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Re: [RFI] Updates on CFLs & LEDs

To: RFI List <rfi@contesting.com>
Subject: Re: [RFI] Updates on CFLs & LEDs
From: dalej <dj2001x@comcast.net>
Date: Sat, 22 Jan 2011 05:06:29 -0600
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>

I've got quite a few CFL's here also and have not found them to be a RFI 
producer yet.  I had one out in the garage which did interfere with a wireless 
intercom that used the power line for the communication line.  Whenever that 
CFL was on the intercom was not useable.  I have two CFL's in my shack luxo 
lamps right above the rigs and they are RFI quiet.  They are turned on for 
hours at a time so they save quite a lot in electricity.    

Your idea of marking the CFL's is a good one.  I will start doing that too.

Dale, k9vuj

On 21, Jan 2011, at 13:55, Dale Svetanoff wrote:

> Fellow RFI/EMC folks,
> I thought I'd provide some update information on two oft-discussed topics on 
> this reflector: CFLs and LEDs.  Here goes.
> First, I just purchased a set of 5 CFLs to relamp the light bar in my master 
> bedroom bath.  I had 5 conventional 60 watt "globe" lamps in there that have 
> worked well for the purpose, but not only do they suck up 300 watts of 
> energy, they deliver just as much heat.  Over the past 3 or 4 years, I have 
> replaced many standard bulbs with CFLs of varying lumen ratings and been 
> mostly happy with both performance and CFL life.  I have had zero RFI issues. 
>  My chief reason for installing CFLs is to reduce heat load on the A/C system 
> in warm weather, with reduced power consumption running a close second.    
> I mention these 5 lamps because of what they are and what the manufacturer 
> says about them.  Please take note:  The bulbs are marketed by Feit Electric 
> of Pico Rivera, CA.  They are called "Ecobulb Plus" and are listed as 60 watt 
> equivalents, drawing 15 watts, delivering 800 lumens, with an estimated life 
> of 8000 hours.  (These specs are for each bulb.)  The home use warranty is 
> for 2 years, and the cost was $4.88/each.  A prominent note on the side of 
> the box discusses "Proper CFL Usage".  I quote: "Globe-shaped covered twist 
> CFLs are best suited for fixtures that are left on for 15 or more minutes at 
> a time."  The rest of the statement deals with airflow, no use of dimmers, 
> and so forth.  I typically run those bathroom lights for about 30 minutes at 
> a time at least twice per day.  A small print notice on the bottom of the box 
> says that "this product complies with Part 18 of FCC rules but may cause 
> interference with radios, televisions, wireless telephones and remote contr
> s."  Note that Part 18 addresses ISM devices, which does include intentional 
> emitters.  I presume that the reference to remote controls is to RF-type 
> remotes, as opposed to the more common IR ones.
> This is the first time, in my CFL-buying experience, that I have seen a 
> manufacturer actually state the recommended operating conditions on the bulb 
> packaging.  I've checked my other in-stock bulbs, and no, none of them make 
> that statement.  I have saved my sales receipt and the proof of purchase for 
> each bulb, just in case they don't last 2 years in my application.  I might 
> add that my normal routine with new CFLs is to use a fine-tip marker and 
> place the date of first use on each bulb (near the base, so that if it dies 
> early, I'll know.  (I have a CFL flood lamp that was installed on 1-31-09 and 
> died on 8/20/10.  The 3 others I installed at the same time are still 
> running.)  As for RFI, I don't expect any, but then again, I'm not usually 
> running those lights while operating.  
> A final CFL note: I ran a test this morning that I should have run long ago, 
> but just never found the round-tuit.  I have a Teac AM-FM tuner in the family 
> room as part of my eclectic stereo system.  (It's a blend of ancient and 
> modern components, with the heart being a Dynaco PAS-2 pre-amp fresh from the 
> 60's.)  The AM part of the tuner uses a factory-supplied wire loop antenna 
> (no ferrite core) that is mounted on a hinge so that the user can pivot the 
> loop (in a vertical plane) to adjust for best reception.  Now that my power 
> line issues are gone (for the moment, anyway), I can enjoy "armchair" 
> listening to the major Chicago AM stations that are located about 150 miles 
> or so to the east.  I first tuned in WBBM-AM on 780 kHz and noted usual band 
> noise, but no significant arcs or buzzes.  I then switched on the 2 separate 
> groups of CFLs (in ceiling fixtures) which light the shared area that 
> includes both the family room and the kitchen (divided by a breakfast 
> counter).  No c
> nge to what I heard.  Then I switched on the wall plate dimmer that controls 
> the set of 4 incandescent bulbs (3 @ 40 watts and 1 @ 60 watts) hanging 
> beneath the family room ceiling fan.  Aaahh - that familiar old buzz-saw 
> sound!  I might add that the dimmer, which was installed by the builder's 
> electrician, is rated as having an RFI filter!  Bottom line: the CFLs are 
> "clean" enough for AM BC band use.   
> Quick note on LED lights:  I recently received an interesting booklet from 
> Digi-Key under their "techzone" magazine name.  The publication appears to be 
> partly sponsored by Cree Technology, a major maker of LEDs and related 
> systems.  There are several articles within dealing with the major topics 
> related to LED lighting technology, including power supplies, thermal issues, 
> and achieving color balance.  I am not quite certain how I got this copy sent 
> to me, I strongly suggest that anyone interested try contacting Digi-Key to 
> see if you can get one for yourself.  
>> From the RFI perspective, one of the more interesting articles was 
>> contributed by National Semiconductor and is entitled "Driving LEDs: To Cap 
>> or Not to Cap".  Huh?  Well, what the title refers to is to use (or not use) 
>> capacitors on the output side of the switching power supply that is integral 
>> to LED lamp array operation.  Not surprisingly, LEDs work best with constant 
>> CURRENT power sources, and the article talks about the design of buck-type 
>> converters that deliver constant current performance AND which offer dimming 
>> control!  Here is the catch:  you can not dim the LEDs using the wall plate 
>> dimmers as discussed above in the CFL discussion.  The dimming control 
>> signal must go directly to the pulse width modulator ("PWM") ship in the 
>> power supply.  If output caps are not used, the limiting factor in the buck 
>> converter design becomes the series inductor, and that allows more precise 
>> control of brightness than if there are filter caps after that inductor.  
>> So, where are th
> e LED dimmers used?  In products, such as displays, not in general lighting.  
> The article also mentions that typical operating frequencies for these buck 
> converters are in the range of 50 kHz to 2 MHz.  
> Hope these comments help.  Disclaimer:  I have no financial interest in any 
> product or supplier mentioned.
> 73, Dale
> WA9ENA                 
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