How to convert 10K Pot raw output ADC data to voltage and resistance from arduino uno

adcarduinopotentiometer

I have a simple and basic question. I am using Arduino uno to read the output from a 10K potentiometer. I understand that Uno uses a 10 bit ADC, therefore it can display outputs from 0 as 0V to 1024 as 5V.

Question: I am getting these values from the pot and displayed on the serial monitor of arduino IDE, while I vary the resistance of the 10K Pot. How am I supposed to calculate or know the output voltage and resistance corresponding to the values from 0 to 1024?

Another question is, when I vary the POT's knob to a maximum point i.e. 5V, the output displayed is 1007 or 1008. Isn't it supposed to output 1024 for 5V?

Best Answer

A converted value of 1024 would correspond to 5v - or to whatever voltage you put on the chip's Vref pin. But with 10 bits, the maximum number the converter can deliver is 1023. It's a small difference, but keep it in mind.

To find the voltage corresponding to a the converted value: V = (value / 1024) * Vref. Thus a reading of 1008 corresponds to 4.92v, assuming 5.00 volts at Vref.

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Electronic – arduino – How to read and display data from a CO2 logger connected via RS-232

I'm assuming that you can already read the string into a buffer so I will start at the buffer. Your code should go something like this (you will need to import the string library):

String wholeString = String(yourLoadedCharBuffer);
int startTag = wholeString.indexOf("<co2>");
int endTag = wholeString.indexOf("</co2>");

String co2FullString = wholeString.substring(startTag+5,endTag-1);

This gives us "5.2527637e2", you add 5 to the start tag because it is 4 characters long and you want to start at the "5", and you subtract 1 from the endtag, because we don't want the first character of it.

int eStart = co2FullString.indexOf("e");
String decimalString = co2FullString.substring(0,eStart-1);
String powerString = co2FullString.substring(estart+1, co2FullString.length-1);

char decimalCharArray[] = decimalString.toCharArray();
char powerCharArray[] = powerString.toCharArray();

float decimal = atof(&decimalCharArray[0]);
float power = atof(&powerCharArray[0]);

float finalCO2Value = pow(decimal,power);

How to shift resistance range of Linear Potentiometers by X ohms in the Positive or Negative direction

If you want to have your potentiometer going from 10k to 20k, simply hook a 10k after the potentiometer (e.g. where you get your changed Voltage).

Formula: Potentiometer range: From x to 10k+x: Add a resistor of x to the potentiometer. If you want to extend the range, then you have to use another approach.

Best Answer

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Electronic – arduino – How to read and display data from a CO2 logger connected via RS-232

How to shift resistance range of Linear Potentiometers by X ohms in the Positive or Negative direction

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