SHT31 on OLED: Temperature & Humidity
Overview & Wiring
What it is: The SHT31 (Sensirion) is a high-accuracy I2C temperature and humidity sensor (±0.3 °C, ±2 % RH) with a built-in heater to clear condensation. It's a step up from the AHT20 for serious measurement.
How it works: I2C device at address 0x44 (or 0x45 if the ADDR pin is tied high). Shares SDA/SCL with the OLED. The Adafruit SHT31 library reads temperature and humidity directly.
Wiring (shared I2C bus with the OLED):
SHT31 SDA -> GPIO4
SHT31 SCL -> GPIO5
SHT31 VCC -> 3V3
SHT31 GND -> GND
OLED VCC=3V3, GND=GND, SDA=GPIO4, SCL=GPIO5
Libraries: "Adafruit SHT31 Library" (installs "Adafruit BusIO"), plus "Adafruit SSD1306" and "Adafruit GFX Library".
On screen / Serial: temperature (°C) and humidity (%), one decimal.
Gotchas: Default address is 0x44; if your board ties ADDR high, change begin() to 0x45. The onboard heater is off by default — only enable it briefly to de-fog, as it warms the temperature reading.
Circuit Diagram
Parts You Need
Source Code (Arduino / ESP32)
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_SHT31.h>
Adafruit_SSD1306 display(128, 64, &Wire, -1);
Adafruit_SHT31 sht = Adafruit_SHT31();
void setup() {
Serial.begin(115200);
Wire.begin(4, 5);
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
if (!sht.begin(0x44)) { // use 0x45 if ADDR is tied high
Serial.println("SHT31 not found");
display.setTextColor(SSD1306_WHITE);
display.setCursor(0, 28); display.println("SHT31 not found");
display.display();
while (1) delay(10);
}
}
void loop() {
float t = sht.readTemperature(); // °C
float h = sht.readHumidity(); // %
display.clearDisplay();
display.setTextColor(SSD1306_WHITE);
display.setTextSize(1);
display.setCursor(0, 0);
display.println("SHT31");
display.setTextSize(2);
display.setCursor(0, 18); display.printf("%.1f C", t);
display.setCursor(0, 42); display.printf("%.1f %%", h);
display.display();
Serial.printf("Temp %.1f C Hum %.1f %%\n", t, h);
delay(1000);
}