Building an AM Transmitter with Arduino and MC1496 RF Mixer

In the realm of electronics and communication, building a simple AM (Amplitude Modulation) transmitter can be an exciting project for beginners and enthusiasts. In this blog post, we'll dive into the details of creating an AM transmitter using an Arduino and the MC1496 Balanced Modulator Demodulator. We'll break down the code step by step to help you understand how the carrier signal is generated and modulated.

Prerequisites:

The hardware and circuit diagram for the AM transmitter code below explained in the blog post AM Transmitter using Arduino.

Hardware Components:

Arduino board (any model will do)
MC1496 Balanced Modulator Demodulator IC
Liquid Crystal Display (LCD) module
Potentiometer
Antenna (for transmitting the RF signal)
Connecting wires

Generating the Carrier Signal: Let's begin by examining the code responsible for generating the carrier signal using the Arduino. The carrier signal is the high-frequency signal that gets modulated to carry the information in AM modulation.


#include <LiquidCrystal.h>

LiquidCrystal lcd(7, 6, 5, 4, 3, 2);

const int N = 1;
const float Fcpu = 16000000;
volatile int anaValue;
char freq[16];

void setup() {
  lcd.begin(16, 2);
  lcd.print("Frequency:");
  timer1generate();
  lcd.setCursor(0, 0);
  delay(100);
}

void loop() {
  // Code for modulation can be added here
}

// Timer 1 Configuration for Carrier Signal Generation
void timer1generate() {
  pinMode(9, OUTPUT);  // Set pin 9 as the output for the carrier signal

  TCCR1A = 0;
  TCCR1B = 0;

  TCCR1B |= (1 << WGM12);  // Set waveform generation mode to CTC
  TCCR1A |= (1 << COM1A0); // Toggle OC1A (pin 9) on compare match

  TCCR1B |= (1 << CS10);   // Set prescaler to 1

  TIMSK1 |= (1 << OCIE1A); // Enable output compare interrupt
  sei();  // Enable global interrupt
}

ISR(TIMER1_COMPA_vect) {
  anaValue = analogRead(0);
  OCR1A = map(anaValue, 0, 1023, 4, 14); // Map analog value to set the carrier frequency

  float Fw = (Fcpu) / ((1 + OCR1A) * 2 * N);
  Fw = Fw / 1000;
  dtostrf(Fw, 3, 2, freq);
  lcd.setCursor(0, 1);
  strcat(freq, "KHz  ");
  lcd.print(freq);
}

Explanation of the Code:

The code starts by including the necessary libraries and initializing the LCD module for displaying frequency information.
The variables N and Fcpu are defined to aid in the calculation of the carrier frequency.
In the setup() function, the LCD is initialized, and the timer1generate() function is called to configure Timer 1 for carrier signal generation.
The loop() function is left empty for now, as it's where you can add code to modulate the carrier signal with the desired audio input.
The timer1generate() function is responsible for configuring Timer 1 to generate the carrier signal. It sets up the appropriate registers for waveform generation, prescaling, and interrupt handling.
The ISR(TIMER1_COMPA_vect) is the Interrupt Service Routine that calculates and updates the carrier frequency based on the analog input read from pin 0. The carrier frequency is mapped according to the analog value, and the LCD displays the frequency information.

Conclusion: In this blog post, we've explored how to create an AM transmitter using an Arduino and the MC1496 RF Mixer. We've dissected the code responsible for generating the carrier signal using Timer 1 and how the carrier frequency is updated based on analog input. This project serves as a foundational step for creating an AM transmitter system and opens doors for further experimentation with amplitude modulation and RF communication.

Remember, building an AM transmitter requires compliance with legal regulations related to RF transmission in your region. Always ensure you are operating within the legal limits and guidelines.

Building an AM Transmitter with Arduino and MC1496 RF Mixer

Post a Comment