Most modern buildings now have bathrooms equipped with amazing stuff…automaic flush toilets, automatic washbasin taps, automatic towel dispensers! My question is: how are these things powered? They don’t appear to have any electrical lines, so they must be battery-powered…but activating a flush valve via a solenoid must take a fair amount of current.
Anybody know how they are powered?
I used to sell these. The ones I sold were battery powered and had an electric eye to determine when someone had used the toilet. There was a urinal version that worked off a timer.
I’ve been wondering about this for a while, and have theorized that you could use the water pressure as a power source for the system. Put a tiny spinner in the water stream to charge a capacitor or rechargeable battery every time it flushes. To prevent the system from dying, the circuit could automatically flush (and recharge) whenever the charge dropped below a certain threshold.
IANA engineer, so I don’t know if this would work, or if it’s the way it’s actually done, but it seems good in theory to me.
IIRC, the device uses a 9 volt and is supposed to run 5-6 months.
I’m a plumber and I’ve seen both battery-operated ones and electrical ones, which use a transformer. Here is one made by Sloan:
The one at my workplace is connected to a metal contact on the door. When the door has been opened twenty times, the urinal flushes.
How much power could you net with an intentional dissimilar metals joint - say copper and steel? 
As for power needed - not much. I’m sure these things are “poppet” valves like what’s used in lawn sprinklers. You just have to give the mechanism a small nudge, rather than hold a large solenoid valve open.
You’re right that the power needed to open the valve is probably minimal, but the device has LEDs that are constantly emitting light and IR sensors that detect the arrival and departure of a user. They don’t need much power either, but my thought was, why use a non-rechargeable battery that will have to be replaced periodically, when you have a free power source right at hand, and could make a system that is nearly maintenance-free.
I suppose that my concept would have a higher initial cost, and if the alternatives are a 9-volt battery once or twice a year (plus the labor cost of replacing it) or a hard-wired device, both with lower purchase price, they would win because the architects or contractors buying them are more concerned with lowering the installation costs and don’t care so much about down-the-road operating expenses.
commasense said:
(Bolding mine)
I find that hard to believe. Don’t architects get a percentage of total cost of a project, and therefore a higher cost benefits them? And contractors usually bid a job by what’s been specced by the architect, therefore having no say in what items are used. IOW, if the specs call for fancy high-dollar infrared flush valves the contractor can’t just say “Well, we’ll save money by installing cheaper manual ones.”.
I just had a look at TOTO, maker of some of these beasties, and **commasense ** gets the prize!
(bolding theirs)
gotpasswords: Thanks for getting my week off to a great start with this cool ego boost.