• 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
Accuracy: ±0.5C typical (between -25C to 85C), ±2C max
Voltage logging (ATtiny84 ADC)
Range: 0V to 22V
Real time clock (MCP7940M)
Accuracy: at 25C, within ±12PPM (1 second a day)
This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License.
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
Shipping rates/Delivery times
We usually ship within 2-3 business days and will let you know when your order has been shipped. We ship overseas all around the world – America, Europe, Asia, etc (except to Brazil or Mexico due to lost packages) and to reduce shipping costs we send via the Airmail letter service for $3. Any item you order will come to you with in a padded envelope due to a restriction that letters can’t be more than 20mm in height.
The usual delivery time is 2 to 4 weeks; we ship via Australia Post. Unfortunately there is no tracking number available for this Airmail letter service.
You are responsible for any import tax/duties or other charges that may apply (so far we have had 1 report of a user having to pay import tax in the UK).
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).