Garden watering Circuit Projects makes use of an OP AMP fitted with hysteresis which automatically switches on the water valve of this garden device. This then waters the plants if the detected soil’s moisture is lowered than you preferred level. You will have to do a few experiments to get the best results.

Two homemade probes made from stainless steel rods are set to be 1 inch apart are usually used in detecting the soil’s moisture. Other dimensions will also do.

The most appropriate power to be used on this circuit is 12V DC; however a 9V DC can also be used provided you have a DC relay which can be motorized up using a 9V power supply.

The op-amp in this circuit will have a yield at pin 3 of high or low (this depends on the voltage levels of yield pins 2 and 3. If pin 2 energy level is higher compared to pin 3, the yield will be small and vice versa.

Probe two is connected to the base of the circuit. Resistors R1 and R2 work as divider which will divide the input energy at pin two to 6V DC. When probes 1 and 2 are placed a few meters into the ground, resistance between probe 1 and probe 2 will be inevitable.

Since the NC connection is not being used, a SPST relay can be used. When the soil surrounding probes 1 and 2 began to damp, due to the opening of these water valves, the resistance will reduce until pin 3 voltage drops below pin 2.

After this, the output of U1 turns off which in turn turns off the RLY. When this occurs, the water valve will be switched off. The position of the probes is determined with the area to be watered.

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