[SOLVED] Help in making a water level sensor

[burrow]

I want to make a water level sensor, i had already implemented it once( a 6 level sensor using transistors and stuff), The electronic part is working, but the problem iam facing is since the water is having bit of salt content the wires iam using in the sensor probe is getting corroded and loosing the connection. So what sort of wire i should use ? .i can use stainless steel screws as probes but then to connect them to the circuitry i have to use wires anyway. and the wire will be exposed to water ( at connection points )
is aluminium any good ? what are the other alternatives ?.

 

[barry]

Interesting problem. Maybe the approach shouldn't be what wire to use, but how to protect the wire from the salt water. There are water-tight connectors available, maybe you should look at those. Without knowing more about the physical aspects of your design, it's hard to speculate. Maybe encase your connections in something like potting compound?

 

[burrow]

Well i live in a place where getting complicated stuffs means searching for needle in hay . And the way out is design something from stuffs available already..
Water proof casing..no not available here.

Stainless steel with the wire joints enclosed in shrinkwrap is what iam gonna try.

Regarding the physical aspects. The probe is a long pvc pipe..with screws inserted through a hole at the desired heights.

 

[chuckey]

I do not know where you are, but fishing tackle shops sell stainless steel wire by the 10m either braided - flexible or single core for sea fishing.
Frank

 

[barry]

But if you attach stainless steel to some other metal, aren't you going to get galvanic corrosion?

 

[shaiko]

Tin plating over copper is very corrosion resistant.
Another option is to use stainless steel and encapsulate it in a sealed galvanic insulator of some kind...(hot glue perhaps)

 

[chuckey]

You connect your probes to the SS wire which is sleeved, you then take these wires to a dry place, where you terminal block them to copper wires.
The water level detectors I worked on, worked by connecting an external glass tube to the bottom and top of the water tank. The SS probes were inside the glass tube with sealing washers and the clamping washers and nuts were on the outside.
You could just seal the end of your plastic tube and allow it to float vertically with guides and sense its position with magnets/switches or lights and photo cells. Or use what dish washers do, Use a vertical tube into the water and connect the open end to a diaphram type pressure switch. As the water column rises in the tube , the air pressure rises and flips the switch.
Frank

 

[Gorgon]

One simple sensor system would be a plastic tube/pipe with reed switches inside, and a floating magnet outside/around the tube. Place the reed switches at the levels you want to detect, and the magnet will float up and down on the tube. You will only get one signal at the time, but I suppose this is not a big problem. Since both the plastic tube and the magnet assy is not in contact with the water, you will not have any problems with corrosion.

Another problem with a metalic sensor in water is when the water is too clean, with no salts at all, and you may have problems getting it to work at all.

One sensor you may try that doesn't corrode easily, is carbon rods, like the type you find inside old 1,5V battery cells. At least if it s not drinking water you monitor.

 

[burrow]

Well..your reed switch idea is good. I am thinking forward to it. Say i can have a long pipe and inside it place the reed switches at desired level, make the pipe water proof. then outside the pipe make a float that just moves up or down along the pipe. and float will have magnet attached to it. Sounds like it will work cool.

By the way can you please throw in some more info on how to use reed switches. just connect the 2 terminals and when its magnetised circuit completes, thats it ?

 

[Gorgon]

Well..your reed switch idea is good. I am thinking forward to it. Say i can have a long pipe and inside it place the reed switches at desired level, make the pipe water proof. then outside the pipe make a float that just moves up or down along the pipe. and float will have magnet attached to it. Sounds like it will work cool.

By the way can you please throw in some more info on how to use reed switches. just connect the 2 terminals and when its magnetised circuit completes, thats it ?

There are several types of reed switches, and the most common type is the normally open, that close when a magnetic field is present. You can also get switch over types and normally closed typse, that switch/open when in a magnetic field.

To use the NO type just connect 2 wires between it and your input device, monitoring the switches. When the magnet pass the switch, it closes as long as it is close to the magnet.

A very simple system. The only possible problem may be growth or sedimentation on the floater so it gets stuck. This is of course depending on the quality of the liquid in question. For relative clean water there is little problem. For unfiltered sewage you may have a possible problem. You can however get past this if you have a perforated bigger pipe or tube that contain the magnet floater and the reed pipe inside, protected more or less from rubbish in the water. There are endless possibilities here.

 

[burrow]

Well iam dealing with sort of almost clean liquid. so i wont have great deal of problem with sediments, een if their is any such problem cleaning up is going to be easy compared to corrosion and replacement.. .. so this seems like a great solution. thanks, iam gonna try it soon