Ishaan Dalal wrote:
> Does anybody know of a datasheet, etc., that provides a coherent
> explanation of interfacing low-voltage DC to the power line? Something
> X10 specific would be icing on the cake.
>
> Also, what would be the best option to power the IR LED/receiver and
> PIC
> *without* using a transformer from AC?

I don't know much about X10, but I assume it uses a carrier that has a much
higher frequency than the 60Hz power frequency.  If so, it should be easy to
capacitively couple the carrier signal into the AC line.

Many years ago in college I built an AM transmitter that injected its signal
onto the AC line instead of using an antenna.  Separating the 1MHz carrier
from the 60Hz power voltage was mostly done with a 200V cap.  Due to the
large ratio between 1MHz and 60Hz, separating the two was trivial.

By the way, injecting about 3W of AM into the AC line works very well to
make a radio station within a building, in this case a college dorm with
about 200 students living in it.  The transmission could be picked up with a
portable radio in a courtyard about 20m from the nearest part of the
building.  (We also discovered that interesting things happen to the city
water supply when everyone in the dorm flushes their toilet at the same
time.  Radio is a great way to coordinate mischief.)


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