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Interfacing TDS/EC Tester/Meter

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ElMobd3

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I am working on a project regarding the water pollution and I am using a TDS Meter to indicate the Total Dissolved Solids (TDS) of a solution, i.e. the concentration of dissolved solids in it. Since dissolved ionized solids such as salts and minerals increase the conductivity of a solution, a TDS meter measures the conductivity of the solution and estimates the TDS from that. Dissolved organic solids such as sugar and microscopic solid particles such as colloids, do not significantly affect the conductivity of a solution so a TDS meter does not include them in its reading.

So I bought a TDS Meter from ebay and it’s a cheap one







I tried to hack on it in order to get the output readings and interface them to an Arduino board. However, I couldn’t locate the output readings because I faced some problems with this IC which was completely new for me. I couldn’t identify either its model or its number

This are the front and the back pictures of TDS meter after being hacked . However, I couldn't find the output of the IC so can anyone help regarding this issue? and thanks.





So do you guys have any suggestions of what I am supposed to do in order to locate the place of the output and interface it with the Arduino board ?

Thanks in advance.
 

BradtheRad

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The IC is under the round black plastic mound. Its output traces go under the 3 small push-buttons to the LCD.

It looks as though there may be a couple more output traces going near the edge of the board as well.

 

bigdogguru

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ElMobd3

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The IC is under the round black plastic mound. Its output traces go under the 3 small push-buttons to the LCD.

It looks as though there may be a couple more output traces going near the edge of the board as well.

I'm trying to check those lines under push-bottoms and take readings for clear water and salty water.
Thanks for your reply.

- - - Updated - - -

The only form of output maybe the LCD control lines, in which case you maybe better off implementing your own TDS/EC sensor.

The following details such a project:

EC/TDS/PPM Meter On Limited Budget

EC/TDS/PPM Meter Schematic

EC/TDS/PPM Meter On Limited Budget - Original Webpage

EC Shield (Assembled)

EC Shield Documentation

EC Shield PCB

EC/pH Sensors

Arduino Controller Project - Forum Thread

BigDog
I've removed the LCD and will check them with my Avometer :)



I hope I can do it, Thanks for your reply
 

bigdogguru

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I suppose you could attempt to interface the Arduino with the LCD control lines, the push button circuits and interpret the numerical value to be displayed.

Although, I would think designing and implementing your own EC Arduino shield from the schematics provided in my previous post would be more practical and advantageous.

You should able to implement a pH sensor instrumentation on the same shield as well.


BigDog
 

ElMobd3

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unfortunately all control lines of the LCD give me 3V (which is the VCC) whatever the meter is in water or not :(

now I'm trying to take the I/P of the sensor then search about a relation to give me the exact TDS
 

BradtheRad

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unfortunately all control lines of the LCD give me 3V (which is the VCC) whatever the meter is in water or not :(
Yes, you would expect to have rapid DC pulses (high and low) coming through the lines. You would expect to see some middle volt level on the wires.

There are 14 lines serving 2 or 3 or 4 digits, with 7 segments per digit. Data is probably multiplexed.

Did you press the button, and then measure? Maybe the display only lights up digits when you press the button? And the rest of the time it's blank?
 

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