Re: Water heater eating X-10 signal

["Jeff Volp" <JeffVolp@xxxxxxx>]

"Dan Lanciani" <ddl@danlan.*com> wrote in message
news:1338642@xxxxxxxxxxxxxxxxxxxxxx
> In article <9bDVh.325907$5j1.101315@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
> JeffVolp@xxxxxxx (Jeff Volp) writes:
>
> Often when referring to "signal suckers" people are talking about local
> loads that effectively form a voltage divider in combination with the
> line back to the transmitter (repeater, whatever).  Usually the
> transmitter
> itself is not noticeably loaded.  Under the simplified model we discussed
> a
> 240V load on a dedicated circuit would pretty much have to impair the
> signal at the transmitter to cause a problem.

That is really the only way signal suckers can effect other circuits on that
phase.

> | I would expect
> | some decrease in signal level at the repeater when confronted with such
> a
> | load, especially if that repeater has a transformerless power supply.
>
> So you are thinking that even though the repeater's driver might have an
> impedance in the fractional ohms there isn't enough power available
> from the supply to maintain voltage?  That might be reasonably easy to
> instrument directly with a meter on the supply rail of my spare/repaired
> CR230 (which uses the typical reactive power supply).

Since the transformerless power supply cannot provide that much energy, I
don't think the output impedance is in the fractional ohm region.

> | By multi-wire branch circuits, you are referring to 120V circuits fed
> off
> | both legs with a common neutral.
>
> Yes, also knows as Edison circuits.
>
> | Yes, the X10 signals would sum on that
> | common.  I suppose it would be possible that each leg might have several
> X10
> | loads,
>
> It's not just X10 loads; it's any loads.  And it doesn't take more than
> one per leg, though obviously for this to be meaningful in the case of
> one load per leg at least one load has to be interested in hearing X10.

I thought we were discussing summing of in-phase X10 signals on the neutral
reducing the end-point signal strength.  That would only be true if there
were multiple X10 loads (or signal suckers) on both legs of that circuit.

> | but I think that is reaching pretty hard to find something that might
> | have a problem.
>
> I'm not looking for a problem; I'm looking for pros of each approach.  I
> probably should not have phrased it in terms of giving something up.  So
> far, out-of-phase drive appears to offer 240V module compatibility and
> the ability to take advantage of shared neutral configurations in much
> the same way the power distribution system itself does.  In-phase drive
> allows you to use a smaller power supply and/or higher impedance drivers
> in the face of 240V loads and may offer better compatibility with in-phase
> couplers.

The XTB and XTB-II do not use a smaller supply or higher impedance drivers.
They both use a 6-watt transformer supply.  The supply is unregulated, and
drops about 25% during transmission.  The TW523 spec says it will deliver
5Vpp across a 5 ohm load.  On the bench I measured the XTB-II delivering
30Vpp across a 5 ohm resistive load.  That's actually about 35 times the
power of a normal X10 transmitter.  The output impedance looks like about .5
ohm.

> These are all pretty minor features, and I'm not convinced that the
> problem
> you fear from 240V loads is any more an issue in real life than the
> ability
> to take advantage of multiwire branch circuits.  I brought it up only
> because the original poster's fact pattern was unusual.  At least to me
> the
> optimal choice is far from obvious and I would still be inclined to make
> it
> an option if I were building a repeater product.
>
> | Actually, here I saw the combined loads have a significant effect on the
> | XTB-II output.  The XTB-II will output over 40Vpp with no load.  I
> measured
> | one leg at 25Vpp, and the other leg at 30Vpp when it was connected to
> the
> | panel.
>
> Was this due to the output impedance of your drivers or a sagging power
> supply?

Since a common power stage drives both output coupling networks, it is due
to the fractional ohm impedance across the coupling networks.  Note that the
higher level was on our "X10 phase" and the lower level was on the phase
used to power "unfriendly" loads.

The voltages above were measured at the panel.  Signal levels decrease as
they propogate away from the panel due to the combined effect of line
inductance and attenuation from distributed loads.

Jeff