[RndTbl] water clock

Gilbert E. Detillieux gedetil at cs.umanitoba.ca
Wed Nov 19 14:00:58 CST 2003


According to millward:
> I was wondering if anyone out there might
> be able to tell me how these water clocks work.
> All you do is fill it up with mildly salty water,
> and that's what it runs on. The one I've got
> has been keeping good time for about 5-6 days
> now. Once in a while a little bubble comes up, so
> it must be producing some kind of waste gas.
> I'd like to build my own circut based on whatever
> devices run this clock, just for fun. Would anyone
> know what kind of electronics run on water?
> And where I could get them?
> I didn't buy my clock through the net, but it's selling
> at:
>   http://www.computergear.com/waterclock.html
> All the site says about how it runs is:
> "The fuel cell extracts electrons from the electrolyte
> forming a steady stream of electrical current that
> drives the clock."  
>     That's all very well, but it doesn't tell me
> what the name of the fuel cell is, where I can
> get them, and how I can build a curcit based
> on the fuel cell's power. 

I would assume it's just your basic electro-chemistry at work here.
You put a couple electrodes in a saline solution or other liquid with
electrolytes in it (e.g. soda pop, Gatorade, etc.), and you'll get
electricity being produced.  You can also get the same results by sticking
electrodes into a potato, lemon, etc.

Granted, the amount of current you get is very small, but it's enough for
the typical low-power LCD digital clock.  There's nothing special about the
electronics, other than the fact that the power consumption has to be very
low.

I don't remember the details of the electro-chemical reactions, but the
electrolytes react chemically with the metal electrodes to produce the
electricity.  Depending on the specific reaction, yes, you could get some
gas produced as a by-product.  You also end up with compounds being
deposited on the metal electrodes, or with something being eaten away from
the electrodes, so eventually they'd have to be replaced too, or the
reaction stops.

Anyone with a better recall of basic chemistry?  (It's been too many decades
since I've looked at this.)

-- 
Gilbert E. Detillieux		E-mail:	<gedetil at cs.umanitoba.ca>
Dept. of Computer Science	Web:	http://www.cs.umanitoba.ca/~gedetil/
University of Manitoba		Phone:	(204)474-8161
Winnipeg, MB, CANADA  R3T 2N2	Fax:	(204)474-7609



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