urgent help regarding automatic water level control

Discussion in 'The Projects Forum' started by vivek.raunak, Mar 12, 2011.

  1. vivek.raunak

    Thread Starter New Member

    Oct 23, 2010
    29
    0
    hi everyone,
    i made a circuit for controlling water level inside water tank automatically.
    i attached my circuit diagram here........
    i used feedback circuit here.for possible inputs 1st i completed truth table and then solved it by K-map to get equation for Q (output) .i have to use it as practical circuit,
    but i have a doubt ......can it would be a practical circuit?
    in practical circuit,input to the circuit is given when water rises up to specified level inside the tank.
    in the lab i used switches for giving input, and LED for showing output.
    can rising water would give instantaneous input as like switches?
    please suggest if any modification is needed here.


    is there any other problem with that circuit?
    suggest modification to avoid that problem too.
     
  2. trader007

    Active Member

    Feb 27, 2010
    222
    19
    when i needed to do this for growing herbal plants i used a toilet tank valve.
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    1. Since you're continually passing a direct current from "A" to ground, these electrodes will corrode over time due to electrolysis. For continuously submerged electrodes it's better to use alternating current excitation and detection. Also, use 316 stainless steel rods for electrodes.
    2. You are using 5V logic and 12V relay. Even with 12V logic (CMOS) you will not be able to drive a 12V relay directly. With either 5V logic and relay or 12V logic and relay you will need a resistor and transistor to drive the relay.

    Haven't evaluated the logic.

    Ken
     
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  4. vivek.raunak

    Thread Starter New Member

    Oct 23, 2010
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    what is relation between current flowing through the level sensor and rate of corrosion in in tank?
    i used 1 M resistor to reduce current inside the tank to reduce corrosion.
     
  5. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
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    I think the corrosion is pretty much directly proportional to the current.

    Ken
     
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  6. vivek.raunak

    Thread Starter New Member

    Oct 23, 2010
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    can you help me to re-configure the relay.
    i dont have much idea about relay.
     
  7. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
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    This is a little different, but should work more reliably if you want to stick with the DC current to the electrodes. "If it works" depends on how conductive the water is. If you have a 5V relay it will work on 5V, as shown. If you have a 12V relay, change the supply voltage from 5V to 12V.

    Ken
     
    Last edited: Mar 21, 2011
  8. vivek.raunak

    Thread Starter New Member

    Oct 23, 2010
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    but why to go for such complication? what would be the benefit of this circuit over my circuit?
    is the same relay configuration will work on the previous circuit?
     
  9. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    With your circuit you're going to have two IC chips, and AND and an OR, using only one gate from each chip. Mine has one chip. Mine has a flip-flop output, so that once a high or low level is reached the output stays in the correct state until the cycle is completed. Yours may change states intermittently due to waves. This is because you're using the 1Meg resistor and water as a voltage divider. That voltage can change slowly between the hi and low logic levels at your gates' inputs, depending on how much of the electrode is submerged. This will not give you reliable high or low water level signals.

    Ken
     
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