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Water level detections system


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Hi

   How I can design water level detection system ? I know a sensor will be used but what type of sensor and what parts are required . thanks


Hiya,

There are a few factors you need to specify first here:

Do you simply want to stop/start a pump at a certain level? or do you want a level to be shown?
Is this industrial or for home?
Do you have a plc that can be used? or will it simply be hardwired?
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  • 2 months later...
  • 2 weeks later...

Hi
Here is a simple circuit i took from a genius that published it on the web with no ref. , i mean genius because he used the 555 in a really intresting way
the circuit uses the treshold and trigger inputs of the 555 because inside the ic are two comparators configured as a window comparator driving a flip flop. r1 and r2 are biasing the rods, when water touches them the voltage on the rod drops dramattically. The only adition i made is the capacitors on the input to avoid some noise, a relay drive capability and a power supply. i made this circuit like 4 times and is a charm. the voltage regulator to 14volts is to keep the 555 below 18v max from datasheet, anyway, if your transformer is between 9v and 11v and around 200ma or more you might save a couple of parts :)

"lo" is the low level rod wich goes to the bottom of the tank with the "com" rod and "hi" is the highest level you want the water to reach. When the tank goes empty the water disconects "lo" from "com" an the circuits turns on the relay until water makes contact between "hi" and "com" rods, and over again.

post-1264-1427914413588_thumb.gif

post-1264-14279144136079_thumb.gif

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A problem with that design is that you are passing a DC current through the common and lo electrodes most of the time.  This will causes electrolysis that will corrode the electrodes.  Designs that have constant submersion of electrodes need AC drive/sensing to minimize this.

Ken

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  Hi KMoffet,

  Yes, you are right, the corrosion factor is present. But, consider this: 14V/100KOhm equals 140uA. With inox steel (sorry for not mentioning that before) corrosion at that current level is not really a trouble. The maintenance of the rods (cleaning with sandpaper or acid) is done every 18 to 24 months, I think is totally cost effective. When I had the oportunity to clean it, the rods were mostly covered of magnesia salts deposits like the ones present on tank's wall waterline.
  Makes sense AC sensing, the sinewave won't be always its peak value and the RMS shall be considered the max voltage in the system, due to the constant invesion of polarity the rods will oxidize but oxide wont adhere to the rod. The problem is that it could be tricky to implement.
  I have considered using a microcontroller to energize the rods momentarily, it would reduce oxidation. On the other hand, uC's are very sensitive devices to be exposed to an antenna, wich becomes the wire that travels to the roof tank.
  Thank you, I will keep it in mind to improve the device.

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