Re: I think they've done it again.

[Marc F Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On Fri, 30 Jun 2006 13:30:30 GMT, nobody@xxxxxxxxxxxx (Dave Houston) wrote in
message  <44a522ab.86149203@xxxxxxxxxxxxx>:

>A consensus seems to be forming among those seeing the flickering that it
>only occurs when a switch has more than ~250W (total) connected and is
>dimmed to 50% or less.
>

This is consistent with the problem being saturation of the L3 inductor in
INSTEON dimmers as I noted earlier and with the unofficially proposed fix by
SmartHome to add series inductance. (I measured L3 inductance as18uH at
minimal load and 120 and 1000hz ).

In other words, a simple fix for a common problem to many wall-mounted
dimmers from many manufacturers over the years.

Typical wall- mounted dimmers for residential use have space constraints that
typically preclude the large chokes found in architectural and theatrical
lighting panels.

By designing a physically small dimmer, INSTEON made their dimmers useable in
widely-used small switch boxes that made installation of other, larger dimmer
-- including many/most X-10 models -- impractical.  This is/was a good
initial trade-off in my opinion -- especially if they promptly identify the
problem and supply the fix for the (apparently) small minority of cases where
this (apparently minor?) problem arises.

Someone that actually has the flickering problem could broadly assess the
proposed fix by adding a pair of inductors (in parallel with each other for
adequate current capacity and to minimize likelihood of saturation) from an
X-10 WS-467 (I measured ~44uH each) in series with the red load lead of an
INSTEON dimmer to raise the total nominal inductance to ~40 uH.

If that solves the problem, a permanent solution that many local authorities
would likely consider compliant with the National Electrical Code would be to
install a RU- (UL component) rated toroid core with conventional 14awg
insulated wire looped through it. The number of turns needed for a given
inductance depends in large part on the composition of the core.

One can calculate the resulting inductance for various toroid compositions
from the data at rfcafe.com, eg:

http://www.rfcafe.com/references/electrical/toriod.htm

(yes, the url spells "toroid" wrong ;-)

There are numerous sources of toroids on the primary and surplus market.

I have a large supply of red+brown T-36 toroids from www.allelectroninc.com
but they seem to be out of stock. Adding 37 turns enameled 15AWG wire yields
~21 uH which would double the nominal inductance of the INSTEON L3 choke.
(This is not an optimum core material for the application.)

... Marc
Marc_F_Hult
www.ECOntrol.org