Here is a circuit combining several circuits that I've used. The electrodes are stainless steel rods.

Ken

 

Here is a circuit combining several circuits that I've used. The electrodes are stainless steel rods.

Ken

So as you mentioned that the AC signal is more easy to send and receive.
Do you have the photo about the stainless steel rods, the metal I can easy get is stainless steel chopsticks, we used the stainless steel chopsticks at home for a long time, and they are easy to wash.

 

AC is not easier to send and receive. It requires more circuitry, but it does reduce the corrosion from electrolysis of the electrodes. The stainless steel rods I used were 3/32 TIG welding rod. Any stainless steel wire will work, though #316 stainless has superior corrosion resistance over other grades.

Ken

 

Looking at the design with probes in the tank there is, depending on water purity, a good possibility the probes will corrode quickly and need frequent cleaning.

OK, then what and how to add another material some solution to avoid is there any need of pull up resistance across micro pins??

 

OK, then what and how to add another material some solution to avoid is there any need of pull up resistance across micro pins??

This was my quote on the subject:

Looking at the design with probes in the tank there is, depending on water purity, a good possibility the probes will corrode quickly and need frequent cleaning.

When using probes in a tank there is going to be, as was mentioned, a process of electrolysis taking place. How frequently the probes need cleaned is a function of the water purity, it all depends on what is in the water. Probe systems like this rely on the water's ability to conduct electricity. If the water was of a very high purity having a very high resistance it would have a very low conductivity and probes wouldn't work. Making the probes out of materials not as prone to corrosion like stainless steel reduces the problem and rather than a DC circuit, using AC, will also reduce probe corrosion but not eliminate it. How quickly the probes become corroded and need cleaning is a direct function of the water's conductivity.

I don't know of any additives that will slow down the electrolysis process. My advice would be to place a few probes in a water sample and try running a very low voltage DC current, maybe a 9 volt battery? Could also try a low voltage AC. See what develops on the probes from the water sample. That will give some idea of how often the probes will need cleaned.

Ron

 

Hi,

Have you considered optical liquid sensors? I did a quick Google and found this: http://www.apollounion.com/en/p-Optomax-Basic-Series-Liquid-Level-Sensor-LLC200A3SH-407.html. They might not be the cheapest method though!

Camerart.

 

Hi,
Can we use ULN2803?

 

You can replace the led driver gates with the Uln2803, but you may get flickering at the precise levels,the Cd4093 is a Schmidt gate ic.