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Automatic Plant Irrigation System

Here is a simple project more useful in watering plants automatically without any human interference. We may call it as Automatic plant irrigation system. We know that people do not pour the water on to the plants in their gardens when they go to vacation or often forget to water plants. As a result, there is a chance to get the plants damaged. This project is an excellent solution for such kind of problems.

Block Diagram of Automatic Plant Irrigation System:

Block Diagram of Electronic Plant Watering System

Automatic Plant Irrigation System:

  • Circuit is not that much complicated. We use the basic concept in this circuit i.e. soil have high resistance when it is dry and has very low resistance when it is wet.
  • By using this concept we will make the system work. We insert two probes in the soil in such a way that that they will conduct when the soil is wet and they will not conduct when the soil is dry. So, when the probes do not conduct, system will automatically detect this condition with the help of HEX inverter which will become high when the input is low.
  • HEX inverter will trigger the NE555 Timer and this NE555 timer will trigger another NE555 which is connected to the output of first NE555. Now the second NE555 which is configured as astable multivibrator will help to switch on the Electric valve and as result, it will allow the water to flow to the soil.
  • When the water wet the soil, probes will again conduct and make the output of 7404 low which will make the first NE555 to low and also drive remaining circuit to low. So, automatically it will switch off the valve.
Main Components in Automatic Plant Irrigation System:

Hex Inverter 7404: the main function of the inverter is to give the complemented output for its input i.e. it will give output which is opposite to input. For example, if the input is low to the inverter, then the output will be high. Just like the normal inverter which gives high output when the input is low and gives low output when the input is high. 7404 IC will be having six independent inverters; Operating supply voltage is around 4.75V minimum to 5.5V maximum, normal supply voltage is 5V. They are used in different applications like inverting buffers, drivers, hex inverters etc. 7404 IC will be available in different packages like DIP (dual inline package), QFP (Quad Flat Package) etc. The pin configuration of Hex Inverter 7404 is shown below.

Inverter Pin Configuration

Circuit Diagram of Automatic Plant Irrigation System:

Circuit Diagram of Electronic Watering Plant System

Circuit Explanation:

  • We are all well aware that the plants will die due to lack of water in the soil. Soil will have high resistance when it is dry and it will have very low resistance when soil is wet. We use this simple logic to water the plants and make the circuit work.
  • Two probes which are connected to the circuit are placed into the soil. The two probes will conduct only when soil is wet (resistance is low) and they cannot conduct when soil is dry due to high resistance. The voltage is given to the probes to conduct is given from the battery connected to the circuit.
  • When the soil is dry it will produce large voltage drop due to high resistance. This is sensed by 7404 hex inverter and makes the first NE555 timer trigger which is configured as monostable multivibrator with the help of a electrical signal.
  • When the first NE555 is triggered at pin 2, it will generate the output at pin 3 which is given to the input of second NE555 timer. The second 555 timer is configured as astable multivibrator which got triggered by the first 555 timer and will generate the output and drive the relay which is connected to the electrically operated value through the transistor SK100. You can use a heat sink for SK100 transistor if it is dissipating more heat.
  • The output of second NE555 timer will switch on the transistor SK100 which will drive the relay. Relay which is connected to the input of electrical value and output of value is given to the plant plots through the pipe.
  • When transistor has turned on relay, it will open the valve and water is poured on to the plants pot. When the water content in the soil is increased, the resistance in the soil will get decreased and conduction of the probes will get started which will make the 7404 Inverter to stop the triggering of first 555 timer. Ultimately it will stop the electrical valve which is connected to the relay. Variable resistor (R5) and capacitor (C1) are used to adjust the valve when to we want to conduct the probes.
  • The capacitor C5 (0.01uf) is used to ground, the CV pin of second NE555 timer. C3 will remove the AC noise and allow only DC to the remaining circuit. C4 and R3 will constitute to configure the NE555 in astable multivibrator.

Values of the Components in the Circuit:

  • Capacitor (C4) = 10u 16V.
  • Capacitor (C5) = 0.01u.
  • Resistor (R3) = 27K
  • Resistor (R4) = 27K
  • Diode (D1 and D2) = IN4148
  • Relay = 6V, 150 ohms


  • Battery should be continuously monitored from power outage or simply you can use 9V DC supply adaptor.
  • Probes must be inserted into the soil. They should not be kept on the soil.
  • Electric valve should be used for best result.

Also Read the Interesting Post: Automatic Street Light Controller using Relays and LDR

81 Responses

  1. what is the function of electric valve?
    the electric valve is connected to the water tank or what ?
    in the circuit, there is 240ac connected to the pin no 5 of the relay,what is the function of that 240 ac?
    please answer me a.s.a.p
    thank you 🙂

  2. This project is jst gr8….!!
    Intially faced problems in several aspects…
    bt vry vry satisfied with its results….!!

    1. hi aishwarya ,
      can you plz send me the abstract and how to do the project and how you did it . It will be very useful for me in doing the project

        1. Hey ,Is it possible to help me ,to explain me the components and process of using automatic irrigation system

        2. Any practical videos of this idea and deep information about this will be much helpful in understanding

          can u send me please

  3. i impresed this topic………plz send more detail and cost of the project……plz send me mail

    1. We are not selling the projects now, just providing the information only. Try to implement it on your own.

  4. which things i have to connect at 2 Points of PORTLEFT -R….

    Please suggest ASAP.

    What is PORTLEFT-R ????

    Are they two probes which i have to test under the soil or what ???

  5. plz upload a video of making of dis project and also add perfomance..
    this project is good idea for speedup the eco atmosphere..go on then upload the process of making

  6. very nice project …. can i run 13 v motor ??? and can you please explain the connection of relay part plzz rpl as soon as possible….

    1. Check out the menu bar links, we have provided almost 300+ projects with circuit diagrams, simulation videos & output videos.

  7. how can we keep the first 555 timer i.e it is in monostable mode output constant .here why u apply the first timer output to second timer output. Why triggering to astable multivibrator? reply me as soon as psble.

  8. The reason behind using IC555 has not been understood.IC 555 has not been used as monostable & astable multivibrator.It has been used as NOR gate.So NOR gate can be used in place of IC555.Can any body endorse/correct?


    D SAHA

  10. Reason behind using IC 555 is not understood. The same logic can be realised by using inverter gate in place of IC 555.. Can somebody endorse/correct?


  12. Please tell me wheather there is any comnection between the capacitor and the first 555 timer at the output terminal of the first 555 timer in the circuit.

    1. No there is no connection.Capacitor is connected to the 6th pin of 555 timer..other end is connected to ground.

  13. Can anyone please explain me of usage of two 555 timers..isnt one 555 timer in astable mode sufficient for thus operation??
    Please reply me asap..
    Thanking you..
    But you people have done a great job..good idea..!

  14. the probes r conducting only when they r physically connected,but not when they r inserted in wet soil,.y?.do v need to make any changes with respect to resistances near input side ,.please suggest

  15. Does any voltage need to be applied to the electric valve on its own? Or will it work just off of the 9V battery with the 6V relay? Please let me know. Thanks

      1. hello,
        Can i get a video of automatic plant irrigation system using two 555 timers?
        how to connect the components ..and will this circuit work correctly ??
        as i am using this for my project .. i need you to help me .. i request you..
        i would get the output with your help .. hope you reply soon
        Thank you.

  16. I like this project its a good idea.
    yeah i did this project it works
    if some one needs help he i can

  17. i want to make a drone i am student of class 9th can i make please anybody give me any site where i get step to make a drone.

  18. Does anyone know where I can get the 6V 150 Ohm Relay or anymore information about it? I haven’t been able to find one.

  19. Hi… Anyone tell me that whether C2 is connected to 4 , 6, 2 and 8 th pins of NE555 (U1) or not ?

    Anyone answer me please..??

  20. Hello.
    Today in history, I just made this circuit work. Thanks a lot for the help #electronics hub you’re the best

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