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



"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."

Does that mean that the pulse width does not vary, but that the level of the
light is determined by how many pulses of a fixed width are received during
an AC cycle?  I assume that would me they are obviously much shorter in
duration than 1/2 the AC cycle.  It sounds like they are "rechopping" the
pulse into smaller pulses and that they aggregate to give the desired end
level.  I am not explaining that well, I fear.   It seems like there are two
pulse aggregations, a wheel within a wheel Ixion sort of thing.

> What I wanted was a single duration-modulated pulse (wider for brighter,
> of course), and here's how I got it:

Why did you want to do this?  What is the benefit of going to pulse width
from their system of number of pulses per cycle?>

> 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)

Bear with someone with no experience but at least a little interest in the
subject.  That's a high speed switching diode, AFAICT, and used in series it
will pass current in only one direction . . .

> 2) Change the 2.2 k resistor to 12 k.

You would normally change a resistor value to change a time value in a
dependent RC circuit or to protect some other component from drawing too
much current, correct?

> 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

OK, I'm lost although after I post this I will probably find out I was lost
far early in the process.  I'll stop here even though I have some more
questions about your other modification suggestions because I'm a NOT a
professional engineer who has been doing things like this (or worse) for
well over forty years.  I also know that my level of competence is NOT
sufficient for me to tackle it without lots and lots more discussion and
education.

I've already discovered that X-10 gear has naked 110VAC running all over the
circuit boards, making tinkering by noobs like me a lot more dicey than
trying to solder remote contacts to a coin cell powered keychain controller
circuit board.  The only way that power source could hurt you is if you ate
it or someone shot it at you with a slingshot.  More my kind of "futzing."
With the lamp module apart in my hands I have to really marvel at all the
engineering that went into them and how well that simple circuitry has
endured.

--
Bobby G.






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