"Bill Jeffrey" wrote in message
...
An alternative would be a Smart Strip power strip
http://catalog.bitsltd.us/power_strips/. This is a power strip that has a
number of outlets, just like the cheap "surge suppressor" strips, the
difference being that there is one outlet that is used to control all the
other outlets. When the device that is plugged into the control outlet is on
(drawing current), the other outlets are switched on. These are usually used
to control computer systems, home theater systems, etc, where a number of
devices need to be turned on at the same time. I have one of these strips in
my home and two more in my shop. Great devices.

If I am not mistaken, the sensor in a smart strip is nothing but a pair of
rectifier diodes connected in anti-parallel. You put the pair in series with
the line. When the load (the pump in this case) draws current, the voltage
across the diodes is a near square wave with an amplitude of 1.4 volts
peak-to-peak. You can use this voltage to pull in a small relay, which in turn
lights your indicator light - or whatever.

Obviously, the diodes have to be hefty enough to withstand the pump's starting
current. And the relay's coil, which is connected to the line at all times,
must be well isolated from the relay frame, from ground, from its own
contacts, etc. But none of this is hard.

Bill

You are mistaken. The Smart Strip that I mentioned uses a current transformer
to sense current. The CT feeds a transistor that switches a relay when current
in the control receptacle is sensed.
However, CTs aren't hard to find, and are pretty cheap. The circuitry behind
the CT is fairly trivial as well... just connect a burden resistor across the CT
secondary, rectify and filter, then feed the resulting voltage to the base of a
transistor. The transistor drives the relay coil, which switches power to the
load(s).
The transistor circuitry can easily be replaced with an opamp if you're more
comfortable with those.
The Smart Strip is rated at 15A.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra