"H2O" Douglas Wood Software Engineer dbwood@kc.rr.com ICQ#: 143841506 Home of the EPICIS Development System for the PIC http://epicis.piclist.com ----- Original Message ----- From: "Larry Bradley" To: Sent: Thursday, January 30, 2003 10:48 AM Subject: Re: waterlevel (on/off) on a PIC pin > Define "water". > > I bought a bilge pump for my sailboat that had electronic water level > sensing, so it would turn on and off automatically when water was in the > bilge. I installed it in my boat (which sails in fresh water) - it didn't > work. So I brought it home and tested it in tap water - worked like a > charm. The guy at the store wouldn't believe me when I tried to return it, > so I brought a bucket of water from where I sail, and got a bucket of water > from the store's tap and showed him - he couldn't believe his eyes. I got > my refund. With an ohmmeter, I could not detect any real difference in the > conductivity of the city water and the river water, but there was obviously > some difference. > > So I built my own using a PIC. I had two stainless steel bolts about 1/2" > apart as the sensors, drove one bolt from a PIC output port via a 100K > resistor, the other bolt connected to a PIC input port via 1.5 K resistor. > When the water covered the pins, the PIC detected the voltage and away we > went. This was a 16C84 - no comparator - just using the threshold of the > I/P pin. > > Larry > > At 07:17 AM 1/30/2003 -0500, you wrote: > > > How can I interface 2 pins of metal to a PIC etc. for detecting > >waterlevel > > > (on/off)? -the resistance between the 2 pins is several Mohms with water > > > and the circiut is of cource open with no water. > > Larry Bradley > Orleans (Ottawa), Ontario, CANADA > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body