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



In article <ldmdnSp8M_e4q9DVnZ2dnUVZ_g2dnZ2d@xxxxxxx>, ROBERT_GREEN1963@xxxxxxxxx (Robert Green) writes:
| "Dan Lanciani" <ddl@danlan.*com> wrote in message
| news:1348348@xxxxxxxxxxxxxxxxxxxxxx
| > In article <VtCdnaFcKJIC0NfVnZ2dnUVZ_rPinZ2d@xxxxxxx>,
| ROBERT_GREEN1963@xxxxxxxxx (Robert Green) writes:
| >
| > | As I looked at the mod schematic, I realized that the switching was
| > | occurring without any polarity reversal of the trigger.
| >
| > No, you were right the first time.  The direction of the gate current is
| > reversing in step with the line, keeping the triggering in the more
| sensitive
| > quadrants.
|
| I'm going to have to trace this out through the schematic.  Do you know of
| any tools that do a "schematic debugging" the way some software debugger
| tools work where each line of code executes in a window that displays
| variable states, etc?

No, but some of the simulators might be close.

| I've heard designers talk about simulators but I
| don't know what they use or how it works.  I would like to see something
| that would tell me what a voltmeter/scope/logic probe would see at a
| particular point in the circuit for each state change.  Not sure I explained
| that well . . . Anyway, so you're saying if I were to put a probe on that
| line going to the triac gate, it would be DC pulse; positive when applied to
| the first half of the AC cycle and then negative for the second half?

It would be a more complicated waveform, but more-or-less yes (and for
some definition of "first" and "second") for the modified module.

| > The unmodified module uses its own DC supply to drive the gate
| > current independent of the line polarity.  Using the more sensitive
| quadrants
| > (or, in general, using two quadrants with the same sensitivity) keeps the
| > triggering times as symmetrical as possible minimizing the DC component in
| > the output.
|
| I'm confused again.  If I applied the probe on the unmodified mod, would I
| only see positive pulses?

The module uses a negative supply, so only negative.  Keep in mind that
the zero-volt reference of the module is the hot side of the line, so you
have to be careful with such measurements.

| I think I have a bit of reading to do but I am thinking the lamp module is a
| small enough device to trace out thoroughly.

It's small, but it's also an exercise in clever cost reduction.  The
aforementioned use of the hot side of the line as a logic zero-volt
reference lets them drive the triac easily without isolation, but it
can be confusing and dangerous if you don't understand what is going
on.  It would not be my first choice to learn circuit analysis...

				Dan Lanciani
				ddl@danlan.*com


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