Tag Archives: Pax Instruments T400

ATmega32u4 powers this open-source temperature datalogger

The Pax Instruments T400 — which recently made its Kickstarter debut — is a simple, inexpensive and open-source temperature datalogger. Designed by Charles Edward Pax, the ATmega32u4 powered T400 is a first in a new class of affordable lab instruments.


According to the Pax, he first came up with the idea of the T400 after finding himself seeking a device that could reliably log several temperatures at the same time without needing to keep a close eye on it. Instead of spending upwards of a thousand dollars on a proprietary instrument, in true Maker form, he decided to create a specialized system using an Atmel based Arduino Leonardo.

“With the help from a few friends, I set out to solve this problem by creating an easy-to-use ‘plug and play’ device that’s more than accurate enough for most purposes, yet still has the flexibility of an open system,” Pax described. After several months of developing, the T400 Temperature Datalogger was successfully completed.


Ready for use right out of the box, the T400 is equipped with everything one would need to track and record the temperature of a solid, liquid or gas. After plugging in one of the provided thermocouples and turning it on, a user can simply read the temperature measurements directly on the T400’s LCD screen.

The trusty T400 can be utilized for a various actions within the household or laboratory. Anything from taking the temperature while cooking meats to monitoring liquid levels during the home brewing of beer can be accomplished. Thanks to its ATmega32u4 based platform, the device can be modified and expanded to fulfill almost any need.


According to Pax, the device can stream live data onto your computer via USB. “But don’t worry about connecting the T400 to another device: all of the data is logged directly to a MicroSD card,” the Maker writes. “It works independently of other devices. The long battery life on the T400 means that you can set it up, walk away, and come back when that work is done, all of your recorded data will stay safe and sound on the SD card.”


For those interested in a detailed look under the hood, you can access the T400 source files on Github. Some of the key features include:

  • ATmega32U4 MCU
  • 132×64 pixel LCD display with blacklight
  • Internal BL-5C LiPo battery with USB charging
  • MicroUSB for streaming data to a computer
  • MicroSD card included for recording data to .csv (FAT16 only)
  • Compatible with industry standard mini-TC connectors
  • MCP9800 junction temperature sensor
  • MCP3424 ADC for measuring thermocouple voltages
  • DS3231 RTC with backup battery to trigger readings while processor is in sleep mode
  • Molded enclosure

With several weeks still go to in its campaign, the datalogger is just shy of its $6,250 goal. Interested in backing this project? Head over to Pax Instruments’ official page here.