RE: RE: STEP DOWN

["Kevin Hawkins" <lists@xxxxxxx>]

Ahh.. that is because you are using an autotransformer - in this
arrangement
there is not a separate primary and secondary winding and therefore the X10
higher frequency signal is already present on the winding in question. The
110V mains and the 240V mains are not isolated (floating) from each other
and have a shared neutral effectively.



Kevin



-----Original Message-----
From: Martin Greenwood [mailto:martin@xxxxxxx]
Sent: 29 July 2003 14:52
To: ukha_d@xxxxxxx
Subject: [ukha_d] RE: STEP DOWN



At 14:11 29/07/2003 +0100, Kevin Hawkins wrote:
>John - you need to couple the primary and secondary with a suitable
>capacitor such that the X10 signals can get from one side of the
transformer
>to the other. I can't remember off hand the value of the capacitor I
used
>but I could probably find out. It was just as stated on the 240V/110V
>conversion site that everyone use. (Dr Bennotto or something).  The
>capacitors must be suitably voltage rated and of course this involves
>actually tapping across the 240V/110V windings so you need to be very
>careful. In fact I think I used two capacitors in series as an added
safety
>step when I did it just in case one went short circuit. (double value).
The
>devices must be deriving their timing from the mains cycles too (most
do as
>they usually get this from zero crossing points) or you get a 50Hz / 60
Hz
>incompatibility. This is a bit of a kludge but it does work.

Maybe in theory, but I found it works fine without any coupling!!
I have various US 110V lights that run on an unmodified step-down
transformer using a 110V X10 dimmer. (The X10 transmitter is on the 240V
side)

This is the transformer I used, (there is a family of 100-600W versions)

Autotransformer, SAT 300
RS Stock No.   310-1162
Manufacturer   BLOCK

Hope this helps,

Martin





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