I would use an relay to switch the pump-motor on/off. (A 120VAC relay will be easiest, assuming your pump is 120VAC). And use a microswitch to switch the relay. The microswitch can be activated by anything that floats. I use a small plastic bottle (200 cc), half filled with water. It activates the microswitch by its weight (keeps the pump OFF). As soon the waterlevel rises the bottle is lifted, de-activates the microswitch. Pump STARTS. Works for 3 years here. I recently did see a 'float-switch' in the hardware store. It was very sturdy. It will switch a small pump ON and OFF directly (no relay needed). Herman in Philippines. ----- Original Message ----- From: "John Waters" To: Sent: Wednesday, June 09, 2004 11:35 AM Subject: [EE]: water level detection, how? > Hi All, > > I have a tank with a submersible pump inside, I want to stop the pump from > running dry when the water level is too low, what sort of sensor could I > use? I'm thinking of using a float with a magnet attached, the magnetic > field will trigger a relay to turn off the power, does anyone get experience > in building this kind of thing and would like to share the experience with > me? > > Thanks in advance! > > John > > _________________________________________________________________ > Tired of spam? Get advanced junk mail protection with MSN Premium > http://join.msn.com/?pgmarket=en-ca&page=byoa/prem&xAPID=1994&DI=1034&SU=http://hotmail.com/enca&HL=Market_MSNIS_Taglines > > -- > 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 hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu