keron Posted May 28, 2007 Author Report Share Posted May 28, 2007 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 ? Quote Link to comment Share on other sites More sharing options...
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