Here is a simple automatic water-level controller for overhead tanks that switches on/off the pump motor when water in the tank goes below/above the minimum/maximum level. The water level is sensed by two floats to operate the switches for controlling the pump motor.
Previously we designed the simple automatic water pump controller circuit.
Table of Contents
Automatic Water Level Controller Circuit
Each sensor float is suspended from above by an aluminum rod. This arrangement is encased in a PVC pipe and securely mounted vertically on the inside wall of the water tank, making these sensors more reliable than induction-type sensors.
Sensor 1 detects the minimum water level, while Sensor 2 detects the maximum water level (refer to the figure).
Leaf switches S1 and S2 (commonly used in tape recorders) are mounted at the top of the sensor units. When the floats are lifted, the attached 5mm diameter aluminum rods push the moving contacts (P1 and P2) of these switches from their normally closed (N/C) position to the normally open (N/O) position.
Conversely, when the water level decreases, the moving contacts return to their original positions.
Under normal conditions, the N/C contact of switch S1 is connected to the ground, while the N/C contact of switch S2 is connected to a 12V power supply.
IC 555 is wired such that when its trigger pin 2 is grounded, it gets triggered, and when reset pin 4 is grounded, it gets reset. Threshold pin 6 and discharge pin 7 are not used in the circuit.
Water Level Controller Working
When the water in the tank goes below the minimum level, moving contacts (P1 and p2) of both leaf switches will be in the N/C position. That means trigger pin 2 and reset pin4 of IC1 are connected to ground and 12V, respectively.
This triggers IC1 and its output goes high to energize relay RL1 through driver transistor SL100 (T1). The pump motor is switched on and it starts pumping water into the overhead tank if switch S3 is ‘on’.
As the water level in the tank rises, the float of sensor 1 goes up. This shifts the moving contact of switch S1 to the N/O position and trigger pin 2 of IC1 gets connected to 12V. This doesn’t have any impact on IC1 and its output remains high to keep the pump motor running.
As the water level rises further to reach the maximum level, the float of sensor 2 pushes the moving contact of S2 to the N/O position and it gets connected to the ground.
Now IC1 is reset and its output goes low to switch the pump off.
As is consumed, its level in the overhead tank goes down. Accordingly, it is consumed, its level in the overhead tank goes down. Accordingly, the float of sensor 2 also goes down.
This causes the moving contact of switch S2 to shift back to the NC position and reset pin 4 of IC1 is again connected to 12V. But IC1 doesn’t get triggered because its trigger pin 2 is still clamped to 12V by switch S1. So the pump remains switched off.
When the water level further goes down to reach the minimum level, the moving contact of switch S1 shifts back to the N/C position to connect trigger pin 2 of IC1 to the ground. This triggers IC1 and the pump is switched on.
Construction & Testing
The float sensor units can be assembled at home. Both the units are identical, except that their length is different. The depth of the water tank from the top to the outlet water pipe can be taken as the length of the minimum-level sensing unit.
The depth of the water tank from the top to the desired fill level serves as the length for the maximum-level sensing unit. The leaf switches are fixed at the top of the tank as shown in the figure.
Each pipe is closed at both ends by using two caps. A 5mm dia. hole is drilled at the center of the top cap so that the aluminum rod can pass through it easily to select the contact of leaf switches.
Similarly, a hole is to be drilled at the bottom cap of the pipe so that water can enter the pipe to lift the float.
When the water reaches the maximum level, the floats should not go up more than the required distance for pushing the moving contact of the leaf switch to the N/O position.
Otherwise, the pressure on the float may break the leaf switch itself. The length of the aluminum rod is to be selected accordingly. It should be affixed on the metal/thermocol float using some glue (such as Araldite).
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The article was originally published in December 2004 and has been recently updated on October 21, 2024.
Could you please send me the schematic circuit diagram for a water level control, I want to install it on my Storex tank , I shall be grateful my request is granted . Thanks Sir
Sir
I want waire less automatic water leval indicater system plzz make a circit degin my according with full explane microcontrol how to install programme contect me my whats up nu. 8432831129 I pay your fees
very good circuit. I have made the same and working fine. I want to control one single phase 1 HP submersible pump. Please modify the same or else kindly publish one which could control one single phase 1 HP or higher submersible pump set.
I love this though but I’ll prefer a different option.
Can you please design for me a circuit that would only automate the switching off of the circuit while I switch it on manually at will.
Thank you!
i have made it and work will automatic off the water pump and on when water is low from adjusted level.
Sir please i need a schematic circuit diagram.can you send me sir if granted?
Hello SIr, Nice Article, How Can we Add Delay on Start and Stop Relay inside this circuit?
I have made same system but little different without seeing this..
dear sir ,can u send me pcb lay out .component lay out for making pcb
Hi Amit, The PCB and Component layouts for this particular circuit is unavailable.
can you send me the complete pcb diagram and electronic components required for designing the water level controller project and its related subjects in pdf form to my email id
Ckt is not working for me as per this Statement “This shifts the moving contact of switch S1 to N/O position and trigger pin 2 of IC1 gets connected to 12V. This doesn’t have any impact on IC1 and its output remains high to keep the pump motor running”. As soon as pin2 is moved from ground it’s o/p changes from +3.3v to 0v. Just would like to inform here my VCC is 3.3v.
Hello. I want to know, how would you connect warning lights on this system for both levels of the water in the tank?
Is this system used where water is pumped directly from the bore well into the overhead tank?
hello,this set up works only if there is a constant supply of water. if the water does not flow in then the pump runs until forever
Please provide the circuit for fully automatic water level controller with OH -Overhead tank and UG- Underground tank with sensors and also provide the internal 12 V /24 Vdc supply generation without need for dc external supply /smps . Also provide the circuit for A/M -Auto Manual operation of the controller as per user requirement .Also provide PCB and Component layout for PCB making.