We have read about conductors and insulators and performed an activity to identify them in a previous article. Here, we are going to discuss a circuit which acts as water sensor by using the fact that water is a good conductor of electricity.
This circuit can also be used as rain sensor or water tank alarm.
It is a simple two transistor amplifier circuit which verifies the fact that water is the conductor of electricity.
When water comes in contact with the probes marked water sensor, the positive supply of 9V will pass through 330KΩ resistance and activate the base of transistor BC 548. This transistor acts as preamplifier and turn on transistor BC558. The output from the collector of BC558 is given to buzzer which makes sound.
If the wires are not kept in water, supply does not reach BC548 and the circuit is incomplete. Buzzer is not activated in this case.