Jump to content
Electronics-Lab.com Community
Sign in to follow this  
keron

WATER LEVEL MONITOR FOR PUMPS

Recommended Posts

hello friends ,i have developed a simple but efficient water level monitor and pump controller for OVER HEAD TANK.it has an added feature of monitoring the water level in sump or well if needed.i developed it mainly for my home,where i need to pump water from a small tank in my basement to a large OHT(over head tank).
i have serached for a circuit like this for weeks,but couldnt find one.so i designed it using CMOS 4001 & 4011.for noise immunity i have used 4093 schmidt trigger IC instead of 4011(i have only a broad idea about all these jargons ,iam not sure if its appropriate)..the pin numbers are clearly shown to make design idea to practical circuit easier.
The input to the logic gates can be either through a float switch or signal through a pair of conducting probes (which need to be amplified using transistors).from circuit its clear that it works on S-R latch feture of logic gates.i have provided visual output for the staus monitoring(it works in a limited way though)of tanks without extra wiring.the building cost for the circuit is less than 10 US$ including the mechanical relay and delay circuit(delayed turn -on) used with it.
Out put from logic circuit is amplified using a darlington pair to drive a 100ohm 6V relay.this relay is used to switch on a delayed turn on relay circuit which switch on the main terminal to pump.(please see the pdf attchement).I used two relays for high voltage isolation as an extra protection.
the probes are made of stainless steel wire (from paper clip)mounted on PVC pipes.wires are soldered to steel pins and joints made water tight with sealent adhesive.(inviting ideas for better as well as cheaper probes) .the central control circuit can work with input from Ultrasonic level sensor probes/IR level sensors as well as float switches and simple moisture probes.just modify slightly according to each type of input.
After 2 months of continuous use the only one problem i have faced so far is sometimes if you switch one and off the circuit rapidly after 3 or 4 attempts it will turn on the pump regardless of water level status.but if the water level in upper tank is at it maximum or in sump if it is below lower limit it will turn off pump immediately(anyway pump will not run dry or no overflow,it fullfill the purpose) )
more details are there in the pdf file.
special thanks for logism for designing this circuit.if you are into simulation of the circuit please get the logisim from website
http://ozark.hendrix.edu/~burch/logisim/
i am ready to send the .*crc file if u are interested in testing and simulation.it is very easy to construct the circuit from the bmp image in the previous post. the site restrictions prevent me from uploading the file.
download link to logisim http://ozark.hendrix.edu/~burch/logisim/download.html
I am inviting attention of all  members to please go through this circuit and provide with ideas to improve the CIRCUIT.Better level indication ideas will be appreciated also please point out the mistakes i made.thank you.

post-31314-14279143515462_thumb.gif

Share this post


Link to post
Share on other sites

in the diagram
UL=UPPER TANK LOWER PROBE
UU=UPPER TANK UPPER PROBE
LL=LOWER TANK(SUMP)LOWER PROBE
LU=LOWER TANK(SUMP) UPPER PROBE
RED led turns on when lower tank is empty and remains on till water reaches upper sensor level.
green led turn on when water reaches upper probe of upper tank& after that when water remains between two sensor probes in upper tank.
invites methods to make circuit more immune to noise.and other possible errors..
                                      one problem i have found so far is sometimes its not switching on  as expected but ONCE  it turns on it will definitely turn off when water level goes beyond lower level in lower tank and upper level in upper tank.but it is not happening always.when i check it it functions normally.(this was detected accidently when i was near the pumpdoing something else. it switched on as the water slowly filled the sup and pumped till it went  beyond lower level probe in sump .this cycle repeated till i turned off the circuit)should i change the schmidt trigger IC4093 back to 4011.OR IS IT DUE TO POOR SUPPLY VOLTAGE(150 TO 170 USUALLY INSTAED OF 230V)..any idea why its happening?i think its in the put stage to logic gate is the problem?not the main circuit...SOMEBODY PLEASE REPLY....... :'(

Share this post


Link to post
Share on other sites

many have send mails to me saying that they are unable to open the picture of main circuit ,the bmp image .so iam including a jpeg format of same pic.sorry for the inconvenience...

post-31314-14279143517557_thumb.jpg

Share this post


Link to post
Share on other sites

Actually, the circuit should have provision for both AC and DC operation.

I am not sure as to the use your pump is designed for...

Example:

Take for instance the typical basement sump that is used when a heavy downpour occurs.
Generally, a home will have a perimeter area drain around the inner walls of the basement, water will collect within the latter and through pitch of the pipe eventually end in the sump container, after the level of water reaches a determined amount a pump float switch will remove the water to the drain or outside.
The above is a good concept but most designers/engineers rarely think outside of the box...

Remember, with a heavy downpour lightning is usually noticed, the latter can easily cause a loss of AC power!  :o
Sadly, the sump is powered by AC, which in turn is now non-functional, the result = overflow...  :-[

A good design will have a 12V (tractor battery) for DC backup in the event AC fails.
Additionally, during the time the AC is operating it is trickle charging the battery.  :)

I designed the above circuit 10 years ago...


-Omni



Share this post


Link to post
Share on other sites

the circuit works in 12 volt DC.CMOS logic gates maximum working voltage is 3- 18 volt.
                            the sump in my use is not what you have mentioned.here in india because water supply line pressure is low we collect water in a tank below floor level from supplypipes and pump it to a overhead tank.its very common here.
                                            you could have published it and saved my valuable time used for designing it...lol .anyway can you suggest any modification especially the rapid switchone cause the circuit to turn on  prob...

Share this post


Link to post
Share on other sites

Hi Keron,

Actually, for the use you specified your design would be more suited.
The type i mentioned is for a particular purpose.

I used a float switch (waterproof) along with a relay, 555, 2N2222A and a small assortment of passive components.
Once the water level in the sump (tank) enabled the float switch the 555 in conjunction with a variable delay provided an ON time to a driver/relay which would empty the tank.
The relay is a DPDT using one half to enable the contact to the pump when initiated, the other half of the relay provides a throughput from an external charger to the DC source battery for charging etc...
Furthermore, a few LEDs depict status concerning pump enable along with DC (activated) in the event of a power outage.

Share this post


Link to post
Share on other sites

hi omni,
        as i metioned before the problem iam facing now is (though actually not a big issue)when i sswitch the pwersupply to circuit on and off rapidly in succesion it makes the pump on.but it still follows the logics and turn soff immediately if no water in lower tank or full tank above.
one day i noticed the pump turning on and off frequently without any reason.i have to switch off the circuit to stop it. 
                                    i have put a MOV across  the relay contacts.i cant find out why its happening.my supply voltage is 160v only(230 v idealy).any idea about the reason?

Share this post


Link to post
Share on other sites

Hi Keron,

Practically, all IC circuits draw a very small amount of currrent, the latter can cause problems since a power supply when turned off will slowly discharge since current consumption of your circuit is not enough to pull it to ground fast enough.

When you rapidly turn your power supply ON/OFF the source voltage is never able to find ground fast enough, the slow decay during ON/OFF is still at a potential to activate your low current circuit.
Remember, filtering capacitors and how they store a charge...

A good way to bring the source voltage to ZERO when turned off is to provide adequate isolation, use the below circuit to OPEN the rail voltage when turned OFF.
The circuit is proven and will allow you to rapidly enable your source supply ON/OFF without any problems.
However, do not add more capacitance to the bottom section of the circuit, keep the small filtering cap at 10uf; one does not need a lot of filtering for a relay!



Furthermore, DO NOT disregard the circuit in replacement for a load resistor to pull the source supply to ground, the latter is counter-productive and will only create more current and heat!

The above is a dilemma with most on-board power supplies, the circuit presented is a very good work around that will address the issue without any drawback!

Finally, i am not completely sure as to how you are using the MOV in your circuit since i believe the problem is associate with the DC level (voltage) powering the CMOS etc...

Another way to mimic the above without building the (pictured) circuit is to power your circuit (CMOS) with a small DC battery with an in-line switch.
Rapidly, switch the DC on/off in rapid sucession and see if your issue is noted.  ;)

-Omni

 

Share this post


Link to post
Share on other sites

hello Omni,
                  can you explain more about  powering your circuit (CMOS) with a small DC battery with an in-line switch.
                                        the MOV is used across the contacts of relay which switch on and off the pump.i used it becuase i have seen sparks acrosss the contacts when pump switches off.
                                              one more question.i have providing input to logic gates from probes which conducts when water come in contact with them.VDD  is the input voltage.but at first i tried connecting it directly that is Vdd through water to gate input.but the probes need to be almost in contactfor that to work.
                                                so instead of that i used BC548 to anplify i think the signal.the signal from probe is connected to base of BC547 through 150k trim pot..VDD (vss)to collector and emitter is connected to input of logic gate.which is pulled down using 10k resistor.
                                          any problem with the said idea?

Share this post


Link to post
Share on other sites

The DC source (battery) is a simple test to determine if rapidly switching your CMOS logic will operate properly without a false trigger.
Once the above is determined you will know if the DC power supply you are using is the culprit.

Arc flash across a relay is somewhat common because of the large motor load that is being switched in, generally you would purchase a relay for the required specification.
When purchasing the relay make sure to specify the MAX voltage/Current, factor in the NEC requirement and ask for the latter with arc supression etc...

Example: 230V/10A pump motor : 10 *1.25% = 12.5A

Sensitivity concerning the sensor/s you plan to use is another variable that requires experimenting.
Generally, a sensor requires an amplification stage to provide a level sufficient for TTL/CMOS, use your knowledge of transistor theory (basic) to determine the output required.
I cannot design a sensor circuit without having the sensor available since the latter does require some bench experimenting.
You appear to have a good knowledge of electronics and can perform the above.

Share this post


Link to post
Share on other sites

i will do it.the battery part.
                                        you are wrong omni for the first time.i have only basic(what i have studied in my school years)knowledge in electronics.i am a physician  with some interest in electronics.can you help me to  design  a water level sensing probe better than what i designed?the sensing part is basicaly conducting electrode.please..

Share this post


Link to post
Share on other sites

Keron,

I located a few circuits on the net that may work in your application.

A slight modification concerning any of the latter circuits may be necessary but the concept appear's proven regarding the designs.

Take a day and view the links below, see if you can make one work in your application.

http://www.uoguelph.ca/~antoon/circ/sensor1.htm

http://www.elecdesign.com/Articles/ArticleID/9137/9137.html


http://www.uoguelph.ca/~antoon/circ/sensor3.htm

http://www.zen22142.zen.co.uk/Circuits/Alarm/water_lev_alm.htm


:)

Share this post


Link to post
Share on other sites

none of them controlls two levels simultaneously.thats why i designed y circuit.i have seen almost every circuits u send to me during my serach for a level controller.i think my circuit is more simple than most of the circuits u send.
but this one
http://www.uoguelph.ca/~antoon/circ/sensor3.htm
is impressive i havent seen this one before.but one thing if this capacitive method is not realy capacitive as some one has comented .why to use so much complicated circuit.anyway its still resistive rt?
and in this one
http://www.zen22142.zen.co.uk/Circuits/Alarm/water_lev_alm.htm
can you tell me why the unmarked probe that carry 5 volt from 7805 is grounded using 100nF and 100uF capacitors.is it for de coupling.then i should try that first.both  caps  needed for it?why that circuit dont use a signal amplifier

Share this post


Link to post
Share on other sites

Keron,

The links provided (schematics/circuits) are used as another alternative.
Perhaps, in some way you may notice a section of the particular circuit that you can apply within your design.

The added capacitance on the output of the 7805 is a simple filtering method used on many regulator designs, the latter is used primarily to reduce stray noise when a long source lead (V) is used.
Additionally, the added capacitance provides a stable output for the regulator (78xx).


Share this post


Link to post
Share on other sites

omni.
              one more doubt.silly it seems.i read somewhere that every gate has to be pulled down /up using resistor.is that means when using the out from one gate as a input to other gate (example pin 2 of 4001 it need to be pulled down too since its input is from pin 4 of same ic,)i havent did  that.i used pulldown resistors only at inputs from probes)will that be a problem?

Share this post


Link to post
Share on other sites

A pull-up/down resistor is generally applied to an unused gate input since leaving the input open can introduce outside noise (electrical) causing the input to change state.
Whenever in doubt read the data sheet concerning the gate/IC you are using concerning the latter.



Share this post


Link to post
Share on other sites


Arc flash across a relay is somewhat common because of the large motor load that is being switched in, generally you would purchase a relay for the required specification.
When purchasing the relay make sure to specify the MAX voltage/Current, factor in the NEC requirement and ask for the latter with arc supression etc...



Arcing is NOT caused by switching IN a load! Arcing is caused when opening the relay contacts (switching out a load)!

Share this post


Link to post
Share on other sites



Arcing is NOT caused by switching IN a load! Arcing is caused when opening the relay contacts (switching out a load)!


The inrush current on a heavily loaded motor can easily cause an arc flash when switched in, i have noted it many times.
Generally, under the above condition a CB will trip but during the latter time an arc is present.
Obviously, the majority of time an arc flash is noted when a load is switched out.

Additionally, the issue concerning an arc flash must be addressed and corrected since contact properties will degrade in a non-linear manner.

The specification pertaining to the relay along with the current demand (potential) present at the contacts is the major issue.

Take some time and read the NEC, you may learn something...  ;)

Share this post


Link to post
Share on other sites

You are way of; start reading up on things before you open up! There is NO arcing when the contacts are closing unless a. the voltage is high enough to jump across the contact pair before they are shut or b. the relay is stupidly under-dimensioned for the purpose! What you might se at the closing moment could be a spark NEVER arcing!
And you know what you can do with the

Share this post


Link to post
Share on other sites

hello guys ,
                       you are deviating from the topic.i have used a MOV for the sparking issue.its nota problem at all.but what about my question on pulldown resistors  please explain .do i need to use them in every  input of logic gates.even in case of output of a logic gate used as input to another.please explain

Share this post


Link to post
Share on other sites

thanks ante.but that is the basic .my question still remains.between output of a gate to input of other  gate pull down/up resistor needed?or just a pull down resistor at the begining of circuit will do fine?

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

×
×
  • Create New...