If you want to get away from monthly maintenance of rods dipped into water there IS another approach. Back on post #19 I postulated the idea of using a float with magnets to activate reed switches. That was one approach to getting around having to clean the rods. Since then there has been a lot of discussion about rods, oxidation and electronic circuitry, some with an oscillator. Frankly I've never seen the need for an oscillated circuit.

Here's another idea: If you want to get away from the maintenance and are willing to do some work - you can get pressure sensitive switches and mount them above the water level. Each switch has a length of CPVC pipe with trapped air. As the water level rises so will the air pressure, causing the switches to switch on sequentially. As the water level drops the sensors will switch off. Every time the water level drops below the end of the CPVC fresh air will become entrapped. The only switch (switch A) will likely be constantly submerged. Care would need to be taken to create a perfect seal so that the trapped air doesn't leak out and cause a false reading.

In the diagram below the water level is at about 60% full. Switches A, B, C and D should be active (switched ON). Switch E, though the tip is submerged doesn't have enough air pressure to activate the switch. As the water level rises (from pumping) eventually the water level is high enough to trigger switches E & F. This way you're not having any metal in the tank to corrode and be in need of cleaning. Of course this means re-thinking your approach, but this way you get away from integrated circuits, resistors and capacitors. All you need is a push button switch to test the water level and some LED's to indicate the level. Of course the LED's will need to have current limiting resistors, so you're not fully away from resistors, but that's a given since you're using LED's as indicators.

Here's my latest drawing. Beyond this I can't think of anything else that could be of help. Floating switches like others have suggested are also good approaches. I'm just trying to think outside the box. Or outside the tank.

 

Thanks for the idea. It might be cost effective. Where can I get the pressure switches? Wiring from each switch might be a complex one.

 

The best way IMHO is using a hydrostatic pressure sensor.
The lowest cost I could find was this one appx 62.00 US dollars.
The electronics would require a rebuild but not complicated.
We use hydrostatic sensors to monitor head water height in our community wells.
Liquid Level Sensor,DC24V 4-20mA Level Level Transmitter 316 Stainless Steel Water Level Sensor, Measuring Range 0-197in Cable Length 19.7ft Input Liquid Level Transmitter


Description of using such device.
https://microsites.wika.com/newscontentgeneric_ms.WIKA?AxID=475

 

The best way IMHO is using a hydrostatic pressure sensor.

Back a ways I suggested a simple pressure gauge. Knowing the overall height of the water column one could calculate the weight and choose an appropriate gauge. Now, suppose as I postulated, 30 feet elevational change between a full tank and 24 feet empty (the water weight in the tubing from the tank to the gauge), at 0.433 lbs. per foot, full tank would read a pressure of about 13 pounds (12.99). When empty the pressure would read 10.4 pounds. So a gauge that reads from zero to 15 pounds would be sufficient. At 13 pounds the tank is full. A six foot high tank (assuming a 5 foot radius) would hold 141 cubic feet of water. That would be 1057 gallons when full. The total deflection of weight from full to empty would be 2.6 pounds. Roughly every half pound would represent 25% increments between full and empty. A gauge rated for 100 pounds would be horrible at discerning how much water is in the tank. But a low pressure gauge such as a 15 pound gauge (don't know if you can find one, my guess is "yes") would give sufficient indication from full to empty. A gauge also has the added benefits of no maintenance and no batteries needed. The math could be worked out to fully be able to mark the gauge as to what water level is present. And you don't have to depend on wondering if the tank is between 20 and 40% full. Or empty and 20%. Or 80% and full.

 

Just did an Amazon search for low pressure gauges and found this:
https://www.amazon.com/UHARBOUR-Gly...D3KBRY/ref=sxin_13_pa_sp_search_thematic_sspa

Do we know the location of the TS? Don't know if Amazon ships world wide. Don't see why not - - - but - - - .

 

Well, I'm from India. This idea will not work for me. Thanks

 

rafiec14, it's hard for me to know what you want - lowest cost or most reliable. You cannot have both. This is a big tank 4,000L going too cheap is not worth it unless it can overflow and not cause too much damage. Also to know what parts are easy to get in your area.
I would say, do not bother with the ULN2003 and DC excitation at the probes - this corrodes them, and you get a problem where the unit will only work with batteries because a mains power supply 9VDC supplying power all the time to the common probe will quickly corrode it. This is because the water tank also has a path for current to earth-ground, through the pipes. It also causes noisy readings.
What will work is using AC excitation to the common probe like in post #63 but with rectifier diodes etc. at the receiver. I have a circuit that will guaranteed work and will dig for it.
Pressure switches I find are expensive and not so reliable, the tubing cracks or diaphragm leaks, air bubbles in the tubing another hassle. A magnetic float and reed switches could be used.

Your electrodes need to be be bigger than just a bare wire. It would have to be the same metal (i.e. aluminum) as the wire so there is no galvanic corrosion. A stainless steel bolt on aluminum wire will soon fall apart.

 

Reed switches and magnets as an alternate option as first proposed by Tonyr1084 is feasible.
I have a different electrical design that indicates levels in relative height. In this design only one LED is ON at a time by the latching action of the SCR and auto resetting by commutation.

 

rafiec14, it's hard for me to know what you want - lowest cost or most reliable. You cannot have both. This is a big tank 4,000L going too cheap is not worth it unless it can overflow and not cause too much damage. Also to know what parts are easy to get in your area.
I would say, do not bother with the ULN2003 and DC excitation at the probes - this corrodes them, and you get a problem where the unit will only work with batteries because a mains power supply 9VDC supplying power all the time to the common probe will quickly corrode it. This is because the water tank also has a path for current to earth-ground, through the pipes. It also causes noisy readings.
What will work is using AC excitation to the common probe like in post #63 but with rectifier diodes etc. at the receiver. I have a circuit that will guaranteed work and will dig for it.
Pressure switches I find are expensive and not so reliable, the tubing cracks or diaphragm leaks, air bubbles in the tubing another hassle. A magnetic float and reed switches could be used.

Your electrodes need to be be bigger than just a bare wire. It would have to be the same metal (i.e. aluminum) as the wire so there is no galvanic corrosion. A stainless steel bolt on aluminum wire will soon fall apart.

Thank you. I'll wait for your circuit.

 

Reed switches and magnets as an alternate option as first proposed by Tonyr1084 is feasible.
I have a different electrical design that indicates levels in relative height. In this design only one LED is ON at a time by the latching action of the SCR and auto resetting by commutation.
View attachment 260616

Placement of the switches physically is crucial and risky.

 

Placement of the switches physically is crucial and risky.

I wouldn't think so. Why do you say that ?

 

I wouldn't think so. Why do you say that ?

I think they should be placed in the tank. So I thought like that.

 

I think they should be placed in the tank. So I thought like that.

The reed switches are on the outside of the tank. The wiring would need to be weather proof.

 

The reed switches are on the outside of the tank. The wiring would need to be weather proof.

OK, can you give any pic like that?

 

rafiec14, it's hard for me to know what you want - lowest cost or most reliable. You cannot have both. This is a big tank 4,000L going too cheap is not worth it unless it can overflow and not cause too much damage. Also to know what parts are easy to get in your area.
I would say, do not bother with the ULN2003 and DC excitation at the probes - this corrodes them, and you get a problem where the unit will only work with batteries because a mains power supply 9VDC supplying power all the time to the common probe will quickly corrode it. This is because the water tank also has a path for current to earth-ground, through the pipes. It also causes noisy readings.
What will work is using AC excitation to the common probe like in post #63 but with rectifier diodes etc. at the receiver. I have a circuit that will guaranteed work and will dig for it.
Pressure switches I find are expensive and not so reliable, the tubing cracks or diaphragm leaks, air bubbles in the tubing another hassle. A magnetic float and reed switches could be used.

Your electrodes need to be be bigger than just a bare wire. It would have to be the same metal (i.e. aluminum) as the wire so there is no galvanic corrosion. A stainless steel bolt on aluminum wire will soon fall apart.

Will it work with CD 40106 as said in post #83? If I use stainless steel probes?

 

OK, can you give any pic like that?

See post #19

 

See post #19

With this system you can have as many LED's as you like.

True, but the LED current will vary greatly from empty to full.

You can eliminate the steering diodes by placing the five LEDs in series, and have each switch connect a successive tap to GND. To get around the varying current issue, replace the current limiting resistor with a 1-transistor current source or sink.

Schematic later if anyone is interested.

ak

 

See post #19

The idea is good.
I have to put a hole to the cement tank and setup all these. Its risky. There may be a chance of leakage. It should be done while constructing the tank. If it has to be done, then I can place a transparent pipe in which I can see the level clearly.
I just want a simple solution with the existing circuit by changing the probes with SS probes. Or change of another circuit

Will it work with CD 40106 as said in post #83? If I use stainless steel probes?

Plz reply

 

Every Washing-Machine ever made has a cheap, reliable, Air-Pressure-Switch for controlling the Fill-Level.
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The idea is good.
I have to put a hole to the cement tank and setup all these. Its risky. There may be a chance of leakage. It should be done while constructing the tank. If it has to be done, then I can place a transparent pipe in which I can see the level clearly.
I just want a simple solution with the existing circuit by changing the probes with SS probes. Or change of another circuit

Plz reply

Then just replace the sensors leads with brand new wire as before. If they last four months as you stated then just replace every four months. Personally I would go with SS probes and see if they last.