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Ok this may seems a little bit strange question.
For my personal educational purpose only I've built the following: there are 2 sensors (one digital, the other analogic) connected to an Arduino Uno rev.3. The Arduino is connected via I2C to my Raspberry Model B. Via cron a python script is executed every 5 minutes. The script asks the Arduino for the values of these sensors, wait to get them and stores them in a csv file. So far, so good. Now I want the Arduino to be powered from a 9V battery. Since the battery won't last very long if the Arduino were to be powered 24/7, I want the Raspberry to power up the Arduino when needed (the Arduino power source has to be the 9V battery), maybe wait a couple of seconds in order to stabilize the sensors, do the magic via I2C and then shutdown the Arduino.
How can I do that?
Thanks in advice.

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Just connect the Arduino a mostfet or power-transitor, to the 9V battery. Have the Pi control whether or not the arduino gets 9V by connecting a GPIO pin to the Gate/Base of the mostfet/transitor.

You could put the arduino into sleepmode, but that's kind of pointless, as the voltage regulation, leds, and other stuff on the UNO board use as much power as the ATMega328 itself.

PS also add a pull down resistor to the gate, so it isn't floating while the pi is booting up, shut-down or powered down. That way the arduino will always be off in those cases.

  • Which kind of spec (if any) does the MOSFET have to have? – Davide Mezzogori Apr 15 '14 at 14:30
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    N-channel mosfet, with a maximum voltage of at least 12V, and a Drain Current of at least 0.5A. But you'd have a hard job finding one that doesn't meet these requirements (-:. – Gerben Apr 15 '14 at 16:03
  • A N channel mosfet has to be connected to the negative side of the battery. This is kind of problematic as the ground of the arduino has to be connected to the ground of the pi. – Gerben Jun 15 '14 at 12:35

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