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Author Topic: How does an end device cause interference?  (Read 3295 times)

tsttm

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How does an end device cause interference?
« on: January 07, 2009, 08:46:36 PM »

Hi all,

I've got a number of AM466 modules & one LM465 dimmable module. The moment I plug my TV to an AM466 module, that module along with a few others cease to function. It happens regardless of whether the TV is on or off. The moment i unplug the TV (even if off), the modules can be triggered.

Also, I've noticed that when this occurs, only the modules that have lights connected to them cease to function. There are two AM466 modules with portable heaters connected that continue to function.

The TV is old- 1970s, turn dials to change channels.

It took me a while to figure this out, but it is reproducible.

Any explanation why this is happening? Anything i can do to fix it?

And it seems to affect modules in different rooms & outlets..not just the outlet the TV is connected to.

thanks.
« Last Edit: January 07, 2009, 08:49:52 PM by tsttm »
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JeffVolp

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Re: How does an end device cause interference?
« Reply #1 on: January 07, 2009, 11:43:19 PM »

That vintage TV would not have a switching supply, but it could have filter capacitors directly across its power input.  Those would attenuate the X10 signal even if the TV is not switched on.

Jeff
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tsttm

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Re: How does an end device cause interference?
« Reply #2 on: January 08, 2009, 01:45:38 AM »

ok thanks. I had some trouble understanding everything you said..but i take it that there is a logical explanation to it & there probably isn't a simple solution for it.

As an extra note- if the module is off & i plug the tv, i can trigger it on. But after that, it won't do anything else (with tv on or off).

That's disappointing, i was hoping to be able to turn the tv on & off using an x10 remote.
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Brian H

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Re: How does an end device cause interference?
« Reply #3 on: January 08, 2009, 06:47:41 AM »

When off the TV does is not connected to the power line as the switch in the appliance module is off.
When you turn it on the TV  effects the X10 signals. You maybe able to add an X10 type filter between the appliance module and the TV. That may help.
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tsttm

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Re: How does an end device cause interference?
« Reply #4 on: January 08, 2009, 01:38:05 PM »

i see. thanks.

Does it make sense that after i've turned the tv on, that once i turn it off (& still plugged in) it still causes interference?

And do you know specifically what/which filter i should be looking for?

thanks.
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JeffVolp

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Re: How does an end device cause interference?
« Reply #5 on: January 08, 2009, 01:55:49 PM »

There are two types of X10 "interference".  One is caused by "signal suckers" that reduce the signal level to the point that devices no longer operate.  The other is from "noise generators" that corrupt the data patterns, and prevent receiving modules from properly decoding signals.  Signal suckers do not have to be switched on to cause a problem because they most likely have bypass capacitors directly where the AC power comes into the unit.  Noise generators must be switched on to cause problems.  However, the little switching supplies we call "wall warts" can cause incredible noise when they are just plugged in.

What you report is exactly what would happen from a signal sucker.  The fix is to install a XPPF filter between the appliance module and your TV set.

Jeff
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tsttm

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Re: How does an end device cause interference?
« Reply #6 on: January 08, 2009, 09:54:19 PM »

Great! thanks for the nice explanation. I will look into it.
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