Re: X10 signals can be TOO strong!

["Alan Vogel" <avogel2@xxxxxxxxxxxxx>]

The inductor in series with the load is there to limit di/dt.  It was
probably required by the FCC to reduce EMI.

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).  This high current pulse must have
coupled back into a high impedance node (either the zero crossing detector,
or the XTAL input pin on the uP).  Either way, the altered timing caused
abnormal conduction angles which showed up as flicker.

Increasing the value of the inductor attenuates the signal enough to
alleviate the symptom.

Alan

"Jeff Volp" <JeffVolp@xxxxxxx> wrote in message
news:ZZlgh.493382$QZ1.96344@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> "Marc_F_Hult" <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote in message
> news:j4p3o2pdau5f4ain79pt1u5dllldhpl6va@xxxxxxxxxx
>> On Thu, 14 Dec 2006 22:56:43 GMT, "Jeff Volp" <JeffVolp@xxxxxxx> wrote in
>> message  <LEkgh.204990$Fi1.128093@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>:
>>
>> >"Marc_F_Hult" <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote in message
>> >news:u7i3o25pmcg42v8cp0co0dn8d75euuk7of@xxxxxxxxxx
>> >>
>> >> Another possibility is saturation of the inductor core at high
> currents.
>> >
>> >I considered that, but there should be virtually no current to saturate
> the
>> >core before the triac switches on.  And even after the triac switches
>> >on,
>> >the inductor would take some time to saturate.
>> >
>> >Jeff
>>
>> Apparently I misunderstand the problem posed,  which I thought included
> the
>> observation you made in the first post, namely:
>>
>> "  All three lamp modules exhibit the same characteristic with
>> that heavy load. None of the modules flicker at all with a dimmed
>> 75W table-lamp load, even at the same receptacle.  The lamp modules
>> are from various eras. "
>>
>> "heavy load" implies high currents.
>
> Yes, but core saturation is an instantaneous phenomenon.  The triac turns
> off at each zero crossing, and current is virtually zero before the triac
> switches on early.  I don't think core saturation can be an issue at that
> instant.
>
> I thought it might be thermal due to the heavy load.  There is some
> evidence
> to support this.  After being on, and then ramped to max dim, the flicker
> is
> more evident for awhile.  So the triac may be more sensitive to premature
> triggering from dV/dt when hot.
>
> Jeff
>
>