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My Experiences With the Raspberry Pi -- Tracking My Learning -- My Pi Projects

Monday, August 19, 2013

Gertboard - Camera Remote Control - Arduino Sketch #2 - Motion Detector

Continued from last post
This final version of the camera remote control project integrates the motion detector and removes the user input. This motion detector is properly called a PIR (Passive Infrared) sensor. It detects heat given off by bodies around it. The sensor is actually split in half. Motion is detected by there being a slight difference in the heat measured by the two halves. An IC mounted on the printed circuit board processes the sensor signals and gives a digital output that we pass to the microcontroller on the Gertboard.
Here is a very informative link about these sensors My sensor is slightly different than the one in that last link. Mine looks exactly like the one you see on Adafruit's web page. It has the advantage of two potentiometers, one to set the sensitivity, the other to set a time delay between the time motion is detected, and the time the output goes to a logic high. I spent a bit of time adjusting the sensitivity. The signal from the motion detector has an LED in the path on the Gertboard (see the block diagram in the introductory post of this project). This LED gives feedback that makes it easier to set the sensitivity.
Here is the new code:
I don't think it's necessary to discuss the code further, we covered it pretty well in the last post. The changes should be pretty easy to understand.
I would like to mention that this version does not require the Gertboard, or the Raspberry PI. Once the ATmega device is programmed, it will not lose the program even if it is lifted off the Gertboard and placed on another PCB. Everything can be bundled on a small printed circuit board like Adafruit's Perma-Proto Half-sized Breadboard PCB and placed in a small box with the motion sensor and the RF transmitter. Connect 5V and away you go.

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