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Float Switch Controlled Water Level Controller Circuit

Float Switch Controlled Water Level Controller Circuit

The post narrates a simple water level controller circuit using a float switch mechanism. The idea was requested by Mr. tpraveenraj.

Technical Specifications

I'm a electronic hobbyist from software field. So I try with the things in the weekend. I saw your blog recently and really admired to test this circuit, and when I went to the market I saw the float switch there.

Can I connect that to this circuit, or else will you please suggest me the way to use that, since we don't have to worry about the corrosion & passing currents to water by using this switch.

Thanks for your great works, they are really helpful for the people like us to learn.

The Design

The proposed water level controller circuit using a float switch is basically a semi-automatic system where the pump is started manually by press of a button, once the water level reaches the brim of the tank, the operation is switched of automatically by means of a float switch.

Referring to the diagram shown below, the various stages and functions may be understood with the help of the following points:

The left side of the image a shows the tank half filled with water along with the associated float and switch mechanism.

The Float Sensor Mechanism

The float mechanism basically consists of a smooth cylindrical water sealed plastic pipe, clamped erect inside the water tank inner base.

A plastic water-tight float surrounds this pipe and is able to slide up/down freely in response to the water level inside the tank.

The float being made up of plastic floats at the water surface and is consequently pushed upwards or downwards across the plastic pipe depending upon whether the water is being filled or consumed from the tank.

The float also has an embedded permanent magnet at its upper surface.

The plastic pipe has an in-built reed switch assembly at the top located just near brim of the tank.

The above two counterparts are intended to interact with each other when the water reaches the upper edge of the tank.

When this happens, the magnet inside the float reaches at a close proximity to the reed switch, closing its contacts and thereby causing the wire terminals to get shorted across these contacts.

The right hand side of the diagram is a transistorized latch circuit.

When the tank is empty and is required to be filed, the push button is pressed manually.

Pressing the push button latches the base of T3 and activates the relay which switches ON the motor and holds it in that position until the water in the tank is filled upto the tank brim wherein the float switch triggers the reed relay as discussed above.

The reed switch shorts the connection between the base and ground of T3, rendering the latch inactive which breaks the whole operation.

The relay and the pump motor are thus switched OFF until the push button is pressed yet again for the next cycle.

C2, C3 make sure that the circuit does not get activated by false or spurious electrical disturbances.

Circuit Diagram

Video Demonstration:

Parts list for the float switch water level controller circuit

R2, R3 = 10k

R4 = 100k

C2, C3 = 100uF/25

VD1 = 1N4007

T3 = BC547

T4 = 2N2907

RL1 = 12V relay, 30 amps

switch = any push-to-ON switch, bell switch type


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!

19 thoughts on “Float Switch Controlled Water Level Controller Circuit”

  1. Hello Sir Swag,
    How can i modify the above circuit to become a fully automatic? i want the relay to stay activated as long as the float switch is actuated and remain off as long as the float switch is in open position? a non-latching relay circuit?
    should i just remove the switch-to-on and connect the R2 to positive rail? thanks!

  2. please give me good working semi automatic water level controller circuit diagram with pcb
    distance between from sump to over head tank is app 60-65 feet

    • Vignesh, presently I do not have the required design, I'll try to find it out if possible.

      the float switch is a simple magnetic float with a reed switch sensor

  3. Hi Swagatman,
    I love your website and just wanted to say thanks for all your effort in sharing your ideas 🙂
    I have built a water level indicator using a Arduino uno some LED's and some float switches, that works similar to this. A push button to start the pump and it stops automatically when the tank is full. Im not really an electronics person so writing a bit of code was easier for me than making circuits 🙂

    Anyway i am learning some electronics from people such as yourself. THANKYOU 😀

    • Thanks so much Jason, that's very interesting, please feel free to inquire anything related to electronics and keep up the good work

  4. Sir
    can i use transformer-less power supply for this circuit.?
    because previously i used transformer type power supply but transformer get faulty very often.

    thanking you

  5. Hello Swagatam,

    Please Post a Capacitive/Body/Touch Sensitive Circuit can be applied on bicycle. Such device seen on car security system, When somebody come closer to car or a simple touch would trigger the alarm for 5 seconds.

    How this type of alarm works, the alarm only trigger when somebody come closer (say 30cm) what type of sensor they use?

  6. Hello Swagatam,

    I'm glad to see that you accept my request and posted a circuit. And I see this as the trimmed down version of "Cheap Semi Automatic, Tank Water Over Flow Controller Circuit" which you posted 2 year ago, is it so ?

    (sorry for being foolish about this question but I never feel shy to reveal my doubts ) Will this work by simply placing the probes inside the tank too ?

    Praveen Raj

    • Hello Praveen,

      Thank you! yes only the latch section from the previous circuit has been employed here. The simple configuration could be possible due to the involvement of a reed switch and also because the design is not fully automatic.

      If only probes are used then you would have to go back to the previous design and include T1/T2 for the intended detection of the water level.

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