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

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Dan Lanciani" <ddl@danlan.*com> wrote in message
news:1348345@xxxxxxxxxxxxxxxxxxxxxx
> In article <XOOdnWtOoK-abdXVnZ2dnUVZ_jidnZ2d@xxxxxxx>,
ROBERT_GREEN1963@xxxxxxxxx (Robert Green) writes:
>
> | You're correct.  At first glance I thought he was talking about putting
a
> | solid state relay inside an appliance module to eliminate the clack.
After
> | your comment, I went and tested the modules I have and while the wall
> | switches respond to All Lights ON/OFF, the lamp modules don't.  They
only
> | respond to All Lights ON.
>
> Although All Lights Off was part of the original command set it was not
> implemented by X10 until pretty late in the game.  I don't think most of
> my cheap wall switches respond to it either.  The relay wall switches have
> responded to it for a long time, though; possibly since their
introduction.

It's a mix here.  When I get a moment I'll try to figure out which lights do
and which do not.  What's clear is a lot more units go on than go off when
using the All Lights On and Off commands.

> | Bummer.  Well, that makes the project somewhat
> | less attractive.  At least the All Lights ON command is more useful to
me
> | than All Lights Off would be.  How is that the X-10 security system
flashes
> | the house lights?
>
> It alternates All Lights On with All Units Off.

> | My whole premise
> | was based on a misunderstanding of how triacs work.  I thought they were
> | merely high speed electronic relays.
>
> They are to a first approximation, but there are a lot of details that
> can trip you up.

Indeed.  I'm tripping all over the place.

> | It's become apparent that the triac can only do its magic when synched
to
> | the zero crossing.
>
> You can turn a triac on any time, but unless you are dimming it is usually
> best to turn it on near a zero crossing.  You can't turn it off unless
> there is no current flowing.

OK - that's a point I was missing and why I thought they had to be synched
to the ZC.

> | Perhaps you could be kind enough to explain what would happen if the
line to
> | the triac gate was high all the time.  Would it conduct only on the
first
> | half cycle, or not at all or would the magic smoke escape?  (-:
>
> Having the gate "high" is probably not the best way to think of it.  A
> triac is triggered by current flowing between gate and MT1.  There are
> two possible directions for that current and two possible polarities for
> the voltage between MT1 and MT2.  Together this gives you four
combinations
> which are commonly referred to as quadrants of operation.  (If you google
> the terms you will find pictures.)  Most garden variety triacs can be
> triggered in any quadrant; however, it may require more current to trigger
> in some quadrants than in others.  Some triacs are designed to be
triggerable
> in only three of the four quadrants to reduce certain kinds of false
> retriggering.  There may be more exotic variations.

I'm having a hard enough time with the garden variety triac.

> Note that the requirement for the trigger current to flow between gate and
> MT1 is independent of the quadrants.  I've read claims that some triacs
> are symmetrical with respect to MT1 and MT2 but I wouldn't want to count
> on it.
>
> So, assuming you have satisfied the triggering polarity requirements (if
> any) and you drive current between the gate and MT1 all the time, the
> triac will conduct all the time.

I am still a bit confused about one thing.  When the AC waveform crosses
over, does current through the device drop to zero and the triac stops
conducting simply because there's no current at that point on the sine wave?
Does the triac have to be "retriggered" at that point and after each
subsequent recrossing or does it start firing again as soon as current
begins to flow again in the opposite direction?

I have another question.  When taking apart the lamp module, I noticed that
the tiny triac has an enormous aluminum heat sink.  What process generates
the high heat developed?  I know it can get pretty hot from someone
accidentally plugging a 1400W hairdryer into one.  It ran the hairdryer,
even as the case melted around all the components.  )=:

FWIW, there's an interesting looking three wheeled car called the Triac:

http://www.inhabitat.com/2008/05/20/transportation-tuesday-the-80mph-triac-g
oes-on-sale/

"The TRIAC is essentially a large, covered trike. The 20kw electric motor
can achieve a very reasonable 80mph, and will take you on travels up to 100
miles on any given charge. It takes about 6 hours for its lithium-ion
battery to recharge fully and, as with most electric vehicles, it comes with
a regenerative braking system. The package for all of this three-wheeled fun
runs about $20,000 dollars."

And the even more interesting stackable car from MIT:


--
Bobby G.