NTC 10k Thermistor on OLED: Temperature
Overview & Wiring
What it is: An NTC thermistor is a resistor whose resistance falls as temperature rises. The common "10k" type reads 10,000 Ω at 25 °C. With one fixed resistor it becomes a cheap, accurate temperature sensor.
How it works: Build a voltage divider — NTC from 3V3 to the junction, a 10k fixed resistor from the junction to GND. Read the junction voltage, compute the NTC's resistance, then convert to temperature with the Beta equation (Beta ≈ 3950 for typical 10k NTCs).
Wiring (voltage divider):
3V3 -> one leg of the NTC
GPIO0 -> junction between the NTC and the 10k resistor (this is "SIG")
GND -> other leg of the 10k resistor
OLED VCC=3V3, GND=GND, SDA=GPIO4, SCL=GPIO5
Libraries: only "Adafruit SSD1306" and "Adafruit GFX Library".
On screen / Serial: temperature in °C. Pinch the thermistor and watch it rise.
Gotchas: If temperature reads backwards (drops when you warm it), swap the NTC and the fixed resistor positions. If your thermistor's Beta or nominal resistance differs, edit BETA / R_NOMINAL in the code. Use a 1% resistor for best accuracy.
Circuit Diagram
Parts You Need
Source Code (Arduino / ESP32)
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <math.h>
Adafruit_SSD1306 display(128, 64, &Wire, -1);
#define NTC 0 // junction on GPIO0 (ADC)
const float VREF = 3.3; // supply voltage across the divider
const float R_FIXED = 10000; // fixed resistor to GND (ohms)
const float R_NOMINAL = 10000;// NTC resistance at 25 °C
const float T_NOMINAL = 25.0; // reference temperature (°C)
const float BETA = 3950; // NTC Beta coefficient
void setup() {
Serial.begin(115200);
Wire.begin(4, 5);
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
}
void loop() {
float v = analogReadMilliVolts(NTC) / 1000.0; // junction volts
float rNtc = R_FIXED * (VREF / v - 1.0); // NTC resistance (divider math)
// Beta equation -> kelvin -> celsius
float tK = 1.0 / (1.0 / (T_NOMINAL + 273.15) + (1.0 / BETA) * log(rNtc / R_NOMINAL));
float tempC = tK - 273.15;
display.clearDisplay();
display.setTextColor(SSD1306_WHITE);
display.setTextSize(1);
display.setCursor(0, 0);
display.println("NTC 10k");
display.setTextSize(3);
display.setCursor(0, 24);
display.printf("%.1f", tempC);
display.setTextSize(2);
display.print(" C");
display.display();
Serial.printf("Temp: %.1f C (R=%.0f ohm)\n", tempC, rNtc);
delay(400);
}