TMP36 temperature sensor explained — pinout, formula and Arduino code

#What it is

The TMP36 is a small temperature sensor in a black plastic body with one flat face and three legs. Give it power and its middle leg puts out a voltage that follows the temperature. Read that voltage on an analog pin, and one line of code turns it into degrees Celsius. See it in 3D.

#How it works inside

Inside is a tiny chip. It uses a property of silicon junctions — the voltage across them changes in a very regular way with temperature — and amplifies it into a neat, simple output:

• 0.5 V at 0 °C,
• plus 10 mV (0.01 V) for every degree warmer.

The 0.5 V start is there so that temperatures below zero still give a positive voltage: −40 °C is 0.1 V.

#The formula

Two steps, both in the code below:

1. Reading to volts: volts = reading × 5.0 ÷ 1023
2. Volts to degrees: °C = (volts − 0.5) × 100

Example: a reading of 153 → 153 × 5 ÷ 1023 = 0.748 V → (0.748 − 0.5) × 100 ≈ 24.8 °C.

#The pins

Hold it with the flat face towards you and the legs down. From left to right:

#How to wire it to an Arduino

This is the sensor's side of the thermostat project:

1. Push the TMP36 into the breadboard, flat face towards you, each leg in its own row.
2. 5V → the left leg (VS).
3. The middle leg (OUT) → A0.
4. The right leg → GND.

No resistor is needed: the TMP36 makes its own voltage.

#Example code

The exact code of the thermostat. The fan sits on pin 6 behind a transistor; the sensor part is just the first two lines of loop():

const int SENSOR = A0;
const int FAN = 6;
bool fanOn = false;

void setup() {
  pinMode(FAN, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  float volts = analogRead(SENSOR) * 5.0 / 1023.0;
  float celsius = (volts - 0.5) * 100.0;
  if (celsius > 30) fanOn = true;
  if (celsius < 28) fanOn = false;
  analogWrite(FAN, fanOn ? 220 : 0);
  Serial.print(celsius, 1);
  Serial.println(fanOn ? " C  fan ON" : " C  fan off");
  delay(300);
}

• float holds numbers with decimals; int would cut 0.748 V to 0.
• 5.0 / 1023.0 — the .0 matters: it makes the division keep its decimals.
• (volts - 0.5) * 100.0 is the TMP36 formula.
• Two limits, 30 °C and 28 °C (hysteresis): the fan switches on above 30 and off only below 28, so it does not flick on and off at 29.9.
• Serial.print(celsius, 1) prints one decimal place.

Play in 3DRun the code · press the parts · turn it around

#Common mistakes

• Sensor in backwards. Very hot and ruined. Flat face towards you: 5V, A0, GND.
• Readings around −50 °C. The OUT leg is not reaching A0, so the pin reads close to 0. Check that wire.
• Integer maths. analogRead(A0) * 5 / 1023 drops the decimals — use 5.0 / 1023.0.
• It reads too warm. The sensor sits next to something hot, like a busy regulator or a lamp. Move it away.

#Check yourself

#Questions people ask

#How do I convert TMP36 readings to Celsius on Arduino?

Turn the reading into volts with reading * 5.0 / 1023.0, then use (volts - 0.5) * 100.0. For Fahrenheit, multiply the Celsius value by 9 ÷ 5 and add 32.

#Why is my TMP36 getting hot?

It is almost certainly in backwards, with 5V on its GND leg. Unplug the USB at once, let it cool, and turn it round — flat face towards you: 5V, OUT, GND.

#How accurate is the TMP36?

Within about 1–2 °C, and the UNO reads it in steps of about 0.5 °C. That is plenty for a thermostat or a weather display, not for a fever thermometer.

#Can I use a TMP36 with 3.3 V?

Yes, it works from 2.7 V up, and its output is the same: 0.5 V at 0 °C, 10 mV per degree. Keep 5.0 in the formula — that number is the UNO's analog reference, not the sensor's supply.

#Where it is used

Build the Arduino thermostat, where the TMP36 switches a fan through a transistor.

Last updated 2026-10-29