Writing speed and power consumption

Hi all, I am working on a weather station powered by 4AA battery pack + a solar panel. I want to reduce the power consumption of my setup and thus I am interested to know if the speed setting (full, half, etc.) affects the battery life. I use the sdfat library.

Moreover, I am planning to use a transistor to turn off sensors when arduino is in sleep mode. Is the sd initialization process required each time I turn on the sd module? I suppose yes, but I want to sure!

Thank you in advance.

The SPI speed won't make much difference.

You need to initialize the SD if you remove power. SD.h has a bug that prevents a second begin call so you will need a patch.

Many low power loggers just allow the SD to sleep at about 100 micro-amps. SD.h has a bug that prevents sleep.

The problem is that SD.h is based on a seven year old version of SdFat and has these bugs.

Please start with this link for low power logger ideas.

https://edwardmallon.wordpress.com/2014/07/01/a-10-diy-data-logger-is-born/

Also look at other articles by Edward Mallon.

First of all, thank you. I already used the SdFat library downloaded from here: https://github.com/greiman/SdFat/tree/master/SdFat/src/FatLib I hope it is the right version.

I am trying to reduce the power consumption of my project, but I still have some problems. One of them is the rx led, which is always on when the SD has been initialized.

I used the following code (I was inspired by the Gammon's webpage http://gammon.com.au/Arduino/Temperature_Monitor.ino ):

// Data saving
void saveData(){
  sd.begin(chipSelect, SPI_HALF_SPEED);
  SPI.begin();
  dataString = String(pause) + "," + String(timer1) + "," + String(timer2) + "," + String(sR1) 
  + "," + String(sR2) + "," + String(sR3) + "," + String(sR4) + "," + String(sR5) + "," + String(sR6) + "," + String(sR7); // convert to CSV
  myFile.open("data.csv", O_WRITE | O_CREAT | O_AT_END);
  myFile.println(dataString);
  myFile.sync();
  myFile.close(); // close the file
  delay(100);
  SPI.end();
} // end of data saving

The SD card is correctly initialized, but the rx led is always on and it is responsible for a higher power consumption.

So take a sharp tool and damage the LED until it no longer draws current.

I have tried many times to desolder the LED and I always end up smashing it.

"Real hacking!"