Thank you for documenting your work on these errant lamps. I am not
surprised by the severity of the problem, however, since the switcher
powering those LEDs is most likely operating in a constant current mode
(see my posting of 1/21 on the topic). I doubt if the use of a modular
array is the issue - more likely is the amount of current beign delivered,
since LEDs designed for lighting applications are capable of much higher
current per diode than those intended as mere indicators (those little
colored light dots we've known for many years now). As noted in my post,
some of these power supply designs have no filtering caps on the output end
of the supply. One question: where did you physically locate the filter
components with which you have been experimenting? If they are not within
the shield of the lamp assembly itself, or of the fixture, then the leads
may be long enough to make for good radiators and/or the filters themselves
radiate due to inadequate shielding.
Keep up the good work and let us know how it goes. I might add that I am
very interested in how well (or not) LEDs work in the floodlamp
application, as I have already discovered that CFLs will not fit into my
outdoor flood holders. (The CFL floods are too fat in the area just above
the screw base - that causes the lamp to not be able to set deeply enough
into the socket to make contact.) I have a pair of floods that are
controlled by a photoeye and run each and every night form many hours
(their main function is for security purposes). I've gone through a lot of
incandescent flood lamps in the 10 years I've lived at this QTH, even
though I use lamps rated for 130 volt operation (on my 123 volt mains).
> [Original Message]
> From: Craig <firstname.lastname@example.org>
> To: <email@example.com>
> Date: 1/23/2011 5:46:25
> Subject: [RFI] LED Floodlight warning!!
> Hi All
> I recently purchased this new LED floodlight which has turned into a
RFI nightmare. I just want to warn other hams about the huge amount of
interference that these lights cause.
> My warning might also help those looking for interference sources around
their neighborhood. LED floodlights are a disaster as big as bad plasma TV
sets because the QRM level is so intense.
> These light are becoming popular because they can save you a lot of
money when compared to running a normal 500 watt floodlight.
> I purchased several of these LED lights from various Ebay sellers. They
all seem to originate from the same factory. They have ratings from 10 to
50 watts. These lights are the ones that use a huge large LED CHIP rather
than discreet individual LEDs
> Here is a link for one on Ebay, if it looks like this light avoid it.
> A generic search for "LED floodlight" will show the many seller listings
for these lights.
> These light cause S9+20db hash right across the HF spectrum. Its the
worst case of switch mode power supply noise that I have ever encountered.
What also amazes me is the strength of this hash that could be detected
from a long distance away, upto 1km away!
> I emailed the supplier, and he advised me that he has paperwork which
certifies the lights with a C tick compliance. The paperwork is obviously
fraudulent or he is just telling lies. Most of the goods from China have
fake EMC compliance documents and certification ..
> When I opened the light, it had a small switch mode power supply module.
This module does not appear to have any mains filter or other output
filtering. The light is well shielded since the whole assembly is cast
aluminum. The power supply module is well shielded, hence the surprise at
the rather high noise levels.
> I added a IEC filter which did nothing to reduce the noise level. I
added 2 X Fair-rite FT240-31 ring cores on the power supply lead and this
did not help either. I added 2 X #31 material cores onto the DC output
and this did help, however the noise was still shocking.
> I am going to try some capacitor bypassing and perhaps a professional
DC filter. So far the signs are not encouraging. The noise is still very
intense. If I dont have luck I will just throw these lights in the bin.
> I have these lights in 10 20 and 50 watts and they all have the same
interference levels. Its a real shock to turn on my SDR receiver and see
the waterfall go red(5/9+) from 1mhz to 30mhz!
> Anyway avoid these lights like the plague!
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