Build and test an Arduino thermostat as a low-voltage controller first: read a temperature sensor, compare it with two switching thresholds, and use a relay module or other suitable interface to switch a safe test load. A DS18B20 is a practical sensor choice, but its published accuracy is only one part of the finished thermostat’s performance. Do not connect a hobby prototype directly to mains-powered heating equipment without appropriately rated components and a compliant installation.
How an Arduino thermostat works
“A thermostat is just a switch that makes an electrical connection when it passes a temperature threshold,” Arduino Team wrote in a July 18, 2024 post about a smart thermostat project. In an Arduino build, the controller reads a sensor, compares the measurement with a target or target band, then changes an output state. For heating, that output can command a relay interface; it should not power the heater directly.
The simplest useful design has four parts: a board, a temperature sensor, control logic with a setpoint and switching band, and an output that is appropriate for the load. Begin with a low-voltage indicator or test load, not household wiring.
Choose a project scope and parts
A straightforward prototype can be assembled with an Arduino-compatible board, a DS18B20 sensor, its required pull-up, a suitable relay module, jumper wires, and a low-voltage test load or indicator. A display, buttons, enclosure, clock, or network connection are optional additions, not requirements for basic temperature switching.
Do these 3 things before closing this tab:
1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minute#1 Best Overall
- 35+ Guided Electronics Projects: Progress from LEDs and buttons to RFID access, real-time clocks, motion and distance sensing, environmental monitoring, motor control and interactive displays for STEM learning, coding clubs and maker projects
- More I/O and Memory for Larger Builds: The MEGA 2560 R3 provides 54 digital I/O pins, including 15 PWM outputs, 16 analog inputs, 4 hardware serial ports and 256 KB flash for projects that combine more sensors, controls and displays
- 200+ Components for Prototyping: Includes LCD1602, RC522 RFID, RTC, DHT11, HC-SR501 PIR, ultrasonic and water-level sensors, GY-521, MAX7219, keypad, joystick, rotary encoder, relay, SG90 servo, stepper motor, DC motor, breadboard and more
- Learn, Modify and Create: Follow 35+ guided lessons with example code, then adjust sensor thresholds, timing, display text, motor behavior and control logic to turn structured exercises into access systems, monitors, alarms and interactive projects
- Organized for Repeatable Learning: Pre-soldered modules, a solderless breadboard, storage case and small-parts box reduce setup time and keep sensors, LEDs, ICs, wires and other components easy to find between projects
| Design direction | What it includes | Scope and caveats |
|---|---|---|
| Basic sensor-and-relay controller | Arduino, DS18B20, pull-up resistor, relay interface | Threshold-based control; use a low-voltage load for initial testing. Example thresholds in tutorials are demonstrations, not recommended home settings. |
| Network-monitored Uno example | Uno, W5100 Ethernet shield, two DS18B20 sensors, screw shield, four-channel relay board, jumper wires | Arduino Project Hub’s example was published July 4, 2017. It is useful as a reference for mapping sensors, pins, and relay rules, but its software stack is an older project example rather than a current platform recommendation. |
| Smart heating-only design | MKR WiFi 1010, SHT31-D temperature/humidity sensor, relay, OLED display, real-time clock, optional MH-Z19C CO2 sensor | Arduino’s July 18, 2024 design controls heat only; Arduino says it does not control a blower fan or air conditioner. It is not a complete HVAC controller. |
What the DS18B20 can—and cannot—tell you
The DS18B20 is a digital 1-Wire thermometer with configurable 9- to 12-bit resolution. Analog Devices / Maxim Integrated’s revision 6 datasheet, dated August 9, 2019, specifies error limits of ±0.5°C from -10°C to +85°C, ±1°C from -30°C to +100°C, and ±2°C from -55°C to +125°C. Those are sensor specifications, not a guarantee of whole-system accuracy: sensor placement, wiring, calibration, airflow, and the enclosure can affect the temperature your thermostat actually observes.
The 1-Wire bus needs a pull-up. The datasheet illustrates a 4.7 kΩ pull-up arrangement; check the specific sensor breakout and voltage configuration before copying a wiring diagram. The breakout may already include components, so do not assume every board has the same circuit.
Rank #2
- TURN CODE INTO REAL-WORLD RESULTS — Follow 22+ guided lessons to make LEDs blink, read temperature and distance, move servo and stepper motors, control an LCD and respond to joystick or IR input; ideal for a family weekend build, homeschool unit, coding club or STEM classroom
- MORE PROJECT VARIETY IN ONE ORGANIZED KIT — Includes the UNO R3 controller, LCD1602 with pre-soldered header, breadboard power module, ultrasonic and DHT11 sensors, joystick, IR receiver and remote, SG90 servo, stepper motor, relay, DC motor, fan blade, displays, LEDs, buttons, resistors and jumper wires
- START WITHOUT SOLDERING — Plug-in modules, a solderless breadboard and the pre-soldered LCD help beginners focus on wiring, code and testing; the illustrated component list makes it easier to find each part and move from one lesson to the next
- LEARN THE LOGIC, THEN CREATE YOUR OWN — Use Arduino IDE and the included example code to understand digital input and output, analog sensing, timing, motor control and display functions, then change thresholds, speeds and sequences for alarms, environmental monitors, reaction games and motion projects
- CLEAR SETUP SUPPORT FOR FIRST-TIME BUILDERS — Download the latest tutorial and code, select the UNO board and correct computer port, check component polarity and breadboard rows, and keep power-module input at 9V or below; younger learners should work with an experienced adult
Keep the Arduino pin in its role
Arduino’s official Uno Rev3 specification lists 5 V digital pins, recommends 20 mA operating current per pin, and gives 7–12 V as the recommended board supply range. A pin is a logic signal, not a source for a relay coil or heater. Use a relay module or driver suitable for the actual board and load, and follow both devices’ specifications.
Wire and test the sensor first
- Power down before wiring. Connect the DS18B20 according to the pinout for the exact sensor or breakout you have. Check whether it is a bare sensor or a module before applying power.
- Add the data-line pull-up. Use the manufacturer’s 1-Wire arrangement, including a pull-up such as the illustrated 4.7 kΩ value where appropriate for your setup. Confirm supply voltage and module details rather than relying on a generic drawing.
- Load a sensor-reading sketch. Read the temperature and display it over Serial or on an optional display. Confirm that the value changes plausibly when the sensor warms or cools; investigate error values, disconnected wiring, or implausible readings before adding switching.
- Keep a record of the sensor’s placement. A sensor exposed to a draft, direct radiant heat, or the controller’s own enclosure can measure a different temperature from the space you intend to regulate.
Add a setpoint and hysteresis
If the heater turns on and off at one exact value, small fluctuations or sensor noise around that value can make the output switch repeatedly. Hysteresis prevents this by using two thresholds with a dead band between them: for heating, turn heat on when the measured temperature falls below the lower threshold and turn it off when it rises above the upper threshold. Between the thresholds, keep the existing state.
Rank #3
- 30+ Guided Electronics Projects: Start with LEDs and build toward LCD1602 displays, RFID access, motion detection, distance sensing, motor control and environmental monitoring for STEM learning, coding clubs, classrooms and hobby projects
- 200+ Components Across 63 Types: Includes an ELEGOO UNO R3 controller, LCD1602, RC522 RFID, RTC, HC-SR501 PIR sensor, ultrasonic sensor, DHT11, GY-521, MAX7219, keypad, joystick, relay, SG90 servo, stepper motor, breadboard and more
- Begin Without Soldering: Pre-soldered modules, a solderless breadboard, organized storage case and small-parts box reduce setup time and help beginners move from lesson to lesson while keeping LEDs, ICs, wires and sensors easy to find
- Learn, Modify and Create: Program the ELEGOO UNO R3 board with Arduino IDE using the included PDF tutorial and example code, then adjust sensor thresholds, timing, display text and motor behavior to turn guided lessons into original projects
- Flexible Power and Project Setup: Includes a 9 V, 1 A power supply, breadboard power module, 9 V battery and USB cable to support controller, breadboard and module experiments without sourcing basic setup accessories separately
Choose the thresholds for the intended space and equipment; values shown in a tutorial are examples, not universal recommendations. Be explicit about the state: “heat on” means the controller is requesting heat, and “heat off” means it is not. This distinction matters because relay boards can be active-low. Arduino Project Hub’s example notes that its relay can trigger on LOW and may require output inversion, so verify the logic of your own module rather than assuming HIGH energizes it.
Control sequence
- Read the sensor and reject errors or values outside the range you consider plausible for the application.
- If heating is currently off and the reading is below the lower threshold, request heat on.
- If heating is currently on and the reading is above the upper threshold, request heat off.
- If the reading falls between the thresholds, preserve the prior state rather than toggling.
- Send the resulting command to the relay interface using the verified active-high or active-low logic for that board.
Test the output without real heating equipment
- Use an indicator or low-voltage load. Connect the relay module’s control side according to its documentation and use a safe low-voltage test load on the switched side.
- Test both switching boundaries. Lower and raise the sensor temperature gradually, or use a controlled test input in your sketch, and confirm that the output changes at the intended lower and upper thresholds.
- Check the relay’s actual logic. Verify which signal state energizes the relay and that the output state matches the sketch’s meaning of heat on and heat off.
- Test failure and reset behavior. Decide what the output should do if the sensor disconnects, reports an error, or the Arduino resets. Put that behavior in the code and verify it; do not let an unverified reading silently leave a heater commanded on.
These checks improve the prototype but do not certify it as a safety controller. A single hobby sensor and controller should not be treated as a substitute for equipment protections or a professionally designed control system.
Rank #4
- All-in-One Starter Kit for Beginners: Part of the Powered by Arduino program, this kit includes an original Arduino UNO R4 WiFi, 300+ high-quality components, 50+ hands-on projects (30 basic, 13 fun, and 8 IoT), and 100+ free video lessons co-created with renowned educator Paul McWhorter. Designed for beginners ages 8+, it provides a complete, step-by-step path to learn Arduino, electronics, coding, and IoT. RoHS compliant for added safety and quality, it also makes a thoughtful gift for tech enthusiasts, students, and aspiring makers for birthdays, holidays, and special occasions
- Powerful Arduino Uno R4 WiFi Board: Upgraded from the Arduino Uno R3, the Arduino Uno R4 WiFi features a 32-bit processor, more memory, and built-in WiFi and Bluetooth, enabling connection to third-party apps for more interactive and practical projects.
- 300+ Components for Endless Possibilities: With 300+ components and sensors, this kit is perfect for portable projects. It features step-by-step tutorials, open-source code, and compatibility with other Arduino boards like Uno R3 and Nano, offering endless customization and learning opportunities.
- Engaging Projects for Every Skill Level: Featuring 50 projects (30 basic, 13 fun, 8 IoT) with IoT app integration like Arduino IoT Cloud , this kit supports Arduino C++ programming, making it perfect for students, teachers, and engineers to learn, code, and create at any skill level.
- Dedicated Support for Beginners: Alongside online resources and video tutorials, SunFounder provides technical support and troubleshooting forums to help beginners solve programming challenges with ease.
Understand the limits before controlling a heater
Keep this build on the low-voltage side unless the entire installation has been designed for the actual equipment and local electrical rules. A mains-connected heater or HVAC system requires a switching device rated for its voltage, current, and load type, plus suitable isolation, enclosure, overcurrent protection, and compliance with applicable requirements. A relay board’s advertised current rating alone does not establish that its board layout, terminals, enclosure, or installation are suitable for mains use. The available project references do not provide a universal safe mains-wiring plan.
Also check environmental limits for the whole assembly. Arduino Help Center’s January 29, 2024 guidance gives -40°C to 85°C as the microprocessor operating range and recommends -25°C to +70°C for Arduino boards. The board, power supply, sensor, relay interface, and enclosure can each have their own limits; keep the installed controller within the specifications of every component.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Best Value
- The most economical kit comes with everything compatible with Arduino to starting programming for beginners .
- This is the upgraded starter kits come with a 9V 1A Power Adapter (At least $5.99 on amazon) to replace a 9V Battery , and the Lcd1602 module come with pin header(not need to be soldered by yourself).
- Include High Quality Base Board base on Arduino UNO R3 compatible with Arduino IED and Sensors, Servo, Motor, ULN2003 driver board, lcds, etc.
- Free PDF Tutorial and Datasheet are available to download from our official website or you can contact our customer service.
- All of the Components and Integrated Circuits are individually packaged and labeled, and packing in a plastic box which is bigger enough for you.
Know whether you need a thermostat or HVAC controller
A thermostat that switches one heating output is not automatically equipped to control cooling, a fan, or a heat pump. Arduino’s 2024 MKR WiFi 1010 example is explicitly heating-only. Before adapting a project, identify the control interface and required sequencing of the specific equipment: heating, cooling, fan, and heat-pump systems may need different outputs and behaviors. If that information is not established, do not infer a wiring plan from a heating-only example.
Quick Recap
Sources and component references
- Arduino Team, “Save money by making your own MKR WiFi 1010-powered smart thermostat,” July 18, 2024.
- Arduino Project Hub, “Arduino Control Center Thermostat Example,” July 4, 2017.
- Analog Devices / Maxim Integrated, DS18B20 datasheet, revision 6, August 9, 2019.
- Arduino Uno Rev3 specification.
- Arduino Help Center, “What is the operating temperature range for Arduino boards?”, updated January 29, 2024.
- ArduinoGetStarted.com, “Arduino – Heating System”, an illustrative hysteresis example rather than primary electrical-safety guidance.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
