Arduino UNO Q - DHT22
The DHT22 offers more accurate temperature and humidity readings than the DHT11 — with a wider range and better precision. This tutorial shows you how to use it with Arduino UNO Q for complete environment monitoring with Telegram alerts.
In this tutorial, you will learn:
- What the DHT22 temperature and humidity sensor is and how it differs from DHT11
- How to wire the DHT22 sensor and module to the Arduino UNO Q MCU
- How to program the MCU (C/C++ Arduino code) to read temperature and humidity from the DHT22
- How to program both the Linux side (Python) and MCU side (C/C++) to read DHT22 data via Bridge
- How to receive Telegram alerts when temperature or humidity exceeds a threshold on Arduino UNO Q
- How to use OpenClaw on Arduino UNO Q with the DHT22 sensor
Hardware Preparation
Or you can buy the following kits:
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you.
Additionally, some of these links are for products from our own brand, DIYables .
Additionally, some of these links are for products from our own brand, DIYables .
Overview of the DHT22 Sensor
The DHT22 (also known as AM2302) is a more precise alternative to the DHT11. Both use the same library and nearly identical code — the main difference is the type constant in the constructor.
| DHT22 | |
|---|---|
| Operating Voltage | 3.3V to 6V |
| Temperature Range | -40°C to 80°C |
| Temperature Accuracy | ±0.5°C |
| Humidity Range | 0% to 100% |
| Humidity Accuracy | ±2% |
| Reading Rate | 0.5Hz (once every 2 seconds) |
Pinout
DHT22 Sensor (4-pin):
- GND: Connect to GND (0V)
- VCC: Connect to 3.3V or 5V
- DATA: Communication pin — connect to a digital pin on the MCU
- NC: Not connected
DHT22 Module (3-pin):
- GND: Connect to GND (0V)
- VCC: Connect to 3.3V or 5V
- DATA: Communication pin (also labeled OUT or S on some modules)
Most DHT22 modules include a built-in pull-up resistor — no external resistor needed.
Wiring Diagram
Arduino UNO Q - DHT22 Sensor Wiring
Requires a 10kΩ pull-up resistor between DATA and VCC.
This image is created using Fritzing. Click to enlarge image
Arduino UNO Q - DHT22 Module Wiring
No external resistor needed — the module includes one.
This image is created using Fritzing. Click to enlarge image
| DHT22 Pin | Arduino UNO Q MCU |
|---|---|
| GND | GND |
| VCC | 3.3V or 5V |
| DATA | D2 |
How To Program For DHT22
- Include the library:
#include <DHT.h>
- Define the pin and create a sensor object:
#define DHT22_PIN 2
DHT dht22(DHT22_PIN, DHT22);
- Initialize the sensor:
dht22.begin();
- Read humidity and temperature:
float humidity = dht22.readHumidity();
float tempC = dht22.readTemperature();
float tempF = dht22.readTemperature(true);
- Always check for failed reads:
if (isnan(humidity) || isnan(tempC) || isnan(tempF)) {
Serial.println("Failed to read from DHT22 sensor!");
}
Arduino UNO Q Code
The Arduino UNO Q has two processors working together:
- The STM32 MCU reads the DHT22 sensor directly — all sensor communication runs on the MCU
- The Qualcomm MPU runs Debian Linux and handles Wi-Fi, Python, and cloud connectivity
- In this section, only the MCU is programmed — the Linux side stays idle. A later section shows how both processors work together via Bridge.
The MCU reads temperature and humidity every 3 seconds and prints to the Serial Monitor.
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-dht22
*/
#include <DHT.h>
#define DHT22_PIN 2 // Arduino UNO Q MCU pin connected to DHT22 DATA pin
DHT dht22(DHT22_PIN, DHT22);
void setup() {
Serial.begin(115200);
delay(1500);
dht22.begin();
Serial.println("Arduino UNO Q DHT22 ready");
}
void loop() {
delay(3000); // DHT22 requires at least 2 seconds between readings
float humidity = dht22.readHumidity();
float tempC = dht22.readTemperature();
float tempF = dht22.readTemperature(true);
if (isnan(humidity) || isnan(tempC) || isnan(tempF)) {
Serial.println("Failed to read from DHT22 sensor!");
} else {
Serial.print("Humidity: ");
Serial.print(humidity);
Serial.print("% | Temperature: ");
Serial.print(tempC);
Serial.print("°C ~ ");
Serial.print(tempF);
Serial.println("°F");
}
}
Detailed Instructions
First time with Arduino UNO Q? Follow the Getting Started with Arduino UNO Q tutorial before proceeding.
- Connect: Wire the DHT22 sensor or module to the Arduino UNO Q MCU as shown in the wiring diagram.
- Open Arduino App Lab: Launch Arduino App Lab and wait until it detects your Arduino UNO Q.
- Create a new App: Click the Create New App button.
- Give the App a name, for example: Dht22
- Click Create to confirm.
- Paste the sketch: Copy the MCU code above and paste it into sketch/sketch.ino. Keep other files as default.
- Install the library: Click the Add sketch library button (the open book icon with a + sign) in the left sidebar.
- Search for DHT sensor library created by Adafruit and click the Install button.
Bricks
No bricks added...
Sketch Libraries
No sketch libra...
Files
python
sketch
.gitignore
README.md
app.yaml
sketch.ino
- Upload: Click the Run button in Arduino App Lab.
- Breathe on the sensor or hold it — watch humidity and temperature readings update every 3 seconds.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:00:01] Arduino UNO Q DHT22 ready
[2026-04-29 09:00:04] Humidity: 55.2% | Temperature: 26.10°C ~ 79.00°F
[2026-04-29 09:00:07] Humidity: 55.8% | Temperature: 26.20°C ~ 79.16°F
[2026-04-29 09:00:10] Humidity: 57.3% | Temperature: 26.50°C ~ 79.70°F
[2026-04-29 09:00:13] Humidity: 61.9% | Temperature: 27.10°C ~ 80.78°F
Bridge: Linux + MCU
This section shows how to program both processors of the Arduino UNO Q so the Linux side can read temperature and humidity via Bridge:
- The DHT22 sensor is connected to the MCU (STM32) — the MCU reads data every 3 seconds and caches the latest values
- The MPU cannot access the DHT22 directly — it must call Bridge functions to retrieve readings
- The MPU has Wi-Fi — running full Debian Linux, it can log data, publish to dashboards, or send alerts over the Internet
- Arduino_RouterBridge enables RPC communication between the two processors
- ⚠️ /dev/ttyHS1 (Linux) and Serial1 (MCU) are RESERVED by the router — never open them in user code
In short: MCU reads DHT22 every 3 seconds and caches the result → MPU polls Bridge to retrieve readings → MPU publishes or alerts over Wi-Fi.
Note: In the Bridge sketch, the loop() function reads the DHT22 every 3 seconds to keep the cached values fresh. All Bridge callbacks are read-only and return cached data without blocking.
MCU Code (Bridge)
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-dht22
*/
#include <DHT.h>#include "Arduino_RouterBridge.h"
#define DHT22_PIN 2
DHT dht22(DHT22_PIN, DHT22);
float last_humidity = 0.0;
float last_temp_c = 0.0;
float last_temp_f = 0.0;
unsigned long last_read_ms = 0;
String get_humidity(String arg) {
return String(last_humidity, 1);
}
String get_temp_c(String arg) {
return String(last_temp_c, 2);
}
String get_temp_f(String arg) {
return String(last_temp_f, 2);
}
String get_status(String arg) {
return "Temp: " + String(last_temp_c, 2) + "°C / " + String(last_temp_f, 2) + "°F Humidity: " + String(last_humidity, 1) + "%";
}
void setup() {
Bridge.begin();
Monitor.begin();
dht22.begin();
delay(2000); // allow sensor to stabilize
float h = dht22.readHumidity();
float c = dht22.readTemperature();
float f = dht22.readTemperature(true);
if (!isnan(h) && !isnan(c) && !isnan(f)) {
last_humidity = h;
last_temp_c = c;
last_temp_f = f;
}
Bridge.provide("get_humidity", get_humidity);
Bridge.provide("get_temp_c", get_temp_c);
Bridge.provide("get_temp_f", get_temp_f);
Bridge.provide("get_status", get_status);
Monitor.println("Arduino UNO Q DHT22 Bridge ready");
}
void loop() {
unsigned long now = millis();
if (now - last_read_ms >= 3000) {
last_read_ms = now;
float h = dht22.readHumidity();
float c = dht22.readTemperature();
float f = dht22.readTemperature(true);
if (isnan(h) || isnan(c) || isnan(f)) {
Monitor.println("Failed to read from DHT22 sensor!");
} else {
last_humidity = h;
last_temp_c = c;
last_temp_f = f;
Monitor.println("Humidity: " + String(h, 1) + "% Temp: " + String(c, 2) + "°C / " + String(f, 2) + "°F");
}
}
}
Python Code (Bridge)
"""
This Arduino UNO Q script was developed by newbiely.com
This Arduino UNO Q script is made available for public use without any restriction
For comprehensive instructions and wiring diagrams, please visit:
https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-dht22
"""
from arduino.app_utils import *
import time
def loop():
status = Bridge.call("get_status")
print(status)
time.sleep(3)
App.run(user_loop=loop)
Detailed Instructions
- Connect: Wire the DHT22 sensor to the Arduino UNO Q as shown in the wiring diagram.
- Open Arduino App Lab: Launch Arduino App Lab and wait for the board to be detected.
- Create a new App: Click Create New App, name it Dht22Bridge, then click Create.
- Paste the MCU sketch: Copy the MCU Bridge code above and paste it into sketch/sketch.ino.
- Paste the Python code: Copy the Python Bridge code above and paste it into the Python file in the App.
- Upload: Click the Run button in Arduino App Lab.
- Watch temperature and humidity readings appear in the Python console every 3 seconds.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:00:01] Arduino UNO Q DHT22 Bridge ready
[2026-04-29 09:00:04] Humidity: 55.2% Temp: 26.10°C / 79.00°F
[2026-04-29 09:00:07] Humidity: 55.8% Temp: 26.20°C / 79.16°F
[2026-04-29 09:00:10] Humidity: 57.3% Temp: 26.50°C / 79.70°F
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:00:04] Temp: 26.10°C / 79.00°F Humidity: 55.2%
[2026-04-29 09:00:07] Temp: 26.20°C / 79.16°F Humidity: 55.8%
[2026-04-29 09:00:10] Temp: 26.50°C / 79.70°F Humidity: 57.3%
[2026-04-29 09:00:13] Temp: 27.10°C / 80.78°F Humidity: 61.9%
Telegram
Monitor temperature and humidity remotely. Receive automatic alerts when temperature exceeds 35°C or humidity exceeds 80%.
MCU sketch: Keep the same MCU sketch from the previous Bridge section.
Python Code (Telegram)
"""
This Arduino UNO Q script was developed by newbiely.com
This Arduino UNO Q script is made available for public use without any restriction
For comprehensive instructions and wiring diagrams, please visit:
https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-dht22
"""
from arduino.app_utils import *
import requests
import time
TELEGRAM_BOT_TOKEN = "YOUR_TELEGRAM_BOT_TOKEN"
CHAT_ID = "YOUR_CHAT_ID"
last_update_id = 0
TEMP_ALERT_C = 35.0
HUMIDITY_ALERT = 80.0
temp_alert_sent = False
humi_alert_sent = False
def get_updates():
global last_update_id
url = f"https://api.telegram.org/bot{TELEGRAM_BOT_TOKEN}/getUpdates"
params = {"offset": last_update_id + 1, "timeout": 5}
try:
response = requests.get(url, params=params, timeout=10)
data = response.json()
if data["ok"]:
return data["result"]
except Exception as e:
print(f"Error getting updates: {e}")
return []
def send_message(chat_id, text):
url = f"https://api.telegram.org/bot{TELEGRAM_BOT_TOKEN}/sendMessage"
payload = {"chat_id": chat_id, "text": text}
try:
requests.post(url, data=payload, timeout=10)
except Exception as e:
print(f"Error sending message: {e}")
def loop():
global temp_alert_sent, humi_alert_sent
# Auto-alerts
temp_c_str = Bridge.call("get_temp_c")
humi_str = Bridge.call("get_humidity")
try:
temp_c = float(temp_c_str)
humi = float(humi_str)
temp_f_str = Bridge.call("get_temp_f")
if temp_c > TEMP_ALERT_C and not temp_alert_sent:
temp_alert_sent = True
msg = f"⚠️ High temperature: {temp_c_str}°C / {temp_f_str}°F"
print(msg)
send_message(CHAT_ID, msg)
elif temp_c <= TEMP_ALERT_C:
temp_alert_sent = False
if humi > HUMIDITY_ALERT and not humi_alert_sent:
humi_alert_sent = True
msg = f"💧 High humidity: {humi_str}%"
print(msg)
send_message(CHAT_ID, msg)
elif humi <= HUMIDITY_ALERT:
humi_alert_sent = False
except ValueError:
pass
# Handle Telegram commands
updates = get_updates()
for update in updates:
last_update_id = update["update_id"]
if "message" not in update:
continue
message = update["message"]
chat_id = message["chat"]["id"]
text = message.get("text", "").strip()
print(f"Received: {text}")
if text == "/start":
send_message(chat_id,
"Arduino UNO Q DHT22 Bot\n"
"/temp - Read temperature (°C and °F)\n"
"/humidity - Read humidity\n"
"/status - Get full sensor status")
elif text == "/temp":
temp_c = Bridge.call("get_temp_c")
temp_f = Bridge.call("get_temp_f")
send_message(chat_id, f"Temperature: {temp_c}°C ~ {temp_f}°F")
elif text == "/humidity":
result = Bridge.call("get_humidity")
send_message(chat_id, f"Humidity: {result}%")
elif text == "/status":
result = Bridge.call("get_status")
send_message(chat_id, result)
else:
send_message(chat_id, "Unknown command. Send /start for help.")
time.sleep(3)
App.run(user_loop=loop)
Detailed Instructions
- Replace YOUR_TELEGRAM_BOT_TOKEN with your actual bot token from BotFather.
- Replace YOUR_CHAT_ID with your Telegram chat ID.
- Paste this Python code into your App's Python file (keep the same MCU sketch).
- Click the Run button. Send /temp or /humidity from Telegram, or breathe on the sensor to trigger alerts.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:10:00] Waiting for Telegram messages...
[2026-04-29 09:10:10] ⚠️ High temperature: 36.00°C / 96.80°F
[2026-04-29 09:10:25] 💧 High humidity: 82.3%
[2026-04-29 09:10:40] Received: /temp
[2026-04-29 09:10:55] Received: /humidity
Telegram
12:45
Welcome to Telegram!
ArduinoBot
10:19
Chatting with Arduino...
BotFather
Yesterday
Your bot has been created.
ArduinoBot
bot
OpenClaw
You can adapt the OpenClaw to this tutorial by refering the instruction on Arduino Uno Q - OpenClaw Tutorial
Project Ideas
You can build many useful projects with the DHT22 sensor and Arduino UNO Q:
- Precision Weather Station: The DHT22's wider range and better accuracy makes it ideal for a precise indoor/outdoor station — the Linux MPU logs data every minute and charts trends over time
- Smart HVAC Controller: Use temperature and humidity data to control a relay that switches your air conditioner or humidifier — Telegram alerts when conditions go out of range
- Seed Germination Monitor: Maintain optimal humidity and temperature for seed germination — receive alerts if humidity drops below threshold and data is logged for review
- Wine Cellar Monitor: The DHT22 covers the lower temperature range needed for wine storage — monitor both temp and humidity with Telegram alerts if either drifts outside safe limits
- Server Room Environmental Monitor: Deploy with Wi-Fi for remote monitoring — the MPU sends hourly reports and instant Telegram alerts if temperature or humidity spikes
Challenge Yourself
Ready to go further with the DHT22 on Arduino UNO Q? Try these challenges:
- Easy: Modify the MCU sketch to blink the built-in LED at different speeds depending on temperature range — slow blink below 20°C, fast blink above 35°C, no blink in between.
- Medium: Calculate the dew point from temperature and humidity on the Python side using the Magnus formula, and include it in the Telegram /status response alongside temperature and humidity.
- Advanced: Build a data visualization pipeline: the MPU reads DHT22 via Bridge every 5 minutes, stores readings in a JSON file, and serves a simple HTTP page with a temperature/humidity chart using Chart.js — accessible from any browser on the local network.