Online Thermometer

Note: An updated version of this project has been created that supports Ethernet shields using the Wiznet W5100 chipset, including the official Arduino Ethernet Shield and the Freetronics Ethernet Shield with PoE Support. For more information please see:

Arduino makes a great building block for data acquisition and logging systems, including sensors commonly used in home automation such as temperature sensors. By combining an Arduino and a few DS18B20 temperature sensors you can install sensors around your home or office and access an up-to-the-moment report using a web browser.

Readings can also be logged and graphed over time, showing trends or measuring the effectiveness of your home heating or cooling system. By placing sensors outside the house, inside your ceiling cavity, and inside every room you can plot how well your home maintains its temperature when climate conditions change.

The information can also be used as part of the feedback loop for a control system such as to control active heating or cooling, or to trigger servos or linear actuators to open and close windows and passive ventilation systems.

Parts Required

Qty Description
1 Arduino Duemilanove, Arduino Pro, Seeeduino, or equivalent
1 Seeed Studio Ethernet Shield or nuElectronics Ethernet Shield with prototyping shield
6 DS18B20 Dallas 1-wire temperature sensors (Note: not DS18S20)
6 4K7 resistor
1%: yellow-violet-brown-brown
5%: yellow-violet-red-gold
6 PCB-mount 3-pin male connectors
6 Line-mount 3-pin female connectors
Twisted-pair cable or alarm cable (minimum 3 conductors)

Online Thermometer Schematic

Download as JPG: online-thermometer-schematic.jpg

Download as PDF: online-thermometer-schematic.pdf

Download as SCH: online-thermometer-schematic.sch

Source Code


DS18B20 datasheet - (PDF)

Seeed Studio Ethernet Shield -


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