Re: Making an X-10 lamp module immune to dimming

[isw <isw@xxxxxxxxxxx>]

In article <Bu2dnWVN2JYNmtTVnZ2dnUVZ_jydnZ2d@xxxxxxx>,
 "Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:

> "Dan Lanciani" <ddl@danlan.*com> wrote in message
> news:1348343@xxxxxxxxxxxxxxxxxxxxxx
> > In article <upJ1k.19034$102.546@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
> JeffVolp@xxxxxxx (Jeff Volp) writes:
> > | "Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote in message
> > | news:hOWdnZPUEpdFotrVnZ2dnUVZ_jWdnZ2d@xxxxxxxxxx
> > |
> > | > I believe the first test will just be to simply disconnect pin 8 from
> the
> > | > control line.  Hopefully it will be easy to rebridge if that turns out
> not
> > | > to work.  Also, hopefully, it won't incinerate itself after snipping
> that
> > | > line.  I guess I can trot out the old 20mm ammo box I have for
> containment
> > | > of explosive experiments - well, maybe just leave it on a fireproof
> > | > surface
> > | > to test . . .
> > |
> > | Whoops, that was a typo before.  Pin 8 is used for the local control.
> > | Snipping that will only disable local control.  Pin 6 drives the triac.
> > | That line is essential.  If snipped there will be no on/off control at
> all.
> > | The dimming phase control is inside the IC.
> > |
> > | It might be possible to extend the pulse coming out of the IC so that if
> > | there is ANY pulse at all, the transistor will remain on through the
> > | beginning of the next cycle so the unit will switch on right after the
> zero
> > | crossing.
> >
> > How much current does the triac's gate draw?  I'd be worried that the
> > module's power supply can't handle leaving the transistor on for long.
> > These supplies are always by design near their limit.
> >
> > The $1 modification avoids the power problem by getting the gate drive
> > directly from the line/load.  The author appears to know what he is doing
> > so I think if there were a simpler way he would have found it.  And it's
> > already pretty simple...
>
> I assume that means that his optoisolator drives the triac gate from the
> powerline itself, and not modified in any way through the module's IC.  I
> also assume that by getting the triggering information from the powerline,
> the unit is now, as I wanted in the first place, quite "blind" to dim or
> brighten commands.
>
> The author of the mod in question wrote:
>
> |   "When the zero-crossing circuit detects a zero crossing
> |   voltage and the LED is illuminated, the gate on the triac in the
> |   optoisolator is triggered with the same phase as the phase of the line
> |   voltage. This line phase current is then used as the gate trigger to the
> |   alternistor."
>
> If I understand this correctly, it doesn't matter what the width of the
> pulses coming out of the X-10 IC are.  Nor does it matter how many small
> pulse occur within each half cycle.

That is correct.

> When the ON signal arrives at the
> module, current starts flowing because the current used to power the gate
> circuit is activated.

As successive "brighten" commands are sent, the leading edge of the
first pulse moves to occur earlier in the half cycle, so the triac is
turned on for progressively greater percentages of time -- and the lamp
grows brighter.

>  However, it no longer gets any information about the
> bright or dim levels because the triac is "beating" to the ZC data that now
> comes from the optoisolator/AC powerline instead and not the IC output.  Is
> that correct?

X-10 commands are sent right at zero crossings, so the triacs in all the
modules are "off".

> I assume what turns the module off is an OFF command that
> interrupts the output from the optoisolator so that there's no longer any
> pulses being sent.  I thought Isaac said there was always a pulse going to
> the triac, even when the unit was off.

I did. But that pulse occurs so late in the half cycle that essentially
no energy gets to the lamp -- just a tiny "blip".

Isaac