The food salt & salinity tester meter circuit

A Salt intake in large quantities is not good for the body and also causes of diseases such as kidney disease, high blood pressure, heart disease and paralysis. We should not eat too much. But the recognition of salinity, but may differ. Therefore should be a good barometer. I highly recommend The food salt & salinity tester meter circuit, because it is simple circuit and cheap too.
The circuit ideals.
We use the comparator circuit by an op-amp IC. Which is the difference between the volume resistance or conductivity of the solution foods has salt is constituent. In with sensing probe immersed or dunk in the water or food. Then Showing amount of salt much, Appropriate salinity, and a little salinity with 3 different LED colors.


How the circuit works.
The circuit ready running When dipping or dip the probe into the solution or food. Then press switch-S1, by has IC1/1(LM324) amplify a differential signal, the voltage output at pin 1 as quantities resistance or conductivity of the solution foods has salt component is measured through the probe.
Which if a water or foods with little salt as an ingredient. The resistance is quite high. Less current to flow through it. The voltage comparator circuit so has the output at pin 1 a few, As a result output at pin 14, pin 8 and pin 7 of IC1/4,IC1/3 and IC1/2(LM324) have all high state, makes the LED5, LED4 and LED3 not glow.
Water or food, that have a salt is very complement. Resistance is relatively low. Current to flow through much, makes the output signal at pin 1 much into the voltage comparator circuit , as a result the output at pin 14, pin 8 or pin 7 of IC1/4, IC1/3 and IC1/2 has state is high only one or all, makes LED5,LED4 or LED3 in order to light up.
Additional will use LED5 yellow. If brightness is represented by the amount of salt. With little food or water. If the green light is LED4 is represented by the amount of salt in food or water has Fitted. And the LED3 will light red when the user is represented by the amount of salt in food or water is too much.

How to customization and applications.

The LED2 and LED1 will light the Showing while running all the time. By the anode pin of LED2 will has setting voltage about 3.2 Volt, By be determined from resistors R7,R8 and R9. The anode of LED1 will has voltage about 1.6 volt is voltage provides to probe by adjustable a voltage at VR1.
To determine the operating point of the circuit can be adjusted by changing the resistor VR1 or R7, R8 and R9. Set the project may be, try dipping the probe into the water and adjust the VR1 and the LED extinguishes all, or Try dipping the probe into the solution containing salt component. Then adjust VR1 to LED5, LED4 or LED3 is lit up by the same sort of salt.
The probe is made of a conductive metal. Or 6.3-mm mono Jack uses it.Connect the power cord to the point probe.
The test should be dipped in a solution of food and then wait about half a minute. The accuracy of the LED display of each test, do not forget to press the switch S1.
Let’s to bulid this circuit
This circuit you can assemble them onto Universal PCB Board because simple and cheap.


  1. duncan August 29, 2013 Reply
  2. symptomatic January 22, 2014 Reply
  3. patrick April 11, 2014 Reply
  4. naga February 22, 2016 Reply

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