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Topic: Help with PIR Motion Sensor output (3V, TTL?) (Read 746 times) previous topic - next topic

jtlns

Hi all,

I have a the following PIR Motion sensor working: https://www.sparkfun.com/products/8630 . The output of the sensor (HIGH when motion is detected) goes into the input of my Arduino and all works great. :)

Now I'd like to run the sensor in "standalone" mode. The PIR sensor only needs power to operate and the output gives 3V, so you can attach a LED to it directly. But instead of the LED, I'd like to have an Arduino, which needs more power than the 3V (I tried connecting a 3.3V Arduino, but the output is not sufficient).

My guess is that I need to use a MOSFET/transistor (that is connected to the output of the PIR motion sensor) which powers the 2nd circuit (the Arduino). Can somebody confirm? Also I'd love to learn which MOSFET/transistor I need to use.

Some additional info: the PIR motion sensor keeps the HIGH output for a while (configurable), so I do *not* need a mechanism that is triggered and stays active longer than the HIGH output. Also, I'd like to run this thing on batteries. So in an ideal scenario the MOSFET/transistor or 2nd circuit don't consume any power when not activated.

Thanks for your help!
Jan

robtillaart

you could also use an analogRead() ... to read 3V ..  dont forget to connect the grounds. probably fast enough

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

jtlns

Thanks, but I can read the output successfully. :-) The thing I want to do is to use the output signal to turn on/off an Arduino.

robtillaart

you might put the Arduino in sleep mode instead?
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

jtlns

That would be possible yes, but I'd consider that as a workaround.

I was hoping a MOSFET or another component could be using the output of the PIR sensor to activate a secondary circuit (like a relay to power higher voltages).

Jan

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