The post explains 6 interesting and useful circuits applicable for automatic toggling of two submersible water pumps alternately in response to a predetermined water level switching. The entire circuit is built using just a single IC and a few other passive parts.

The idea was requested by one of the interested members of this blog.

The Request

Can you help me with this problem: In a basement sump, there are two submersible pumps with float switches (P1 and P2) installed to achieve some level of redundancy.

In order to use both pumps equally, we want to alternate between P1 and P2 whenever a preset water level is reached. That is, the first time the preset level is reached P1 should start and pump the water out. Next time when the preset level is reached P2 should start and pump the water out.

On next occasion it will be P1's turn and so forth. What we need is an "alternating" relay control running P1 and P2 turn by turn.

1) The Design

The shown circuit of an automatic submersible pump controller can be understood as given under:

As can be seen the entire circuit is built around four NAND gates from a single IC 4093.
The gates N1--N3 form a standard flip flop circuit wherein the output of N2 toggles from high to low and vice versa in response to every positive trigger at the junction of C5/R6.

N4 is positioned as a buffer whose input is terminated as the sensing input for detecting the presence of water over a predetermined fixed level inside the tank.

The link from the ground or the negative of the circuit is also stationed into the tank water close and parallel to the above sensing input of N4.

Initially assuming no water in the tank keeps the input of N4 at high via R8, resulting in a low output at the junction of C5/R6.

This renders N1, N2, N3 and the entire configuration in a unresponsive standby position, resulting in T1, T2 being in a switched OFF position.

This holds the respective relays REL1/2 in an deactivated position with their contacts at N/C levels.
Here REL2 contacts make sure that the supply voltage stays cut off during the absence of water in the tank.

Now suppose water in the tank starts rising and bridges the ground with N4 input rendering it low, this prompts a high signal at the output of N4.

This high at the output of N4 activates T2, REL2 and also flips the output of N2 such that REL1 also gets activated. Now REL2 allows the mains voltage to reach the motors.

And with REL1 also activated actuates the pump P2 via its N/O contacts.

As soon as the water level sinks below the preset point reverts the situation at the input of N4, creating a low a its output.

However this low signal from N4 produces no effect on REL1 as N1, N2, N3 hold REL1 in the activated position.

REL2 being directly dependent on N4 output switches OFF cutting off mains supply to the motors and switching P2 OFF.

During the next cycle when water level reaches the sensing points, N4 output toggles REL2 as usual allowing mains supply to reach the motors, and also switches REL1 but this time toward is N/C contact.

This instantly flips P1 into operation because P1 is configured with the N/C of REL1 thus resting P2 and actuating P1 on this occasion.

The above alternate flipping of P1/P2 keeps repeating with the ongoing cycles as per the above operations.

Circuit Diagram

Parts list for the above automatic submersible pump controller circuit:

R3, R9 = 10K,
R4, R5, R8 = 2M2,
R6, R7 = 39K,
R4, R5 = 0.22, DISC,
C6 = 100µF/25V,
D4, D5 = 1N4148,
C4, C5, C7 = 0.22uF
T1, T2 = BC 547,
N1---N4 = IC4093,

Relays = 12V, SPDT, 20 amp contactsrelay dides = 1N4007

The next concept explains an automatic submersible pump start, stop circuit with dry run protection in order to implement an automatic ON/OFF switching of the motor in response to the high/low water levels of the overhead tank.

2) Circuit Concept

In one of the previous posts we learned a similar concept which also dealt with an automatic start/stop function of the submersible pump contactor button, however since here the sensors involved float switches, the design looked a bit complex and not suitable for everyone.

Moreover, the dry run protection included in the design relied on the temperature change of the motor for executing the required protection of the motor. This feature too was not too desirable for a layman since installing the heat sensor over the underground motor was not easy.

In this post I have tried to eliminate all these hassles and designed a circuit that is featured to sense the water presence solely through metal sensors immersed in the relevant water sources.

Simulation and Working

Let's understand the proposed Automatic submersible pump start, stop circuit with dry run protection.

A single IC 4049 can be seen engaged for the entire sensing, start stop actions and the dry run protection execution.

The gates involved here are 6 NOT gates from the IC 4049 which are basically rigged as inverters (for inverting the polarity of the fed voltage at its input).

Let's assume the water inside the over head tank goes below the desired lower threshold, as indicated in the above diagram.

The situation removes the positive potential that ws supplied through the water to the input of N1. N1 responds to this by causing a positive to appear at its output pin, which instantly causes C1 to begin charging via R2.

The above condition also allows the positive from the output of N1 to reach the input of N2, which in turn produces a low or a negative at the base of T1 via R3....the associated relay now toggles ON and activates the "START"  button of the contactor....however the relay activation is sustained only for a second or so until C1 is fully charged, this length may be set by appropriately tweaking the values of C1/R2.

For the moment let's forget about N5/N6 stage which are positioned for the dry run protection implementation.

Let's assume the pump is running and pouring water into the shown OH tank.

The water now begins filling inside the tank, until the level reaches the brim of the tank "kissing" the sensor corresponding to the N3 input.

This allow a positive through the water to feed the input of N3, enabling its output to go low (negative), which instantly causes C2 to begin charging via R5, but in the process the input of N4 also becomes low and its output inverts to a high prompting the relay driver to activate the relay.

The upper relay instantly activates but only for a second, toggling the "STOP" button of the contactor, and halting the pump motor. The relay timing may be set by appropriately tweaking the values of C2/R5.

The above explanation takes care of the automatic water level control by toggling the submersible start/stop button through the circuit's relays. Now it may be interesting to learn how the dry run protection is designed to prevent a dry run hazard in the absence of water inside the borewell or a underground tank.

Let's go back to the initial situation when the water in the OHT has fallen below the lower threshold and rendered a low at the input of N1....which also renders a low at the input N5.

N5 output turns high due to this and provides a positive supply for C3 so that it can begin charging.

However since the process is also supposed to start the motor, if water is present, the pump may start pouring water in the OHT which is supposed to be detected by the input of N6, causing its output to go low.

With N6 output at low, C3 is inhibited from charging, and the situation stays stalemate...and the motor continues to pump water with no change in the previously explained procedures.

But, suppose the motor experiences a dry run due to an absence of water in the stated above C3 begins charging and the output of N6 never turns negative to stop C3 from charging fully....therefore C3 is able to complete its charging within a predetermined span of time (decided by C3/R8) and finally producing a high (positive) at the input N3.

N3 responds to this in the same way as it would do when the water in the tank is detected at the uppermost threshold....prompting the switching of the upper relay and stopping the motor from running any further.

The dry run protection for the discussed submersible pump start, stop circuit is thus executed.

Parts List

R1,R4,R9 = 6M8
R3,R7,R6 = 10K
R8 = 100K
R2,R5,C1,C2,C3 = to be dteremined with experimentation
N1------N6 = IC 4049
T1 = BC557
T2 = BC547

The 3rd idea below details a timer circuit for submersible borewell pumpset which alternately switches the pumpset ON/OFF at a predetermined rate in order to allow the ground water sufficient time to restore at regular intervals and to ensure a consistent water supply to the attached overhead tank. 

The idea was requested by Mr. Siva.

Switching Submersible Pump with 1 Hour Delay

I want to run a submersible pumpset only in 3 phase with major interval of 1 hour interval duration. There is no available ground water supply for continuous running for the pump. So i need a AC circuit to operate automatically timely for 1 hour running & 1 hour idle.

Please provide a circuit to operate without any drawbacks because if anything happens wrongly need to spend more money & time to resolve it.More than that only source of water for us(borewell only).


Pump Specifications

100mm(4")borewell submersible pumpset

Power:3 phase A.C
Rpm :2850

Rpm :2850
No.of stage:45

3) Designing the Pump Timer Circuit

The requested submersible bore well pump timer circuit can be simply built using a single IC 4060 timer circuit and a relay, as indicated below

As may be seen in the above diagram, the IC 4060 is wired as a simple timer circuit whose timing limit is determined by the combined values of C1 and of P1/R1.

P1 can be adjusted for getting any desired delay ON/OFF at pin#3 of the IC, within a stipulated range.

Since the IC is configured as a free running astable multivibrator, the ON/OFF delays at the output pin#3 continues to toggle the transistor driver stage and the relay infinitely as long as power is available to the circuit.

If as per the specifications, P1 is adjusted to obtain a 1 hour ON/OFF delay at pin#3, the relay could be expected to switch ON/OFF at the same rate continuously as long as the circuit may remain powered.

The relay contacts can be seen wired with the 3 phase motor's contactor coil, which correspondingly operates at an identical delay rate during the course of ON/OFF switching.

This results in the switch ON and OFF of the borewell motor at a precise interval of 1 hour, which in turn makes sure that the ground water gets ample time to replenish and enable a sustained water supply for the motor to pump in.

Other time delays may be achieved for the proposed submersible pumpset timer circuit by appropriately adjusting P1, as per the given specifications or the ground water conditions.

In the 4rth concept below we'll discusses a simple remote controlled submersible pump circuit which could be simply configured using any standard 2 channel 433MHz remote control modules.

The idea was requested by Mr. James Smith

 Remote Controlled Start/Stop for Pump Motor

I have read a lot of your post and have successfully implemented them several times.

Now I want a design for switching my submersible single phase motor on and off via remote control.

On the starter there a push button for on and push button for off.

The push button is pushed only for 2 seconds and released and the motor is ON.

The same for stop. The push button is pushed for 2 seconds and the motor is OFF.

Pls help me in doing this as we are having trouble going up and down the staircase from 7 floor to ground floor to just ON and OFF the submersible motor.

If the circuit is ready, I will just connect it to the push buttons.

James Smith

4) The Design

We have already witnessed the basic triggering concept of a submersible pump using an automatic "start" and "stop" implementation of the pump contactor switches.

In this remote controlled submersible pump circuit also we follow a similar concept but instead of water sensors, here we do it using a remote controlled modules and subsequent momentary relays switching for initiating the relevant start stop buttons.

For this we can employ a two channel 433 MHz RF remote control modules, which are extremely accurate with their working.

I would recommend buying this unit instead of building one, because these are quite cheap and are easily accessible through online electronic stores.

However if you are interested to make it, you could try it out by procuring the recommended chips for these remote controlled modules which are also available through all standard online electronic retailer.

If you purchase the units readymade, then it's just about configuring the relay contacts with the submersible start, and stop buttons, as shown below.

To be precise, it's the N/O and the pole of the relays which needs to be connected across the submersible buttons.

For identifying the relay contacts of the remote receiver unit one may take the help of one my earlier pasts which explained how to understand and use relays in circuits.

However since the contactor start stop buttons could be specified to work with high switching current, these may require special high current relay driver stages for the individual buttons.

Therefore the triggering supply from the remote receiver relays needs to be further integrated with the above mentioned high power relay driver stages as demonstrated in the following figure:

Circuit Diagram

The relay driver stages shown at the right side of the diagram is made by configuring transistor relay drivers with the respective high power relays.

The bases of the transistors can be seen connected with series high value capacitors, this is to ensure that the relays remain activated only for a couple of seconds, regardless of the switching periods of the remote control module's relays, or regardless of how long the user keeps the remote transmitter handset button pressed.

The shown remote control receiver module consisting of the receiver circuitry and the two relays will need 12V supply from an appropriate DC source, such as a 12V AC DC adapter.

This 12V further needs to be configured with the relay contacts and the relay driver stages also, for enabling the intended remote controlled start/stop switching of the submersible ON/OFF buttons.

The 5th idea below explains a circuit which controls a submersible borewell motor by operating its red (Start) and green (Stop) buttons, in response to low level, high level water conditions, and also in a condition where the motor may experience a dry run situation. 

The idea was requested by Mr. Vamsi.

Automatic Start/Stop Controller for Borewell Contactor

Hi sir, i'm an electronics hobbyist and a regular viewer of ur blog , also a very big fan for U sir... :) i have learned very much from YOU. and THANK YOU VERY MUCH SIR... :)

Sir, can u pls suggest me, i need the circuit design of fully automatic water overflow controller cum dry run protector circuit with showing level indicators.

The circuit needed for the borewell starter like generally all of the borewell starters will have a GREEN and a RED push type buttons. manually we will start up the motor by pressing the GREEN for 1sec. and 1sec. for shutting OFF as the same way, the design i need is, the controller works with Dual Relay ( 2 individual Relays) one is for starting winding.

i.e Relay1 activates for 1 sec. to START motor and the other Relay2 is to STOP the motor activates for 1 sec. respectively and the main thing is we can not drop sensors such a lengthy to the ground level of the deep wells

so, all i need is in case if there is less water in the bore well, the sensor in the OHT is connected to upper water pipe which falls in the tank,sensors should activate and energise the Relay2 which in turn shutting OFF the motor if water discharges very low. the water which discharges from the pipe will take atleast 15sec. so, it will be needed ON time delay for at least 20 sec.(relay1 activates and wait for water discharge up to mentioned time.)

Now the motor should works in these conditions:

1.when water low level in OHT, Relay1 gets energized for 1sec & switching ON the motor.

2 Relay2 should activates in two conditions: a) when water filled up in OHT activates for 1sec. shutting OFF motor , and b) when borewell DRY RUN, time delayed for at least for 20sec and activates the Relay2 for 1sec to shut OFF the motor.

The circuit need to works in 12v dc. and also if possible need a RESET push button, when the water in the OHT is suppose a half of the tank, if we need to make tank full, the motor should start by pressing RESET button.

This is my brief explanation. i tried very much for this desired circuit design. but i'm not such expert to say but i have a technical, logical and basic knowledge in this field. i hope that u understand my request. Pls do the needful Sir, Hopefully awaiting for ur valuable reply. For posting the circuit diagram, my ID :

Thanks and Regards

Vamsi Krishna

The Design

In a couple of my earlier articles, I discussed about a similar circuit concerning a semi-automatic submersible pump controller circuit, however the design utilized an ordinary moisture sensing metal probes for the detection and activation.

The present design relies on a reed/magnet based float switch operation, which not only makes the operations easier but also a lot reliable.

The proposed submersible borewell motor starter controller circuit may be understood by referring to the following diagram:

Circuit Diagram

The diagram above shows a very straightforward set up using a couple of identical IC 555 monostable stages.

The IC2 stage forms the submersible pump starter circuit, while the IC2 stage is positioned to stop the pump switch.

Both the circuits work with reed switches (float switch) which may be seen positioned inside the overhead tank, one at the bottom, the other at the top of the tank.

The bottom reed closes when the water level is near the bottom threshold, and parallel to the reed switch, while the upper reed switch closes when the water level reaches at the level where its been installed.

Assuming the water level to be near the bottom reed switch, the reed switch closes, triggering the IC1 stage, which in turn momentarily clicks the associated relay.

The relay being wired across the START button of the submersible pump, the motor gets initiated and it starts pumping water to the overhead tank.

The water level in the OHT now begins rising, and when it reaches near the upper reed switch reed#2, it closes triggering the IC2 relay for a moment activating the STOP switch of the motor. The motor now stops and discontinues the pumping of water inside the OHT.

Motor Dry Run Protection

As requested, the STOP circuit also needs to be signaled in case a dry running of the motor is detected.

In the absence of water to pump, the motor may be subjected to a "dry run" situation which in turn might heat up the motor to dangerous levels.

A simple heat sensor thus can be introduced to sense the rising heat of the pump motor and signal the IC1 stage so that the STOP button is instantly activated on time and the motor is saved from burning.

A simple yet very effective heat sensor circuit may be witnessed below. It ensures the vital dry run protection for the borewell motor and also facilitates the action externally without

Using 3 opamps from IC LM324

The circuit is configured around three opamps (LM324 or three separate 741 ICs), where A2 forms the temperature sensor through D1.

D1 which is a 1N4148 diode is used as an effective heat sensor, and is supposed to be glued to the motor body for the sensing.

P1 is set such that when the motor tends to heat up, the output of A3 becomes high enough to trigger the opto transistor into conduction, therefore in case a motor goes through a dry run situation and begins getting hotter, D1 detects this triggering the connected opto coupler (4n35).

Now since the collector of the opto coupler is attached with the pin#2 of IC2 (STOP relay), the IC2 responds to this and quickly initiates the relay and halts the motor.

The motor gradually cools down, which causes the opto coupler too to shut down and the situation reverts to normal and in the original state.

The first circuit was successfully built by one of the avid readers of this blog Mr. Chandan, the following figure was sent by him, updated with the correct and the tested values of the R and C components for producing a 2 sec ON delay for the relevant start/stop switches.

The final 6th idea below explains a simple  3 phase solar submersible pump inverter circuit which can be made by configuring a few ICs and a few power devices.

The idea was requested by Mr. Lufono and Mr. Sami.

Solar Inverter for 3 Phase Pumps

First of all i must say thanks to you and  Mr. Lufono, i have many solar projects of solar tube well and want to make a three phase inverter and i connected 14 to 23 solar panels of 250 watts every solar panel 31 volts 8amp in series than i have 450 vdc to 750 vdc .my submersible pumps 5.5kw to 7.5 kw 3phase 220v and 380v 3phase. 

Please i also request that in the circuit auto motor speed control also needed, means when solar panel voltages up or down with the time and sunlight motor speed also adjust automatically. if igbt needed GP50R12KT3 or other no problem plz help me so so thanks . 


5) The Design

I have already explained a simple single chip 3 phase full bridge inverter circuit, the same IC can be used for the proposed solar pump inverter circuit. The standard configuration of the 3 phase driver IC IRS2330 can be seen below:

Circuit Diagram

However since the mentioned 3 phase driver requires a dedicated 3 phase signal across its triggering inputs marked as HIN....LIN, it would be first important to learn about a simple 3 phase signal generator circuit using opamps which could be integrated with the above design for the intended outcome..

It doesn't need to be a sine wave 3 phase signals a simple square wave 120 degree phase shift PWM generator could be used for the application, as illustrated below:

3-Phase Generator Schematic

The above 3 phase generator circuit can be further modified in the following manner so that it can be fed to the 3 phase driver IC shown in the first image:

Using BJT Buffer Stage

Here we see how the outputs from the 3 phase generator opamps are buffered using transistor inverters for producing the required 3 out-of-phase channels for the HIN...LIN inputs of the IRS2330 3 phase inverter driver IC.

The load connected with the driver mosfets or IGBTs now would receive a square wave 3 phase operating voltage, which could be a submersible pump motor in our application as per the request.

In case the IC IRS2330 looks difficult to acquire in the local market, the following cheaper half wave solar submersible inverter circuit concept could be implemented, although with 50% less wattage efficiency.

The BJTs could be replaced with appropriately rated mosfets or of the configuration is pretty straightforward and does not need much explanation.

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