What I wanted to learn, and why it interested me: I wanted to learn how to use a thermal receipt printer to explore an interactive method of displaying fun art.

Process and reflection: 

My project began with the rough idea of creating an interactive project that I can place in my house for visitors. I wanted to explore a new type of sensor and explore different ways for displaying fun art. While researching inspo for the receipt design, I thought that it would be interesting to add a real-time clock module to implement as part of my receipt.  

Printing images and a straight horizontal line was surprisingly the most difficult part of the process. As for printing out the image, I needed to download a separate software (Processing) to convert my image into a bitmap. This process was a bit complex, but once I had figured out the workflow, it was interesting to play with. As for printing a horizontal line on the receipt, I'm still not quite sure why it does not print a series of dashes. However, I was able to find a way to work around it by printing out dotted lines instead. 

Overall, I'm proud of the final outcome. It's satisfying to see how a simple technical experiment could turn into a tangible, playful interaction! In the future, I hope to explore more about how to install the receipt printer in my house and test out the exact sensitivity of the motion detector.

/*

    60-223 Intro to Physical Computing, fall 2025

    Domain-specific Skill Building exercise: [Motion-Activated Thermal Printer]

    [This Arduino sketch connects to a thermal printer, a motion sensor, and a real-time clock module. When the motion sensor detects movement, the printer automatically prints a custom "receipt". Each printout includes a message, the current date and time from the RTC, and a small image.]

    Pin mapping:

    Arduino pin | role  | details

    ------------------------------

    2             input   motion detector

    6             output  thermal printer

Sketch written by ChatGPT on 10/04/2025

    Released to the public domain by the author, January 2024

    Robert Zacharias, rzachari@andrew.cmu.edu

*/

#include "Adafruit_Thermal.h"

#include "SoftwareSerial.h"

#include <Wire.h>

#include "RTClib.h"

// Define pins for the printer

#define TX_PIN 6

#define RX_PIN 5

SoftwareSerial mySerial(RX_PIN, TX_PIN);

Adafruit_Thermal printer(&mySerial);

// Motion sensor pin

#define MOTION_PIN 2

// RTC object

RTC_DS3231 rtc;

// Include generated bitmap header

#include "IMG_4535_imresizer.h"  // Defines IMG_4535_width, IMG_4535_height, IMG_4535_data

bool printed = false; // Ensure we print only once per motion event

void setup() {

 pinMode(MOTION_PIN, INPUT); // Motion sensor output

 mySerial.begin(19200);

 printer.begin();

 // Initialize RTC

 if (!rtc.begin()) {

   while (1); // RTC not found

 }

 if (rtc.lostPower()) {

   rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));

 }

}

void loop() {

 // Motion detected is HIGH

 if (digitalRead(MOTION_PIN) == HIGH) {

   if (!printed) {

     DateTime now = rtc.now();

     // ===== HEADER =====

     printer.justify('C');       // Centered text

     printer.setSize('L');       // Large text for main heading

     printer.println("HEY!");

     printer.setSize('S');       // Small text for subheading

     printer.println("Yutong's house :)");

     // Date & time on one line, small centered text

     String dateTimeStr = String(now.month()) + "/" + String(now.day()) + "/" + String(now.year()) + " " +

                          String(now.hour()) + ":" + (now.minute() < 10 ? "0" : "") + String(now.minute()) + ":" +

                          (now.second() < 10 ? "0" : "") + String(now.second());

     printer.println(dateTimeStr);

     // Full-width dotted line

     printer.justify('C');

     printer.setSize('S');

     printer.println("................................");

     // ===== BODY =====

     printer.setSize('M');        // Medium text for product label

     printer.justify('L');        // Left aligned

     printer.println("PRODUCT");

     // Print bitmap

     printer.printBitmap(IMG_4535_imresizer_width, IMG_4535_imresizer_height, IMG_4535_imresizer_data);

     // ===== TOTAL =====

     printer.setSize('M');        // Medium text

     printer.justify('R');        // Right aligned

     printer.println("TOTAL $$$$");

     // ===== SIGNATURE SECTION =====

     printer.justify('L');

     printer.setSize('M');

     printer.println("SIGNATURE");

     printer.justify('C');

     printer.setSize('S');

     printer.println("................................");

     printer.println(); // Empty line for signature

     printer.println(); // Empty line for signature

     printer.println(); // Empty line for signature

     printer.println("................................");

     // ===== THANK YOU NOTE =====

     printer.println(); // Empty line

     printer.setSize('S');        // Smallest text

     printer.justify('C');        // Centered

     printer.println("SEE YOU AGAIN?");

     printer.println(); // Empty line

     // Advance paper

     printer.feed(2);

     printed = true; // Prevent multiple prints per motion

   }

 } else {

   printed = false; // Reset flag when no motion

 }

}