Weird Electrical Noise - Page 1
Forum section: electronics / projects

author: hazmoment
author_rank: Contributor
timestamp: October 17, 2020, 04:48:11 am
content: Experiencing this weird electrical noise every now and then.and managed to capture it (badly) on the scope today (Attached)Noticed most prominently this noise audibly through the Primary side filter PCB on my Panasonic Microwave.As the Microwave was brand new (New house too) I didnt think much of it and made a warranty claim to have it repaired. The Authorised repair agents for Panasonic replaced the filter board. It came back doing the same exact thing. Microwave was replaced for a new one and sure enough is still putting out the noise (same audible noise as in the video clip) note the noise occurs when the microwave is not in use but is plugged into the mains.Today I noticed my Sonos Port was triggering my Audio Amplifier (it sends a 12vDC trigger when audio is played on the Port via the app) Although the app was definitely not playing audio or sending the play command. At more or less the same time we noticed the TV (Samsung Frame) switching off from Art mode on its own accord.On closer inspection (when going to the AV equipment rack to isolate everything) I noticed the same audible noise from my Control4 EA1 - probably from the onboard power filter choke, just like the microwave. So I Decided to Isolate all circuits at the switchboard except one. And plugged the Microwave in only. The noise was still present at random intervals.The Video was taken after all of this faultfinding and the oscilloscope probes are across the Secondary side of the Filter circuit in the Panasonic Microwave and is plugged in elsewhere (in my workshop) Struggled to capture the noise on the scope but Im almost 100% its not being generated from within my property at this stage. The Noise was viewed to be riding on the positive peaks of the 240v ac.Im thinking of informing the local power distribution company (Delta) But wondered if theres anyone clued up on this on the EEVBlog first. Any Ideas what it could be? Potential solutions? after doing a quick search I see Clipsal make a product which is DIN mounted and acts as a mains filter/ Surge protector. I wonder if I need to invest in something like this...http://updates.clipsal.com/clipsalonline/files/brochures/w0000594.pdfIts especially strange as its a new sub division here and is residential only. There are local water supply pumps nearby ( 200mtrs away) Any Thoughts would be appreciated! Oh, and if anyone can offer a better way of capturing noise like this on the oscilloscope i would be interested to hear about that too! Harry. * I think I may have sacrificed the audio when uploading the video as it seems .Mov is not supported, Ive uploaded as Gif and seperately as mp3

author: hazmoment
author_rank: Contributor
timestamp: October 18, 2020, 03:24:43 am
content: Bit of an update on this. This issue is directly related to a neighbours Drop-Saw. As he has been cutting timber all weekend on it I have noticed the electrical noise presenting itself in time with the noise of the drop saw. Could this be due to the lack of an integral filter in the appliance or lack of an earth? And the first filter to ground the transients are seeing is in the appliances in my house?Seems strange that it is Audible either way.. Any one have any suggestions?

author: nigelwright7557
author_rank: Frequent Contributor
timestamp: October 18, 2020, 03:31:52 am
content: There are two types on interference.Conducted and radiated emissions.Conducted comes through the mains and is usually stopped by a good mains filter.Radiated comes in as RF and needs a RC filter on input to audio systems.I had an old amplifier that picked up police broadcasts really well.An RC on the front end fixed it.

author: hazmoment
author_rank: Contributor
timestamp: October 18, 2020, 03:40:28 am
content: Thanks Nigel. I suppose in my instance its got to be conducted emissions through the mains wiring. We are 3 doors apart. The interesting thing is that the interference is audible through the mains filters on the individual appliances.Im now looking into options/advice for DIN mounted filters for my mains board to filter noise at the main switch rather than at the individual appliances. Hope it works!

author: james_s
author_rank: Super Contributor
timestamp: October 18, 2020, 05:33:04 am
content: Power saws usually use universal motors, they tend to be extremely noisy electrically speaking, and they draw quite a large load too. It wouldn't surprise me if the saw is creating a significant sag as well as injecting lots of noise into the line.

author: DimitriP
author_rank: Super Contributor
timestamp: October 18, 2020, 07:45:52 pm
content: QuoteDo you mean new to you or new construction?If the neighbor's saw is able to wreck this kind of havoc what happens when your own A/C comes on?Kinda makes me wonder if one of the two (or both) houses have a "creative wiring" issue, from a bad connection to a loose ground and everything in between.

author: hazmoment
author_rank: Contributor
timestamp: October 18, 2020, 07:55:40 pm
content: Hi!This entire street is new in the last year. Both houses newly constructed. I wired my own house. Im a sparky by trade. I know my earthing and wiring in general is adequate and tested correctly. And I also happen to know that my neighbour had some issues with his electrician at the pre-wire stage as he was from overseas and wasnt quite up with it. I may suggest giving it a once over for my neighbour to prove his earthing etc is ok.They have said they havnt noticed any issues in their house when the saw is used. I willreport back what I find!

author: Benta
author_rank: Super Contributor
timestamp: October 18, 2020, 08:09:52 pm
content: As we've no idea where in the world you're located, it's hard to say.If you have 3-phase service distribution, it's in many locations usual to rotate the phases from house to house or apartment to apartment to try to balance phase loading (eg, not all ovens on the same phase). As you mention "3 doors apart", that would put you on the same phase.And yes, universal motors (especially cheap chinese ones) make a lot of conducted noise.

author: hazmoment
author_rank: Contributor
timestamp: October 18, 2020, 09:27:08 pm
content: Hi Benta. Yep we are on a distributed 3 phase supply but in theory we will be on a separate phase to him. I wasn't clear about the spacing between houses in the earlier post. there is one other house between me and him, meaning I would for example be on L1, next door would be L2 and he would be L3. I am located in New Zealand BTW. We use a TT grounding system. Neutral Screened phase conductor into the property from the underground distribution system and a Separate Earth Rod per dwelling. The switchboards within each property should contain an MEN link between the Earth and Neutral bars. Im wondering if theres something amiss with his installation. There is plenty of work still going on around the sub division and most people are using power tools all weekend. The only problem is seemingly his saw from his property. I plan on trying this saw out plugged into my property to see if the fault remains or if it concluded that theres something up with his installation. Will post the results when i know more.

author: DimitriP
author_rank: Super Contributor
timestamp: October 18, 2020, 09:46:54 pm
content: QuoteSuspicious "coincidence"QuoteQuoteBorrowing the saw seems a lot less intrusive and the perfect next step before going on a fishing expedition getting a headache by whatever "creative" wiring issues you might discover!Quote"They" never doI have "fixed" many software and networking issues by having the customer call their new electrician out to check out the wiring their old electrician left them withWe seem to be on the same page, I'll be quiet now and let you do you do your thing