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Temp Sensor

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The Temp Sensor is capable of turning the Arduino into an instant thermometer, plugging directly into Arduino Duemilanove Analog Pins 2-5.

The TMP421 chip is a 12 bit I2C chip that works from minus – 40 to 125 degrees C, so the sensor is able to resolve .04 degrees C per bit. The absolute accuracy is guaranteed to be +/- 1 degree C. The relative resolution should make the sensor useful for a range of higher resolution activities such as sniffing out drafts around windows.

The Temp Sensor comes with a 4-pin male header (unsoldered) and 8 total pin-outs to allow for maximal flexibility in project use. With a small, narrow form factor, it’s easy to set up multiple Temp Sensors for local temperature monitoring as well.

A ready-to-go Arduino library is also available free for download at the Liquidware App Store for full, off-the-shelf integration with any Arduino project.

The chip communicates via I2C and also has an onboard remote temperature sensing capability as well.


  • TMP421 chip
  • 4-pin male header included (unsoldered)
  • Communicates over I2C protocol
  • 1 Bi-directional data pin
  • 1 Clock pin
  • Ranges from – 40C to +125C with +/ – 1C accuracy
  • Optional remote temperature probe input
  • I2C Digital Interface
  • Arduino Pin Compatible
  • +5V Tolerant I/O

Arduino Pin Mapping

Analog 2 = Ground Analog 3 = Vin Analog 4 = Data Analog 5 = Clock




Temp Sensor Cheatsheet Temp Sensor Cheatsheet (209.002 KBytes, Document file, Apr 10, 2010)

Code and pin connections to get the temp sensor up and running in 5 minutes or less.

Get in touch if you have any questions, or ideas for something you want me to build.