WATER LEVEL MONITOR FOR PUMPS

[keron]

i have made some modification in the circuit.i am using two Metal oxide varistors .one for protecting relay terminals from arcing and the second protects the entrie circuit.
                            i have also included green and red LED as in diagram.they are connected from pins shown through a 330ohm resistor.
                                   also grounded the 12 volt supply rail through 330uF(electrolytic) and 0.1uF as in this pic
http://www.zen22142.zen.co.uk/Circuits/Alarm/water_lev_alm.htm
                         now iam facing two critical problems.one the green LED  remain on most of the time on switching on the supply to circuit  regardless of water level.after that circuit is not working properly.you can say not pumping at all.it has become entirely non functional.but sometimes in between testing it works properly.should i use a transistor switch than directly connecting the out from 4001 AND 4011 to LED through a resistor?
                                         as i said before iam using a transistor  comon collector circuit with only 100k resistor across base to amplify signal from probes.what can be the problem,any idea?                                           
                                             in the same  circuit please someone tell me(http://www.zen22142.zen.co.uk/Circuits/Alarm/water_lev_alm.htm)why there is a 1Mohm resistor with 1uF cap inbetween the logic gates ,also the 47k and 10nF cap.please ?

[audioguru]

I answered your questions about the Classic Cmos Oscillators in your other post.

[keron]

but what about my other questions?please help

[audioguru]

but what about my other questions?please help

you made many modifications to the circuit. Post your new schematic and we will see what is wrong with it.

[keron]

the modification is i have used red and green LED S in my first diagram.i have not used them in the original circuit.it was only in the theory part i used the LED.WHEN I USED IN MY REAL CIRCUIT NOW .The  circuit  malfunctioned.please see the diagram.there is some serious problem with the current schematic.i havent used the LED in my original working circuit.when i used  there is severe problemsin the circuit.no idea what is the problem.

[audioguru]

The circuit should work fine without the LEDs. The Cmos gates don't have enough output voltage when directly driving LEDs. So they don't have the proper logic voltage levels.
Fix it by using inverters, gates or transistors as LED drivers.

[keron]

ok if i use a 500k resistor through which i connect a NPN transistor as a switch to the output pin it should work fine rt?
                                i think the powersupply is also a problem.i get shock from the neutral wire in my home.can it be a reason for my logic gate malfunctioning.when i touched the tip of soldering iron when the circuit was working it made the relay to switch on.what to do to make a good powersupply?rt now iam using a 12 volt fullwave rectfier and 1000uf capacitor .out put regulated through 9 volt regulator ic.when i test it somewhere it work fine.any solution to make a proper ground..

[keron]

i found out the problem finally.it was not the circuit.it is perfect.the probe was defective.it was made of paper clips .it got corroded and made electrical contact through the mixture of rust and the glue i used to fix it.i changed into a brass electrode and a silicone adhesive.now i guess no problem.thank you all for scraching your brain with me for finding a solution.any one with a better idea for probes.????
                                    http://www.uoguelph.ca/~antoon/circ/sensor3.htm
how to modify this for my use...

[Omni]

"the probe was defective.it was made of paper clips..."


Hehe, if you are every stranded on a deserted island i am sure you will survive!"  ::)

Good job!  :)

[keron]

    http://www.uoguelph.ca/~antoon/circ/sensor3.htm
how to modify this for my use...
or any idea to make ac signal for sensing water level?and then make it work with logic gates.