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

[isw <isw@xxxxxxxxxxx>]

In article <RaKdnZxhvNZSZtXVnZ2dnUVZ_o7inZ2d@xxxxxxx>,
 "Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:

> "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?

The level of light is determined by when the leading edge of the
earliest pulse arrives. The other pulses have no effect.

> 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.

The fact that there is a train of pulses is probably an artifact of the
way the IC in the X-10 unit accomplishes phase delay (to retard the
timing of the gate drive).

> > 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?>

I was interested in using X-10 units to remotely control stuff other
than lamps and coffee pots. Getting an optically isolated variable width
pulse was a good starting place. I was not going to use that signal to
drive a triac in amy way.

> > 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 . . .

Yup. It allows the pulses from the IC to pass into a capacitor (for
filtering them to an average DC level), while preventing the internals
of the IC from (possibly) drawing a current that would prevent taht
filtering from taking place.

> > 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?

Yup. In this case, I raised the value to allow a smaller capacitor to be
used to get the time constant I wanted.

> > 3) Connect a 0.1 mfd. capacitor (ceramic is fine) from the cathode of
> > the diode to V-

That's the cap that integrates the pulse train into a DC value

> > 4) Change the 330 ohm resistor to 2.2 k

Simplistically, the 12K resistor determines how fast the cap charges
(but not discharges, because the diode prevents that), while the 2.2K
controls the discharge time.

--snip--

> 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.

True, but if you're careful to make sure it's not plugged in while you
have your fingers in it, there's not much to worry about. There are no
components in there that can store large chunks of energy, for example.

Keep on hacking; that's the way to get better and more confident at it.

Isaac