Circuit Documentation

Summary

This circuit is designed to read temperature data from multiple DS18B20 temperature sensors, display the data on a 0.96" OLED screen, and log the data to an SD card using an Arduino UNO microcontroller. The Arduino UNO manages the data acquisition from the temperature sensors, controls the OLED display via I2C communication, and writes the temperature data to a file on the SD card through the SPI interface.

Component List

Arduino UNO

• Microcontroller board based on the ATmega328P
• It has 14 digital input/output pins, 6 analog inputs, a 16 MHz quartz crystal, a USB connection, a power jack, an ICSP header, and a reset button.

DS18B20 Temperature Sensor (Wokwi Compatible)

• Digital temperature sensor that provides 9-bit to 12-bit Celsius temperature measurements.
• Communicates over a 1-Wire bus that by definition requires only one data line (and ground) for communication with a central microprocessor.

Resistor

• A passive two-terminal electrical component that implements electrical resistance as a circuit element.
• In this circuit, a 4.7kΩ resistor is used, likely as a pull-up for the 1-Wire data line.

0.96" OLED

• A small display screen that uses OLED technology.
• It is capable of displaying text, images, and animations.

SD Module

• A module that allows an Arduino board to read and write data to and from an SD card.
• It operates over the SPI interface.

Wiring Details

Arduino UNO

• 3.3V connected to OLED VDD
• 5V connected to VCC of all DS18B20 sensors, SD module, and one side of the resistor
• GND connected to GND of all DS18B20 sensors, OLED, and SD module
• SCL connected to OLED SCK
• SDA connected to OLED SDA
• D13 connected to SD module SCK
• D12 connected to SD module MISO
• D11 connected to SD module MOSI
• D10 connected to SD module CS
• D2 connected to DQ of all DS18B20 sensors and the other side of the resistor

DS18B20 Temperature Sensors

• VCC connected to Arduino 5V (through a resistor for one sensor)
• GND connected to Arduino GND
• DQ connected to Arduino D2 (through a 4.7kΩ resistor)

Resistor

• One side connected to Arduino 5V
• The other side connected to DQ of all DS18B20 sensors

0.96" OLED

• GND connected to Arduino GND
• VDD connected to Arduino 3.3V
• SCK connected to Arduino SCL
• SDA connected to Arduino SDA

SD Module

• CS connected to Arduino D10
• SCK connected to Arduino D13
• MOSI connected to Arduino D11
• MISO connected to Arduino D12
• VCC connected to Arduino 5V
• GND connected to Arduino GND

Documented Code

/*
 * This Arduino sketch reads temperature data from multiple DS18B20 sensors,
 * displays the data on an OLED screen, and logs the data to an SD card.
 */

#include <OneWire.h>
#include <DallasTemperature.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <SPI.h>
#include <SD.h>

#define ONE_WIRE_BUS 2
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1
#define SD_CS_PIN 10

OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
File dataFile;

void setup() {
  Serial.begin(9600);
  sensors.begin();
  if(!display.begin(SSD1306_I2C_ADDRESS, OLED_RESET)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }
  display.display();
  delay(2000);
  display.clearDisplay();
  if (!SD.begin(SD_CS_PIN)) {
    Serial.println("Card failed, or not present");
    return;
  }
  dataFile = SD.open("datalog.txt", FILE_WRITE);
  if (!dataFile) {
    Serial.println("Error opening datalog.txt");
  }
}

void loop() {
  sensors.requestTemperatures();
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0,0);
  for (int i = 0; i < sensors.getDeviceCount(); i++) {
    float tempC = sensors.getTempCByIndex(i);
    display.print("Sensor ");
    display.print(i);
    display.print(": ");
    display.print(tempC);
    display.println(" C");
    if (dataFile) {
      dataFile.print("Sensor ");
      dataFile.print(i);
      dataFile.print(": ");
      dataFile.print(tempC);
      dataFile.println(" C");
    }
  }
  display.display();
  if (dataFile) {
    dataFile.flush();
  }
  delay(2000);
}

This code initializes the sensors, display, and SD card on startup and enters a loop where it reads temperatures from the sensors, displays them on the OLED, and logs them to the SD card.