Hi,

I'm making a mini motion data logger using the 9-axis shield, RTC shield and Micro SD card module, stacked onto a button-cell tinyduino mainboard.

The button cell seems not to have the current draw ability to power the SD card module on it's own, but with some parallel ceramic capacitors, I can manage to write to the SD card in bursts as required.

My code puts the tinyduino into full power off sleep between write operations, so the draw from the main board is minimal. However, when the SD card is inserted, the power draw is high all the time, even when the 'duino is asleep. As a result, the button cell drains really quickly and I end up with <2.8v and brown-out within minutes.

Is there any way to stop the MicroSD drawing power all the time? Or is there an alternative memory I could use that doesn't draw power constantly?

Any help much appreciated.

:-) Thanks

I can't find a good reference for this, but I believe that the default SD card library included with the Arduino IDE does not put the card to sleep. Try some of the SDFat library examples and see if you can get a lower sleep current.

Keep in mind that SD cards shouldn't really be used under 3.3V, so a coin cell/SD card option isn't a good solution. The straightforward alternatives are EEPROM or external flash that's happy under 3V, or switching to a 3.7v rechargeable lithium battery.