One common problem
having an electric bilgepump for your boat or yacht is that the bilge pump
is not able to empty the boat from all the water. This is true for two
reasons: firstly the bilge pump is often controlled by a level
sensor requiring a certain abont of water for activation, and secondly
the piece of plastic tube between the bilge pump and the water outlet contains
a certain amount of water, pouring back into the boat when the bilge pump
stops.
With the help of the electronic
circuit described in the schematic below utilizing
som easy available components (including an ordinary
12 V car relay), the former amount of water may be eliminated by having
the bilge pump running for another 15 seconds after the water indication
has disappeared.
The curcuit will not
draw any leakage current from the battery when not activated, because
it is powered only through the sensor switch and the pump motor relay.
The the diode serve a dual purpose of powering the circuit and also prevent
the bilge pump from being powered through the sensor switch.
