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LED RFI

05/09/2012 6:55 AM

I've just invested >$1000 in LEDs for our home. What can be done to mitigate the FM radio distortion experienced when the lights are turned on?

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#1

Re: LED RFI

05/09/2012 7:28 AM

Separate the FM radio antenna and the lighting so that the effect on each other is minimised.

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#3
In reply to #1

Re: LED RFI

05/09/2012 7:58 AM

That's difficult as every fixture in the house has LED bulbs. I was hoping to learn of some sort of filter that can be installed on the radio's.

You are correct that seperation minimizes the effect. My wife & I are currently putting the finishing touches on our retirement home and have already noticed that the portable radio is not affected until the lights are activated in the same room as the radio.

We have installed an FM antenna in the attic; so, perhaps, when the permanent av equipment is installed the reception will improve.

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#2

Re: LED RFI

05/09/2012 7:56 AM

LEDs are low voltage devices that use DC or pulsed DC power. It doesn't seem likely that DC, even pulsed DC, could cause enough RFI to affect your radio. I'd guess that it's the power inverters driving the LEDs that are causing the interference, not the LEDs themselves. [Though if a luminaire is composed of about 40 LEDs in series the net drop across all of them would be 110-120 volts.]

Is this RFI conducted through the house wiring and getting into the radio? If so, perhaps plugging the radio into a UPS would filter-out the RFI.(?) Otherwise, an antenna mounted outside might be needed.

--Well, those are my thoughts as an optics/lighting engineer. No doubt there are EMI/RFI experts out there who know way more about this than I do.

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#4
In reply to #2

Re: LED RFI

05/09/2012 8:06 AM

If your LED lamp fully comply with CE or FCC requirement on EMC, such problem should be minimum, unless your led lamp is very near to the radio. The EMI can be either conducted or radiated. If it is conducted, you can block it by adding common mode choke on the supply line. If it is radiated, you can cut the radiation path by shielding and grounding the led power supply unit. These are general method. If you did not get the right filter with the right frequency on the offending interference frequency, or the ground of the shield is not correct, it may not work also.

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#5

Re: LED RFI

05/09/2012 11:21 AM

I assume you are talking about the 88-108 MHz FM band...? Describe the distortion...static over the entire spectrum, popping, hissing, fading?

Did the LED fixtures come with an FCC statement? Maybe the manufacturer has a fix already for the lone few people who actually listen to FM radio at home...but I doubt it.

Proper shielding for the LED system comes to mind...filtering for the FM radio would pretty much filter out what you are trying to receive to begin with, if you know what I am saying.

Switch to satellite radio.

Music Choice (if you have that available on cable) normally carries the local stations as well.

It may seem like it's not right to compromise, but you have made a huge investment that may require changing some of your regular methods.

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#6

Re: LED RFI

05/09/2012 10:54 PM

Leds are no good, just get rid of them.Led's are nothing but a waste of money right now.

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#7

Re: LED RFI

05/09/2012 11:49 PM

This interference is the odd-order harmonics created by the switching power supplies that power the LEDs. These switchers are more efficient than the older analog type with a rectifier and filter. Switchers often run at 100 Khz, and are mainly square wave pulse width modulation technology. As you know, a square wave is the sum of all the odd-order harmonics of a sine wave from fundamental to daylight. Some power supply makers round the edges of the square waves and reduce the higher harmonics - these cost more. Others use low pass filters on the input and output legs of the power supply and shield the power supply unit with foil.

I would suggest you buy some ferrite beads to place over all wires going into and out of a unit. These beads placed round a wire create a low pass filter - the highs are blocked. The lumps you see on video lines and USB cables aare ferrite beads wrapped up. Test this by trying it on a single unit with all other LED lights turned off.

Ferrite bead

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#10
In reply to #7

Re: LED RFI

05/10/2012 2:15 AM

You may also want to wrap the power supply in foil and ground it. This is of course assuming the power supply is insulated. If there is any exposed metal a more involved plan including insulation and possibly cooling would be needed.

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#13
In reply to #7

Re: LED RFI

05/10/2012 8:32 AM

He should do it to the radio first as it may be mains carried interference rather than RFI.....he did not say if the radio was mains or battery driven at the time it happened.....nor was it continuous or just at switch on or not.....

Just a thought.....

Ga for your post!!

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#8

Re: LED RFI

05/10/2012 12:59 AM

As you described the situation, I feel for you. As a LED power supply is a switching, digital one, it is a broad spectrum polluter. No good at all.

You want FM reception? Put a directional antenna on a high pole. See Radio Shack.

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#9

Re: LED RFI

05/10/2012 1:32 AM

I recently purchased and installed 8 LED replacement lamps. I live in a weak signal area, and temporarily have my roof antenna disconnected. My current antenna is a single alligator clip lead about 20 inches long, clipped to the center conductor of a short piece of type 'F' coax, and laying on the floor. My receiver is around 20 or 30 years old.

A set of three LED lamps (16 LEDs and 4W per lamp) is mounted in the ceiling about 6 feet away horizontally, and I have no discernible interference. Another single larger lamp (9.5W, with 27 LEDs) is also turned on in a floor lamp around 15 feet from the antenna. I'm listening to NPR @ 88.9MHz.

These lamps are "Lights of America" brand, sold at Costco.

Just in case, try other FM receivers to see whether they are affected the same way. If they are, then it sounds like you got some inferior LED lamps!

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#11

Re: LED RFI

05/10/2012 2:55 AM

If the FM distortion really comes from the LED fixtures, you are having a problem.

In fact you are not allowed to use them: the rules are strict: no appliance should interfere with any other.

If your neighbours would have issues too due your lamps they can take legal action.

Try to contact the supplier, for sure the responsible who has taken the responsibility to put an FCC mark on the lamp.

I don't know the actual levels of EMC allowed in the US, but for the EU it has been lowered recently.

Ferrite beads could solve issues.

Shielded power cables can also solve it. (used more and more in industry to shied the power cables related to frequency drives)

But when you are not used to work with electricity: try to stay alive and get those lamps exchanged with correct models.

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#12

Re: LED RFI

05/10/2012 8:15 AM

A bit of reflection brings me to the conclusion that the interference is entering via the AC mains to your FM. FM is immune to AM distortion. Test this with a portable FM radio.

Then use filters on the radios.

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#14

Re: LED RFI

05/10/2012 11:35 AM

You just Wasted your money.These are new,a trial,not prefected yet,you will burn your house down ,companies just want your money, prices falling fast. your lights will be Out-dated in only months then what will you do?

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#15
In reply to #14

Re: LED RFI

05/10/2012 9:41 PM

Sir, I respectfully disagree with you.

You just Wasted your money. No, even though they are significantly higher in price than other light sources. Compared to incandescent they are cost effective for equal light output; compared to compact fluorescent they will last the number of hours they claim (the only CFL I have had that lasted close to its stated life was never turned off).

These are new,a trial,.. The light emitting characteristic used for LED's is true for all diodes. This has been known for decades. For a long time it was considered a curiosity and was absorbed by the insulating housing around the diode. At first they were only available in red, then other diode junctions were found to give the shorter wavelengths, with blue and even ultra-violet being the most recent.

not prefected yet... The major problem is with aging of the clear adhesive to pot the LED to its lens. The second problem is with elevated temperatures leading to shortened life. The temperature problem is common to all electronic devices and designs of fixtures with adequate heat removal are rapidly coming to the market.

you will burn your house down,... Definitely No, despite my mention of heat above. LED fixtures and bulbs run much cooler than incandescent or halogen bulbs. Those are the ones that will burn your house down. LED fixtures and bulbs run much cooler than the CPU of your computer.

companies just want your money,... A generic complaint that probably fits many other types of companies much better than it fits the LED portion of the lighting industry, which is very competitive. (For example, think of the oil companies).

prices falling fast. Generally correct, following a curve similar to the maturing of other products, such as computers, CFL's, etc.

your lights will be Out-dated in only months then what will you do? First part is semi-true and second part is valid. Since they will last years instead of months, by the time they are inadequate for the desired job, I am sure that even more appropriate ones will be ready and be better.

--JMM

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#16
In reply to #15

Re: LED RFI

05/10/2012 9:53 PM

Thank you

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#17
In reply to #15

Re: LED RFI

05/11/2012 3:39 AM

GA

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