A flood can occur suddenly due to a cloud burst or due or consistent rains. Floods can cause huge damage and loss to lives and property if it is not detected at the onset.
The circuit presented here could be used for detecting floods and operating an alarm or preferred device such as gate opener, water pump or water blocking system, so that an undesired situation could be avoided due to water logging and floods.
This specific circuit makes it possible for us to switch on a device that may be hooked up in series with the contacts of the relay, whenever the indicated probes get immersed in liquids such as water, during a situation of a flood.
As can be seen, only standard parts are being used, like resistors, capacitors, diodes and transistors, and others.
Its operation is dependent on the recognition of a small current which is sensed by transistor Q1. This current will be the one that passes across the liquid and becomes responsible for triggering the relay along with the activate the alarm. Since it is too small, a couple of transistors in Darlington configuration should be used so as to have a high amplification coefficient, sufficient to switch on the base of transistor Q1 to prevent incorrect alerts and enable it to be activated not until we have a True current over the probes.
Besides serving the purpose as a flood alarm, this circuit additionally functions like a level control, for instance when filling a tank, or while it is unfilled (using relay NC contacts).