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    Description of water sensor: in most houses, water is first stored in an underground tank (UGT) and from there it is pumped up to the overhead tank (OHT) located on the roof. People generally switch on the pump when their taps go dry and switch off the pump when the overhead tank starts overflowing. This results in the unnecessary wastage and sometimes non-availability of water in the case of emergency. Check out the new water level sensor circuit.

    The simple water level indicator circuit presented here makes this system automatic, i.e. it switches on the pump when the water level in the overhead tank goes low and switches it off as soon as the water level reaches a pre-determined level. It also prevents ‘dry run’ of the pump in case the level in the underground tank goes below the suction level.

    Water level sensor, indicator circuit diagram

    We are sorry for the poor quality of the water level indicator schematic quality. If you have higher quality pictures of this water level diagram use the discussion form below.

    In the water level sensor schematic, the common probes connecting the underground tank and the overhead tank to +9V supply are marked ‘C’. The other probe in underground tank, which is slightly above the ‘dry run’ level, is marked ‘S’. The low-level and high-level probes in the overhead tank are marked ‘L’ and ‘H’, respectively.

    Presets VR1, VR2, and VR3 are to be adjusted in such a way that transistors T1, T3, and T5 are turned on when the water level touches probe pairs C-S, C-H, and C-L, respectively. Resistor R4 ensures that transistor T2 is ‘off’ in the absence of any base voltage. Similarly, resistors R5 and R6 ensure that transistors T4 and T6 are ‘on’ in the absence of any base voltage. Switches S1 and S2 can be used to switch on and switch off, respectively, the pump manually.

    The author used a piece of non-metallic conduit pipe slightly longer than the depth of the overhead tank. The common wire C goes up to the end of the pipe through the conduit. The wire for probes L and H goes along with the conduit from the outside and enters the conduit through two small holes bored into it as shown in Fig. 2.

    Water level sensor installation

    water level sensor

    Care has to be taken to ensure that probes H and L do not touch wire C directly. Insulation of wires is to be removed from the points shown. The same arrangement can be followed for the underground tank also. To avoid any false triggering due to interference, a shielded wire may be used.

    This water level indicator circuit has not been tested. Check out the water level indicator circuit too!

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    19 Responses to "Water Level Indicator/Sensor Circuit"

    1. i want a circuit on water lever control

      • Shree Krishna says: on November 10, 2013 at 4:53 pm

        Hi…The circuit is very simple. I will explain it for You..This explanation is for begineers in electronics.
        The transistors T1, T2, T3 and T5 are npn.NPN transistors are ON when high (voltage) is applied on its base.The transistors T4 and T6 are pnp. PNP transistors conduct when low (voltage) is applied on its base. The upper probe is S probe which checks under-ground tank. if there is water in the underground tank, S probe is high which means base of T1 recives high, so T1 is ON. When T1 is on, base of T2 receives high, so T2 is also ON. (If T1 is off, base of T2 is directly connected to ground. and when T1 is ON, base of T2 is connected to VCC). Its the task of transistor…to know more about transistor’s operation, google it….
        consider underground tank has water, so T1 receives high on its base so it is ON and T2 is also on, since base of T2 is shorted to VCC by T1.Now comes the overhead water tank. Transistor T4 is PNP i.e. it needs low on its base. If the tank is full, transistor T3 receives high on its base. this makes T3 to conduct (ie. T3 is ON). If T3 is ON, it gives high on its emitter. The emitter of T3 is connected to the base of T4. so T4 turns OFF. Consider the tank is not fully filled. so T3 doesnt receive high on its base hence T3 is off. If T3 is off, the base of T4 is directly connected to Ground through R5(10K) resistor.This makes T4 ON, since its base is low.
        Now lets come to the part when tank is empty. When tank is empty the L probe doesnt receive any high voltage i.e. Base of T5 doesnt receive high to turn ON. so T6 turns on as it is directly connected to ground through resistor R6. When T2, T4 and T6 simultaneously (at the same time) turn on, relay turns on as the path is complete through T2, T4 and T6.
        When Relay Turns ON, NO (Normally Open) pins are connected to common pin. (To understand about the operation about Relay, google it…). At closer look, there are two relays bound into one. to make the discussion simpler, lets divide the relay into two relays, the upper one with NO (Normally Open) and NC (Normally Closed) and the identical lower one. This relay has two switches under the control of one coil. when the relay is ON, the middle pin(Common) touches the NO(normally open) pin. Common pin is connected to relay’s coil and NO pin is connected to emitter of T4. so even if T6 is OFF, (after the level of water has risen upward, this maks L probe high which makes T5 ON and this inturn makes T6 becomes off), current is supplied from transistor T4. So this mechanism is used to turn on the Water Pump until the tank is filled.
        Lets see the lower relay. Its task is to turn on the Power supply to the Water Pump. and the mechanism is same as upper relay.
        In summary. If underground tank is empty, T1 is off, T2 is off, so whole circuit is off,since current passes to the relay through T2. If the underground tank is filled, T1 goes ON so T2 is also ON. Then the circuit proceeds to check the overhead tank. if over head tank is empty, T5 goes off, so T6 is ON. this makes relay on and the pump starts. after starting of the pump, the circuit checks only if tank is fully filled. if the tank is full, T3 goes ON and T4 is Off, which makes relay to go off, and the pump is off. Another case, if initially the tank is half filled, then T3 goes off, so T4 is ON. But T5 is ON since L probe is high. so T6 is off. so the relay is also off and hence pump is also off.
        resistors and VARs used on the bases of transistors are not your concern for now. Just copy as given. if you want to learn then just google on ‘voltage biasing resistor on base of Transistor’. The circuit is very much simple. You just have to trace the path of current flow through each transistor.
        OK. Thats it. Best of luck, NEWBEE.

    2. Aakash Sharma says: on April 28, 2010 at 4:49 pm

      I wanna have a better & simple circuit for water level control.

    3. Antim Sharma says: on April 28, 2010 at 4:50 pm

      I wanna better & simple circuit for water level control.

    4. Shridhan Automation is a Manufactures, Exporters & Suppliers a wide variety of Level switches, Level switches for liquids and Level Transmitters for liquids in India.

    5. i want simple circuit diagram for water level indicator

    6. Julius A. Woodson says: on October 27, 2010 at 5:15 pm

      Please I like the above circuit, but can you send me a clearer diagram and notes on the operation of the circuit.

    7. Onyekwere Uchenna says: on November 4, 2010 at 1:45 pm

      Please I need a circuit diagram for an automatic pump control where the pump switches off at a set point and starts pumping again when the water level reduces to a certain set level. The system should be such that operates with Relays.

    8. Aruah Endurance says: on February 23, 2011 at 10:33 pm

      Pls i want a simple circuit whereby either sound or light can activate an alarm

    9. addinul says: on March 17, 2011 at 4:21 am

      plis i want the schematic water sensor, and i want the pcb project,thanks

    10. yogesh jain says: on March 29, 2011 at 10:03 pm

      i wanna simple circuit digram for water level sensor

    11. p n singh says: on October 13, 2011 at 12:31 pm

      plz. contact mr p n singh for water level controllers on his mobile 09375410771

    12. shahruk khan says: on January 25, 2012 at 12:23 pm

      water se gaand dho lee

    13. jagdish prasad gupta says: on March 26, 2012 at 9:20 am

      i want a simple water level indicator circuit.
      please reply as soon as possible

    14. Schematic is fine for my needed application,thanks so much.

    15. gud schemetic as i searching…

    16. This is a good simple circuit but I have two gripes as it stands Many summers ago there was a diagram in a mag where the probes were fed with high audio frequency as the D.C. that is used to feed the sensing probes after a while through the build up of hydrogen and oxygen on these probes get isolated and they must be removed to get rid of these electrolysis I know that the detector and the oscillator make the circuit much more complicated but this was the solution to this phenomena on the sensing probes
      The second problem is the availability of those AC128 transistors The only source are some radio’s that were built before 1980 or a hobbyist that still have them from the organ building fad of the early ’70′s

    17. lekhya raja says: on April 9, 2014 at 2:50 pm

      this is very simple project and please provide a documentation in detail

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