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Re: 120 khz X-10 / INSTEON 'filters' ; was Re: X10 Interference from the Cellet Cellphone Charger



Several X10 filters are bandstop, including the little Leviton 6287.  You
can make a pretty efficient 120KHz trap with a small inductor and capacitor.
However, a low-pass needs much larger components to have the same
attenuation at 120KHz.  The Leviton 6288 and XPPF are low-pass with an
initial break at 13Khz.  As you know, they are rated 5A, but run warm (and
stink) when pushed that hard.  FYI, the AF120 schematic I have shows the
inductors are 7.2uH, and all caps are 0.22uF.  The fuse may be needed for UL
approval if the center cap is not rated for across-line applications.
Interestingly, the center cap on the little 6287 is listed as 1.0uF.

Since these filters were designed as companions for X10 modules, they
probably take advantage of the bandpass characteristics of the modules
themselves.  The module's input network will attenuate out-of-band signals,
so the in-line filters only have to block in-band noise.

Jeff

"Marc_F_Hult" <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:4243g31r2rvv6mg43a5g3uli7lji7jsrid@xxxxxxxxxx
>
>I recently added what I thought were going to be "X-10 filters" to the
> relay controlled air-gap disconnect and filter unit that I use to protect
> and isolate (i.e., "filter") X-10 and INSTEON ~120khz signals from the AC
> circuit used for audio and instrumentation.
>
> These are X-10 PR brand , model " XPF 20-amp Wired in-Filter " with a
> documentation sheet dated 10/98.
>
> To my surprise, they are  band-stop, rather than low-pass, filters.
>
> The low-pass part of the design is  L-C-L-C-L with 7.7 uH ferrite stick
> inductors (measured at 1 kHz) in series and 1.0uF capacitors to neutral.
> But the three inductors are each bypassed with 0.22uF capacitors. My need
> and intention is to filter high frequencies from the power line so I
> removed them.
>
> Interestingly, ACT's popular AF120 filter uses an L-C-L configuration with
> 8.0 ufd toroidal inductors, 2.2uF cap that presumably has a lower cutoff
> frequency and lower slope. It also has 0.22uf  bypass caps on each
> inductor. There is a 1-amp fast-blow AGC fuse in series with the 2.2uF
> capacitor's signal path to neutral. The AF120 is marked as "No User
> Serviceable Parts Inside  Tampering Voids Warranty" on the sticker/label
> that serves to seal the case. So if the internal fuse were to blow,
> filtering performance would suffer but the user would have no indication
> of
> decreased attenuation. (The AF120 also has a user-accessible 15amp fuse in
> series with the load but that's not what I am referring to.)
>
> I haven't done a SPICE model or other calculation of these devices/
> schematics in part because I haven't located  the reference that I had on
> measured/estimated typical impedances of household AC networks/circuits.
>
> My question is why are these filters bandstop and not lowpass? Is this for
> circuit protection as implied by AF120's internal fuse. Or to purposely
> transmit X-10 across the filters? Or ?
>
> ... Marc
> Marc_F_Hult
> www.ECOntrol.org




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