Vermes
Advanced Member level 4
It is a re-built version of a temperature logger. This device is smaller and stable, also functionality of the software was improved. Memory card slot was placed underneath, so you can opt out of the top layer. The system can fit in about 8x7cm. Transistors which control the peripherals power (clock/thermometer/card/lcd), backlit the display and a second crystal oscillator 32k for the clock waking from standby mode. All the elements are closed in the housing for hole mounting (except for the SD/MMC slot). The system can be easily expanded by adding slots e.g. for humidity or pressure sensors, anemometer, etc.
The program was written in C. It is divided into modules, optimized and stable. FATFS library was used. Besides FAT32, the logger supports FAT12 and FAT16. Also energy saving mode was added, when the display is off, the peripherals turned on only when it is needed, and after saving the microcontroller goes to the standby mode until the next measurement. All that significantly reduces power consumption.
According to a cheap Chinese multimeter, the logger takes about 13-14uA in standby mode.
The first tests came out positive. The system works very well.
Components:
- Atmega32
- DS1307 + DS18B20 + LF33CV
- LCD
- CR2032 battery + slot
- SD slot
Link to original thread (useful attachment) – Rejestrator temperatury z SD - v3