Automatic plant Irrigation (AT89C2051)

R15, R16, R17: 330ohm
sensors are nothing but metal strips.

what you mean by size?
Its value is 100k

A 12v, 5A SPDT relay is used.

For power supply diagram visit the "CODE LIBRARY" page

Is the block diagram is correct?



Ligin Mathew

Sir, I didn't understand the PCB.
Connections fron Opamp to Microcontroller (uC).




There is no connection in the pin no 17 of uC.
But I Pcb, it is connected to Pin no 1 of opamp.


Sir, what is the use of the Variable resistor?
Where it is connected in the PCB?


Is 230/0-12 V, 500mA is enough for the power supply?

Is there any specification for the metal strip???

Ligin Mathew

The PCB is wrong and i will soon add the correct PCB

The variable resistor can be replaced by fixed resistor of 47k.

Yes 500ma is enough for this project.

No specification is required for the metal strip.

what is the use of variable resistor?

Ligin Mathew

Its to adjust the sensitivity of wet/Dry

Sir, I didn't get 230/12, 500ma transformer for the power supply.
So brought 230/6-0-6, 1A. From this i obtained 5V and 12 V.
But the current rating in the transfrmr is double than rating.
Does it affect my circuit ?

Can you please tell me the design of the comparator?
How does 10K and 100 K pot came.

I wired the circuit of the comparator, but when the probes are shorted, the o/p becomes low, then how it becomes Wet=1 and Dry=0 ?


Also please publish the new pcb layout.

Ligin Mathew

No it wont affect the circuit.

Did the o/p goes high when the probes are opened.

Yes. o/p goes high when probe is openned.

Ligin Mathew

Its correct then, check it with metal strips on soil.