miniLOG – Precision Standalone Voltage Logger

miniLOG is a precise standalone voltage logger that save the data on a SD card. It has 4 basic analog channels:
– one has 12bit resolution for voltage measurements,
– two channels have 10bit resolution for voltage measurements and
– one channel has 10 bit resolution for current measurements.
Input voltage range is 0-25V and current range is 0-500mA. The data are written on a simple .txt file on SD card and can be further proccessed using spreadsheet software.


This is my latest project called miniLOG. It’s a basic data logger designed to have similar functionality to a data logging mode on some expensive $300+ multimeters for a fraction of the cost.  It has four basic channels: a high resolution 12-bit voltage measurement channel with an MCP3201 ADC, two 10-bit voltage measurement and a 10-bit current measurement channel. It’s capable of measuring voltage from 0 to 25V (with 0.0061V steps on the 12-bit channel and 0.025V steps on the 10-bit channels) and current from 0 to 500mA.


The miniLOG logs the readings onto an SD card which you can later plug into your computer, import the .txt file to a spreadsheet software like MS Excel and make graphs, charts etc.

AVR microcontroller

The miniLOG is based on ATmega328P-AU microcontroller in the TQFP32 package. It’s Arduino compatible so you can easily modify the code. It’s accompanied by a 16MHz crystal oscillator to reproduce the Arduino UNO circuit. You probably could get by without the crystal but since the entire Arduino bootloader operates based on that 16MHz crystal it’s a good idea to keep it. Also the miniLOG uses SPI interface to communicate with the ADC and the SD card so a little bit more clock accuracy is a good thing to have.

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You can probably notice the 5 pin header. Its purpose is to connect to an external UART module like for instance a USB-UART or bluetooth-UART module. With a bit of extra code you can communicate with the miniLOG using USB or bluetooth. These modules are really cheap (~5 USD on eBay).


For more detail:  miniLOG – Precision Standalone Voltage Logger

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