Measure amount of salt in water softener?

[Squintz]

A friend of mine wants to drill a small hole in the top of his water softner and insert some sort of device that will convert the amount of salt in his tank to a voltage.

His current idea is to use multiple strings and weights dangling from a switch which is connected to a resistor network. As the the level of salt lessend the weights would activate the switch and put out a voltage depending on the amount of switches that were triggered.

Although this wa will work it doesnt seem to be the best idea. I was wonderin if anyone has a circuit such as a sonar circuit that could put out a voltage between 0 and 5V based on the distance the object is from the circuit.

 

[jbeng]

What your friend wants to do sounds like a variant of a hydrometer, which measures the density of the solution to measure the salt concentration. Here's a couple of links to a company which makes them:
https://www.ertco.com/hydrometers.html
https://www.ertco.com/hydrometers_salt_brine.html
If you could figure out a way to mechanically (electronically) read one, the problem is solved.
JB

 

[Squintz]

Actually he just wants to measure the amount of salt that is in the tank. In other words there may 6inches of salt in the tank. If the tank is a foot tall then the sonar would only measure 6 inches from its position to the top of the salt bed. Meaning that the amount of salt in the tank is 6 inches. The way he wants to do this now is by simply using 3 micro switches outside the tank. Then by droping three strings of differnt length into the tank as the amount of salt lessens it will trigger another switch.

Doing this method he can only measure 3 levels. Those three levels are then fed into the INPUTS of a device called a Ocelot which can be tied into his PC. By having the information in is PC he can trigger oter event to take place such as E-mail notification or having his Home Automation Audio system annouce that he needs to add salt.

Here is a link to the discussion where he asked for people opinions.
**broken link removed**

Even if he doesnt decide to use the sonar i would still like to know how to build my own sonar circuit. I have seen the circuit where i can hack a old polaroid but i would like to build something from scratch. Perhaps you guys could offer me a block diagram displaying all the things i would have to consider when trying to build such a circuit.

 

[John Sorensen]

His current idea is to use multiple strings and weights dangling from a switch which is connected to a resistor network. As the the level of salt lessend the weights would activate the switch and put out a voltage depending on the amount of switches that were triggered.

Actually, that sounds pretty clever!

j.

 

[TheOne]

What about this way;

Weight pulls down on a thin cable wrapped around a pulley that is fitted onto the shaft of a multiturn pot. At the same time the other end is given back tension by a spring (if you use a long one, you should get enough expansion out of it). Should be able to get a pretty linear indication of the salt level this way

 

[mechie]

Salt Level Measurement

I have been thinking about this idea of weights and strings...
In a saline solution there are likely to be problems with corrosion on any ferrous components
AND
when the salt reservoir is refilled each weight will have to be lifted so that they are supported by the salt and not still actuating the switch.
This seems to be a problematic design.

If you fabricate a carrier rod with a vertical slot in it, on one side of this slot is a row of LEDs, on the other side is a matching row of phototransistors, each pair forming a light beam that can be interrupted by the solid salt ... the whole thing can be plastic and water-tight, no corrosion, no moving parts.
It would be relatively simple to create a column with a detector every inch to give a reasonable resolution on some form of indicator panel, a 'mimic' column of LEDs or (via a simple resistor D-A) on a moving coil meter.
:?:

 

[williB]

Isnt this whole system under pressure?
meaning that the weights and pully idea isnt going to work