Published March 4, 2021 © GPL3+

Build a 4-Bit Digital to Analog Convertor using Arduino UNO

Design a Digital to Analog Converter using the R-2R Ladder circuit and Arduino UNO board/a microcontroller interface, a Beginners Project!

BeginnerFull instructions provided6,220

Build a 4-Bit Digital to Analog Convertor using Arduino UNO

Things used in this project

Hardware components

Arduino UNO

1kOhm Resistors

2kOhm Resistors

Jumper wires (generic)

Software apps and online services

Arduino Web Editor

Story

Introduction & Materials I Used

Because I've been pretty intrigued by DACs and how they really work, I wanted to go ahead a build a simple implementation of it! A DAC is a system which converts a digital signal to an analog signal. If you want to know more about DACs and their applications, I've talked a bit more about that here.We are going to be designing a Digital to Analog system by building a circuit called an R-2R ladder. This circuit converts high/low voltage outputs (binary weights - with 1 referring to 5V and 0 referring to 0V) to an analog voltage (such as 4.6777). It accomplishes this through circuit analysis and voltage division.

About the Arduino UNO

Arduino is an open-source hardware platform, where you can program a microcontroller board to read in inputs, light up an LED when you push a button, or even to run a motor for a robot! The microcontroller is part of the Arduino board, and to feed it a set of instructions you need to use the Arduino programming language and its Integrated Development Environment, or its Web Editor. I’ve been so drawn into Arduino lately, especially because it opens up so many possibilities when it comes to projects, and it is easy to use and learn as well! This actually marks my second project with this board, so I’m kind of a newbie, but I LOVE IT!!! The board that I’ll be working with is called an Arduino UNO board.

Diagram by Yours Truly

Some of the main parts of this board are the Digital Pins. The Digital pins can serve as output or input pins. When used as output pins, they can act as power/voltage sources. When used as input pins, they take in signals as digital input! We will be using these pins to build our digital to analog converter, since we will need digital inputs to convert them into continuous analog form!!Another important part of the UNO board is the TX/RX LEDs. These LEDs indicate whether the UNO is transmitting (TX) or receiving (RX) data. When it's transmitting data, the TX LED blinks and when it's receiving data the RX LED blinks.

How it works

R-2R Resistor Ladder Circuit, diagram by yours truly

The circuit drawing above describes the R-2R ladder circuit. The configuration of this circuit resembles a ladder; 3 R resistors are all in horizontally faced as 4 2R resistors are placed vertically, in between the R resistors. The circles highlighted in color represent two resistors which are in parallel. 2 2R resistors in parallel result in an R resistor equivalent, since, by parallel resistor calculations, 1/2R + 1/2R = 2/2R, inverse is 2R/2 = R.

So with this circuit, we can simplify the resistors in the blue circle to just R. We can then add the two R's in series, and the equivalent resistance once again evaluates to 2R (just like the original circuit).

This calculation gradually continues (as you can see from the highlighted circles appearing over and over again) until we are left with an output resistance or R, with Vout, being the output voltage (what we want). This goes back to the point where I mentioned about it being easy to calculate -- the output resistance is always R regardless of the number of bits, which is why the ladder configuration is very efficient.
I decided to go for a 4-bit DAC (just like the one shown above), meaning our system will take in 4 bits (the binary weights) through 4 digital input pins (D2, D3, D4, D5) on the board. The DAC system then outputs the analog voltage and we will be outputting this into the Analog pin (A0) of our board. I used the 1Kohm resistors for R and 2Kohm resistors for 2R.
The best thing about the resistor ladder circuit is that it's implementation is very self-explanatory. You place the resistors exactly how its indicated in the diagram! The 2R resistors are placed in parallel (one 2R to the left is connected to ground), and the R resistors are horizontally connected. This configuration ensures that the output resistance is R, and that the Vout calculates to an analog voltage. When I set 1's into every Digital pin, the output analog voltage was 4.68. Ideally, it should be close to 5, but this is because of the accuracy of our DAC. The more bits we have, the more close or accurate the results will be!! I feel like that was something I could have improved on, definitely by scaling the DAC and adding more digital pins as binary weights.

Procedure

There are actually multiple ways to build a digital to analog converter, but implementing a circuit called R-2R ladder is a popular and an effective method. The R-2Rladder circuit is a configuration of resistors in a "ladder like" format, which take in binary weights (bits) as inputs and convert them to an analog voltage. There are many advantages to implementing an R-2R ladder for a DAC.

Procedure is in this video!

Code to experiment with the DAC

//feel free to experiment with the code by setting different inputs (1, or 0) to the Digital Pins 

//Digital to Analog Convertor Testing
//For a 4-bit DAC Circuit.

//set the delay
int timer = 100;

void setup() {
    //set the Digital Pins- D2 to D6
    for(int thisPin = 2; thisPin < 6; thisPin++){
      pinMode(thisPin, OUTPUT);
    }
    Serial.begin(9600);
}

void loop() {
    //turns the 4 Digital pins into HIGH (1) state
    //experiment by changing the 4 pin values
    for(int thisPin = 2; thisPin < 6; thisPin++){
      digitalWrite(thisPin, HIGH);
      delay(timer);
    }
    
    int sensorValue = analogRead(A0);
    // convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):
    float voltage = sensorValue * (5.0 / 1023.0);
    
    // print out the analog voltage value we read
    Serial.println(voltage);
    
    //turn the pins off
    for (int thisPin = 5; thisPin >= 2; thisPin--) {
      digitalWrite(thisPin, LOW);
      delay(timer);
    }
    
}

Credits

aarushiramesh

1 project • 0 followers

Student.

Contact

Thanks to Jeremy Cook, Arrow.com.

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Build a 4-Bit Digital to Analog Convertor using Arduino UNO

Build a 4-Bit Digital to Analog Convertor using Arduino UNO

Things used in this project

Hardware components

Software apps and online services

Story

Introduction & Materials I Used

About the Arduino UNO

How it works

Procedure

Code

Code to experiment with the DAC

Credits

aarushiramesh

Comments

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