Xanura: Voodoo enginering

[MindBender]

Here's the phenomenon: Under <i>some</i> circumstances, the SAIX will fail to respond to their electrical input. When the button is pushed (or the switch is flipped) the module doesn't turn the load on or off. When the module is power-cycled, it works for one or two switches, but after that it's stuck again. Other units besides the SAIX and units from OEM brands as Marmitek may suffer from this too. Personally I think this behavior is unacceptable, but opinions may differ and it's probably the price to pay as an 'early' adopter or modern technology.

Two of my modules suffered from this problem; The lights in the garage and a floodlight in living room. I discovered the problem in the garage first and I had to open the water-proof fixtures an remove the lamps to get the lights off. Secondly the floodlight in the living room refused to go out. In that case the module is build into the standing fixture itself so I could easily unplug the lamp and therefore also the unit. I quickly discovered that power cycling the unit gave me a couple of switches, but after that the unit refused again. I don't know if the units responded to X10 signals because I don't have any software in place yet. And I wanted to go to bed.

Tonight I replaced the unit in the garage by a new replacement unit. But to my surprise I got the same behavior. So I took it out again, measured everything, tested the switch and tried again. No avail. So I removed the unit, attached a loose chord and a loose switch to it and tried it in an outlet. The unit worked fine. So I tried the 'defective' unit that way. It also worked fine. So again I measured and checked everything, and reinstalled the unit. Again not working. Then I saw a correlation with the floodlight. I took the lamp and tried it in another outlet, in the kitchen. It worked perfectly. Back in its original outlet it failed. Hm, its geographically close to the garage, so there may be something wrong with the power... But all other units on the electricity group worked fine. And the voltage was 228 volts, so nothing wrong there too. I couldn't image that other devices connected to the mains could influence Xanura modules in a way that they'd no longer respond this way. But when I was about the start unplugging things I noticed a soft hum from the speaker of my Voip Ethernet telephone (Grandstream GPX2000). So I unplugged its little wall ward first and the floodlight immediately responded again, just like the light in the garage. When I plugged it back it, both units stopped responding again. When leaving the wall ward in the outlet and disconnecting the phone everything worked too and it even outputted a nice 12 volt. But when reconnecting the phone, the phone started humming again and the units stopped responding.

I was just thinking about wheeling my Tektronix DSO upstairs to treat you people with a couple of screen shots when the wall wart made the phones lights go out. I was also thinking about sending the wall wart to Eaton for product improvement, but that’s of no use now. It was a small switch mode power supply, so it could have cause all kinds of interferences, but I’ve had it for over a year and it’s been in the same outlet all the time. The hum from the phone sounded more like a 50Hz hum to me and the phone was operating normally. I guess we’ll never know.

The bottom line is: Switch mode power supplies, including the ones often found in wall warts, can disturb the functioning of X10 modules in a way that they won’t even respond to switched connected to them. I my opinion this makes the system highly susceptible for strange behavior.

[Niknik]

At least you found the cause.
There always have been a lot of report of those strange "issues" caused by switching power supplies (and other devices that might cause "noise" in the powerlines), but we would hope newer modules with better SNR would make it a lot less frequent. Guess that's not the case...
(Though it probably is also related with the power supply "quality")

[joevpt]

X10/A10 works by sending signals on the mains. Switched mode power supplies which are not correctly filtered will put localised noise on the mains which may cause problems.

There are many filters available to fix these poor power supplies.

I think for any installation, you need to test X10 with all devices switched on and any devices which absorb or upset the X10 protocol should be fitted with a filter. This is easy to do and gives trouble free operation.