Arduino UNO Q - LM35 Temperature Sensor
The LM35 is a simple analog temperature sensor that outputs a voltage proportional to temperature. On Arduino UNO Q, the MCU's 12-bit ADC delivers higher precision than standard 10-bit boards. This tutorial shows you how to wire and program the LM35 — and monitor it remotely via Telegram.
In this tutorial, you will learn:
- What the LM35 temperature sensor is and how it works
- How to wire the LM35 to the Arduino UNO Q MCU analog pin
- How to program the MCU (C/C++ Arduino code) to read temperature from the LM35 using 12-bit ADC
- How to program both the Linux side (Python) and MCU side (C/C++) to read LM35 data via Bridge
- How to receive Telegram alerts when temperature exceeds a threshold on Arduino UNO Q
- How to use OpenClaw on Arduino UNO Q with the LM35 sensor
Hardware Preparation
Or you can buy the following kits:
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
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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 LM35 Temperature Sensor
Pinout
The LM35 has three pins:
- GND: Connect to GND (0V)
- VCC: Connect to 5V (the LM35 requires at least 4V supply)
- OUT: Analog output — connect to an analog pin on the Arduino UNO Q MCU
How It Works
The LM35 outputs a voltage that increases linearly with temperature: each 1°C rise increases the output by 10mV. To read temperature, measure the output voltage and divide by 10.
On Arduino UNO Q, the MCU (STM32U585) uses a 12-bit ADC (values 0–4095) with a 3.3V reference. This gives better resolution than standard 10-bit Arduino boards.
Wiring Diagram
This image is created using Fritzing. Click to enlarge image
| LM35 Pin | Arduino UNO Q MCU |
|---|---|
| GND | GND |
| VCC | 5V |
| OUT | A0 |
※ NOTE THAT:
Connect LM35 VCC to the 5V pin, not 3.3V — the LM35 requires at least 4V to operate. The analog output will still be within the 3.3V ADC range of the MCU.
How To Program For LM35
- Read the ADC value from the analog pin:
int adcVal = analogRead(PIN_LM35);
- Convert ADC value to voltage in millivolts (using 3.3V reference and 12-bit resolution):
float milliVolt = adcVal * (ADC_VREF_mV / ADC_RESOLUTION);
// ADC_VREF_mV = 3300.0 (3.3V reference on UNO Q MCU)
// ADC_RESOLUTION = 4096.0 (12-bit ADC on UNO Q MCU)
- Convert millivolts to Celsius:
float tempC = milliVolt / 10;
- Convert Celsius to Fahrenheit:
float tempF = tempC * 9.0 / 5.0 + 32.0;
Arduino UNO Q Code
The Arduino UNO Q has two processors working together:
- The STM32 MCU reads the LM35 analog output directly via its 12-bit ADC — all sensor reading and conversion 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 the LM35 every second and prints temperature 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-lm35-temperature-sensor
*/
// COPYRIGHT newbiely.com
// AUTHOR: newbiely
// This code is made available for public use without restriction.
// For complete instructions, tutorials, and further information, visit:
// https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-lm35-temperature-sensor
// Arduino UNO Q MCU (STM32U585) uses a 12-bit ADC (0–4095) with a 3.3V reference
#define ADC_VREF_mV 3300.0 // MCU reference voltage in millivolts
#define ADC_RESOLUTION 4096.0 // 12-bit ADC resolution
#define PIN_LM35 A0 // Analog pin connected to LM35 OUT pin
void setup() {
Serial.begin(115200);
delay(1500);
Serial.println("Arduino UNO Q LM35 Temperature Sensor ready");
}
void loop() {
int adcVal = analogRead(PIN_LM35);
float milliVolt = adcVal * (ADC_VREF_mV / ADC_RESOLUTION);
float tempC = milliVolt / 10;
float tempF = tempC * 9.0 / 5.0 + 32.0;
Serial.print("Temperature: ");
Serial.print(tempC);
Serial.print("°C = ");
Serial.print(tempF);
Serial.println("°F");
delay(1000);
}
Detailed Instructions
First time with Arduino UNO Q? Follow the Getting Started with Arduino UNO Q tutorial before proceeding.
- Connect: Wire the LM35 sensor 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: Lm35TemperatureSensor
- Click Create to confirm.
- Paste the sketch: Copy the MCU code above and paste it into sketch/sketch.ino. Keep other files as default.
- No library required — the LM35 uses only the built-in analogRead() function.
- Upload: Click the Run button in Arduino App Lab.
- Hold the sensor in your hand — watch the temperature rise in the console.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:00:01] Arduino UNO Q LM35 Temperature Sensor ready
[2026-04-29 09:00:02] Temperature: 26.31°C = 79.36°F
[2026-04-29 09:00:03] Temperature: 26.44°C = 79.59°F
[2026-04-29 09:00:04] Temperature: 26.87°C = 80.37°F
[2026-04-29 09:00:05] Temperature: 27.25°C = 81.05°F
Bridge: Linux + MCU
This section shows how to program both processors of the Arduino UNO Q so the Linux side can read LM35 temperature via Bridge:
- The LM35 sensor is connected to the MCU (STM32) analog pin — the MCU reads and converts the ADC value every second
- The MPU cannot access the analog pin 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 LM35 every second via 12-bit ADC → MPU reads temperature via Bridge → MPU publishes or alerts over Wi-Fi.
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-lm35-temperature-sensor
*/
// COPYRIGHT newbiely.com
// AUTHOR: newbiely
// This code is made available for public use without restriction.
// For complete instructions, tutorials, and further information, visit:
// https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-lm35-temperature-sensor
// Arduino UNO Q MCU (STM32U585) uses a 12-bit ADC (0–4095) with a 3.3V reference
#include "Arduino_RouterBridge.h"
#define ADC_VREF_mV 3300.0
#define ADC_RESOLUTION 4096.0
#define PIN_LM35 A0
float last_temp_c = 0.0;
float last_temp_f = 0.0;
unsigned long last_read_ms = 0;
void read_lm35() {
int adcVal = analogRead(PIN_LM35);
float milliVolt = adcVal * (ADC_VREF_mV / ADC_RESOLUTION);
last_temp_c = milliVolt / 10.0;
last_temp_f = last_temp_c * 9.0 / 5.0 + 32.0;
}
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";
}
void setup() {
Bridge.begin();
Monitor.begin();
read_lm35();
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 LM35 Temperature Sensor Bridge ready");
}
void loop() {
unsigned long now = millis();
if (now - last_read_ms >= 1000) {
last_read_ms = now;
read_lm35();
Monitor.println("Temp: " + String(last_temp_c, 2) + "°C / " + String(last_temp_f, 2) + "°F");
}
}
Python 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-lm35-temperature-sensor
*/
# COPYRIGHT newbiely.com
# AUTHOR: newbiely
# This code is made available for public use without restriction.
# For complete instructions, tutorials, and further information, visit:
# https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-lm35-temperature-sensor
from arduino.app_utils import *
import time
def loop():
temp_c = Bridge.call("get_temp_c")
temp_f = Bridge.call("get_temp_f")
print(f"Temperature: {temp_c}°C = {temp_f}°F")
time.sleep(1)
App.run(user_loop=loop)
Detailed Instructions
- Connect: Wire the LM35 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 Lm35TemperatureSensorBridge, 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.
- Install the library: Click the Add sketch library button (the open book icon with a + sign) in the left sidebar.
- Search for Arduino_RouterBridge created by Arduino 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.
- Watch temperature readings appear in the Python console every second.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:00:01] Arduino UNO Q LM35 Temperature Sensor Bridge ready
[2026-04-29 09:00:02] Temp: 26.31°C / 79.36°F
[2026-04-29 09:00:03] Temp: 26.44°C / 79.59°F
[2026-04-29 09:00:04] Temp: 26.87°C / 80.37°F
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:00:02] Temperature: 26.31°C = 79.36°F
[2026-04-29 09:00:03] Temperature: 26.44°C = 79.59°F
[2026-04-29 09:00:04] Temperature: 26.87°C = 80.37°F
[2026-04-29 09:00:05] Temperature: 27.25°C = 81.05°F
Telegram
Monitor LM35 temperature remotely and receive automatic Telegram alerts when temperature rises above 35°C.
MCU sketch: Keep the same MCU sketch from the previous Bridge section.
Python Code (Telegram)
/*
* 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-lm35-temperature-sensor
*/
# COPYRIGHT newbiely.com
# AUTHOR: newbiely
# This code is made available for public use without restriction.
# For complete instructions, tutorials, and further information, visit:
# https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-lm35-temperature-sensor
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
ALERT_THRESHOLD_C = 35.0
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 alert_sent
# Auto-alert on high temperature
temp_c_str = Bridge.call("get_temp_c")
try:
temp_c = float(temp_c_str)
if temp_c > ALERT_THRESHOLD_C and not alert_sent:
alert_sent = True
temp_f = Bridge.call("get_temp_f")
msg = f"⚠️ High temperature alert: {temp_c_str}°C / {temp_f}°F"
print(msg)
send_message(CHAT_ID, msg)
elif temp_c <= ALERT_THRESHOLD_C:
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 LM35 Temperature Sensor Bot\n"
"/temp - Read temperature (°C and °F)\n"
"/tempC - Read temperature in Celsius\n"
"/tempF - Read temperature in Fahrenheit\n"
"/status - Get 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 == "/tempC":
result = Bridge.call("get_temp_c")
send_message(chat_id, f"Temperature: {result}°C")
elif text == "/tempF":
result = Bridge.call("get_temp_f")
send_message(chat_id, f"Temperature: {result}°F")
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(1)
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 from Telegram or hold the sensor to trigger the high-temperature alert.
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 09:10:15] ⚠️ High temperature alert: 36.25°C / 97.25°F
[2026-04-29 09:10:30] Received: /temp
[2026-04-29 09:10:45] Received: /tempC
Telegram
12:45
Welcome to Telegram!
ArduinoBot
10:19
Chatting with Arduino...
BotFather
Yesterday
Your bot has been created.
ArduinoBot
bot
OpenClaw
...OPENCLAW
OpenClaw support for Arduino UNO Q LM35 Temperature Sensor is coming soon.
...OPENCLAW
Project Ideas
You can build many useful projects with the LM35 and Arduino UNO Q:
- Analog Temperature Monitor: The LM35's continuous analog output and the MCU's 12-bit ADC give smooth, high-resolution readings — log every second and identify micro-temperature trends
- Overheating Protector: Use the LM35 to monitor a device (motor, circuit) — the MCU triggers a relay via Bridge when temperature exceeds a safe limit, and Telegram notifies you
- Multi-Zone Temperature Survey: Connect multiple LM35 sensors to different analog pins — the Python side queries each via Bridge and displays a side-by-side temperature comparison
- Calibrated Thermometer: Use the LM35's factory accuracy (±0.5°C) to build a precise digital thermometer with Telegram commands for on-demand readings
- Temperature-Based Fan Speed Controller: Map the LM35 ADC reading directly to a PWM output value on the MCU to control fan speed — the Python side can monitor the fan duty cycle via Bridge
Challenge Yourself
Ready to go further with the LM35 on Arduino UNO Q? Try these challenges:
- Easy: Add a moving average filter in the MCU sketch that averages the last 10 ADC readings before computing temperature — this reduces noise in the output.
- Medium: Compare LM35 and DS18B20 readings side by side: connect both sensors and add a compare_sensors(String) Bridge function that returns both readings in a single response for easy comparison.
- Advanced: Build a calibration tool: take 100 LM35 readings over 10 seconds, compute mean and standard deviation, and return them as a JSON string via a get_stats(String) Bridge function — Python displays and logs the calibration results.