Circuit Documentation

Summary

This circuit is designed to create an OLED clock using an Arduino Nano as the main microcontroller. The clock time is maintained by an RTC (Real-Time Clock) module and displayed on an OLED screen. The circuit is powered by a 3.7V LiPo battery, which is charged and protected by a TP4056 charging module. A toggle switch is included to control the power supply to the Arduino Nano.

Component List

Arduino Nano

• Microcontroller board based on the ATmega328P
• It has a variety of digital and analog I/O pins
• Capable of I2C communication

TP4056

• Lithium Battery Charger module
• Provides charging and protection for the LiPo battery
• Has designated pins for battery input and charging output

OLED Display (128x32)

• Small display for visual output
• Communicates over I2C
• Powered by 3.3V

Toggle Switch

• Single-pole double-throw (SPDT) switch
• Used to control the power supply to the Arduino Nano

RTC Module

• Maintains accurate time
• Communicates with the Arduino Nano via I2C
• Powered by 5V from the Arduino Nano

3.7V LiPo Battery

• Provides power to the circuit
• Connected to the TP4056 for charging

Wiring Details

Arduino Nano

• GND connected to OLED Display GND and RTC Module GND
• VIN connected to Toggle Switch COM
• 5V connected to RTC Module VCC
• 3V3 connected to OLED Display VCC
• A5 connected to RTC Module SCL and OLED Display SCL
• A4 connected to RTC Module SDA and OLED Display SDA

TP4056

• OUT- connected to RTC Module GND and Arduino Nano GND
• B+ connected to both 3.7V LiPo batteries +Ve
• B- connected to both 3.7V LiPo batteries GND
• OUT+ connected to Toggle Switch L1

OLED Display (128x32)

• SDA connected to Arduino Nano A4 and RTC Module SDA
• SCL connected to Arduino Nano A5 and RTC Module SCL
• VCC connected to Arduino Nano 3V3
• GND connected to Arduino Nano GND

Toggle Switch

• COM connected to Arduino Nano VIN
• L1 connected to TP4056 OUT+

RTC Module

• SCL connected to Arduino Nano A5 and OLED Display SCL
• SDA connected to Arduino Nano A4 and OLED Display SDA
• VCC connected to Arduino Nano 5V
• GND connected to Arduino Nano GND

3.7V LiPo Battery

• +Ve connected to TP4056 B+
• GND connected to TP4056 B-

Documented Code

/*
 * This Arduino Nano code was developed by newbiely.com
 *
 * This Arduino Nano code is made available for public use without any restriction
 *
 * For comprehensive instructions and wiring diagrams, please visit:
 * https://newbiely.com/tutorials/arduino-nano/arduino-nano-oled-clock
 */

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <RTClib.h>

#define OLED_WIDTH 128 // OLED display width,  in pixels
#define OLED_HEIGHT 32 // OLED display height, in pixels

Adafruit_SSD1306 oled(OLED_WIDTH, OLED_HEIGHT, &Wire, -1); // create SSD1306 display object connected to I2C
RTC_DS3231 rtc;

String time;

void setup() {
  Serial.begin(9600);

  // initialize OLED display with address 0x3C for 128x64
  if (!oled.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    while (true);
  }

  delay(2000);         // wait for initializing
  oled.clearDisplay(); // clear display

  oled.setTextSize(2);          // text size
  oled.setTextColor(WHITE);     // text color
  oled.setCursor(0, 10);        // position to display

  // SETUP RTC MODULE
  if (! rtc.begin()) {
    Serial.println("Couldn't find RTC");
    Serial.flush();
    while (true);
  }

  // automatically sets the RTC to the date & time on PC this sketch was compiled
  rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  time.reserve(10); // to avoid fragmenting memory when using String
}

void loop() {
  DateTime now = rtc.now();

  time = "";
  time += now.hour();
  time += ':';
  time += now.minute();
  time += ':';
  time += now.second();

  oled_display_center(time);
}

void oled_display_center(String text) {
  int16_t x1;
  int16_t y1;
  uint16_t width;
  uint16_t height;

  oled.getTextBounds(text, 0, 0, &x1, &y1, &width, &height);

  // center the display both horizontally and vertically
  oled.clearDisplay(); // clear display
  oled.setCursor((OLED_WIDTH - width) / 2, (OLED_HEIGHT - height) / 2);
  oled.println(text); // text to display
  oled.display();
}

This code initializes the OLED display and RTC module, then enters a loop where it continuously updates the display with the current time. The oled_display_center function is used to center the text on the OLED screen.