Subject: Re: Water sensor
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NNTP-Posting-Date: Wed, 15 Jan 2003 23:06:54 GMT
Organization: Insight Broadband
Date: Wed, 15 Jan 2003 23:06:54 GMT
On Tue, 14 Jan 2003 12:54:27 -0500, Terry King wrote in
>Probe suggestion: El Cheapo: I used several .1 Uf 200V
>ceramic capacitors, in parallel on a twisted pair, in
>cellar locations such as behind the washer. Stapled
>each cap to the baseboard, bent almost touching floor.
>Each disc capacitor was intentionally broken so the 'bottom'
>1/8" or more was removed, and the two electrodes,
>separated by their thin ceramic insulator were exposed.
>I ran this connected to ground and +5V through a 47K
>resistor and into a comparator set at about 2 volts.
>This 'fired' with a drop of tap water on the capacitor
>edge, and dried out in about a hour. Only once did
>I have to "wash off" a sensor that got dirtied up.
>But this also only "got wet and alarmed" once in about
>Needless to say, this was provoked by a not-to-be-repeated
>major problem with a washer hose...
>I think I better add one of these setups in the house I have
>now, now that I shot my mouth off about it: Murphy MUST
*That* is a neat solution/approach to inexpensive probe construction. I wonder
how a silver-mica cap would work vis-a-vis long-term stability.