FCC EMI testing and certification

Thread Starter

meadows

Joined Nov 9, 2017
5
Hi all,

I want to make sure I understand the laws concerning FCC EMI tests, and whether my project is actually exempted from all that, as I think it might be.

I've been reading FCC part 15.103, "Exempted Devices" (and other parts of course) and if i understand it right, it says that circuit boards used exclusively in a vehicle or an aircraft are exempted from the requirement to be tested or certified in any way. I was surprised by that, and thought I should ask those who are more familiar with the FCC rules than I am. I figured some of you guys have probably been through FCC testing before.

My project is a product (to be sold in large number hopefully) that is a part of the electrical system of an aircraft, and it has a lithium battery stack of 16 cells. It has an active battery balancer that uses flyback transformers to move charge from one cell to another in the stack to maintain accurate balance during both charge or discharge, or while unloaded completely. I figured I should expect some EMI emissions, so I was planning to do my best, and then put the whole thing inside a MU metal box anyway. I already have my own reasons to keep EMI as low as I can of course because it's for an aircraft and nobody wants radio interference.

The big question:
Is it true that this is exempted from FCC testing under part 15.103 just because it will be used exclusively in an aircraft and have no other purpose? And does it matter that it's an unmanned aircraft, and not a passenger plane? I found that to be good luck that was hard to believe, since I'd like to avoid the expense of FCC testing. The system never gets connected to an AC power line and does not get charged on the ground. It only charges from the gas engine while in the air.

Another related question is about the small boards that are sold by companies like Adafruit and Parallax. Do things as simple as the breakout boards they sell also have to be FCC tested and certified?

I think I correctly understand the FCC stuff I've read so far. I'm finding it hard to believe I might have just side stepped some expensive government regulations just because it's part of an airplane. I was expecting my circuit boards to be buried in FCC test requirements, but I hope it's not.

Thanks a ton in advance for any replies.
 

BR-549

Joined Sep 22, 2013
4,938
I haven't had to work with the FCC for years. But they used to have regions. And whenever I had a compliance question.......I always called the regional office and asked for the engineer in charge. I always got quick and clear answers. And they always appreciated calling to check. They were great to work with.

That was many years ago. Good luck.
 

DickCappels

Joined Aug 21, 2008
7,534
Yes, the CFR has exemptions like that but there is often more detail.

Would you please mention the paragraph to which you refer.
 

Thread Starter

meadows

Joined Nov 9, 2017
5
Yes, the CFR has exemptions like that but there is often more detail.

Would you please mention the paragraph to which you refer.
Part 15.103 is what I'm referring to.
It's very short, little more than one paragraph, but there are indeed other details. There is still the requirement that you might have to stop selling a product IF the FCC ever discovers too much EMI emissions from it later on, even though it was initially exempted from the requirement to be tested. So they suggest that an exempted device should still be designed so that it would pass, if tested. And I was planning to make sure of that. But even so, if the law allows me to do my own testing and make my own determination, I'd rather do that than pay a certified FCC test lab thousands of bucks.

Another detail, as I understand it, is whether or not a product ever gets plugged into AC power lines. If it does, that can mean that the product is not exempted from the need for FCC certification. That's why I mentioned that my product is never plugged into power lines on the ground and only operates during flight.

And BR-549:
Thanks for the suggestion that I simply call the FCC on the phone. I'll bet there's an email address I could look up for them as well. I don't know why I didn't think of that, since I've already communicated directly with the EPA myself over regulations on gas engines for a different project, and the EPA engineers very helpful.

But I'd still appreciate any comments from anyone who has their own experience with circuit boards that either did, or specifically did not, need to be certified by the FCC.

Initially, I was under the impression that nobody could sell a circuit board for anything without first paying through the nose to the FCC for the test, so I figured most electrical engineers would have had to deal with this in the past for almost everything they design. I'm actually more of a mechanical engineer than an electrical one, so the hoops I gotta jump through for the government concerning electronics is all new to me.

Do most of you simply design and market products without FCC testing being a common issue? Most, but not all, of the FCC code makes it sound like their test requirements are a dark tornado cloud that sucks up money, hovering over every electronic product anyone could possibly want to sell.
 

DickCappels

Joined Aug 21, 2008
7,534
A few years ago I took advantage of these exceptions.
I
think that you have the "Ok-to go" with this. You should probably include a statement on the label and probably in the manual telling the user that they must accept interference with other services and that they must suspend use when use of this device causes interference with other services.
 

MisterBill2

Joined Jan 23, 2018
8,989
The FCC rules would be the least of your problems. Avionics has so many reliability ans safety requirements that I totally avoid that very profitable field completely. And the airlines are even more picky.
SO GOOD LUCK!!!
 

Thread Starter

meadows

Joined Nov 9, 2017
5
The FCC rules would be the least of your problems. Avionics has so many reliability ans safety requirements that I totally avoid that very profitable field completely. And the airlines are even more picky.
SO GOOD LUCK!!!

Thanks for pointing that out, since most people would not have known that, but I'm a pilot and I'm already aware of how the FAA is. This product is for ultralights, experimentals and drones, which are regulated under a different set of rules, and in many areas of endeavor not regulated in any way at all. It also is not an avionics product. Many electrical parts of aircraft are not "avionics". The FAA has no problem with this. Only the FCC might be at this point.
 
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