DS18B20 on OLED: 1-Wire Temperature
Overview & Wiring
What it is: The DS18B20 is a precise digital temperature sensor (-55 to +125 °C, ±0.5 °C) that talks over Maxim's 1-Wire bus. It comes as a small TO-92 chip or a waterproof stainless probe.
How it works: Each sensor has a unique 64-bit address, so many can share one data wire. The ESP32 sends a "convert" command, waits, then reads back the temperature over the same wire.
Wiring:
DS18B20 DATA (middle) -> GPIO10
DS18B20 VDD -> 3V3
DS18B20 GND -> GND
IMPORTANT: add a 4.7k pull-up resistor between DATA and 3V3 — the bus does not work reliably without it.
OLED VCC=3V3, GND=GND, SDA=GPIO4, SCL=GPIO5
Libraries: "OneWire" by Paul Stoffregen, "DallasTemperature" by Miles Burton, plus "Adafruit SSD1306" and "Adafruit GFX Library".
On screen / Serial: temperature in °C with one decimal, updated about twice a second. A reading of -127 °C means the sensor wasn't found — check the pull-up and the DATA wire.
Gotchas: The waterproof probe's wire colors vary; commonly red=VDD, black=GND, yellow=DATA, but verify with a multimeter. Don't skip the 4.7k pull-up.
Circuit Diagram
Parts You Need
Source Code (Arduino / ESP32)
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <OneWire.h> // low-level 1-Wire bus
#include <DallasTemperature.h> // DS18B20 helper
Adafruit_SSD1306 display(128, 64, &Wire, -1);
#define ONE_WIRE 10 // DS18B20 DATA on GPIO10
OneWire oneWire(ONE_WIRE);
DallasTemperature sensors(&oneWire);
void setup() {
Serial.begin(115200);
Wire.begin(4, 5);
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
sensors.begin();
}
void loop() {
sensors.requestTemperatures(); // ask all sensors to measure
float t = sensors.getTempCByIndex(0); // read the first sensor, °C
display.clearDisplay();
display.setTextColor(SSD1306_WHITE);
display.setTextSize(1);
display.setCursor(0, 0);
display.println("DS18B20");
if (t == DEVICE_DISCONNECTED_C) { // -127 = not found
display.setCursor(0, 26);
display.println("No sensor");
Serial.println("DS18B20 not found");
} else {
display.setTextSize(3);
display.setCursor(0, 24);
display.printf("%.1f", t);
display.setTextSize(2);
display.print(" C");
Serial.printf("Temp: %.2f C\n", t);
}
display.display();
delay(500);
}