PIR motion sensor output to power Arduino

Hi everyone,

I have this PIR motion sensor: PIR (motion) sensor : ID 189 : $9.95 : Adafruit Industries, Unique & fun DIY electronics and kits. It works great when powered and connected to an Arduino board, like in this circuit:

The thing I want to accomplish is actually the other way around: having the PIR sensor powered by a power source (batteries for example) and the Arduino powered by the output of the PIR sensor. As a result, the Arduino will power on when movement is detected and shut down when there is no movement. It's basically like this circuit, just replace the LED with an Arduino board:

The reason I'm trying to accomplish this is that I can run the PIR sensor on batteries for a long time, it uses around 65uA when idle. The Arduino should take care of sending a signal (wireless) to a receiver when booted. This combination should allow me to have a wireless motion sensor running for a long time on batteries.

The issue I'm facing is that it seems the output of the PIR sensor (3.3V when high) is not sufficient to power the Arduino (I have a board that's capable of running on 3.3V). Is there a way to only power the Arduino when motion is detected? Would a transistor work?

Many thanks!!
Jan

You would be on the right track with using a transistor to switch power on to the arduino. Since the PIR will go off again when the stimulus is gone, you'll need to make sure your transistor switch holds itself on long enough for the Arduino to startup and run whatever code it is supposed to run before it loses power again.