Evolution of a Blog

This blog has evolved as I have as a maker. It starts at the beginning of my journey where I began to re-tread my tires in the useful lore of micro electronics and the open-source software that can drive them. While building solutions around micro-electronics are still an occasional topic my more recent focus has been on the 3D Printing side of making.

Tuesday, April 9, 2013

CritterCam Version 2

I have now refined my "CritterCam" based on experiences to date and am pretty happy with the result.   It meets most requirements of the brief though there are one or two refinements that might get added.

In short, the CritterCam is a RPi based device that will operate as a wireless motion detector, capturing images using either a WebCam for 720p resolution or a DSLR for 12mb resolution.  It is integrated with a small PHP application that also runs on the RPi courtesy of a LAMP install.   The device will operate in either of two modes, the first being the most portable, using a 720p webcam and being based on the OpenCV library.   The second uses a USB connected DSLR, in my case a Canon 500D, and relies on the gphoto2 library (libgphoto2) augmented by a wrapper called "piggyphoto".  Obviously, portability goes down when you add a DSLR!

The options provided by the CritterCam are shown below:
Usage: CritterCam.py [options]

  -h, --help            show this help message and exit
  -k, --keep            Save a static file (/var/www/camimages/stream.jpg

                        and do nothing else
  -d DELAY, --delay=DELAY
                        Delay between captures
  -s, --stream          Stream timestamped images
  -m, --motion          Stream time stamped images triggered by motion
  -r, --dslr            Use DSLR capture rather than using webcam

  -t THRESHOLD, --threshold=THRESHOLD
                        Motion threshold
  -v, --verbose         Produce extra status and progress messages

Within it's processing loop CritterCam will check for the existance of several action generating flag files left in the /var/www/ by it's PHP partner:
  • Restart.flg - Causes an exit with a zero return code.  Invoking shell script  loops
  • Shutdown.flg - Causes an exit with a one return code.  Invoking shell script  exits
  • Reset.flg - Causes a reset of the current base image to the most recent capture.  Useful in case the app itself has not detected a change in background.
  • Force.flg - Causes the app to capture a full resolution image even without the motion trigger.
To detect motion the CritterCam uses  a very simple, ok maybe rudimentary, approach of using the OpenCV absdif function to compare the matrice from the current image and that of the base image.  If the mean difference is greater than a threshold we assume motion.   While processing, the script will attempt to detect a change in the conditions of the base image and will replace it if necessary.

Here is a link to the source code for the CritterCam.   It still does some weird stuff now and again and will continue to be enhanced.    It is partnered with a PHP application but that app is based on my own forms development environment so is a little complicated to easily make available for download.

The most major enhancement that I would like to add would be an external batter for the DSLR.   I know that I could buy one but I already have the AC adapter and am thinking I would just hijack it, add a couple of 5.2mm plugs and sockets, splice in a DC power regulator and have something that could also live on the tripod.

I have to confess to a major issue with my CritterCam.   Namely that it has a hard time detecting a change to the ambient light.   Unless I manually reset the base image it will decide that the change is motion......bad CritterCam!

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