'POT' issues with long cable

[Byte_Butcher]

Basically 3 tanks 2K to 5K litre capacity, non-metallic, heights 6 to 8 feet. Having got a quantitative reading from all 3 tanks, there's logic that also controls a pump to keep the levels at a required level..

I have a similar project I need to build, but haven't had the time yet.
Same type of deal... need to read the water level in two 11,000+ liter (3000 gallon) tanks and one 1200 gallon (4600 liter) tank.

I was thinking of using a 16F726 at each tank and using the built in capacitive sensing module. I would use small strips or squares of copper tape stuck to the outside of the tank at 10 different levels. That would sense the water level directly, with each square of foil being one capacitor plate, the water being the other, and the plastic tank wall the dielectric.

Water level data from each PIC would be transmitted down the hill (about 500 feet) through Cat5 cable to a "master controller" PIC located here at the house.

I'll be curious to see what solution you come up with and how well it works.


steve

steve

[Darrel Taylor]

How about an ultrasonic transducer like the parallax Ping.

Put a vertical PVC pipe in the tank, open at both ends, with a float in the middle.
At the top is the Ping measuring the distance down the pipe to the float.

Then you have a continuous level sensor.
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[Byte_Butcher]

The Ping is cute. And its 3 meter range would be just enough for my tallest tank.

The $30 each price tag is a little tough to swallow since I'd need 3 of them.
But it would only require a pipe up the side of the tank with a ping pong ball floating in it.

Hmmm....




steve

[Darrel Taylor]

With the pipe acting as a "wave guide", the range is much further than it would be in open air.

I think even the previous ideas of submerged capcitors etc. would cost at least $30 in man-hours alone building it.
You can mount a pipe in a few minutes.

And you could always "roll your own" with an ultrasonic sensor @ $5.00, if the $30 is too much, but then there's that time vs. money problem again ...
http://www.sparkfun.com/commerce/pro...oducts_id=8505
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[ardhuru]

Sounds good, Darrel.

However, I wonder about 2 things; (a) how would the ambient humidity in a tank (or even that inside the pipe column) affect the transducer's life, and (b) how would the sound of water splashing about, especially when the tank fills up affect the readings?

[comwarrior]

Would it not be far more acurite to use a cheep pic at the tank with 'digital' probes and then comm lines back to main pic?

Other than that, i'm wondering why your using cap/resister solution...
Would two rods running all the way down the tank, one charged with say 5V DC and the other connected to a analogue port... as the water rises the resistance between the two rods changes and therefor the voltage on the analogue port would rise...

Just a thaught...

[Sphere]

Why not use a pressure switch like the kind you find in a washing machine, you can use the switch to turn the pumps on and once the required pressure is reached the pumps will cut off.

Sphere.