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

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

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




On Mon, 01 Oct 2007 14:59:57 GMT, "Jeff Volp" <JeffVolp@xxxxxxx> wrote in
message  <NX7Mi.622516$p47.428228@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>:

various snips

>FYI, the receptacle on the XTB & XTB-II is powered through a L-C-L filter
to
>totally isolate it from the powerline.  That is essential to prevent a
>feedback loop when the XTB or XTB-II is transmitting.  Since it was only
>intended to provide power to a X10 transmitter, the inductors are sized
for
>that current.
>
>Jeff
>
>"Marc_F_Hult" <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote in message
>news:j1t0g39qfhlv9or7oosvfru7i4r6p5kauq@xxxxxxxxxx
>> On Sun, 30 Sep 2007 23:50:04 -0400, Marc_F_Hult

various snips

>> Using an enclosure based on an AC outlet power strip would provide
needed
>> volume for filter/isolator and circuitry and allow the outlets to be
used
>> for different purposes including device testing as discussed above, X-10
>> isolation ( aka "filtering") and even ON-OFF switching. The latter is a
>> common need for controlling (eg) routers and cable/dsl 'modems'. What
>> better place to add an X-10 or INSTEON appliance module for that purpose
>> than immediately adjacent the transmitter on the protected
('firewalled')
>> side of an isolation device (ala Lightolier Compose).
>>
>> The volume made available by using a power strip might allow for
>> incorporation of existing XTB-xx PCBs with little modification -- add-on
>> PCBs providing additional functionality. The extra volume would also
allow
>> for use of a conventional L-C-L-C-L filter ala X-10/Leviton and ACT that
>> could be available through one or more of the AC receptacles on the s