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Low EMI lighting for labs and work areas
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I'm in the process of moving and am thinking about the design of my new lab/work area and am trying to decide on the lighting.? In particular I would like to minimize the effect of radiated noise from the lights but also other factors such as the layout, CRI and color temperature.? Does anyone have any recommendations or experience they would share?? Thoughts so far are to have 4400K in general and 4800-5000K lighting over the task areas.? Having a high CRI is a plus but not strictly necessary.? The lowest noise solution would be custom LED arrays with a linear power supply - fairly straightforward to do but expensive.? Currently I am using 54W HO T-5 fluorescent fixtures in 4400K but they are fairly noisy in emissions so I would love to find alternatives.
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TIA,
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Hal |
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Hal, I was just about to post on this - really interested?in the conversation and solutions proposed/found! I am currently using a couple of those LED fixtures that replicate the format of fluorescent lights. As muy bench is on one side of a low, grade level garage in Southern California - therefore a lot of high hills and mountains?all around - and that I do quite a bit of FM tuner alignments?and such work - the reception?conditions are terrible depending on what lights I turn on in the lab and where my tuner or receiver?is. Effectively, because of the lighting?situation, I am unable to use a radio on the bench in any consistent way (I turned to streaming due to that).? And that may seem trivial, but except for FM alignments, I also do a lot of audio or RF measurements (some where the threshold for noise is critical) and I wonder how much this garbage influences my readings. Looking forward to some solutions and a feasible path forward! Radu.? On Fri, Mar 4, 2022 at 4:59 AM Harold Foster <halfoster@...> wrote:
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开云体育A few years ago we decided to go with LED bulbs in the household, I found that there was a significant difference in RFI between models (20dB+, 1-30MHz) and no correlation whatsoever to price/well known brands/unknown makes. On 2022-03-04 14:16, Radu Bogdan Dicher wrote:
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FWIW, here's another possibility. I use 12V LED strips, powered directly from the 12V side of my solar power system. I have only fairly light loads on that side of the system, and with 940AH of storage, I can run them a very long time even when the panels are covered in snow. No switching, pure DC by the time it gets into the house. However, not everyone will have the 12VDC distribution infrastructure that I've built up over the years.
Steve Hendrix |
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It sounds like almost worth putting together a list of "known low emission" LED fixtures for others to refer to when selecting their bench lights.? I am aware this will be very market-dependent, but maybe, then, a few lists?... Sounds like a big project, but any list starts with one entry and by the time there's two, it's a list! :) Radu.? On Fri, Mar 4, 2022 at 5:35 AM Tommy <tommy@...> wrote:
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开云体育few years ago- most likely still true. the 40W LED 4 foot replacements for fluorescent bulbs - (remove the ballast and wire to 120VAC) generated horrible RF noise ( 50khz -to 50Mhz+). I took one apart-they left off the line filters!!. Installing external filter for the 4 bulbs solved the issue.....it is the switching supply at the mains.the company HYPERIKON did not care....IIRC the quote "we do not care about anything except the light output. radiated RF noise is not our concern." so do beware 搁别苍é别 On 3/4/22 5:35 AM, Tommy wrote:
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Gary Johnson
I maintain a short list of known-quiet devices including lightning and power supplies. Creating an extensive list with exact model numbers is a fool’s errand. Manufacturers change the internals of their products without notice. What was good last year may be a disaster this year. You MUST buy and test sample fixtures before committing.
Gary NA6O? |
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I'd vote with the "run 'em on clean DC" crowd, for lowest added interference. The key word though, is "added" - we're already awash in EMC interference from almost all electronic equipment around, so percentage-wise, it may hardly matter. All line-powered LED bulbs and fixtures that I've studied, above about a few W actual input power, use some sort of SMPS, so some noise is guaranteed.
Over the past couple years, I've been replacing under-cabinet fluorescent fixtures with nice low voltage LED strips that run on 24 VDC actual, but that comes from a SMPS wall-wart provided in the kit. You can find all sorts of LV LED strips and fixtures, and make your own DC, but again, the practicality versus relative EMC improvement comes into play. Another complication is finding the right sort of fixtures in the right color temperatures. I try to get 2700-3300 K for general indoor lighting, since it's close to the old incandescent bulbs, and easy on the eyes. For overhead task lighting, up to 4000 K or so seems OK to me. I wouldn't go much higher, unless CRI needs to be very good - I consider the 6500 K ones only good for outdoor flood lighting. Lastly, for close-in task lighting, you want the light to be well diffused. If you get LED ones that are just a cluster of point sources, that image will reflect off of everything, and be very irritating. When I did the LED under-cabinet lights in our kitchen years ago, I found that the LED point source types reflected right off the counter tops, very offensively. I searched far and wide, and finally found some that were right, with great diffusers, and about 3000 K - they were the most expensive ones, of course. When I needed some more, more recently, I found they had disappeared off the market, so I had to find alternatives. These little strip ones that I found have awesome diffusion, but are a bit on the hot side, maybe 4000 K. Ed |
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I gave up and use LED strip lighting, fluorescent style lamp assemblies.? They emit less noise than?fluorescent lamps did, and I know where the peak is so I live with it.? Mind you, if needed I screw in a pair of incandescent light bulbs and turn off the LED unit.? Quiet, lower light but when taking measurements it's actually easier to read the screens on scopes and spec-ans.
You really can't beat LED sources for the quality of light and if you can live with a little noise you'll be fine as long as you know where the spectral peaks live.? You can always fall back to old style lamps when needed.? Being below ground really helps with other radiated noise short of using a faraday cage approach.? If you need that level of low EMI, then you'll be filtering your AC feeds at the room edge and using a variac on incandescent light bulbs. I think the idea of a linear supply running 12 VDC LED assemblies designed for a car might also be a great answer.? They do make flat, rectangular emissive surfaces.? That might actually answer my issues in the future (been thinking about it) and enable you to spread the lamps out.? Being flat they can be surface mounted.? Probably look a little mad scientisity, but could be fun.? Brightness is easily varied with the supply voltage (again a linear supply).? For now I can live with the LED assemblies that mount and look like fluorescent lamp assemblies.? They are lighter and easier to install too! -Chris |
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Even lower emission.
Battery and filament bulb.?? Heck, AC Line filament bulbs may still be available in some territories, for "special purposes". The downside is heat output, and electrical power used.? (In the UK, we're about to be hit with huge energy price hikes on April 1st, and sadly it is no joke..) Pure DC driven LED's are indeed EMI quiet, but is the PSU that drives them? *THAT* is where the issues are, many cheap LED "Drivers" (small SMPS's) are very dirty on the AC line in (should be filtered, but...)? And on the DC output to the LED's, also often poorly filtered, if at all. Some "Drivers" also, though having filters on the input (and maybe output) still emit a lot of noise "common mode" on the DC out, so creating a wide band wide area noise source, an antenna fed against the (mostly) RF Ground that is the AC input cabling. As others have found, you cannot guarantee that an expensive "Brand Name" LED lighting driver, will be RF quiet, even if it has all the correct safety and EMC compliance markings.?? Even if you find some that are, the next production batch may not be... Sad really. 73. Dave G8KBV. PS:??? Candles & oil lamps? -- Created on and sent from a Unix like PC running and using free and open source software: |
开云体育Greetings,Jumping in late here. Curious - why not use a linear (not switching)?regulated DC power supply to drive incandescent lamps? Then, if you so desired, you could even have dimmer control. Regards, Ken
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开云体育Even if the lights on your bench don't
cause interference, how about the myriad other devices in a
typical home and neighborhood? I spent a weekend with a friend
in a nice mountain camp that was lit by propnae mantle lamps.
Everything else was gas too, although there was a generator when
power was needed. It was amazing how low the background noise
was, especially on LF.? ?? Bruce Gentry, KA2IVY On 3/5/22 9:27, Matt Harris wrote:
Lamplight. |
开云体育Why would it matter if incandescent
bulbs were operated on AC or DC? As for a source of bulbs, how
about multiple bulbs normally used for automobile signals and
markers? They tend to be more efficient as well. I also can not
understand banning incandescent bulbs in areas where structures
are heated with electric resistance heaters, at least during the
heating season. ??? Bruce Gentry, KA2IVY On 3/6/22 6:10, Dave_G0WBX via
groups.io wrote:
Even lower emission. |
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DC operated LEDs seems like the leading DIY (or "quasi~") proposition. "LED Lights and Parts" seems a pretty legit source, though I guess I'd personally?need to find a similar outfit in the US. Yesterday I started a bit of a chase for other sources?of noise on my bench. It shares space with my actual, current "work office" in this "work-from-home" age (meaning my work laptop is sat on one end of the bench, and the two large screens mounted on arms on the bench/wall are shared between work and hobby, depending on time of day or week), and another major source of noise are these monitors. Not naming brands here, but one is distinctly noisier than the other - and there's no noise/price?ratio I can discern. It seems overall it's a complete tossup whether a certain?piece of equipment?will turn out noisy or not so much so, probably regardless of labels on it.? I guess one possible solution here is some sort of filters on their AC feed. Has anyone tried to cure this garbage this way? Any known routes to take? I'd not hold back from opening the units and installing some EMI parts in there but if it's easy to build something they'd plug into for 120V etc., that may be much more practical. Obviously, the power cords to there would be noise emitting antennas but at least I'd begin on the path of diminishing the issue. Radu.? On Sun, Mar 6, 2022 at 8:41 AM greenboxmaven via <ka2ivy=[email protected]> wrote:
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开云体育or even the sale/use of small space heaters...but then bureaucrats not understanding the full scope of their actions ( trying to regulate common sense) causing the law of unintended consequences which seems to permeate most regulations imposed upon us. A lot of things done are knee jerk reactions thinking we need it now syndrome or it is good for the environment...never looking at the entire chain to produce/obtain an item. ( do not forget ...not in my backyard syndrome)... Do not forget our throw away society created by profit...I have said enough. back to subject. Are Automotive bulbs really more efficient? I would think same physics to all incandescent bulbs or is it just the envelope makes it appear such? I do not know. I know they do get hot! 搁别苍é别 On 3/6/22 8:41 AM, greenboxmaven via
groups.io wrote:
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Gary Johnson
Common-mode chokes are by far the most effective way to reduce conducted emissions. Ferrite chokes are cheap and easy to apply but do require some care. Note that you need to treat EVERY cable connected to the offending device. And the choke(s) must be designed for the frequency ranges of interest. For instance, a large type 31 toroid with 6-12 turns is appropriate for the HF bands while multiple snap-on type 61s are appropriate for UHF. See this reference:? Radiated emissions, e.g. right off the screen of a plasma TV, are an entirely different problem and can only be addressed by shielding or distance. When doing any kind of low-level measurements, I have to completely remove known offenders from the test area. Not having a home screen room, I’m still stuck with RFI from nearby, including FM broadcast. Gets into everything… |
Harold Foster
Froggie the Gremlin
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