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Filter load - line

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Scarr

Member
Hi all,

I am thinking about making a point to point power line comms project, I ideally want to make one unit that is used at either end, I also want a filter to stop noise on the line side, this all looks possible but I noticed that the FN406 filter I was going to use has a LINE- LOAD arrangement, my question is do you need to follow this arrangement or can you reverse the LOAD - LINE without issue, as this allows me to make a universal unit

If you did reverse the arrangement what issues would you potentially have?

Thx

Steve
 

ronsimpson

Well-Known Member
Most Helpful Member
That filter has a load and a line side.
Please tell me more about this communication project!
Why do you need a filter?
This filter is the wrong type.
Are you going to send tones down the power line? 100khz? or 200khz or 5mhz?
 

Scarr

Member
Hi Ron,

The comm's is via this module "KQ-130F" I want to ensure the data remains inside the point to point piece of cable

Steve
 

ronsimpson

Well-Known Member
Most Helpful Member
Capacitors pass high frequencies like the 130khz from the KQ-130. So the capacitors in the EN460 will short out the signals from the KQ-130.
Here I made a filter using two inductors which will open up at high frequencies. Now the signals from the KQ-130 will not pass back into the power line. All KQ-130s going to the right can talk just fine.
Capacitor C1 is optional. It will short out any 130khz signal that leaks through the inductors.
upload_2016-9-7_8-22-38.png
QUESTION: Why keep the signals off the power line? I am using X-10 power line communication which is about the same thing. It works with out filters.
What load is on the line with the KQ-130s?
 

Tony Stewart

Well-Known Member
Most Helpful Member
You can consider the Pi line filter as reversible but may also attenuate your PLC signals unless care is taken to correct the Return Loss.
 

Scarr

Member
Capacitors pass high frequencies like the 130khz from the KQ-130. So the capacitors in the EN460 will short out the signals from the KQ-130.
Here I made a filter using two inductors which will open up at high frequencies. Now the signals from the KQ-130 will not pass back into the power line. All KQ-130s going to the right can talk just fine.
Capacitor C1 is optional. It will short out any 130khz signal that leaks through the inductors.
View attachment 101127
QUESTION: Why keep the signals off the power line? I am using X-10 power line communication which is about the same thing. It works with out filters.
What load is on the line with the KQ-130s?
Hi Ron,

Can you recommend an inductor and capacitor for the job based on 5A load (max)

Thx

Steve
 

Tony Stewart

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Most Helpful Member
To attenuate Line noise and raise impedance of line source , you need a T filter rather than Pi filter
L-C-L 10-50uH and >30nF X cap to neutral for LPF <0.5MHz
 

AnalogKid

Well-Known Member
Most Helpful Member
I think you need to rethink your overall approach. If you buy or build a circuit that produces a 130 kHz signal on the AC powerline, then place a power line filter between that circuit and the line, that attenuates the 130 kHz signal by over 40 dB, why bother? What is your reasoning for including the powerline filter? It is designed specifically to prevent your carrier signal from getting through to the powerline.

ak
 

Tony Stewart

Well-Known Member
Most Helpful Member
after looking at the board , it looks like it has a large choke and plastic cap for low SRF, series resonant frequency coupling to line which is a BPF at 130kHz, probably with a Q <10
so no line filter required.
You do have to be on the same line phase (L1 or L2)
 

Scarr

Member
I think you need to rethink your overall approach. If you buy or build a circuit that produces a 130 kHz signal on the AC powerline, then place a power line filter between that circuit and the line, that attenuates the 130 kHz signal by over 40 dB, why bother? What is your reasoning for including the powerline filter? It is designed specifically to prevent your carrier signal from getting through to the powerline.
Not sure if it is me describing it badly but here is a diagram that should help, if anyone can do a quick diag / schematic with values it would help a lot as I am not confident at all about how to create this filter.

Steve

P.S. Maybe I am being a bit anal about this but as it is a P to P comms there is no need for the data to go outside the system.
 

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AnalogKid

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Most Helpful Member
MUCH more clear. that whole picture 1000 words thing is alive and well. The filters will keep your carrier current signal off the external mains lines, although in reality the signal is so low that it doesn't cause problems, especially with industrially-hardened electronics. The left and right "clean mains" go to the line side of each filter, and the left and right PLCs are powered from the load side of each filter.

ak
 

Scarr

Member
that's good, I do suffer from thinking everyone knows what I have in my head :)

Now, can anyone post a diag with values for a 5A load :)

Thx

Steve
 

ronsimpson

Well-Known Member
Most Helpful Member
I missed the answer; Why, the filters?
--------------------------------------
I have been using power line communications for years. I started when there were no switching power supplies in the house.
In my house:
High voltage is from the power company. There is a transformer that reduces the 3000V to 110/220V. This transformer passes 60hz and does not pass 130khz. I have tested it. Signals will not pass to the neighbors house.
Every time I added a computer with a Switching Power Supply the noise level went up and the signal level went down. Many switching supplies run in the 100 to 200khz range. This adds noise to the wires. The noise filters in side the power supplies place a large capacitor across the power line to short out the noise. (100khz range)
By the time I had 5 computers + 5 CRT monitors in the house communications was not good. So I added inductors to each power strip. (L7+L8) This 47uH choke dose not pass the high frequencies well. So most of the house has the 130khz signals on the wires. Each power strip will not allow the 130khz in and keeps the 120khz switching noise from getting on the house wiring.
upload_2016-9-8_15-1-20.png
This solved my problems.
--------
I used 47uH. You will need to pass 5A and not saturate at 7A. (You said 5A load)
There is no problem with having small 130khz signals on the power line.
 

Scarr

Member
Ron,

It's was / is to stop my data escaping outside my "defined" P2P link or have the ability to block / isolate a section of the wiring should I need to, maybe now it's because I am intrigued if / how it would be done, either way if you would be so kind as to show how I would block the 130khz data but allow 5A this would be great.

Thx Steve

P.S. I now get it that this 130khz data would not cause issues but still want the ability to block it if possible.
 

ronsimpson

Well-Known Member
Most Helpful Member
Inductor PM2110-470K-RC can be found at digikey.com 47uH 0.024 ohms, 6.5A
Capacitor 0.47uF "X" power line rated.
On the left side the 130khz sees 47uH and it can move the wire up/down in voltage.
On the right side 130khz sees a capacitor and will find low impedance.
The graph shows attenuation.
At low frequencies like 60hz (dc to 10khz) signals flow through.
At 120khz there is -23db. The signal is blocked. (some snicks through)
I don't know if this is enough attenuation. We can use more inductance or a larger cap. OR Use a LCLC filter.
This is a place to start.
upload_2016-9-8_17-3-13.png
 

Scarr

Member
Brilliant Ron thanks a million, if I understand you diagram "out" is load and what size is that resistor "ohms + watt"
 

Scarr

Member
Sorry, I meant I can put a 5A load on the wires, e.g. a lamp or something. OK so I don't need the resistor. Another thought I have had is in my diagram I show two filters, this is because the boards are identical PCB's, I assume there are on issues with having two filters doing the same thing?

Capture (1).JPG
 

ronsimpson

Well-Known Member
Most Helpful Member
I don't see a need to filter the load. The lamp does not care. 50hz, 60hz, 200hz, 130khz the lamp only turns current X voltage into light+heat.
 
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