have any affect on how the radiated emissions from the screen interact with the stainless steel of the machine? Can it absorb more and reflect less if it is grounded?
The urethane is certainly no obstacle to the radiated emissions from the screen, but the stainless steel of the machinery is. If iremove the safety ground from the equipment, then the equipment is floating relative to ground. Above 500MHz, does this have any affect on how the radiated emissions from the screen interact with the stainless steel of the machine? Can it absorb more and reflect less if it is grounded?
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