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Mini Temp Logger

A small temperature logger with a real time clock for sensing -55C to 128C with up to 65,536 logging data points, customisable logging time and powered by a coin cell. Can log voltage as well.

(v1.0 pictured)

• Measure temperature using the TMP102 sensor from -55C to 128C
• Measure voltage from 0V to 22V
• Uses an I2C EEPROM to support up to 65,536 logging data recordings
• High time accuracy using the MCP7940M real time clock. Set the time via the PC application so it records the start time when logging. Features trim and auto trim from temperature settings.
• Configurable logging delay available between 1 second to 255 days via PC application
• Easily transfer the logged data to your PC via USB by running an PC application
• Operates from a 3V CR1220 coin cell
Note: You can only log temperature or voltage, not both at the same time.

If you will be logging in below 0 temperatures, we recommend applying PCB lacquer spray to the board to protect it from water condensation. Just remember to cover up the Mini USB connector, button and battery contacts.

USB Mini cable & CR1220 battery

Battery required: CR1220 3V coin cell
PCB Board size: 31mm (L) x 22mm (W) x 15mm (H)
Operating voltage: 1.8V to 3.6V
Sleep current: 5uA
Operating temperature: -40C to 85C
(Most CR1220 batteries only support -30C to 70C)

Temperature sensor (TMP102)
Range: -55C to 128C
Resolution: 0.0625C
Accuracy: ±0.5C typical (between -25C to 85C), ±2C max

Voltage logging (ATtiny84 ADC)
Range: 0V to 22V
Resolution: 22mV
Accuracy: ±66mV

Real time clock (MCP7940M)
Accuracy: at 25C, within ±12PPM (1 second a day)


Includes schematic (with Eagle .sch file), drivers, GUI/Console program (with console source), AVR source code and manual. View the manual online: MiniTempLogger Manual Rev3

Software Revision History
v1.1 – 4 April 2017
– Bug fix when reading voltage while plugging into PC, it seemed to work until I tried another
PC. Was using ADC sleep when it should have used delay_ms instead (Firmware update
– Added updated settings text to show when updating settings is in progress
– Changes to GUI so it’s not as laggy when moving it around the screen
– Added config.ini to support changing voltage divider / calibration numbers easily through

v1.0 – 3 March 2017
– Initial Release

Hardware Revision History
v1.0 – 23 March 2017
– Initial Release

Example Logged Results

(Graphs created with Plot.ly)

Logging files from the device:
Temperature example: 2017-03-27_22-15-07
Voltage example: 2017-03-29_22-57-12


Comes assembled, no soldering required.

Stock status: In stock

We ship within 2-3 business days and will let you know once shipped. We ship overseas and to reduce shipping costs the kit is sent via the Airmail letter service for $3 and the usual delivery time is 7 – 12 working days (however it sometimes can take 20 working days depending on your location); we ship via Australia Post.

If you are looking for faster delivery times, please contact us for a quote, please note that shipping prices can start from $36 for 2-3 days delivery to the US (via DHL).

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License.

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