n Mon, 21 Sep 2015 10:12:44 -0300, Dagmar Carnier Neto wrote:
:: Hello all,
::                 I'm developing a digital water-level probe to be
:: installed inside wells, and last week found some of them stop
:: working.
:: They were installed inside deep wells, around 250 meters deep. A 4-
:: wire cable connect them to the top, being 2-wires for power (5V and GND)

If you are providing your probes with DC they will eventually corrode due
to electrolysis.

You need to provide them with an AC voltage, a simple square wave will
work, either using a 555 timer or a set of NAND gates set up as an RC
oscillator.

I have no answer to your pump dying problem, apart from maybe the cable
goes high resistance or corrodes due to impurities in the water.

I'm attaching a circuit separately.

Colin
--
cdb, colin@btech-online.co.uk on 22/09/2015
=20
Web presence: www.btech-online.co.uk =20
=20
Hosted by:  www.justhost.com.au
=20
=20
This email is to be considered private if addressed to a named  individual=
=20
or Personnel Department, and public if addressed to a blog,  forum or news=
=20
article.
=20
=20
=20
--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.