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Water tank level control system

  1. Mar 6, 2016 #1
    I have a project to build a water level control system. Basically I will have two sensor probes one connected near the bottom and the other near the top. When the water level goes below the bottom sensor it will trigger a pump to pump water back into the tank until it reaches the top sensor. That's the basic idea. I have looked at some schematics online and basically to design the trigger I could use:

    1) Logic gate
    2) 555 timer in bistable mode
    3) Comparator with JK flip flop

    What would be the best approach ?, like in terms of less power and components needed
  2. jcsd
  3. Mar 6, 2016 #2


    Staff: Mentor

    Relays or limit switches are the traditional way to do that. You can handle a lot more power with a relay than with most logic gates.
  4. Mar 6, 2016 #3
    Yes, I am going to use a relay to control the pump. The system that triggers the relay based on the water level is what I am trying to design
  5. Mar 6, 2016 #4


    Staff: Mentor

    You may find this helpful.

  6. Mar 7, 2016 #5


    User Avatar
    Science Advisor

    I created such a system many years ago (≈1978). It turned out that the hardest part was finding a reliable water level sensor. A magnetic sensor does not work and a capacitive sensor detected "water" as long as just one drop of water clung to the sensor. I ended up using a pressure transducer...
  7. Mar 7, 2016 #6
    You might think about how this problem has already been solved. The water in a toilet tank does the same thing. It's reliable, mass produced, and cheap. A standard well pump shares the same characteristics. It provides pressure to run the toilet valve.

    If you need something bigger, I like Svein's pressure transducer. Electricity and water don't play well together.

    Another option would be a sonar range detector (like used in robotics) mounted on the top of the tank facing down.

    You might want a back up shut off system using a different technique. This could reduce the chance of accidental overflow.

    You might also check with the materials and chemical engineering forum. Chemical Engineers use lots of tanks for reactions and stuff. They might know some tricks.
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