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Power consumption on the microDrive

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  • Power consumption on the microDrive

    Hello!I am going to use the microDrive for a data logging application where conserving battery power is going to be critical. I noticed that the data sheet lists a pretty high current draw (15mA) even without a card inserted, and doesn't seem to list one for when you are actively writing to the card. My question is, does anyone know of a way to cut down on the power consumption of the microDrive during use, and how effective would such a method be? For example, I don't need the indicator LEDs to be working once I seal up the data logger and start it recording - what's the best way to turn them off and roughly how much difference might that make? Any ideas would be appreciated.
    Thanks for taking the time to answer my questions!Gen

  • #2

    You haven't said much about just how long you want a set of batteries to last for or what sort of batteries you intend to use, so it's a bit hard to work out exactly how to help.

    I would suggest removing the LEDs will give you your biggest saving, at the expense of the simple diagnostics they provide.

    You should be aware some uSD cards can draw as much as 100ma when active and also draw more once 'initted' than when just inserted.


    • #3

      Thank you for the reply!
      Ideally I would want this data logger to last 15 days on roughly a 1000mAh battery, logging data at 30bytes/second - so I need at least 16MB of data storage capacity. The rest of the circuit is very simple and only consumes about 0.5mA, which leaves me roughly 2mA for the microDrive. I hadn't realized that the microSD card itself would consume so much during the write cycles, but it seems that there are some that consume low levels of power in standby mode. I guess this would mean I would need to cut down on the microDrive power consumption, and also use a low-power memory buffer such as an EEPROM to write the data to before transferring the buffer to the microSD to minimize the write cycles on the card. So then the question becomes whether it is even possible to get the standby power consumption of the microDrive below 2mA. If not I would need to find another high density memory storage method.

      Once again, thank you for your help!



      • #4

        I don't know how long you can go between writes, but even if you were to power off the uDrive (with external circuitry) between writes you would still be facing difficulties.

        Some quick measurements I just took before the 3.3v regulator (i.e. you will get better if you can supply 3.3 volts and bypass the regulator)

        10ma uDrive powered, no uSD, Leds off
        +2.3 ma 64mb card inserted
        +0.06ma 2gb card inserted
        +8.7ma 64mb card inserted and inited, idle
        +13.3ma 2gb card inserted and inited, idle

        Then there's the consumption during writing


        • #5

          Thanks for those measurements! You are right, I suppose I will have to consider other options.


          • #6

            Hi, is it safe to remove the 3.3v regulator and use a 3.6v battery directly?
            And is the regulator in the most left side near Reset Pin, I mean the 2 pin one.



            • #7

              3.6v is the absolute maximum rating of both the Goldelox chip and the uSD card, so I would not be feeding 3.6v in from a battery unless I was very sure I wasn't going to exceed 3.6v when the batter was fresh.

              I think a better approach would be to bridge the protection diode (near pin 1) and feed 3.6v into the Vcc pin. But remember, any modification voids your warranty.

              The onboard regulator has a very low dropout and will be fine regulating 3.6v down to 3.3v.


              • #8

                Thanks, we'll try to bridge the diode then.