Temperature Sensor with ESP32

Easy 30 min $10

A temperature/humidity sensor is a good place to start: three wires, a handful of YAML lines, and you have live readings from the room in Home Assistant. The parts cost around $10.

📋 Prerequisites

Before you start:

• ✅ ESP32 set up with ESPHome
• ✅ Home Assistant up and running

Note

New to ESP32? Start with our Getting started guide first.

🛒 Components

Part	Description	Approx. price
ESP32 DevKit	WiFi microcontroller	$5
DHT22 sensor	Temperature + humidity	$3
Jumper wires	3x male-female	$2
Total		~$10

DHT22 vs DHT11

• DHT22: ±0.5°C accuracy, 0-100% humidity - recommended
• DHT11: ±2°C accuracy, 20-80% humidity - cheaper but imprecise

🔌 Wiring

Wiring diagram

Step by step

1. Red wire (VCC/+) → ESP32 3.3V pin

2. Yellow/white wire (DATA/OUT) → ESP32 GPIO4 pin

3. Black wire (GND/-) → ESP32 GND pin

Pull-up resistor

A bare 4-pin DHT22 needs a 10 kΩ resistor (pull-up) between DATA and 3.3V for stable readings. Most 3-pin breakout modules have the resistor built in, so there the three wires are all you need.

Power the sensor from 3.3V

The DHT22 itself tolerates 3.3-5.5 V, but the ESP32’s GPIO pins are not 5V-tolerant. Power the sensor from 5V and the data line follows it up, which can damage the ESP32. Stick to the 3.3V pin.

⚙️ ESPHome Configuration

Open your device in ESPHome and add this sensor configuration:

living-room-sensor.yaml

esphome:
  name: living-room-sensor
  friendly_name: Living Room Sensor

esp32:
  board: esp32dev

logger:
api:
  encryption:
    key: "your-key-here"
ota:
  platform: esphome

# DHT22 Sensor
sensor:
  - platform: dht
    pin: GPIO4
    model: DHT22
    temperature:
      name: "Living Room Temperature"
      filters:
        - offset: 0.0  # Adjust if needed
    humidity:
      name: "Living Room Humidity"
    update_interval: 60s

wifi:
  ssid: "your-wifi"
  password: "your-password"

Calibration

If the temperature reads wrong, compare against a thermometer you trust and adjust the offset value. For example, offset: -1.5 subtracts 1.5°C from the reading, while a positive value adds to it.

Alternative: DS18B20 (waterproof)

For outdoor or in-liquid measurements, a waterproof DS18B20 is a better choice than the DHT22. It uses 1-wire and needs a 4.7 kΩ pull-up resistor between DATA and 3.3V:

DS18B20 instead of DHT22

one_wire:
  - platform: gpio
    pin: GPIO4

sensor:
  - platform: dallas_temp
    name: "Living Room Temperature"
    update_interval: 60s

With only one sensor on the bus you can leave out address. Note that the DS18B20 only measures temperature, not humidity.

📤 Upload to ESP32

Wirelessly (if already flashed)

1. Click INSTALL in ESPHome
2. Choose Wirelessly
3. Wait ~1 minute

USB (first time)

1. Connect the ESP32 via USB
2. Click INSTALL → Plug into this computer
3. Select the COM port
4. Wait ~2 minutes

✅ Verify in Home Assistant

1. Go to Settings → Devices & Services

2. Find your ESP32 device and click it

3. You should see two new sensors:

   • sensor.living_room_temperature
   • sensor.living_room_humidity

4. Click a sensor to see its graph over time

📊 Add to Dashboard

Simple sensor card

Lovelace card

type: sensor
entity: sensor.living_room_temperature
name: Living room
icon: mdi:thermometer
graph: line
hours_to_show: 24

Combined temperature/humidity

Lovelace card

type: glance
entities:
  - entity: sensor.living_room_temperature
    name: Temperature
  - entity: sensor.living_room_humidity
    name: Humidity
title: Living Room Climate

🔧 Troubleshooting

Sensor shows 'Unavailable'?

Check these things:

1. Are the wires connected correctly? (VCC→3.3V)
2. Is the GPIO pin correct in the configuration?
3. Bare sensor: is the 10 kΩ pull-up resistor in place between DATA and 3.3V?
4. Try a different GPIO pin (e.g. GPIO5)
5. Check the ESPHome log for error messages

Temperature reads wrong?

Possible causes:

• The DHT22 has a ±0.5°C tolerance from the factory
• Sensor placed too close to the ESP32 (self-heating)
• Direct sunlight or a nearby heat source

Fix:

• Use the offset filter for calibration
• Move the sensor away from the ESP32 with longer wires
• Compare against a known thermometer

Humidity reads wrong?

DHT22 humidity is often 5-10% off. Calibrate with:

humidity:
  name: "Living Room Humidity"
  filters:
    - offset: -5.0  # Subtract 5%

💡 Tips for accurate readings

Tip	Explanation
Placement	Avoid direct sunlight, radiators, and windows
Height	Mount at ~1.5 m for room temperature
Airflow	Not in corners or behind furniture
Update interval	60s is fine, the DHT22 can be read at most every 2 seconds

🤖 Automation ideas

Example: warn on high humidity

automation:
  - alias: "High humidity alert"
    trigger:
      - platform: numeric_state
        entity_id: sensor.living_room_humidity
        above: 70
        for: "00:30:00"
    action:
      - service: notify.mobile_app_your_phone  # replace with your own device's notify service
        data:
          title: "⚠️ High humidity"
          message: "Humidity in the living room is {{ states('sensor.living_room_humidity') }}%"

Replace notify.mobile_app_your_phone with the name of your own phone’s notify service - you can find it under Developer Tools → Actions.

🚀 Next steps

🚶 Motion Sensor

Add a PIR sensor to detect movement.

Build a motion sensor →

💡 LED Strip

Control addressable RGB LEDs based on temperature.

Build an LED strip →