Intel Edisson: Digital Ohmmeter (voltage Divider)

This is how to make a simple digital Ohmmeter using Intel Edison, LCD screen, 1kOhm resistor and a few wires.

Voltage divider is based on Ohms law. Read more from here!

Step 1: Components.

You will need a Arduino based board. I used Intel Edison.

Then you will need a LCD screen if you want to view the output from somewhere else than serial.

A 1 kOhm resistor for the voltage divider and a few cables.

Step 2: Install

Install the wires like in the picture. (in the picture there is intel Galileo but the pins are the same)

R1 = 1 kOhm.

R2 = X = The resistor you are going to measure.

The R1 resistor can be almost anything but you will have to change the R1 value from the code.

Step 3: Coding

This ohmmeter works that the 2 resistors in series forms a voltage divider circuit. (R1+R2)

One end of the resistor pair is hooked up to Vcc +5V and the other end is hooked up to GND.

The 5 volts that the Arduino provides gets divided up between the 2 resistors.

The resistor which holds the greater resistance gets more of the voltage, according to ohm's law, V=IR, where V is Voltage, I is current and R is Resistance

The voltage that falls across a component is directly proportional to the amount of resistance it contains.

Using this principle, we can set up a mathematical model to determine the resistance, based on the voltage division.

The formula can be found directly from the code.


int analogPin= 0;
int reading= 0;
int Vin= 5;
float Vout= 0;
float R1= 1000;
float R2= 0;
float buffer= 0;
#include 
#include "rgb_lcd.h"
rgb_lcd lcd;
const int colorR = 255;
const int colorG = 255;
const int colorB = 255;
void setup()
{
Serial.begin(115200);
lcd.begin(16, 2);

    lcd.setRGB(colorR, colorG, colorB);
}
void loop()
{
reading= analogRead(analogPin);
if(reading) 
{
buffer= reading * Vin;
Vout= (buffer)/1024.0;
buffer= (Vin/Vout) -1;
R2= R1 * buffer;
Serial.print("Vout: ");
Serial.println(Vout);
Serial.print("R2: ");
Serial.println(R2);
lcd.setCursor(0,1);
lcd.print(R2);
lcd.setCursor(0,0);
lcd.write(0b11110100);
delay(1000);
lcd.clear();
}
}