High Frequency Shunt for In-wall Power Wiring

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pnielsen

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Is it technically possible to produce a device that can be plugged into a standard wall socket that will remove, from the entirety of a small building's in-wall wiring, all signals in excess of 50/60Hz, ie. by shunting them to ground?

If so, please describe how the circuit would work, and where I might learn about the appropriate design procedure.
 
The simplest method to remove frequencies other than 50/60Hz for placement in a wall socket would be to use a parallel tuned LC filter. It possesses a large impedance at the resonant frequency and low impedance at all others.

The amount of errant signal you can remove from the building's wiring depends on the filter, of course, but will be very dependant on the wiring layout of the building itself. The wiring will have parasitic effects on your filter.
 
Correct me if I am wrong, but I thought an LC filter was tuned to a singular frequency. But maybe you have some specific configuration in mind. Here is a good reference on the former:

What I am looking for is something like a 50/60Hz low pass. IOW _ALL_ frequencies higher than that (within reason) are to be excluded from the building's wiring.
 

Sorry, but you are wrong

An LC filter 'can' be designed for a specific frequency, but it can just as easily (if not easier?) be designed as a low-pass or high-pass filter.

However, perhaps you might like to explain what you are trying to do?, and why?.
 
pnielsen said:
Correct me if I am wrong, but I thought an LC filter was tuned to a singular frequency.
Click to expand...
You are correct. The single LC described will remove the frequency it is tuned to the most, and surrounding frequencies to a lesser extent; you can see the response in the linked page. Why do you want to keep the lower frequencies?

If you really do want to shunt the high frequencies, I guess you could try a shunting element (e.g. transistor) controlled by the signal from a HPF...
 
To shunt away all high frequencies you just add a non-polarized capacitor (such as a motor run capacitor) across the line. But it's effectiveness for high frequencies will be limited by the wiring inductance. The capacitor will draw some reactive current at the line frequency but that will just improve the lag power factor that a power line typically has.

What is the source of these high frequencies?
 
Most mains powered electronic devices these days have low pass line filtering already built in. You could have a google for "ac mains line filter" and see all the commercial devices and circuits.
 
I stand corrected Nigel. There are online calculators for same, such as: http://www.calculatoredge.com/electronics/ch pi low pass.htm

I have two questions please.

1. A wall socket has three wires, active, neutral and ground. How would the above circuit connect to these so as to remove/shunt HF artifact from the building's wiring grid?

2. There is a field in the online calculators for entering impedance. How would this be ascertained given the described application?

The purpose is to overcome low level ambient radiation caused by interferrence riding upon the power line. The "why" is to allow placement of discrete sensors in a room that would be disturbed by same. IOW the object is not to protect a single device, which, as some respondents have pointed out, could be achieved with a commericial line filter.
 
Can you please advise where I can find more information on this type of circuit? IOW how is the "signal" from the HPF derived and processed to control the transistor. How would I estimate the current to be shunted so as to select properly rated components?
 

Typically low level interference from commercial transmitters.
 
If you want to filter a mains supply, you need a filter which is correctly designed and built for the job
A single tuned circuit does not do it and neither does the low-pass filter shown in your link.


I would suggest something like this (or better):
https://www.electro-tech-online.com/custompdfs/2013/02/DS_FN2020_20110616_web43_01.pdf

I do not know why you want to have a room which is free from HF signals and noise radiated from the mains wiring, but also be aware that unless the room is screened, ie a Faraday Cage, there will be a significant amounts of normal radio signals in there which are of greater amplitude than anything radiated from the mains cable.
Unless of course the mains cable is exceptionally "dirty".

JimB
 

The device in the link provided is for an EMI filter dedicated to a particular device. There are a wide range commercially available.

As per my OP, I instead want to filter the entire mains cabling of a building. IOW nullify its ability to radiate anything over 50/60Hz. How can this be achieved with a portable device that will plug into any socket on the circuit?
 

I'm confused about what you want to do. The entire mains of a building can be hundreds of amps. Something that will plug into any socket will be less than 15 amps.
 
ChrisP58 said:
I'm confused about what you want to do. The entire mains of a building can be hundreds of amps. Something that will plug into any socket will be less than 15 amps.
Click to expand...

Yes, but the embedded HF component (noise) would be proportionally far far less. This is what I want to shunt away, not filter the entire 50/60Hz load. IOW I do not want something like a convnetional ripple or interferrence filter. As you imply, that would be affected by every connected downstream appliance.

The question is how to isolate frequencies above 50/60Hz and divert them to the building's grounding rod. By analogy, this is closer to a decoupler or the RC network on an active filter.

Again, is this possible for the stated application? What design process and components would be involved?
 

I would suggest your sensors are poorly designed, I've NEVER heard of any such problems - if they are sensitive to incoming mains interference, why don't they have internal filtering?.

In order to do what you want (and I don't know if it would help or not?), you would need to put a filter on the incoming mains supply to the building - this would need to pass the entire current from the supply, so would be large, expensive, and difficult to source.

There were thoughts about such devices back in the 70's, when the idea was that the mains wiring would be used for sending control signals around houses, so each house would need blocking from the neighbours. However, in the event it never really happened - with only a tiny number of units ever used, such as the X10 system.
 
As per my OP, I instead want to filter the entire mains cabling of a building. IOW nullify its ability to radiate anything over 50/60Hz. How can this be achieved with a portable device that will plug into any socket on the circuit?
Click to expand...
I suggest that such a thing is impossible.

JimB
 

The sensors do not use internal filtering for several reasons. One is phase distortion.

X-10 filters are still sold. They are for 120Hz specifically, not LP. They do not filter the entire circuit but only discrete appliances.

Looks like I am drawing a blank here. Maybe I should apply for a speculative patent? Seriously, I recall seeing something like this years ago but can't find the details.
 
pnielsen said:
Looks like I am drawing a blank here. Maybe I should apply for a speculative patent? Seriously, I recall seeing something like this years ago but can't find the details.
Click to expand...

How could you apply for a patent on something you don't understand, and can't provide working details on?.

But you're still providing far too view details - you've now introduced a strange reason for no filtering in the sensors - assuming 'phase distortion' is a valid reason?, then external filters would suffer from exactly the same problem.
 
A filter/shunt plugged into an arbitrary socket will only attenuate high frequencies at points downstream of that socket. I agree with JimB; you can't filter the whole house wiring system with something plugged in at an arbitrary point.
 
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