A member of my Hardware Academy had built a sensor that monitors activity for seniors living alone, and the hardware worked.
Then he sent it for FCC testing, and it failed conducted emissions.
That's exactly the kind of result that can stall a launch for months of redesigning and retesting.
Everyone thinks of radiated emissions when it comes to FCC certification, but forgets about conducted emissions, which is the noise the device pushes back down the power cord.
It's why a lot of power cords have a ferrite bead, that little cylinder molded near one end. Its job is to choke that noise off before it reaches the wall.
Most people assume certification only looks at their board, but that's not true.
It tests your whole product as a system, exactly the way a customer would plug it in and use it.
That includes the power supply and the cables, right down to every cheap part you bought off the shelf and never thought twice about.
So he shared the design with us, and we helped him trace the failure to its source. It wasn't his board at all.
It was the generic USB wall charger powering it, which carried FCC and CE marks it had never actually earned, like plenty of cheap chargers do.
He swapped in a properly certified charger with real published test data, sent it back, and passed.
So there are two lessons here.
First, a printed logo on a part means nothing without the test report behind it. On cheap parts you often can't trust the markings at all.
Second, when something fails certification, the problem isn't always in the part you designed.
Checking the whole system first can save you weeks chasing a problem that was never there.
Inside the Hardware Academy, experienced engineers help you read results like these and find the real cause, before it costs you a round of testing.
Talk soon,
John Teel
Predictable Designs
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