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Water-level sensor

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Hi,
I have a deep water-well that is full of bacterial iron in solution that I use for simple irrigation. I have a float system setup for pump control, but because the water-level changes so slowly, it doesn't work very well. Because of the iron I'm limited in what methods of detection I can use. Probes foul very quickly, optics and magnetics are useless, and floats are too unreliable. What I need is something not too expensive, readily available or buildable, and can be interfaced to logic control. Four points of detection are required; i.e., (bottom up) Extreme low-water shutdown, Off, Pump Enable/Reset, and Overflow.
So far, the best idea I've found is a float connected to a switch buffered by a Schmitt trigger. The problem with this is I can't get the switches to stay dry. Sooner or later, (mostly sooner) they all have failed and I really, REALLY, hate climbing down into the well to replace them.
Anybody got any ideas? Thanks.
 

nettron1000

New Member
Have you considered an ultrasonic transmitter receiver ?
 

Mosfet

New Member
Quantum's Qprox sensor ICs will work thru sealed enclosures, even metal.
You might try one, or a series, sealed in plastic tubing and lowered to optimum levels in your well.
**broken link removed**
They also have evaluation boards and a users forum.
For example, a metal rod inside tubing will act as an actual sensor.
It's capacitance will change relative to the water that surrounds it.
 

e

New Member
what about some stainless steel sensors that conduct to ground when in water, amplify if needed and use to interface circuit... I used a similar setup with stainless steel bolts in a set-up that controls my sump pump. I dont think that stainless would corrode very fast...
 

stevez

Active Member
If you insert a tube (plastic) into the well and apply air pressure you will find that the air pressure will push the water column downward. Apply enough pressure and the air will blow (or bubble) out the bottom of the tube. The pressure required to get significant amounts of air flow out the bottom of the tube will tell you the height of water above the bottom of the tube. This might serve as the basis for your level indicator.
 

stevez

Active Member
I had to take a call so here's a little more - if you bleed a small amount of air into the tube via a small orifice AND the pressure behind the orifice will always be enough to push air out the bottom of the tube, then air will always be bubbling out the bottom of the tube - the resulting pressure (or backpressure if you will) will give an indication of water level. Measure the pressure and you've got what you need. If water level changes very slowly this is something you might program to run on a cycle.

This can and has been done manually to indicate the depth of water in a well - a small hand pump can supply enough air and a pressure gage serves as the indicator. You'll need to know where the bottom of the tube is relative to some point (presumably ground level) because the indication will be based on the height of the water above the bottom of the tube.

Example: if the pressure in the tube were measured at 10 psi the water column would be about 23 ft high.
 
More on the Water-level sensor

Hi again,
I looked into the RF system and the capacative style and, yee haw, they are expensive! They are not in my budget!
I came up with a 5-switch arrangement of magnetic reed switches triggered by a floating ring magnet around a plastic rod. Does anyone have any ideas about interfacing reed switches to control a 220-volt 2HP pump motor? Due to high humidity, I would prefer a solid-state solution over relays. Thanks.
 
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