Inductance LC Meter Using Arduino

In this project, we will display Inductance as well as capacitance along with frequency on 16X2 LCD.

Hardware Components

Arduino Uno

741 OPAMP IC

3V battery

1n4007 diode

Resistor 100ohm, 10k

Potentiometer 10k ohm

Pushbutton switch

Inductor

Capacitor

Connecting wires

Software Components

Arduino IDE

First, we estimate the frequency by utilizing Arduino and by using a few mathematical calculations we can determine the inductance or capacitance.

We are going to use an LC circuit frequency response formula.

f=1/(2*time) where time is output of pulseIn() function

then we have LC circuit Frequency:

f=1/2*Pi* (square root of LC)

by solving the above equations we get inductance as follows

L=1/(4* pi* pi* f* f* c)

We have a frequency that can be turned into inductance by utilizing the above formula. We have used Arduino for further operation. The LC circuit contains an inductor and a capacitor. We have used an operational amplifier ( 741 ) to convert sinusoidal resonance frequency to a digital or square wave.

We have used a 3v battery connected in reverse polarity to get the correct output frequency. Another we have used the push button to change the operation mode (either we are measuring inductance or capacitance). LCD is used for display purposes.

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#include

LiquidCrystal lcd(A5, A4, A3, A2, A1, A0);

#define serial

#define charge 3 #define freqIn 2 #define mode 10

#define Delay 15

double frequency, capacitance, inductance;

typedef struct { int flag: 1; }Flag;

Flag Bit;

void setup() { #ifdef serial Serial.begin(9600); #endif lcd.begin(16, 2); pinMode(freqIn, INPUT); pinMode(charge, OUTPUT); pinMode(mode, INPUT_PULLUP); lcd.print(" LC Meter Using "); lcd.setCursor(0, 1); lcd.print(" Arduino "); delay(2000); lcd.clear(); lcd.print("Circuit Digest"); delay(2000); }

void loop() { for(int i=0;i 0.1) frequency+= 1.E6 / (2 * Pulse); delay(20); } frequency/=Delay; #ifdef serial Serial.print("frequency:"); Serial.print( frequency ); Serial.print(" Hz "); #endif

lcd.setCursor(0, 0); lcd.print("freq:"); lcd.print( frequency ); lcd.print(" Hz ");

if (Bit.flag) { inductance = 1.E-3; capacitance = ((1. / (inductance * frequency * frequency * 4.*3.14159 * 3.14159)) * 1.E9); if((int)capacitance < 0) capacitance=0; #ifdef serial Serial.print("Capacitance:"); Serial.print( capacitance,6); Serial.println(" uF "); #endif lcd.setCursor(0, 1); lcd.print("Cap: "); if(capacitance > 47) { lcd.print( (capacitance/1000)); lcd.print(" uF "); } else { lcd.print(capacitance); lcd.print(" nF "); } } else { capacitance = 0.1E-6; inductance = (1. / (capacitance * frequency * frequency * 4.*3.14159 * 3.14159)) * 1.E6; #ifdef serial Serial.print("Ind:"); if(inductance>=1000) { Serial.print( inductance/1000 ); Serial.println(" mH"); } else { Serial.print( inductance ); Serial.println(" uH"); } #endif

lcd.setCursor(0, 1); lcd.print("Ind:"); if(inductance>=1000) { lcd.print( inductance/1000 ); lcd.print(" mH "); } else { lcd.print( inductance ); lcd.print(" uH "); } }

if (digitalRead(mode) == LOW) { Bit.flag = !Bit.flag; delay(1000); while (digitalRead(mode) == LOW); } delay(50); }