On May 6, 2009 at 01:18, Jim Fouch in Southern California said...
Sounds like another example of X-10's value engineering. They don't do much engineering and the customer does not get much value.
I am far from an EE, but there are certainly ways to switch power without using a relay that can be heard in the next room.
X-10 devices and the PC switch mode power supply
are neck-and-neck for the award in cost reduction
to the point of pain while apparently completing UL testing
without generating smoke.
But to be fair the relay-based modules were designed
to function with a mechanically latching relay such that
the power state of the load persists across module
power loss. A conventional latching relay with equivalent
current carrying capacity would likely itself exceed the
cost of an X-10 module.
While non-volatile storage is pretty common these days
in a ~$1 uC it wasn't back when X-10 was initially
developed. Even if that wasn't an issue you wouldn't
really want a 50-cent, 60Hz energized relay to be
buzzing in the wall while the load was being powered.
Also an energy and heat savings is realized by use of
a latching mechanism. The click upon latch transitions
can be annoying but it still seems to be a reasonable
compromise given the set of design constraints.
