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We recommend our replacement device, the Mini Temp Logger, a smaller, more accurate temperature logger with real time clock for better time keeping. It logs voltage as well.

A standalone temperature/voltage logger in a small compact form factor using minimal parts including the ATtiny85 and an I2C EEPROM powered by a 3V coin cell. Logged data can be extracted to a computer with a USB cable.

The standalone temperature/voltage logger uses V-USB: http://www.obdev.at/vusb/



  • Low power consumption, at least 1 year battery life
  • Measure temperature from -40C to 125C saving to EEPROM as 8 bit (as 1 byte) or 10 bit (as 2 bytes)
  • Measure voltage from 0V to 28V saving to EEPROM as 8 bit (as 1 byte) or 10 bit (as 2 bytes)
  • Uses an I2C EEPROM, supports up to 512Kbit which is 65,536 recordings (with 1 byte values) or 32,768 (with 2 byte values)
  • Configurable logging delay available between 1 second to 255 days via PC application or 12 logging delay times available using the button(30secs, 1min, 5mins, 10mins, 15mins, 30mins, 1hr, 2hrs, 4hrs, 8hrs, 12hrs, 24hrs)
  • Easily transfer the logged data to your PC via USB by running an application
    Note: You can only log temperature or voltage, not both at the same time. No information on time is recorded when logging.


  • PCB Board: 37.8mm x 28.5mm
  • Voltage: 2.7V to 5.5V
  • Current used when sleeping: 5uA
  • Current used when logging – Watchdog sleep routine: 0.3mA for 30ms approximately every 4 seconds
  • Current used when logging – Thermistor on, LED on and write to EEPROM: 3mA (max) for 50ms
  • Resolution of temperature (1 byte): 0.65C (rounded up or down in 0.5 – 1C increments)
  • Resolution of temperature (2 bytes): 0.16C (rounded up or down in 0.2C increments)
  • Accuracy of thermistor: within 5% -/+ (between -40C to 25C is 1.25C -/+, 25C to 50C is 1.5C -/+, 50C – 70C+ is 1.9C -/+)
  • Resolution of voltage (1 byte): 0.06V
  • Resolution of voltage (2 bytes): 0.03V
  • Accuracy of voltage logging: 0.2V -/+
  • Accuracy of timer: within 10% -/+
  • Operating temperature: -40C to 125C (Most CR2032 batteries only support -40C to 70C)

Includes source code, compiled main.hex file, manual with step by step guide and instructions and parts list, PCB bottom ready for home etching, PCB top ready for home etching (rotated horizontally), PCB Guide, schematic, example results and pictures of finished product. View the manual – SATVL_v1.3_Manual

v1.3 Rev. 1  (3 Apr 2015)
– Updated PCB with new voltage switcher circuit and removed 2 protection diodes on input voltage
– Updated code with various small improvements
– Now allows for programming delay times/function in use via PC

v1.2 Rev. 9 (28 March 2015)
– Updated documentation formatting

v1.2 Rev. 8 (10 October 2014)
– Updated documentation to merge temperature and voltage assembly together,
removed any v1.0 or v1.1 references including errata and moved programming the
ATtiny to the bottom

v1.2 Rev. 3 (11 December 2012)
– Added the usblib0.sys driver for SATVL v1.2 in the “/SATVL_v1.2/driver” folder

See older revisions

v1.2 Rev. 2 (11 October 2012)
– Added pictures of PCB v1.0 and v1.0
– Started revision history of zip files
– Updated PDF to Rev. 7

v1.2 (4 October 2012)
– Fixed bug where calibrateOscillator function wasn’t been called when USB was plugged in
– Enabled ADC noise cancel sleep mode

v1.1 (12 August 2012)
– The data transfer now uses the satvltransfer program to transfer the data from the SATVL more quickly

v1.0.1 (9 June 2012)
– Now prints the logging delay time (e.g “28sec delay”) at the start of the data transfer to the PC

v1.0b (16 May 2012)
– Reverted calibrateOscillator function back to the default as my patch wasn’t needed
– After a USB transfer is complete, made OSCCAL go back to the factory default settings in steps of 32

v1.0a (2 May 2012)
– Corrected EEPROM size test code to work with 32Kbit EEPROMs

v1.0 (18 April 2012)
– Initial Release

Example Logging Results

The graphs below show the results, you can also download the Excel files to see the raw data.

Temperature logging (1 byte)

Temperature logging (2 bytes)

Voltage logging (2 bytes)

Buy the Kit [Discontinued as of 2016]

This kit requires assembly and soldering, SMD parts are pre-soldered. 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.

Standalone Temperature-Voltage Logger with Voltage Logging Add-on
This is the recommended version of this kit to purchase as it allows for temperature or voltage logging and allows you to purchase an EEPROM if you don’t already have one.

EEPROM options

[Discontinued as of 2016]

Standalone Temperature-Voltage Logger PCB board only
This is for the bare PCB itself and comes with the SMD parts pre-soldered.
[Discontinued as of 2016]

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

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