Published October 14, 2016 © GPL3+

An Isolated Analog Output for Arduino Uno

This project uses the Arduino PWM Uno or other systems to realize a fully isolated analog output with a range of 0-5 volts or more.

IntermediateFull instructions provided3 hours1,463

Story

This project completes the series of my articles about the Arduino analog I/O with the aim to use it as a controller of small automation systems.

In control systems of the industrial plants it is always advisable to isolate both the inputs and the outputs coming from the field. This prevents disturbances caused by power surges, lightning strikes or other EMI sources and also by ground potential differences.

Arduino Uno, or systems based on the ATmega328 chip has no a true analog output, but it may be realized using a PWM output averaged with a low-pass filter.

The use of an averaged PWM signal with 8-bit setting is not comparable with a real DAC, but in the insulation case presents undoubted advantages of simplicity since it is sufficient to use an optocoupler for isolating the PWM digital signal. Recently I designed another circuit to generate a 4-20 mA current with Arduino, that experience gave me the idea for this new project.

More details, the components list and test results can be found on my blog ArduPicLab.

Code

Untitled file

// program to test Arduino Uno PWM
// G. Carrera 30 sett 2016

#include <LiquidCrystal.h>

int PWMpin = 9;      // PWM out on digital pin 9
int analogPin = 0;   // potentiometer connected to A0
int val = 0;         // variable to store the read value
char spacestring[17] ="                ";

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);

void setup() {
  pinMode(PWMpin, OUTPUT); // sets the pin as output
  lcd.begin(16, 2);// set up number of columns and rows
  lcd.setCursor(0, 0);// set the cursor to column 0, line 0
  lcd.print("Stalker PWM");// Print a message to the LCD
  // set timer 1 prescaler to 8 for PWM frequency of 3921.57 Hz
  //TCCR1B = TCCR1B & B11111000 | B00000010;
}

void loop() {
  val = analogRead(analogPin) >> 2;// read the potentiometer as 8 bit

  analogWrite(PWMpin, val);
  val = 255-val;// complement
  lcd.setCursor(0, 1);
  lcd.print(spacestring);
  lcd.setCursor(0, 1);
  lcd.print(val);
  delay(500);
}

Credits

Giovanni Carrera

14 projects • 50 followers

Electronic Engineer

An Isolated Analog Output for Arduino Uno

Story

Schematics

IsolatedAnalogOut_logo.jpg

Code

Untitled file

Credits

Giovanni Carrera

Comments

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An Isolated Analog Output for Arduino Uno

An Isolated Analog Output for Arduino Uno

Story

Schematics

IsolatedAnalogOut_logo.jpg

Code

Untitled file

Credits

Giovanni Carrera

Comments

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