[TriLUG] Raspberry Pi, linux, motion and the R.Pi camera board

R Radford rradford at mindspring.com
Mon Jan 13 11:05:28 EST 2014

I am definitely interested.  I have a couple RPis and RPI cameras and have
built several small projects with them and would love to team up with
others locally to compare and build ideas.  One of my projects was placing
an RPi in a nearspace balloon and I had APRS telemetry, as well as passed
the RPi video output back through an ATV link to the ground for live
video/data.  It was launched as part of the "First Library in Space"
project (www.firstlibraryinspace.org).

I briefly looked at the Python and I will look at it in more detail with it
later, although I have also used Python to just control the standard
raspivid and rapsistill cli commands to take images and video clips, but I
like the fact that this package allows modification of settings while the
camera is already running.

As to the comment about using an IR sensor, I am not sure if you just meant
an IR light sensor or one of the IR range sensors. If just a light sensor,
it reminded me of a funny issue we had at work years ago...

I was involved in the hardware and software teams for the self checkout
systems built by NCR and used at Walmart.  If you look at the monitor, you
will see a small square about 0.25" x 0.25" in the middle of the bottom
frame. That is for a simple IR light sensor that is passed to an analog max
circuit (signal through op-amp to a cap and another op-amp), then to an
op-amp window comparator and then to an interrupt. This was chosen to save
about 2-3$ over a real distance sensor (on a multi-thousand dollar device).
 This was needed because the same monitor and computer system was also
designed as a kiosk system and the idea was to have the monitor off, or
displaying a video commercial in a loop until someone stood in front of it.
 The thought was that someone stepping in front would block off the light
from the overhead, trigger an interrupt that was used to switch modes.

Hang on - almost getting to the funny part...

On our very first deployment of the system at a Home Depot in Atlanta, the
system worked great the first day.  At the end of the day, each of the
monitors were instructed to shut down, and then the lights were turned off.
 Much to the surprise of everyone there (and the engineers watching it),
every one of the systems woke up again and started talking.  After a couple
times repeating this and scratching heads, the obvious became obvious to us
- we had to disable the interrupt before sending the shutdown sequence and
then powering off the lights.

At that same customer base, we had one unit that would constantly trigger
over temp alarms - which were passed all the way back to NCR daily.  It was
strange, it would typically occur the most on cold days and not warmer
days.  We finally sent out an engineer on site to stay there until the
problem occurred to diagnose it.  It was another "duh" moment when we
realized that one of the employees was using the kiosk unit near the back
door as a coat rack - he would come in from moving lumber and through his
coat over it.  Of course, that caused the unit to heat up, but by the time
anyone looked at it, the coat was always gone.

Sorry to ramble... but it is funny how simple things can cause so much
stress at times... but back to your original idea - yes, I am definitely

On Mon, Jan 13, 2014 at 10:30 AM, Greg Brown <gwbrown1 at gmail.com> wrote:

> I've been running internet-connected webcams using the linux "motion"
> package and USB webcams for some time now (running on the Raspberry Pi
> using Raspbian as the base OS).  This morning I read a new Python package
> that allows control of the R.Pi camera has been released and is available
> via apt-get:
> http://www.raspberrypi.org/archives/5672
> I am thinking of ditching the USB cameras and using Python and an IR sensor
> as the motion trigger for the hardwired R.Pi camera.
> Is anyone else doing anything like this?  If so let me know and we can toss
> ideas to one another - what works and most importantly what does not.
> Greg
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