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Micro SD card to log reading from four force sensors connected to the microcontroller. Controller logs reading to the SD card every 15 minutes and goes to sleep.

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  • \$\begingroup\$ You probably want a power switch or regulator with enable to let you power down the card when not in use. You might also consider if you can use a large SPI flash instead of a card, in order to have a device with actual engineering specifications rather than a consumer product which may change without notice. \$\endgroup\$ – Chris Stratton Jun 21 '17 at 4:34
  • \$\begingroup\$ keep the sdcard detached with a mosfet. write sensor data to MCU's internal flash/eeprom, or RTC RAM (if available). Once you run out of internal storage, turn on sdcard, write buffer to card, turn off and flush internal buffers. make an unmount routine to manually flush. \$\endgroup\$ – dandavis Jun 21 '17 at 4:43
  • \$\begingroup\$ Can't we use one of the GPIO pin of the controller to switch off the microSD card. \$\endgroup\$ – TapasX Jun 25 '17 at 16:24
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You seem to be closing the FAT when you finish writing, so the SDCard should automatically go into IDLE mode (clocks stopped). Make sure you do a read at the end of your write to ensure you cleared any write/erase. I'm not sure what SDCard you are using but here is a typical spec. The IDLE current is about 150 uA.

If you want to get lower than this then you could use a digital pin plus FET switch to turn the Vcc off when you are asleep, and turn it back on before initializing the FAT when you wake up.

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  • \$\begingroup\$ Is it possible to change the power consumption of SD card without changing the schematic. \$\endgroup\$ – TapasX Jun 21 '17 at 10:14
  • \$\begingroup\$ Not that I know of, once you stop the clock it will go to IDLE ....that is low power. \$\endgroup\$ – Jack Creasey Jun 21 '17 at 15:24
  • \$\begingroup\$ Can you help with the part number. Will load switch work such as TPS22910 from TI will work. \$\endgroup\$ – TapasX Jun 25 '17 at 16:35

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