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Old 03-08-2008, 11:51   #1
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LED Noise?

We anchored out over night and found an interesting problem that I had not expected. All systems checked out fine before we left the dock. When we anchored a short time later - all systems were fine. As dark approached, we found that there was full scale interference on both the VHF, 2 meter ham and the portable radios. The portable radio was not as bad, but that told me that it was not a problem in the electrical system.
After doing some quick checks we found that it was the masthead LED anchor light (and probably the trilight which was not on). Turn the anchor light off - the problem is instantly gone. Turn it on, the interference comes on with the switch.
Has anybody else come across this problem? Did miss something in the installation or is there something I can do besides going to an incandescent bulb? I really don't want to go back to incandescent.
With thirty plus LEDs operating a foot or so away from my antenna, I guess I can understand some noise. But I never considered this problem nor do I know what to do about it. The portable was 40' away (top of the mast to inside the cabin) from the LED so moving the antenna does not appear to be a good solution.
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Old 03-08-2008, 12:11   #2
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I did not know LED's could make electrical noise. I wonder if its some sort of circuitry that powers the LED's? Things that step up a voltage can cause electrical noise so I wonder if that is whats going on? I would call the manufacturer and ask if they know about such a thing in their product. If they can't fix the problem then I would ask for a full refund.

Also, is that light the only thing on that circuit? Is there anything else that comes on when you turn on that circuit such as other night lighting?
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Old 03-08-2008, 12:13   #3
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LEDs don't make electrical noise, but certain brands of LED masthead lights have been documented and confirmed to cause radio interference because of the driver circuits they use with their LEDs.

Your best bet is to contact the manufacturer, who probably is aware of the problem and should offer you a replacement or a refund or some mitigation scheme.
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Old 03-08-2008, 12:26   #4
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David M and HelloSailor:
There is nothing else on the anchor light circuit. It is only for the anchor light. I will try to contact the manufacturer on this. That is a good idea. That makes sense that it may be the driver circuit. I had not thought of that.
I am not looking forward to going up the mast again to work on the thing Oh, well. What must be done - must be done
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Old 03-08-2008, 13:08   #5
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Since LEDs are constant-current devices, the most efficient way to drive them is with PWM (pulse width modulation), allowing their brightness to be independent of supply voltage. The crude method is a series resistor, but you lose a lot of power to heat. There are good and bad ways to design a PWM circuit, and the bad ones are massive noise generators... big sharp square waves turning a load on and off, worsened by the inductive antenna of the wires between them.

I haven't yet seen a decent survey of competing marine LED products that specifically addresses this... there needs to be one. You can improve things somewhat with strategically placed ferrites and capacitors to eat some of the noise impressed on the antennas (power leads), but it can be frustrating.

Cheers!
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Old 03-08-2008, 13:22   #6
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I'm wondering why these manufacturers cant incorporate plain old 12V LED's into a nav light and leave all the noisy circuitry out? I have a few 12 volt LEDs on my 12 volt DC panel and they work just fine....even when the charging voltage is close to 14 volts or when the DC system voltage drops below 12 volts. Seems like they are being made unnecessarily complicated to me.
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Old 03-08-2008, 13:30   #7
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There is actually no such thing as a 12-volt LED - they need just enough voltage to start passing current (the "forward drop"), and then the current must be limited to the actual specification of the device to keep it from self-destructing (the little old standard ones, before bright stuff came along, were typically around 10-20 mA). An LED that can just be attached to 12 volts will have an internal resistor that limits the current. For an panel display, that's no problem as the wasted power is minimal, but for a superbright it can be much more significant (not to mention having to dump the additional heat in something that must be sealed from the elements).

My first homebrew LED navlights on the Microship were on the mast of the VHF antenna on the bow, and were a real noise headache... though there are some folks who are apparently doing it right. I haven't been able to hear the cabin Sensibulbs with a casual VHF test, though to be fair that's squelched and not really a proper test. And Dr. LED claims to be low noise.

I'll take a closer look at the ones I have aboard with the scope and see if I can add useful product suggestions...

Cheers,
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Old 03-08-2008, 14:31   #8
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That would be great Steve. I had no idea before I went all LED on my boat that there was a noise problem with them. I should have done my research better on that point. I don't have the equipment nor knowledge (or time!) to do any kind of product testing. That would be fantastic if anyone can share their information on quiet LED equipment. I guess maybe this is a common problem.
Question: In the interim, can I replace the LED "bulbs" (which have a standard 2 contact base) with an incandescent bulb until I find a quiet replacement?

Thanks Again.
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Old 03-08-2008, 15:02   #9
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I read some stuff on this from this site.

Bebi Ultrabright White LED Marine, RV, and Off-Grid Light Bulb Assemblies

["The last basic type of current regulator is what is called a PWM (pulse width modulation) regulator. This is the most efficient type of regulator, but it does (currently) suffer from a cost an order of magnitude above that of our regulator and if improperly implemented, will cause interference ('hash') on your VHF and HF ('SSB') radio. If you'd like some further reading about these types of problems which can occur, you might want to follow this thread on the SSCA Discussion Board"]
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Old 03-08-2008, 16:47   #10
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Both of those are excellent Therapy! Thanks for that information. I have a little more testing to do to see just what the route of the interference is.
Sounds like everyone is pretty familiar with these LEDs.
BTW- We had a wonderful weekend with the kids. We anchored out near a beach and in the morning took all five of the kids over to the beach so they could play. It was a beautiful morning for Oregon and was very enjoyable.
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Old 03-08-2008, 17:09   #11
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"Question: In the interim, can I replace the LED "bulbs" (which have a standard 2 contact base) with an incandescent bulb until I find a quiet replacement"
No, you can't. Remember that the LEDs themselves DO NOT CREATE INTERFERENCE. So replacing them will not solve any interference problems. The interference is coming from the electronics circuits that are driving some of them. Those circuits are usually designed with some admirable purposes, like cutting power consumption (sometimes by 10x or more), ensuring long LED life, protecting the LEDs form surges and spikes, etc.
Odds are that they were designed by someone who had little or no boating experience, or little electronics experience, because most electrical engineers would know these circuits were liable to create interference, and most boaters would know that masthead lights were going to be installed right next to the radio antenna--the worst possible place for a "radio noisy" device.
Famous last words: "It seemed like a good idea at the time". <G>
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Old 04-08-2008, 05:13   #12
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Quote:
Originally Posted by hellosailor View Post
LEDs don't make electrical noise,
Just to set the record straight, all semiconductors make electrical noise. The PN junction of an LED generates shot noise, flicker noise and thermal noise. The noise you hear on your VHF radio when you turn the squelch off is this noise generated and amplified by receiver components. But this is not what is causing the problem with the LED lighting fixtures. As stated before, it's the control circuitry causing this problem.

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Old 04-08-2008, 05:28   #13
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Ive been installing some leds in cabin and instead of using resistors Ive been hooking them up in 4 in series which at 3.6 volts apiece seems to work well in the 12-14 volt range. No heat from resistors and dont know if Ill get 150k hrs but I havent had any fail yet.
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Old 04-08-2008, 08:10   #14
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Quote:
Originally Posted by clausont View Post
That would be great Steve. I had no idea before I went all LED on my boat that there was a noise problem with them. I should have done my research better on that point. I don't have the equipment nor knowledge (or time!) to do any kind of product testing. That would be fantastic if anyone can share their information on quiet LED equipment. I guess maybe this is a common problem.
Question: In the interim, can I replace the LED "bulbs" (which have a standard 2 contact base) with an incandescent bulb until I find a quiet replacement?

Thanks Again.
Depends.

I have seen two types of LED products. One is a self contained potted fixture with wires coming out. Obviously not one you can replace with bulbs.

Two is a bulb that plugs into the original incandescent base. (Ala Dr. LED which has all the electronics in the bulb.) If you had an incandescent in there before you went LED, why would you think that you couldn't put an incandescent back in?

Three, other choices out there that I'm not aware of that makes Hellosailor's answer the correct one.

John
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Old 04-08-2008, 08:52   #15
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John-
"If you had an incandescent in there before you went LED, why would you think that you couldn't put an incandescent back in? "
Ah. If you change "bulb" to "fixture assembly" you certainly could.<G> But an LED "bulb" itself? Nope. I figure if someone had retrofitted whole replacements, they'd certainly KNOW they could put the old bulbs back in, there' d be no point in asking the question from that point of view, would there? So...I'm treating "bulb" as "bulb", even if that's really a misnomer for an LED itself.
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