Re: X10 signals can be TOO strong!

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On Fri, 15 Dec 2006 13:53:03 GMT, "Alan Vogel" <avogel2@xxxxxxxxxxxxx> wrote
in message  <3Nxgh.2688$yC5.836@xxxxxxxxxxxxxxxxxxxxxxxxxx>:

>
>"Marc_F_Hult" <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote in message
>news:oq74o2t9ac60teh956n96lah30ej7l165d@xxxxxxxxxx
>> On Fri, 15 Dec 2006 03:18:50 GMT, "Alan Vogel" <avogel2@xxxxxxxxxxxxx>
>> wrote in
>> message  <uuogh.5921$Gr2.922@xxxxxxxxxxxxxxxxxxxxxxxxxx>:
>>
>>>The inductor in series with the load is there to limit di/dt.  It was
>>>probably required by the FCC to reduce EMI.
>>
>> CE has EMI standards but US seem non-existent. Consumer tolerance for
>> dimmer
>> and filament hum and buzz may be the controlling factor. Whatever the
>> reason,
>> the snubber circuit is an LRC  network even if the inductance is entirely
>> owing
>> to the load and not part of the device as is the case with a built-in
>> choke.
>
>Because the Insteon dimmer uses a uP, and its frequency is greater than
>9kHz, FCC part 15 regulations will have to be met.

Some confusion here. We were talking about different devices. I was responding
to Jeff's post which involved x-10 lamp modules from various eras. I doubt
that early x-10 modules (pre-1991) met current FCC part 15. You were referring
to INSTEON where it does pertain.

>>>I think this is all starting to make sense.  The highest di/dt transition
>>>is when there is a heavy load and the conduction angle for the triac is
~4.16
>>>ms in from the zero crossing (50% dim).
>>
>> 4.16 ms is indeed 50% into the half-cycle, and so is peak voltage, and,
>> assuming the filament is as at constant temperature during any given cycle
>> and
>> thus R ~ constant, is also peak current. But at the peak,  di/dt = 0 , not
>> "highest".  Or by "di/dt transition" did you mean the second derivative?
>
>For dimming, the triac is abrubtly turned on mid-cycle, so di/dt is high.
>The triac turns off at the next zero crossing.  The uP repeats this process
>for a set dim level.

Right. I think I understand what you mean now, namely, that the _longest_
period of _time_ from ON to 0 volts occurs at  Vpeak =  Ipeak = 4.16 ms past
zero-xing. I was referring to the fact that di/dt during turn on -- the
derivative, 'instantaneous' -- is similar regardless of what part of the cycle
(delay in ms) the TRIAC turns on.  And it is the slew rate which is the
instantaneous change in voltage wrt t and so is dv/dt. (leastwise that's how
I've construed for years ;-)

>> (And FWIW, 4.16 ms is about 71% of RMS voltage and 33% of luminous
>> intensity  for typical incandescent lamp and not "50% dim" by those
>> measures of  dimming.)
>
>Yes, this is the RMS value.  But 33% dim as measured by RMS may appear to >be
brighter to the viewer.  Doesn't the eye work more as a peak detector >than an
RMS detector?  Isn't this why multiplexed LED displays appear >brighter than
they otherwise should?

"Luminous intensity" is physical property and is not measured with respect to
human perception. The cited 33% (of the undimmed output) is a calculated value
based on typical incandescent lamp properties. See my spreadsheet at
http://www.econtrol.org/dimmers/TRIACDimmerCalcs_MFHult.pdf  for relevant
equations, tables and graphs.

[snip]

>>>Increasing the value of the inductor attenuates the signal enough to
>>>alleviate the symptom.
>>
>> This the fix I mentioned that SmartLabs put in place for INSTEON .
>
>Yes.  This is the subject that I was talking about.

And I was coming _back_ to the topic you were already on -- we were out of
phase as it were ;-)

... Marc
Marc_F_Hult
www.ECOntrol.org