water level indicator!

[shanky25]

hello friends!

Actually I am about to build a water level indicator circuit using a 555 in monostable mode!.. hope you understood! water when reaches a particular reference level! generates a pulse which will be an input to the monostable multibrator and depending on the state of this monostable. the motor will be on or off!.. now my doubt is!.. how to build a circuit such that! if water level reaches a particular reference point, a pulse will be generated!

 

[audioguru]

Pure distilled water is an insulator.
Water with acids or salts in it conducts electricity and can trigger a 555 if the probes are long enough and are close together.

Since your probes have DC then they will corrode and one will plate the other. A circuit that uses low voltage AC at the probes is better.

 

[Salgat]

Switches do exist that are pushed up when the water level reaches a certain point.

 

[mrmonteith]

I've heard of people using two probes and just using the capacitance difference to determine when water is in between the probes and how much.

 

[k7elp60]

It is possible to use a float that activates a microswitch, then the switch would trigger the 555 directly.

 

[Boncuk]

Water level

Hi,

this is a method with no contact of corrosive parts with water. Use the magnet of a salvaged loudspeaker and make a floating unit using a ping pong ball encapsuled in epoxy. Put it in a PVC hose connected at the buttom of the water tank. Use a hall sensor to determine the pump activation point. Further use a flip flop to activate and deactivate the pump.

Boncuk

 

[Analog]

Capacitance is a good way to go. This can be done with insulated wires, as the water acts as an additional dielectric.

 

[Dean Huster]

There're lots of methods of liquid level detection. Float switches of various kinds, whether similar to the old toiled tank float or a waterproof floating magnet actuating reed switches inside a PVC column; conductive buttons in the side of the tank; ultrasonic reflection; capacitive methods as mentioned just before this post; optical means, including reflecting off the surface or optical transmission of the fluid.

Many methods will only give you a "bang-bang" detection scheme: either you're over the limit or under. Other methods can provide infinite resolution so that actual volumn can be calculated and displayed, either as "E, 1/4, 1/2, 3/4, F" or a display that says "34.52 gallons remaining, 18.56 gallons used, 576 estimated miles before the next fuel stop".

Whatever you do, the trick is that it can't be corrosive and whatever you put into the tank cannot leak. As waterproof as silicone sealant is, it's not rated to remain dunked in water, so extraordinary measures are needed, for instance with the capacitive method, to seal the ends of the wires.

One spin off the capacitive method is to loop the two conductors down and back up outside the tank so there are no possible voids in the insulation. In addition, you've effectively doubled the plate area for a higher capacitance to work with.

Dean