Re: Preventing Random X-10 Code interference...

[nobody@xxxxxxxxxxxx (Dave Houston)]

"Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:

>Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message

[snip]

>> Most, if not all, X-10 _brand_ PLC receivers (i.e. switches, lamp and
>> appliance modules) count the number of cycles in the "acceptance window"
>> between ZC+250µS and ZC+900µS.
>
>Ah ha!  THAT'S what the .2mS to .9mS is looking at.  I assume that if there
>a voltage above a certain range in that window, it means the X-10 signal is
>being "stepped on."  Is that correct?  What are they looking at the .5mV
>range?  It that where the 120kHz X-10 burst is optimally supposed to be
>found?

X-10 devices vary in sensitivity. Some need 100mV, others respond to less.
0.5mV is probably much lower than any can distinguish. From memory (which
may be foggy) I think most of the studies (from that now gone web site) saw
20-50mV backgound noise.

>> Noise that is greater than ~80kHz can cause a receiver to think it's
>> seeing X-10 carrier while noise lower than ~80kHz
>> might mask the carrier. So far, nobody has determined the
>>  upper/lower frequency/amplitude limits although
>> Dan Lanciani has documented a case where a weak +200kHz
>> was jamming X-10 signals.
>
>The documentation says they are looking for noise greater than 110kHz.  Is
>it reasonable to conclude that since their lower range is 10kHz lower than
>the target value that their upper range might be 10kHz over, namely 130kHz?
>Or would it be just as likely that they are looking well above 120kHz?

There's no way to guess what range they look at. X-10 says 48 cycles within
the "acceptance window" make a 1. That a very low level ~200kHz noise was
blocking a receiver is evidence that the receiver probably does not try to
calculate the frequency of any perceived signal so any frequency that will
result in 48 or more counts within the 0.65 window might be seen as a 1.
74kHz and higher will give 48 or more counts but even lower frequencies
might mask the presence of 120kHz.


>I've seen some other interesting readings, BTW.  Sometimes the bathroom
>light (on a Hawkeye) command reads in lower case, which the documentation
>says "one good start code and one good message block (of the two identical
>ones) has been received ."  Does that mean the code was mangled but not
>badly enough to prohibit firing?  Would this explain why people report a
>slight delay in when the bathroom light fires?

It may mean that there was a powerline collision but one transmitter backed
off allowing the second copy of the other to go through. Most X-10 receivers
will respond to a single copy of the code.