Electronic Design Software

Water level controller circuit,Can i connect Relay?

http://www.electronics-lab.com/blog/wp-content/uploads/2008/02/water-sensor-circuit.GIF Please see the circuit diagram,in that there is a buzzer,instead of buzzer can i connect a relay and so that motor to fill the water tank will start automatically,rite,please help me

Public Comments

1. You may need a relay driver circuit if the relay requires more than a few milliamps to operate. The PIC is a solid micro but its output current capability isn't all that high. (You'll need to check the relay specs and the PIC datasheet to be sure.)
2. well considering that its only being run off 4.5V id rather doubt it, unless you found a motor that can handle it at that low voltage. if it were me making one id remove the buzzer and hook it up to a 12V relay and a seperate power source and independant motor
3. Yes you can. You will need a transistor to drive the relay. The easiest way to do that is t o use a 1K resistor to the base of a darlington transistor par, emitter to ground, collector to one coil terminal of a relay, the other coil terminal to positive power (voltage at relay coil rating). Be sure to include an appropriate snubber diode. You will need to re-write the code for the PIC to drive a relay instead of a buzzer.