Author Topic: 120Hz noise source  (Read 4167 times)

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Offline dfroula

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120Hz noise source
« on: April 14, 2015, 11:13:00 PM »
This noise problem is being experienced by the new Komoka, ON station, as I work with Paul to optimize his new installation.

This one is intermittent, always producing exactly 120 signals/second when present, meaning it is generating triggers on the positive and negative peaks at 60Hz. There seems to be a slight ringing on the signal.

The power supply is clean after being changed out a few times/ It's likely being picked up as a radiated signal. Any thoughts?

Regards,

Don
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Offline dfroula

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Re: 120Hz noise source
« Reply #1 on: April 15, 2015, 09:26:32 AM »
Last year, I experienced a similar noise issue. What I found was similar interference that appeared to be below the trigger thresholds but would still drive the station into interference.

This started after replacing my standard PSC furnace blower motor with a high efficiency ECM variable speed DC motor. The power supply in the motor was not drawing current smoothly from the power mains, but pulling very high-current pulses 120 times/second. Current pulses were causing EMI, which was being radiated from the house wiring. The pulses were so fast that the A to D converters in the BO hardware could not fully display them on the Signals page. I had to use an oscilloscope connected to the test pins of the H-field amp to see the pulses. Since the re-radiated noise from the house wiring was inductive, the electrostatic antenna shields did nothing to attenuate the noise.

GE, the manufacturer of the motor, sent me a high-current choke that I put in-line with the hot lead to the furnace. That cleaned up 90% of the noise.

Has anyone experienced similar noise at exactly 120Hz and found a source/solution?

Don

Offline miraculon

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Re: 120Hz noise source
« Reply #2 on: April 15, 2015, 12:49:04 PM »
I remember having anxiety about this very issue when I was going to get a new furnace last year. Fortunately, the new furnace has no issues even though it has a pretty sophisticated motor controller. (ramps down, runs after A/C shutoff for a while, etc.)

I did by a V****** heater that wreaked havoc with both detectors and AM radio. I used the AM radio excuse to return it to the store. It had a continuously variable motor control. I replaced it with a "simple Simon" fixed heater control (two speed, with a dropping resistor). No problems with it.

Greg H.
 
« Last Edit: April 19, 2015, 09:50:52 PM by miraculon »




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Offline PaulMy

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Re: 120Hz noise source
« Reply #3 on: April 15, 2015, 07:06:31 PM »
I do have a newer Lennox SLP98UHV furnace installed June 2013 also the icomfort Wi-Fi Thermostat Touch Screen Programmable Communicating Thermostat.  As it is fairly warm during the day the furnace is off at present, and BO signals look good at the moment and over the past few hours (from what I can tell). I will see what happens when the furnace motor comes on (it is still warm inside so won't force it to go on, but will get cooler soon).  I could not get it out of interference last night and will see what tonight brings. 
 
I have an Ethernet Bridge coming  on Thursday and that will give me more location options.
 
Paul
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Offline PaulMy

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Re: 120Hz noise source
« Reply #4 on: April 15, 2015, 08:38:57 PM »
Have been using Manual, Noise Adaption settings and that worked very well again until a little while ago and then suddenly went into interference with signals 120 /sec.  Furnace fan hasn't come back on yet.  Nothing else changed at that time that I am aware of.
 
Gains settings of A= 5x2 B= 5x2 keeps it out of interference.
 
Paul
 
 

Offline PaulMy

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Re: 120Hz noise source
« Reply #5 on: April 17, 2015, 02:17:29 PM »
Just received the Ethernet Bridge and will relocate the controller once major interference occurs again, likely later this afternoon and see if that makes any difference.  From observation over the past few days it seems to work excellent in late morning into late afternoon, like it has been for a few hours now, then into interference mode.  Doesn't look like it is when the furnace motor comes on.
 
Paul

Offline PaulMy

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Re: 120Hz noise source
« Reply #6 on: April 19, 2015, 05:21:43 PM »
With DonF's continued help and persistence I discovered at least one major source and that is a dimmer light switch in the family room adjacent to my weather station room.  Not turning it on made a world of difference.  Station 1076 doing very well today.
 
Paul

Offline Cutty Sark Sailor

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Re: 120Hz noise source
« Reply #7 on: April 19, 2015, 05:54:31 PM »
 UU
With DonF's continued help and persistence I discovered at least one major source and that is a dimmer light switch in the family room adjacent to my weather station room.  Not turning it on made a world of difference.  Station 1076 doing very well today.
 
Paul

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Offline Old Tele man

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Re: 120Hz noise source
« Reply #8 on: April 19, 2015, 06:04:06 PM »
BEWARE of any electrical devices that have "variable" control of any sort, such as dimmers, motor speed, etc., because they typically use SCR-phase control of 120Hz-fullwave rectified 60Hz line voltage and silicon controlled rectifiers (SCR's) are notorious "noise" generators.
« Last Edit: April 20, 2015, 06:08:24 PM by Old Tele man »
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Offline spark_finder

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Re: 120Hz noise source
« Reply #9 on: April 20, 2015, 05:43:10 PM »
about 20 years ago I discovered that a solid state dimmer made the same double pulse that lightning makes if using an e-field antenna, out to about 10 feet from the wiring, at 120Hz.  Long story is I was trying to read the double e-field pulse a bullet makes as it passes through certain types of target paper, trying to make a new type of chronograph.  It would false trigger and read the same velocity near the dimmer.  I developed it in the winter, and in the summer I found it was a far better lightning detector than it was a chronograph :shock:.

Offline PaulMy

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Re: 120Hz noise source
« Reply #10 on: April 25, 2015, 08:40:00 PM »
It seems I can't learn from just the first issue ](*,)   The station worked excellent for extended hours after I learned not to turn on the family room dimmer lights, then often go back into interference.  Just discovered this afternoon I had another dimmer light switch for our new kitchen pot lights.  Turning this off has kept the station in full participation.  So another source identified \:D/ 
 
I can live without the family room lights until I change the light switch.  Another thing is to convince the kitchen tenant to not use the kitchen light and more so to permit alteration after she got a new kitchen after 40 years :roll: 
 
Paul

Offline Cutty Sark Sailor

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Re: 120Hz noise source
« Reply #11 on: April 25, 2015, 08:48:46 PM »
It seems I can't learn from just the first issue ](*,)   The station worked excellent for extended hours after I learned not to turn on the family room dimmer lights, then often go back into interference.  Just discovered this afternoon I had another dimmer light switch for our new kitchen pot lights.  Turning this off has kept the station in full participation.  So another source identified \:D/ 
 
I can live without the family room lights until I change the light switch.  Another thing is to convince the kitchen tenant to not use the kitchen light and more so to permit alteration after she got a new kitchen after 40 years :roll: 
 
Paul
One of my favorite anecdotes concerns Dr Obbins... 'operator emeritus' moving to St Croix (original station 946 Cave City KY, system is now Tom's in Sherman Connecticut, 946, and was built by Don F...)  it goes something like this:
Wife went shopping. Dave changed out dimmers while wife was gone.  Dave slept on couch.

Or similar...  :twisted:

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Offline PaulMy

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Re: 120Hz noise source
« Reply #12 on: April 27, 2015, 03:26:38 PM »
Would the noise I get when the dimmer light switch is turned on be "Radiated" or "Conducted" or both?  http://www.residential-landscape-lighting-design.com/PPF/thread/RFI---Radio-Frequency-Interfer/forum.asp

I haven't yet called the electrician who installed the pot lights and dimmer switches during the new kitchen renovation last fall but see a LDC is nearly $200 each and I have 2 dimmer switches there, ouch!

Paul

Offline Dr Obbins

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Re: 120Hz noise source
« Reply #13 on: April 27, 2015, 07:49:20 PM »
It seems I can't learn from just the first issue ](*,)   The station worked excellent for extended hours after I learned not to turn on the family room dimmer lights, then often go back into interference.  Just discovered this afternoon I had another dimmer light switch for our new kitchen pot lights.  Turning this off has kept the station in full participation.  So another source identified \:D/ 
 
I can live without the family room lights until I change the light switch.  Another thing is to convince the kitchen tenant to not use the kitchen light and more so to permit alteration after she got a new kitchen after 40 years :roll: 

 
Paul
One of my favorite anecdotes concerns Dr Obbins... 'operator emeritus' moving to St Croix (original station 946 Cave City KY, system is now Tom's in Sherman Connecticut, 946, and was built by Don F...)  it goes something like this:
Wife went shopping. Dave changed out dimmers while wife was gone.  Dave slept on couch.

Or similar...  :twisted:
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Offline Old Tele man

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Re: 120Hz noise source
« Reply #14 on: April 27, 2015, 11:02:06 PM »
Radiated vs. Conducted?

Radiated dissipates as "inverse-square of the distance" while Conducted hitches a 'free ride' along existing copper/aluminum wires throughout your house.
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Offline dfroula

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Re: 120Hz noise source
« Reply #15 on: April 28, 2015, 07:30:28 AM »
Would the noise I get when the dimmer light switch is turned on be "Radiated" or "Conducted" or both?  http://www.residential-landscape-lighting-design.com/PPF/thread/RFI---Radio-Frequency-Interfer/forum.asp

I haven't yet called the electrician who installed the pot lights and dimmer switches during the new kitchen renovation last fall but see a LDC is nearly $200 each and I have 2 dimmer switches there, ouch!

Paul

Paul,

The dimmer works by abruptly chopping off the AC waveform on each half-cycle with a triac device. This creates a sharp cutoff on the voltage to zero, 120 times/second where there would normally be  smooth sinusoidal voltage transitions. The abrupt transition creates harmonics at integral multiples of the 60Hz power line frequency. These harmonics extend up into the <= 100KHz range of the BO detection system.

The interference is both conducted and radiated. It is conducted along the power wiring of the house and will be worst on the branch circuit to which the dimmers are connected. This noise can find its way into the BO system through a poorly filtered power supply.

The current variations in the conductors also radiate E and H near-field noise. If you are using properly shielded and grounded shields over the ferrite antennas, they will do a good job of attenuating the E-field noise radiated from the power line. However, the shields will not attenuate inductively-coupled magnetic H-field noise from the power wiring. Current variations from the dimmer create both types of radiated noise. Sometimes moving the antennas away from a wall containing power conductors helps dramatically.

Different brands of dimmers vary dramatically in their built-in noise filters. A different brand may help.

Best,

Don F.
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Offline PaulMy

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Re: 120Hz noise source
« Reply #16 on: April 28, 2015, 09:52:40 AM »
Thanks Don and all.
 
Looks like the "Use a lamp debuzzing coil (available from Lutron) to filter the RFI" applies to both.  Changing the dimmer switches to another brand will also be a trial and error I suppose.  And there are 3 of them (found that the window light also has a dimmer). 
 
The solution, or work around, will be found eventually!
 
Paul

Offline Dr Obbins

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Re: 120Hz noise source
« Reply #17 on: April 28, 2015, 10:09:47 AM »
Previously when the dimmer issue was plaguing my unit, I had called Lutron about a solution and talked to an engineer. Take it for what it is worth, he stated that their dimmers were the best in the business for minimizing noise. Thats why I ended up taking mine out. Now when I moved the BO unit to it's final location in the attic, I replaced the non-shielded CAT5 wire with a decent shielded wire. Then months later as part of the moving project I restored the dimmers to their original location. For what ever reason whether the new location or new CAT5 wire, the noise issue went away.