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Author Topic: Powerline Noise  (Read 34570 times)

JeffVolp

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Powerline Noise
« on: November 22, 2008, 05:24:20 PM »

I have been investigating some powerline noise that cropped up here.  As far as I can tell it isn't coming from anywhere inside our home.  We recently got new neighbors, and I suspect the noise is coming from over there.  We do have a PZZ01 whole-house blocking coupler, but it does nothing to eliminate the noise.  The noise is actually slightly stronger when the blocking coupler is “on line”.  It is possible that the noise is originating on the opposite phase from my lab, and the blocking coupler helps to propagate it across the phases.

I have been monitoring the noise through the XTB return signal amplifier because that removes most of the AC component.  I took some photos showing the noise by itself and with a weak X10 signal embedded in it.  Since the X10 burst occurs immediately after the zero crossing, the noise source apparently does not have enough voltage to operate at that point in the waveform.  So that leaves a small open window for the X10 burst.  The XTB-IIR will recover that X10 signal and repeat it just fine.

I also looked at a minor mod to the XTB that adds a bandpass filter to the return signal amplifier.  The photos show the bandpass filter does reduce the noise somewhat.  However, the noise source appears to be coming from a switching supply that runs very close to the 120KHz X10 carrier frequency at the peak of the waveform.  As a result, most of it gets through the bandpass filter at that point.  As the frequency drifts away from the X10 carrier frequency, the bandpass filter rejects most of it.

The X10 signal bursts are more clearly seen with the added bandpass filter.  The wandering 3rd phase burst can also be seen, which is a characteristic I had previously noted from the RR501 X10 transceiver.

Noise by itself:  http://jvde.us/x10/line_noise_XTB_X10-in.jpg

Noise with X10 signal:  http://jvde.us/x10/line_noise+X10_XTB_X10-in.jpg

Noise through BPF:  http://jvde.us/x10/line_noise_XTB_X10-in+BPF.jpg

Noise with X10 signal through BPF:  http://jvde.us/x10/line_noise+X10_XTB_X10-in+BPF.jpg

UPDATE:  The noise has been identified as coming from a 120V 4-watt Lumoform 240 lumen E27-base LED light.  I installed this to provide some background light in an otherwise dark interior hallway last spring.  While controlled by a Leviton X10 switch, the light is left on 24/7 because it lights the way to the bathroom at night.  The X10 switch had been used to dim the previous incandescent bulb to a lower level at night.

When first installed, it worked fine with the Leviton X10 switch, and I did not see any noise.  Since the noise started months later after the new neighbors moved in, I never thought to re-examine this particular LED bulb.  However, I had read a report of someone else having trouble with a 120V LED light, so I thought I'd check this again.  Sure enough, it is now a significant noise source - so bad that the Leviton X10 switch controlling it no longer works.  I confirmed the Leviton switch was OK by substituting an incandescent back into that fixture.  Since the noise is very close to the X10 frequency band (I measured 117KHz), I suspect a Leviton 6287 filter will block it.


Jeff
« Last Edit: February 06, 2009, 06:31:21 PM by JeffVolp »
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HA Dave

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Re: Powerline Noise
« Reply #1 on: November 22, 2008, 07:52:44 PM »

.... We recently got new neighbors, and I suspect the noise is coming from over there. 

This is extremely interesting. Does the noise have periods of activity... and can that activity be predicted. Or does it run 24/7 without let-up like a huge bank of growlights hidden away in the basement?
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JeffVolp

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Re: Powerline Noise
« Reply #2 on: November 22, 2008, 08:08:16 PM »

Does the noise have periods of activity... and can that activity be predicted.

It is not there all the time.  I suspect it might be from a flat panel TV, or perhaps something as simple as a cellphone charger.  Sometimes I see it when I'm testing XTBs.  Isolating my bench with a X10 filter kills it completely.  The neighbors with the wireless intercom (probably a baby monitor) moved out, so I don't see that modulated carrier anymore.

Jeff
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HA Dave

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Re: Powerline Noise
« Reply #3 on: November 22, 2008, 08:30:22 PM »

... I suspect it might be from a flat panel TV, or perhaps something as simple as a cellphone charger. 

Wow if you can detect that..... I am impressed!
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JeffVolp

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Re: Powerline Noise
« Reply #4 on: November 22, 2008, 10:30:06 PM »

... I suspect it might be from a flat panel TV, or perhaps something as simple as a cellphone charger. 

Wow if you can detect that..... I am impressed!

One little cellphone charger is one of the nastiest noise generators I have seen yet:  http://jvde.us/x10/x10_cellet_noise.htm

Note that the ESM1 even thought it was sending a "Good" X10 signal.

Jeff

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dave w

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Re: Powerline Noise
« Reply #5 on: November 23, 2008, 07:45:08 PM »

  We recently got new neighbors, and I suspect the noise is coming from over there. 
I'd nuke 'em.   rofl

Seriously, Are they nice neighbors that would let you install a filter when you find their offending appliance?

Otherwise....nuke 'em.
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Dan Lawrence

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Re: Powerline Noise
« Reply #6 on: November 23, 2008, 08:03:40 PM »

  We recently got new neighbors, and I suspect the noise is coming from over there. 
I'd nuke 'em.   rofl

Seriously, Are they nice neighbors that would let you install a filter when you find their offending appliance?

Otherwise....nuke 'em.

Not a good idea.  Last thing you want is a next door neighbor who is mad at you or a radioactive pit next door to you.  :o
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JeffVolp

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Re: Powerline Noise
« Reply #7 on: November 24, 2008, 01:49:03 AM »

They are very nice people, and I'm sure they would accommodate filtering an offending device.

The real issue is that the PZZ01 is supposed to "keep extraneous electronic noise and signals from entering or leaving" over the powerline.  I thought installing that on the utility feed would isolate our house from others sharing the same utility transformer.

Jeff
« Last Edit: November 24, 2008, 11:34:31 PM by JeffVolp »
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Brian H

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Re: Powerline Noise
« Reply #8 on: November 24, 2008, 06:47:49 AM »

Jeff; Yes you would think a whole house filter for X10 power line signals would block the 120 KHz and close frequencies.
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dave w

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Re: Powerline Noise
« Reply #9 on: November 24, 2008, 12:32:47 PM »

  We recently got new neighbors, and I suspect the noise is coming from over there. 
I'd nuke 'em.   rofl

Seriously, Are they nice neighbors that would let you install a filter when you find their offending appliance?

Otherwise....nuke 'em.

Not a good idea.  Last thing you want is a next door neighbor who is mad at you or a radioactive pit next door to you.  :o
Rats, hadn't considered the fallout aspect.....so wait until the wind is strong.  ;D
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dave w

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Re: Powerline Noise
« Reply #10 on: November 24, 2008, 12:44:02 PM »

They are very nice people, and I'm sure they would accommodate filtering an offending device.

The real issue is that the PZZ01 is supposed to "keep extraneous electronics noise and signals from entering or leaving" over the powerline.  I thought installing that on the utility feed would isolate our house from others sharing the same utility transformer.

Jeff

Jeff,
Doesn't the PZZ01 work by inverting the noise and inducing it on to the neutral for cancellation? Do you know the  level of the noise coming into the house (before the PZZ01)? Or better question, are you sure the PZZ01 is still working?
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JeffVolp

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Re: Powerline Noise
« Reply #11 on: November 24, 2008, 01:56:14 PM »

I do know the PZZ01 is supposed to sense the noise and create an opposite phase cancellation signal to null it out.  Phil Kingery's description says the cancellation is superimposed onto the neutral.

I haven't measured the noise directly at the power panel.  I will pursue this more if I can get away from the soldering iron for awhile.  I don't think there is anything inside the PZZ01 that can fail.  The fact that the noise is actually worse with the breaker on leads me to believe the coupling is working.

Thinking about this more, let's say there is noise just coming in on one phase.  The PZZ01 senses that, and induces a voltage on the neutral to cancel that signal.  But, the other phase that had relatively little noise now is referenced to neutral with the cancellation signal superimposed on it.  So, the previously "clean" phase will then have the noise.  If that explains what is happening, perhaps the best way to attack this is to couple the phases so they both have identical noise.  Then the neutral cancellation should work.  I don't normally drive both phases here because all X10 devices are on one phase.  Why waste signal where it isn't needed?  (My workshop/lab is on the non-X10 phase.)

Jeff

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Jsnlong

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Re: Powerline Noise
« Reply #12 on: November 24, 2008, 02:30:35 PM »

Wow that's pretty good that all your X10 stuff is on one phase.Do you have allot of X10 stuff or is just most of your house on one phase. If it is ... Did you wire the house yourself?
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Re: Powerline Noise
« Reply #13 on: November 24, 2008, 04:24:21 PM »

Thinking about this more, let's say there is noise just coming in on one phase.  The PZZ01 senses that, and induces a voltage on the neutral to cancel that signal.  But, the other phase that had relatively little noise now is referenced to neutral with the cancellation signal superimposed on it.  So, the previously "clean" phase will then have the noise.  If that explains what is happening, perhaps the best way to attack this is to couple the phases so they both have identical noise.  Then the neutral cancellation should work.  I don't normally drive both phases here because all X10 devices are on one phase.  Why waste signal where it isn't needed?  (My workshop/lab is on the non-X10 phase.)


Jeff,

I thought the PZZ01 also passively coupled the phases.  Shouldn't the noise be present on both?

Is it possible that you only connected to the phase that is being used for X10?
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JeffVolp

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Re: Powerline Noise
« Reply #14 on: November 24, 2008, 07:24:23 PM »

Wow that's pretty good that all your X10 stuff is on one phase.Do you have allot of X10 stuff or is just most of your house on one phase. If it is ... Did you wire the house yourself?
I finished the lower level myself, and rewired the panel when I did all that electrical work.

Jeff
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