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Water level detection

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Full Member level 1
Sep 29, 2005
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water level detector schematics

I am making a motor controlling device for controlling the motor of a water pump.The motor is switched on and off by a relay depending on the level of water in a tank.
Wires are placed in the tank at different levels. When the water reaches the appropriate level the wires are shorted and the coil of the relay is activated and the motor is switched off.
The trouble is, I am having problem with conduction through water.The relay coil is about 400 Ω and it operates at 28V DC. The circuit works perfectly well when I short the wires manually but when shorted through water the coil does not activate.Why does this happen ? What do you suggest I do ? How can I make it work ?

how does water level detector work

a 400 ohms relay can not be driven by water resistance.waterresistance is above several kilo ohms. so you need to make a circuit like current booster, level sensor or buy a ready-made a controller called "sivi seviye rolesi"....


the resistance of wather is not so small (theoretycally the resistance of pure wather is 0). You should try to mesaure current when you connect yours coil nodes schort and over the wather to see the difference.


i hope that circuit can help you greetings!:D

From my little experince in designing the electronic circuits;

i suggest the following:

1-you can use pressre sensor,when water reach certain level;the corresponding

pressre of it will be a function of the water head and the area of the tank

2-you can use 555 chip but i dont remember the circuit that can sense the level of


check out this
**broken link removed**

for 28 volt relay change the power supply but add regulator for rest of the circuit


I am posting the actual schematic diagram of my project.The metal strips are placed at three different levels in the tank and the motor is turned on and off depending on the water level in the tank. Please note that normally the distance between these strips will be about a foot or more. Will the relay work when the strips are such a large distance apart in water ?

Relay 1 operates at 28V
Relay 2 is also 28V and about 450Ω to 500Ω
Relay 3 operates at 220V

The motor also runs at 220V.

Also does the amount of conduction through water depend on the surface area and the material of the strips.

Please help me out. I shall be very grateful.

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