Spehro said:
My wall switch timer for electric lights uses a tiny electric motor
and a gear train and cam to operate a microswitch. A single AAA
alkaline battery powers it for something like a year. It will switch
120, 240 or whatever, the microcontroller and all runs from the single
cell, so the microswitch is the only thing that needs to be connected
to the outside world. The circuitry wouldn't even have to be hot if
they didn't use the NC contact of the microswitch to tell the micro
the switch state.
It also turns the lights on at a calculated dusk time based on the
calendar and approximate latitude. Not bad for $35 US.
Best regards,
Spehro Pefhany
Battery-operated water control devices generally use a pilot type of
valve, i.e., a valve with 2 fluid circuits, one small and one large.
The small 'pilot' circuit has a tiny solenoid valve that doesn't
require much current. The small flow in the pilot circuit is used to
operate a much larger valve. It's a kind of hydraulic amplifier, using
the water pressure as a free source of energy. The longest-life devices
use magnet-biased solenoids, so the pilot solenoid is pulsed on and
off. The Sloan Optima series is rated for 5 yrs or 50K flushes, and
it's an honest spec. The power budget for the 4AA cells was divided
about equally among these consumers: CMOS microcontroller,
photoelectric sensor circuitry, solenoid driving, and battery
self-discharge.
Most of the reliability issues with electronic water control is due to
particulates in the water supply that clog the tiny pilot circuits.
There are several important patents relating to how to design the
internals such that they don't tend to clog. The ubiquitous Sloan
Royal's success was originally based on its patented centrifugal inner
chamber, that forced larger particles in the water away from the pilot
orifices.
Paul Mathews
