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Method to convert raw analog data back into voltage and then convert back to actual voltage before divider.

/* This sketch serial outputs a voltage through a voltage divider into

analog pin 0

This is written in as simple terms as possible, so its long.

Actual real numbers math is only 3 lines of code so skip to the code if you understand voltage dividers.

Resistance divider follows Vout = Vin * (R2 / (R1 + R2))

This sketch is assuming 25V max is measured. Resistance values used for 1/5 divider are R1 = 10k and R2 = 2.5K

BEFORE YOU CONNECT voltage divider to arduino, test with a meter to verify.

If you connect 25Vdc to arduino... its bad.

Meter Black Lead to Gnd

Gnd -- R2 -- Meter Red Lead -- R1 -- V+ (measured voltage 0-25Vdc)

Connection: Gnd -- R2 -- arduino pin A0 -- R1 -- V+ (measured voltage 0-25Vdc)

I can get to within 0.05 Vdc by measuring actual value of resistors

*/

//Analog volt read pin

const int voltPin = 0;

//Variables for voltage divider

float denominator;

int resistor1 = 10000;

int resistor2 = 2500;

void setup() {

Serial.begin(9600); //Convert resistor values to division value // Equation is previously mentions voltage divider equation // R2 / (R1 + R2) // In this case returns 0.20 or 1/5 denominator = (float)resistor2 / (resistor1 + resistor2);

} // Void Setup Close

void loop() {

float voltage; //Obtain RAW voltage data voltage = analogRead(voltPin);

//Convert to actual voltage (0 - 5 Vdc) voltage = (voltage / 1024) * 5.0;

//Convert to voltage before divider // Divide by divider = multiply // Divide by 1/5 = multiply by 5 voltage = voltage / denominator;

//Output to serial Serial.print("Volts: "); Serial.println(voltage);

//Delay to make serial out readable delay(500);

} // void loop close