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Salt-Taster introduction

2017-08-11 09:35  
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This article is a salt guided introduction. The principle of combining text comprehension is a good suggestion. The principle is very simple but very practical and effective. See figure: IC1A op amp is wired as a DC differential amplifier, the output voltage increases, the DC resistance measurement the probe down. In fact, fresh water has a relatively high DC resistance value will decrease proportionally more and more salt. IC1B, IC1C and IC1D are connected to the comparator and the driver, D4, and D5 D3, in turn, as the voltage at its inverting input increases. Thus, no lead salt content in the liquid when the testing is very low, the yellow LED D5 will illuminate when the salt content is low, the green  LED  D4 will light if the salt content is normal and the red light emitting diode D3 will shine bright if the salt content is high. D1 and D2 are always on, and their purpose is to provide the two reference voltages, thereby enhancing the accuracy of the circuit. In D2 anode stable 3.2 v supply feed comparator noninverting input through the reference resistor chain R8, R9 and R10. 1.6 v reference voltage can be set D1 anode feeds fine probe and R4. One of the two red led can be used as an indicator displayed on the device. Found through experiments, a good and inexpensive probes can use 6.3 mm. mono plug. Two plugs leadership is connected to the circuit input via a two-wire cable (a shielded cable to work). Setting circuit to obtain a more precise reading, you can use a DC voltmeter connected on 10 v range of the pin # 1 IC1A and negative supply. Set R4 to obtain a zero reading on the voltmeter probe when immersed in fresh water. You are free to change the level of the threshold voltage led lights illuminate cut through R4. Different ranges of values ??are changed R8 and R9 D4 D5 range of changes in value. P1 button instead of a common single-pole, single-throw switch. 

Salt Taster


R1________________470R   1/4W Resistor
R2,R5______________10K   1/4W Resistors
R3,R6_____________220K   1/4W Resistors
R4__________________5K   1/2W Trimmer Cermet
R7________________680R   1/4W Resistor
R8__________________2K2  1/4W Resistor
R9,R10,R11,R12,R13__1K   1/4W Resistors

C1________________100μF   25V Electrolytic Capacitor

D1,D2,D3______3 or 5mm. Red LEDs
D4____________3 or 5mm. Green LED
D5____________3 or 5mm. Yellow LED

IC1_______________LM324 Low Power Quad Op-amp

P1_________________SPST Pushbutton

Probes_________________ (See Text)

B1___________________9V PP3 Battery

Clip for PP3 Battery




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