sgsguru: (Default)
 Machines lie.  Everybody knows this; the Automated House of the Future is going to do everything for us, but can't make consistent toast.  One thing I may have figured out, however, is how to put a thermostat on a shower, without any electronics (Batteries!  Electric shocks!).

The basis of a mechanical thermostat is a bimetallic strip.  It bends one way if it's hot and the opposite way if it's cold.  So if the water is too cold, it opens the hot water a bit and closes the cold water a bit.  Too hot, less hot, more cold.  We set the temperature by physically turning the strip.  If it can't generate the proper temperature, it goes to the end of its travel, where it hits a lever that pops up a little flag on the shower head.  I'd say blue for "too cold" and red for "too hot".

Problems:
  • Scale buildups.  Ideally, the strip bending from the temperature changes would cause scale to flake off.  In practice, who knows?
  • Force.  A bimetallic strip doesn't produce much force.  Is it enough to work the hot and cold valves?
  • Corrosion.  This is a definite problem as we have dissimilar metals by definition.  I'd say just coat the whole thing with plastic.  A sacrificial anode would probably be overkill.
Other Ideas:
  • We could direct the water straight down the drain if it's too cold or too hot.
  • If we wanted to get "just a little bit electric", we could put a little generator in the water flow.  We could get enough juice to run a couple of LEDs so we could see if the shower was ready from outside the shower.  Or hook it to the Internet (only half kidding!)
  • To get really fancy, we could hook the whole setup to a demand (tankless) water heater.  (It's a waste of energy to keep a big tank full of hot water in the basement all the time, in case we might need it.)

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October 2016

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