Low power data logging shield
- It is an extreme low power data logger shield for Arduino.
- The circuitry is set up so the Arduino draws no power when the logger is sleeping in-between measurements.
- This means that the logger can be running for weeks, months and even years on regular batteries.
- All log data can be stored on an onboard micro SD card. I don’t know the maximum size that can be used, but I have had no problems with a 2Gb micro SD card.
Why use this shield?
- The shield is for applications that could stay unattended for weeks and months, -even years before the battery needs replacement. What is unique with this data logger shield is that it takes control over the power input to the Arduino.
- It cuts power to the Arduino altogether and only awakes Arduino to take a measurement and log it, and then Arduino resets the RTC in effect cutting its own power supply.
- Other designs are available that does all kinds of tricks with the Atmel chip to conserve power but no matter how good these techniques are, you still have the quiescent current of the onboard voltage regulators and that could be en the range of 5-15mA.
- A regular Arduino draws about 25mA and with my 900mAh LiPo that would give you something like 36 hours of running time and 4370 measurement (one entry every 30 seconds) With my shield the same unmodified Arduino ran for 14 days giving me 32.000 measurements from the same 900mAh LiPo.
The following pins are used by the shield;
- A3 – Voltage monitor for the input voltage. If not needed a trace (marked on the PCB) can be cut to release it for other use.
- A4, A5 – is used for I2C communictation with the RTC. Other I2C devices can be added to the bus.
- D8 – is used for chip select for the SD card
- D11, D12, D13 – is used by the SD card but other SPI devices may be added