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

[isw <isw@xxxxxxxxxxx>]

In article <1348343@xxxxxxxxxxxxxxxxxxx>,
 ddl@danlan.*com (Dan Lanciani) wrote:

> 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.

As I said, and according to my notes, there is *always* at least one
pulse there, even if the unit is fully dimmed.

> 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.

There's already a current limiting resistor there (39 ohms). One could
try increasing it, but if the drive current gets too low, the triac may
not trigger completely, and could dissipate more heat than would be a
good idea. Based on my memory of the pulse train that drives the triac,
I'd say that with the circuit I suggested, the integrated gate current
is no more than two or three times what it is in the original circuit.

Isaac