RFI from LEDs.

[Shockwave]

Yesterday I was called by a tech at one of the local marinas about a troubling new problem. All of the new boats are being equipped with the latest high efficiency LED lighting. Everything from overhead lighting to under the water line lighting is using them. Turn any of them on and all VHF reception is completely knocked out and you can't even squelch the receivers on dozens of expensive yachts. It even takes out most of the FM stereo band.

The RFI is particularly stubborn to remove too. Often requiring L/C filtering with both a choke and capacitor as close to the LED as possible. The source of the interference is not the LED lamps. It's the cheap Chinese strobe circuit that flashes the individual LEDs at a rate fast enough to make them all look on to the eye to increase efficiency.

It gets worse. It only took a little effort to find many more sources of this same interference and I didn't have to go far. The LED traffic lights are doing the same thing. Not every light or color. Just the lamps that got replaced with cheap junk. Then a DPW truck went by with his blinker on. Each time the LED blinker went off, it made the same RFI. Good thing his 2-Way radio has a PL squelch.

Now we have lighting becoming the fastest growing source of RFI. Everyone from pot growers to the department of public works has become an unsuspecting RFI generator. Hard to believe there are specific laws against this and a huge government organization to watch over and guard us from it.

 

[Mudfoot]

Buddy of mine lives next to a flashing LED traffic light. I can pick it up within several hundred feet of approaching it. He listens to WLW, or used to anyways.

 

[222DBFL]

Yep I pick up traffic lights, other vehicles, and at night the lights on the highway are a killer too!!

 

[Captain Kilowatt]

Just another reason I am glad I don't live in a city or even a town really. Going into town for me is either a three minute trip or a ten minute trip depending which town I go to. The short trip is into only 1100 people and the longer trip is to about 3000. My biggest source of RFI is the digital motor control board in the washer and that I can cure with the flip of a breaker.

 

[binrat]

Just another reason I am glad I don't live in a city or even a town really. Going into town for me is either a three minute trip or a ten minute trip depending which town I go to. The short trip is into only 1100 people and the longer trip is to about 3000. My biggest source of RFI is the digital motor control board in the washer and that I can cure with the flip of a breaker.

:sad: I went from 30+ km away from the closest town, to living in a town to 13k and working in a city. HF mobile is fuunnn.

 

[Robb]

The FCC should be on top of this issue, but they are not.
Too busy with almost useless activity.

 

[Captain Kilowatt]

The FCC should be on top of this issue, but they are not.
Too busy with almost useless activity.

Not enough people stand up and shoit loud enough. 99% of the public have no idea what RFI is or what causes it or what problems it causes. They just know that "the new radio doesn't work as good as the old one" having no clue it probably works just as good however it is being interfered with by the new noise generators. Non-radio people have no idea nor interest.

 

[Robb]

Wonder what those LED circuits look like?
Can you give us an example Shockwave or CK?

Sure hope the aren't half rectifying the AC with the LED itself; wouldn't that have the net result/effect of demodulating 60hz?

 

[Mudfoot]

The FCC should be on top of this issue, but they are not.
Too busy with almost useless activity.

Yep!

Just sending WARNINGS to the .313 assholes????? Why just a warning? It's not like they wouldn't have a solid case against them the way it is. They need to start making an example out of them, NOW!

 

[Captain Kilowatt]

They would just be a switched DC pulse most likely. The pulse rate would be fast enough so we could not see flicker and the power source a switch mode power supply, you know, the type everybody raves about these days. Say what you will but there is a good reason why I still prefer my BIG old HEAVY linear type power supply and it's awfull efficiency. The only noise it generates is a THUNK!! when the 100,000 uF filter capacitor charges and the surge current rattles the transformer laminations.

 

[Shockwave]

The ones that are causing problems are powered directly from 12 volts DC. They did not appear to be using a DC to DC switch mode power supply. However the strobing of the individual LEDs could easily be based off the same type of filthy switching circuit. The heart of the circuit was a small surface mount IC. When I look at these boards, I'm curious how they ever managed to get them to create this much RFI? There is no reason whatsoever that an LED strobe would cause any RFI.

 

[Captain Kilowatt]

The ones that are causing problems are powered directly from 12 volts DC. They did not appear to be using a DC to DC switch mode power supply. However the strobing of the individual LEDs could easily be based off the same type of filthy switching circuit. The heart of the circuit was a small surface mount IC. When I look at these boards, I'm curious how they ever managed to get them to create this much RFI? There is no reason whatsoever that an LED strobe would cause any RFI.

I'm wondering if some of them might have the switcher built right into the LED case itself. You can buy blinking LED's that have the circuit built in so I imagine that the strobe function can be built in to each LED.

 

[unit_399]

I'm wondering if some of them might have the switcher built right into the LED case itself. You can buy blinking LED's that have the circuit built in so I imagine that the strobe function can be built in to each LED.

If that is true, and I think you're right CK, then the circuit would have absolutely no shielding since it's totally encased in plastic.

 

[Shockwave]

I'm wondering if some of them might have the switcher built right into the LED case itself. You can buy blinking LED's that have the circuit built in so I imagine that the strobe function can be built in to each LED.

Not in these lamps since that would cause a random strobe where more than one could be on at a time or none at all. It almost reminds me of the way the old fashioned scanners would flash the channel LED down the line but much faster. I noticed this effect when the oscillator went defective in one and the strobe speed slowed down enough to see it. The use of a digital camera should also show only one LED is on at a time.

 

[The Bruce]

Not enough people stand up and shoit loud enough. 99% of the public have no idea what RFI is or what causes it or what problems it causes. They just know that "the new radio doesn't work as good as the old one" having no clue it probably works just as good however it is being interfered with by the new noise generators. Non-radio people have no idea nor interest.

He did mention that the FM stereo band was getting wiped out too so, who knows, maybe the commercial radio stations will complain to the FCC.