The 5 simple dry run protector circuits presented here shows simple methods by which insufficient water conditions inside an underground tank can be sensed without introducing probes inside the underground tank, and thus preventing any possibility of motor dry running. The circuit also incorporates an overhead water overflow control feature.
The idea was requested by one of the interested readers of this blog.
Technical Specifications
Do you have any idea of how to sense dry run motor by checking at the overhead tank inlet without checking at the underground tank since it takes more work in getting the wire from underground to motor place.
My requirement is motor should go off if no water is flowing at the tank inlet. Also motor should not off initially since it will take at least 5 seconds to push the water at the tank inlet.
My requirement is to switch off the motor when motor is not able to pump the water. This may be due to water level become less than certain threshold in the underground tank Or pump has malfunction.
My preference is not linking any wire from the underground tank to the circuit. My preference would be sensing the water flow in the overhead tank inlet. Hope you understood my requirement.
I would like to switch on the motor manually. If we replace the buzzer with a relay, then motor will be switched off immediately upon switching on motor,since it will few seconds for water to flow on the tank inlet.
We need to provide some time delay to sense the water flow at the tank inlet to avoid this problem. but I am not sure how to introduce a delay. Please help me on this.
Design #1
The circuit of the proposed underground water pump motor dry run protector can be understood with the help of the following details:
The circuit is powered with a 12V AC/DC adapter.
When the push-button is pressed momentarily, the BC547 transistor along with the BC557 relay driver stage is switched ON.
The 470uF capacitor and the 1M resistor forms a time delay network and locks the entire relay driver stage for some predetermined delay after the push button is released.
This delay interval can be adjusted by experimenting with the 470uF capacitor and/or the 1M resistor.
As soon as the relay activates, the motor is switched ON which instantly starts pulling water in the overhead tank.
The moment water inside the overhead tank pipe connects with its residual water, the submerged probe which is the positive probe gets linked with the probe that's introduced at the mouth of the pipe. This enables voltage from the lower probe to reach the base of the relevant BC547 transistor via the water, and the 1K resistor.
The above action now latches the relay driver stage such that even after the time delay lapses, the relay holds and sustains the operation.
Now the motor halts only under two conditions:
1) If the water level reaches the overflowing level of the overhead tank wherein the positive potential from the lower probe gets connected with the probe that's connected with the base of the upper BC547 transistor.
The condition switches ON the upper BC547 which instantly breaks the relay driver stage latch and the motor stops.
2) If the water inside the underground tank dries out, which obviously stops the water link inside the overhead tank pipe and breaks the relay driver latch.
An Automatic version of the above sump motor controller with dry run protection system may be witnessed below:
Using Logic Gates: Design #2
A fully automatic version can be also built using 6 NOT gates from the IC 4049 as shown below, this configuration can be expected to work much more accurately than the above transistorized version of the automatic underground submersible water pump dry run protection circuit.
Feedback from Mr. Prashant Zingade
Hello Swagatam,
How are you? Your Idea and logic are awesome. hats-off to you. I tried IC4049 version, It is working fine except one issue.(I done one modification base on your previous design and it is working now).
I am facing one issue in IC version like when we put it on auto mode, dry run function is not working. Please see attached simulated video file.
Case 1: I observe If water level reach below bottom level relay will on pump but it fail to sense dry run and pump will continue to on.
Case 2: In manual operation it works perfectly. Excuse for any typo.
Warm Regard
Prashant P Zingade
Solving the Circuit Problem
Hello Prashant,
Yes you are right.
To correct the situation we will need to connect the output of N6 to the base of the BC547 through a capacitor, you can try connecting a 10uF here.
Negative of the capacitor will go towards the base.
But the problem is, this operation will activate the system only once, and if water is not detected then the system will switch OFF the relay and remain switched OFF permanently until it is activated manually using the switch, and until the yellow sensor comes in contact with water yet again. Regards.
Update
Dry Run Protection for Motor Reed Switch: Design#3
The following diagram shows an effective dry run protection that can be added to the pump motor, in cases where water is unavailable in the tank and no water flows out from the pipe outlet.
Here the push-button is initially pressed to start the motor.
The 1000uF capacitor and the 56k resistor acts like a delay off timer and keeps the transistor switch ON even after the push button is released so that the motor keeps running for a few seconds.
During this time water can be expected to flow out from the pipe outlet, and this will fill up the small container introduced near the mouth of the hose pipe. This container can be seen having a float magnet and a reed switch relay arranged inside.
As soon as water starts filling inside the container the float magnet quickly rises at the top and reaches at a close proximity to the reed relay, latching it ON. The reed relay now feeds a positive voltage to the base of the transistor ensuring that the transistor gets latched up and keeps the motor running.
However in an absence of water, the reed relay feedback is unable to turn ON, which causes the motor to shut down once the delay OFF time elapses after the predetermined amount of delay.
Dry Run Protection without Reed Switch and Magnet
If you are not interested to use a reed switch or a magnetic float sensor arrangement, you can simplify the above design as indicated in the following diagram:
When the push button is pressed BC547 and the BC557 conduct to operate the relay. The relay switches ON the connected pump motor. The pump motor begins attempting to pump water through the pipe.
If water is available, it flows through the pipe outlet and bridges the positive supply with the base of BC547. This causes the whole circuit to latch through the water contact, so that the pump keeps pumping water continuously.
However, in a situation where water is dry or unavailable, no water is able to feed the base of the BC547. Therefore BC547 remains switched ON only for a period determined by the charge on the 100uF capacitor.
The 100uF capacitor and the 1 M resistor decides for how much time the BC547, the BC557, the relay and pump motor can remain switched ON.
As soon as the above time elapses, the circuit automatically switches OFF itself and the pump motor and saves the motor from burning due to a dry run situation.
Current Sensed Dry Run Protector Circuit: Design #4
In the above ideas the circuits mostly depend on detection of water which makes the designs a little outdated and cumbersome.
The following idea unlike the above depends on load sensing or current sensing for executing the dry run protection feature.Thus it is contactless, and does not rely on having a direct contact with the motor or water.
Here, the two transistors along with the associated components form a simple delay ON timer circuit. When SW1 is switched ON, the transistor T1 remains switched OFF because of C1 which initially grounds the base drive of T1 coming via R2, while C1 charges.
This keeps T2 switched ON and the relay also switches ON. The N/O of the relay switches ON the pump motor. Depending on the value of C1, the motor is allowed to run for sometime. In case there's no water, the motor runs unloaded with relatively low current passing through RX. Due to this RX is unable to develop sufficient potential across itself, which in turn keeps the opto-coupler LED switch OFF. This allows C1 to get charged fully unhindered during the stipulated period.
As soon as C1 is fully charged T1 switches ON, and this switches OFF T2 and also the relay. The motor is finally shut off protecting it from a dry run situation.
On the contrary suppose the motor gets the normal supply of water, and starts pumping it normally, this instantly loads the motor causing it to consume more current.
As per the calculated value of the resistor Rx, this develops sufficient voltage across it to switch ON the LED of the opto-coupler. Once the opto is activated C1 is inhibited from charging, and the delay ON timer is disabled. The relay now continues to supply the 220V to the motor allowing it to run as long as water is available.
Another Simple Motor Dry Run Protector Circuit: Design #5
Here;s yet another idea which explains a very simple overflow controller circuit which is able to implement and restrict overhead water overflow as well as dry running of the pump motor.
The idea was requested by Mr. S.R. Paranjape.
Technical Specifications
I came across your site while searching for Timer circuit. I am very surprised by seeing how much one individual can do!
I refer to your write up of Friday 20, 2012.
I have a similar problem. I have a designed a circuit, which appears to work on breadboard.I want to start pumping only if there is a need in upper tank and lower tank has enough water. Further if water in lower tank goes below certain level while pumping, the pumping should stop.
I am trying to find a way for satisfying my last condition.
I want to start this circuit manually and when the circuit stops pumping action, it should also nullify my start action. This will stop the total operation of filling the upper tank.
Somehow I feel that combination of two relays( outside the circuit) in ON/Off part of total project should work. I am unable to figure how so far.
The above drawing may express what I want.Project/circuit is powered by the outer source. The output(that is used to stop umping) from the circuit should open the outer source, which was activated manually.
I hope you will excuse me in taking this root to pose my problem. If you find merit in my problem, you are welcome to put it on your blog.
I am attaching the circuit that I have devised.
As an introduction to myself- I am senior person(age 75 years) and has taken this as hobby to use my time interestingly.I was Professor of Statistics, University of Pune.
I enjoy reading your projects.
Thanking you
S.R.Paranjape
.bmp)
The Design
I appreciate the effort from Mr. S.R. Paranjpe, however the above design may not be correct due to many different reasons.
The correct version is shown below (please click to enlarge), the circuit functioning may be understood with the help of the following points:
The point "L" is positioned at some desired point inside the lower tank, which determines the tanks lower water level at which the motor is in the permitted zone of operation.
The terminal "O" is fixed at the topmost level of the upper tank or the overhead tank at which the motor should halt and stop filling the upper tank.
The basic switch ON sensing is done by the central NPN transistor whose base is connected to point "L", while the switch OFF action is performed by the lower NPN transistor whose base is connected to point "O".
However the above operations cannot initiate until the water itself is supplied with a positive potential or voltage.
A push-button switch has been included as requested for facilitating the required manual start function.
On pressing the given push button momentarily, allows a positive potential to enter the tank water via the push button contacts.
Assuming the lower tank level to be above the point "L" allows the above voltage to reach the base of the central transistor via the water, which instantly triggers the central transistor into conduction.
This triggering of the central transistor switches ON the relay driver stage along with the the motor, and it also latches the relay driver transistor such that now even if the push button is released sustains the operation of the circuit and the motor.
In the above latched situation, the motor halts under two conditions: either the water level goes below the point "L" or if the water is pumped until the overhead tanks upper limit is reached, that is at point"O"
With the first condition, the voltage from the relay driver collector is inhibited from reaching point "L" breaking the latch and the motor operation.
With the second condition, the lower BC547 gets triggered and breaks the latch by grounding the central transistors base.
Thus the overhead water level controller circuit is allowed to remain operational only as long as the water level is at or above point "L" or is below point "O", and also, the initialization is solely dependent on the pressing of the given push button.
IC 555 Dry run protection circuit
The dry run protection can be added to an existing IC 555 based controller circuit, a shown below:
The dry run function in the above design works in the following manner:
When the water level goes below the "low level" probe, causes the positive potential to be removed from pin#2 of the IC. This in turn causes pin#2 to go low, which instantly turns pi#3 high.
This high signal passes through the 470uF capacitor swithing ON the relay driver stage, and the pump motor is switched ON.
The relay driver and the pump remains switched ON only as long as the 470 uF charges, this may be for around 3 to 5 seconds.
Within this time span, if the pumps starts drawing water will allow the water sensor connected with the blue wires to be bridged by the pumped water.
The associated BC547 will now get the base bias and begin conducting, bypassing the 470 uF capacitor. This will enable the relay driver BC547 to conduct freely until the full tank level is reached.
On the other hand, if suppose there's no water, and the pump runs dry, will be unable to bias the upper BC547, and eventually the 470 uF will be charged full blocking any further base current to the relay driver stage. Due to this relay will be switched OFF preventing the dry run condition.
hi sir,
I have tested the circuit with motor in that I faced an issue. when I touch upper BC547 Base wire thru the hand motor started jerking and when water touched upper transistor base wire not the terminal then also motor started jerking. I think induction is more how to overcome this?
Hi Sathish,
please try connecting a 0.22uF, or a 0.47uF between the base and the ground of the upper BC547 and check the results….
hi sir,
i have tried the given LED indication circuit everything but updates required on below.
1. when no water flow detected the green LED taking long time turn off but relay turned off early it should be same time.
2.when tank full at high level indicator organe LED only to be turned but for me yellow and orange both are turning on. Yellow to be turned off only when is turned off not all at high level indication l.
Hi Sathish,
With reference to this diagram, here are the possible solutions for your questions:
1) Please connect a 3V zener diode or a 6V zener diode in series with the green LED, anode of the zener diode will be towards the collector of the lower BC547.
2) The only solution for this to remove the yellow LED entirely, because it is not serving any purpose.
hi sir,
As per new diagram when no water flow then yellow LED turned on but at the same time high level sense RED LED also turned on. This is not expected in our dry run scenario.
Sathish, yes that’s the correct response from the LEDs in the following diagram:
https://www.homemade-circuits.com/wp-content/uploads/2024/09/555-water-level-controller-with-dry-run-protection-and-LED-indications.jpg
The yellow LED indicates that the relay has been turned OFF (because there’s no water detected by the dry-run sensor and the 470uF is fully charged)
The RED LED indicates that although the relay is turned OFF, the water in the tank is below the LOW level.
hi sir,
pls share the updated diagram url or specify the article section because am unable to find it.
thanks
Sure, here is the URL of the new diagram:
https://www.homemade-circuits.com/wp-content/uploads/2024/09/555-water-level-controller-with-dry-run-protection-and-LED-indications.jpg
I have assembled the design 1 circuit where in the timer is controlled by 1M resistor and 470micro farad capacitor. It takes long time to to de energize the relay. My requirement is only 10seconds. This i have resolved by connecting 18k resistor in parallel with the capacitor. The other problem is the relay voltage is gradually fading and at particular voltage the relay is cut off. Pl suggest how fading of relay can be avoided and cut off should take place instantaneously.
Hi, thanks for trying the first circuit.
The relay voltage will get weaker and ultimately turn off if the BC547 near the push-button does not remain latched by the feedback voltage coming from the header tank water flow from the pipe. In the first diagram you can see the feedback voltage coming from the header tank to the base of the BC547 through a 1k resistor.
Please verify whether the BC547 base is getting this feedback voltage or not.
To ensure that the relay trips off quickly when the header tank is full, please attach the positive supply probe close to the upper sensor probe of the tank. Keep the positive supply probe at around 1 inch distance from the upper probe.
Thanks for the explanation. The transistor Bc 547 base is getting very good positive feedback through water out let pipe sensor and getting immediate latch. When there is discontinuity of water the realy de energize immediately and no problem. If you assume a situation after pressing the push button motor starts and no water then relay is held for few seconds and de energize due to absence of positive feedback through water. Such de energizing is only happening gradually may be due gradual discharge of timer capacitor 470mfarad. This weak opening may create arcing of rela relay contact as 230v motor is connected. Hope made the issue clear.
Ok, now I understand what you are trying to say.
In that case the only way to ensure that the relay deactivates sharply is to put an LM393 comparator IC or a 741 opamp IC between the two transistors.
Let me know if you are able to configure it yourself or not.
Yes I can configure. The situation I have told may be a rare case. I will try as per circuit and difficulty if any I will go as per your suggestions. Thanks for your guidance please.
Ok, great, let me know if you have any issues with the implementation…
Thank you sir
hello swagatam
thanks for the knowledge and idea given on design 4
it has really opened up my mind
but how can create one using an arduino uno r3
your response will be highly appreciated
Thank you Nathan, Glad you found the post helpful.
However, since my Arduino knowledge is not good, it can be difficult for me to provide an Arduino version of the circuit.
Nevertheless, an Arduino design could be an overkill for this simple concept.
from Kesavachandran
hello Swagatam many thanks for your current sense circuit (Current Sensed Dry Run Protector Circuit: Design #4). I again thank you for your quick response. But one doubt. In the circuit I cannot see C2. Also kindly note the value and wattage of RX. Regards
My pleasure Kesavachandran,
C2 was mistakenly written, actually it should be be C1, I have corrected it now, thanks for pointing out the mistake.
RX wattage can be calculated using the following formula:
Wattage = 1.2 x Motor current with load
thank you mr. swagatam for your reponse.
Kesavachasndran
You are welcome Kesavachandran.
Once again I thank you sir for your reply
You are welcome Kesavachandran
Electrical current sensing circuit for avoid dry run submersible motor
Now a days there is a protection sensor in submersible motor Panel. Can you tell me what kind of circuit thay are using ? Swagatam please . With regards
Hi kesavachandran, I Can’t seem to figure out that circuit, if I happen to get one will surely let you know about it.
Thank you sir for your prompt response
You are welcome Kesavachandran!
Hi, Swagatam!!!
Design #4
Question: maybe it is necessary to put a resistor of about 2-10 kilo ohms between the diode bridge and the optocoupler?
May I use 4N35 optocoupler in this circuit?
Thank you for response.
Respectfully,
Jorge
Hi Jorge, yes you are right, may be a 100 ohm resistor should be enough. You can use any opto coupler which works with an LED and transistor internally, 4n35 will also do!
@Swagatam! Can PC817 be used in place of 4N35?
Thanks for your attention!
Hi Dang, yes, you can use PC817 in place of 4N35
hi,
i have tried 555 IC controller low/high level detection working perfectly but when no water flow still motor remains on. but it should off when no water flow right.
That should not happen, because once the 470uF capacitor charges up, it will cut off the base bias for the BC547 and turn off the relay.
Please remove the dry run (upper BC547 section) completely and check again, if the motor keeps running then the problem could be with the 470uF capacitor at pin#3 of the IC 555, let me know how it goes…
hi sir,
what is the recommended capacitor voltage ? for 470uf.
Hi Sathish, if the 555 operating voltage is 12V then the capacitor voltages can be 25V.
hi sir,
correct as you said after removed the upper BC547 no supply to relay. what could the issue any idea?
So, now, do you mean when the low water level is detected the relay is turned ON for a few seconds and turned off, right? Please let me know…
hi Sir,
Relay not turned on for few seconds also it’s completely not working. after install the upper BC547 water controller working fine concern is water flow sensor not working. any other circuit for 555 ic circuit for flow sensor.
Satish, short circuit the 470uF capacitor terminals and check again, if still it doesn’t work then something may be wrong with your circuit.
You must first make the circuit work without the upper BC547, once the low level, full level detections work normally only after that we can proceed with the dry run integration.
hi sir,
Thanks for your efforts and timely reply.
This worked perfectly, including dry run protection. I need to add two more LEDs apart from the existing. I can take the existing circuit LED-1 for motor On. Same like that, I need another LED-2 for the motor off. And LED-3 for dry run if motor on but there is no water flow, then in case LED-3 is on. Each LED’s to be worked on their specific function.
That’s great Sathish,
Glad it is working now!
Please check the updated diagram in the above article, I have added all the necessary LED indicators in it, you can keep or remove them as you want.
hi sir,
after changing the IC low level and high level along with flow sensor working now. But what happen when water flow is there capacitor keep on charging and discharging during the time low level and high level working perfectly. when no flow is there capacitor got charged full and relay the turned off. But the problem here is capacitor is not allowing relay to turn on even in low level as next attempt i tried with power off and on also still not worked after short the capacitor manually allowing relay to on. Any solution on this.
No problem Sathish, i will make sure you succeed with this project.
Please try the following modifications in the design:
https://www.homemade-circuits.com/wp-content/uploads/2024/09/simple-555-water-level-cut-off-circuit-design.jpg
I have done the following modifications in this design:
1) added a 10k on the negative side of the 470uF capacitor so that iit can discharge effectively whenever pin#3 of the IC turns low (when water high level is detected)
2) moved the 1k resistor from the collector of the upper BC547 to the emitter of the upper BC547, to ensure proper safety for the transistor.
3) connected the anode of the 1N4148 to the base of the upper Bc547 to ensure effective turn off for the transistor whenever high water level is detected and pin#3 of the IC turns low.
4) Reduced the lower BC547 base resistor to 4.7k to enhance the turn ON capability of the transistor and the relay.
Let me know how it works….
Sir,
Greetings..!!
This is not a mail to pointing a fault or critisise you.This is for appreciate you for your effort to give us industry standard circuits to hobbyists around the globe.all were very nice and work properly at first time morover every doubt you clear through mail as express as possible.Your circuit of water level indicater with 4049 successfully install at 6 of my relatives house past 2years all of them working fine up today.Anyway appreciate great effort.Keep post more circuits.Thanks alot…!!!
From Kerala
With love
Sison.c.s
Thank you so much Sison, I appreciate your genuine feedback. Please keep up the good work!
Sir,Regarding the #4 idea how can we calculate the current sensing resistor Rx?
to different loads.Appreciate if you could explain with 1hp motor as example.Thank you.
regards.
SISON
Kerala
Sison, the formula is
RX = 2.5 / Normal Motor Current while it is pumping water
Hi! What the power (WATT) of RX, how I can calculate it?
In this calculation (RX = 2.5 / Normal Motor Current while it is pumping water) current in amp, milliamp value?
Thank you, sir!
Current will be in Amps.
Wattage = 2.5 x Normal Motor Current while it is loaded and pumping water.
Can we replace RX with current sensing coil? Swagtam. I am thinking of Opamp and an inductive current sensing coil.
Any advice Swag?
Hi Dang, yes that may be possible, if the current sensing coil can produce sufficient voltage to operate the opto coupler.
The barzer will ring just when the pump is off for a dry run. From which I can see that there is a problem with the pump. So please tell me how to set this buzer?
Which circuit are you referring to?
Thank you for quick answering! If you don’t mind- please explain: at the over head tank, where the lower prob carries 12 volt DC, and whenever it completes cct with pin 2 and pin 6 at a time( both are receiving12 v dc), the relay not going off! 1M resistor getting heated. Please help me. Thanking you.
You are Welcome! A 1 M resistor has a very high resistance and can never heat up, even if you connect it with 220 V mains AC. So it seems something’s may not be correct with your resistors, because it is impossible for a 1M to become hot.
Please check the probe actions by manually connecting the 12V with the two sensor probes, alternately. This should set/reset the IC output ON/OFF alternately
Once the actions are confirmed make sure that the 12V supply in water is held close to the two sensing probes so that the sensing probes are able to detect the 12V supply through water optimally.
Dear Sir, I have tried your circuit with dry run along with 555 ic, but the relay not operating as the water level goes high or low. Only the relay being operated- for dry run! What is the function of 470 up electrolytic capacitor, as there is ac current is absent? And output of pin 3 of 555 being blocked. As a result relay driver not functioning. I’m not an expert. Please help me to build it. Thank you.
Hi Sujit, try operating the circuit by touching the probes manually with the positive line, and check whether the relay operates or not. If the relay operates then it means the water is conducting the 12V supply to the respective probes….in that case try placing the positive probe very close to the pin2 and pi6 probes, so that when water reaches these probes, the 12V positive connects with the sensing probes adequately.
The 470uF is a timing capacitor which allows the relay to operate for sometime until the 470uF charges fully then the supply to the transistor base is blocked by the 470uF. In the meantime if the pump starts pumping water the dry run transistor starts supplying the base current to the transistor so that the relay continues to remain switched ON
Hi Swagatam,
I want to put LED indication for overflow and dry run cutoff in IC 555 circuit, where can I place it ?
Hi Dipak, for the tank full indication you can put an LED between the positive and the pin#3 of the IC, via a 4k7 resistor.
For dry run indication you can put an LED in series with the upper BD547 base wire. If this LED does not light up after a few seconds and the relay switches OFF then it will indicate a dry run shut down.
Thanks Swagatam for prompt reply, LED for tank full indication is fine but any other idea for dry run indication with LED “ON” condition where I can visually see from the distance that the pump is stopped due to dry run.
Hi Dipak, there’s no other easy idea to monitor the dry run except putting an LED in series with the upper BC547 base…
Hi Swagatam,
Hope you are doing good.
I have tested your IC 555 based circuit in my table. It is working but there is a minor issue is that when dry run cut, the circuit doesn’t reset (even doing power off and on after a while ) unless I short the capacitor (to discharge). Could you please tell me how to solve this issue. Shall I provide a push button in parallel to the capacitor (to discharge) so that the circuit can be reset manually.
Please, awaiting for your reply.
Regards,
Babu Yousuf
Hi Babu, I think you can apply the following trick….take a BC547, connect its collector with the positive side of the cap and emitter with the negative side, and then connect the base of the transistor with the positive line via a 0.22uF series capacitor