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

["Jeff Volp" <JeffVolp@xxxxxxx>]

Your are correct about transposing pins 6 & 8.  I caught that myself in an
earlier post.

I was thinking along the lines of a diode and cap too.  I have not looked at
that signal myself.  However, if there is always a pulse there, a simple
circuit may not be sufficient.  A pulse late in the cycle fed through a
diode - capacitor network into the transistor would trigger the triac early
in the next cycle.  Or, does that pulse go away completely when the module
is OFF?

Jeff

"isw" <isw@xxxxxxxxxxx> wrote in message
news:isw-A19801.21235504062008@xxxxxxxxxxxxxxxxxxxxxxxxx
> In article <08F1k.18467$102.2347@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
> "Jeff Volp" <JeffVolp@xxxxxxx> wrote:
>
>> IC pin 8 is the output that drives the triac.  The delay of that pulse
>> with
>> respect to powerline zero crossings determine the brightness.
>
> Actually, I think it's pin 6 that drives the triac, via C337 (assuming
> that schematic is correct).
>
>
> A while back, I hacked around in those controllers. Here are some of my
> notes:
>
> "The IC generates a series of pulses, with at least one always present,
> near but before the zero-crossing (i.e. even at "off" the triac is
> triggered, just very late in the half-cycle).
>
> "As the "brighten" signal is sent, the pulse first slides earlier in the
> half-cycle, and then multiple pulses appear, with more and more as full
> on is approached."
>
> What I wanted was a single duration-modulated pulse (wider for brighter,
> of course), and here's how I got it:
>
> 1) Add a signal diode (1N4148) in series with the signal from IC pin 6
> (i.e. cut the trace and hook it between the two points "B" on the
> schematic, cathode towards the transistor)
>
> 2) Change the 2.2 k resistor to 12 k.
>
> 3) Connect a 0.1 mfd. capacitor (ceramic is fine) from the cathode of
> the diode to V-
>
> 4) Change the 330 ohm resistor to 2.2 k
>
> --
>
> As an interesting side-note, connecting the LED of a *high voltage*
> optical isolator in series between the 39 ohm resistor and the collector
> of C337 will give a safely isolated version of that pulse (or the
> original pulse bursts, if that's what you want).
>
> --
>
> Now, to go on to an "on or off" version, here's what I'd try (Note that
> I haven't done it, so I'm just guessing here):
>
> Replace transistor C337 with a very high-beta Darlington transistor
> (that will make for a much narrower "linear zone" between cutoff and
> saturation.
>
> Increase the size of the added 0.1 mfd. capacitor until the base signal
> to C337 is integrated to a DC level (which will rise as the pulse
> widens).
>
> So now, the transistor should move from off to on at some fairly well
> defined pulse width (adding some feedback to make the C337 act like a
> Schmitt trigger will help).
>
> IF this works, it will almost certainly have some "lag" because that cap
> has to charge or discharge before the triac gate signal can change.
>
> It'll surely take some fiddling around to find optimum values for some
> of the added parts (but having that optically-isolated signal to look at
> will make the process a whole lot safer). Maybe a cap from the collector
> of C337 to V- would help. Maybe adding a couple of forward-biased diodes
> or a low-voltage zener in series with C337's base (to increase the
> voltage where it starts to turn on, something the Darlington also does).
> I'd try it both with and without that 1N4148,  too.
>
> CAUTION. WARNING. If anything you do as a result of trying to follow
> these notes gets you injured or dead, or kills your cat, or burns your
> house down, I'll be very sorry, but I will *not* be responsible. I'm a
> professional engineer who has been doing things like this (or worse) for
> well over forty years. You get to decide for yourself whether your level
> of competence is sufficient for you to tackle it.
>
> Isaac