All things Raspberry Pi and Time Lapse

Posts tagged ‘cron’

Raspberry Pi – how to set the system clock using a Canon Camera

Now that I have my Raspberry Pi I wrote and tested the script to set the time on the Raspberry Pi using my Canon Powershot A510. This is a follow up of my previous post. This is tested and works with a Canon Powershot A510 but it may work with other Canon Cameras, however some may require a little modification to the script.

#!/bin/bash
# jamesmiller
# 2012-07-16
# this script works with the Canon Powershot A510
# other models may or may not work
#
# use gphoto2 to get the camera time
camera_time=`gphoto2 –summary | grep -i “unix time” | cut -d ” ” -f4`
# for some reason I had to subtract some time to get it to be correct
camera_time=$(($camera_time – 3592))
# convert UNIX time to readable time
time=`date -d @$camera_time`
# the next four (4) lines cut the timestamp into specific parts so
# that it can be used when setting the time
b=`echo $time | cut -d ” ” -f2`
c=`echo $time | cut -d ” ” -f3`
d=`echo $time | cut -d ” ” -f4`
f=`echo $time | cut -d ” ” -f6`
# this sets the variable real_time equal to the values from gphoto2
# and puts them in the correct order
real_time=`echo $c $b $f $d`
# set the system time equal to the time from gphoto2
date -s “$real_time”

And this script is put into a cron job that is set to run at startup using these details here.

@reboot /path/to/script

If the power goes out and the camera and the Raspberry Pi shut down, when the power comes back the camera should startup faster than the Raspberry Pi and when the script runs it can set the time correctly. The camera has a small battery to keep time, and it will last for a long time with no power and still keep time.

Everything is setup outside my window taking pictures of our garden today. This is my chance to test and get all of the bugs worked out before I setup for a long period of time. Already I have changed several things and I updated the scripts post to reflect these changes.

I will probably post pictures of the setup tomorrow along with the time lapse that it is taking today.

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gphoto2 camera scripts

I could not wait for my Raspberry Pi to arrive so I went ahead and wrote the scripts using gphoto to take pictures. These were written on a Fedora desktop, but since it is using standard Linux commands it should work from any distribution.

A very good tutorial on cron and at are availble here at IBM.

This first one is pretty standard. It will take a picture at noon once a day… The actual scheduling of the script will take place using the cron daemon.

#!/bin/bash
# jamesmiller
# 6-22-2012
#
# change directories to the correct folder to save the image
cd /home/jamesmiller/gphoto/1day
# actually take the picture using gphoto2
gphoto2 –capture-image-and-download –filename “%Y%m%d%H%M%S_1day.jpg”

Note the last line is supposed to be all on one line. The crontab entry for this first script will look like this… The twelve in the second position means to take the picture at 12:00 (noon) every day of the month, every month, every day of the week. Note that the time in cron uses a 24 hour clock.

0 12 * * * /home/jamesmiller/gphoto/1day

And the second one is very similar to the first. Except it will take a picture once every 5 minutes for an entire day on the first and fifth days of the month. In the final I will only use one of the days a month, but by shooting two days that gives me an error margin (if the power goes out that day) or some other unforeseen accident occurs.

#!/bin/bash
# jamesmiller
# 6-22-2012
#
# change directories to the correct folder to save the image
cd /home/jamesmiller/gphoto/5min
# actually take the picture using gphoto2
gphoto2 –capture-image-and-download –filename “%Y%m%d%H%M%S_5min.jpg”

Note the last line is supposed to be all on one line. This script is very similar to the last script except for the file location where it will store the images. This will keep the different scripts separate. However the crontab entry for this script is very different! The first (*/5) means to take a picture every 5 minutes, the second piece (4-20) means to only take the picture if the time is between 4am and 8pm, and the (1,5) means on the first and fifth of the month to execute. the last two stars mean every month, every day of the week. This script will provide a time-lapse that looks like 12 days – one for each month of the year.

*/5 4-20 1,5 * * /home/jamesmiller/gphoto/5min

The last script is more complicated. It uses cron and it also uses a different scheduling daemon called at.

#!/bin/bash
# jamesmiller
# 6-22-2012
#
# change directories to the correct folder to save the image
cd /home/jamesmiller/gphoto/1443min
# schedule the next runtime of this script
at -f ../camera_1443min now + 1443min
# store the date and time in a file to be read as the time
# when the picture was taken.
echo `date +%Y%m%d%H%M%S` >> ../1443_time
# actually take the picture using gphoto2
gphoto2 –capture-image-and-download –filename “%Y%m%d%H%M%S_1443min.jpg”

Note the last line is supposed to be all on one line. The purpose of this script is to take a picture at like 4:00am the first day, then the next day at 4:03, and the next day at 4:06 and so on. This last script will provide a very interesting time lapse as it will take one year and compress it into time lapse that looks like a day. It will start in the morning and end at night, but all 4 seasons will have passed. I am not totally sure at what time I want this to start, because there is no reason to take pictures in the dark. The cron details I have not finished working on yet, but I will add them here when I finish it.

cron details to follow

Those are my ideas for a year-long time lapse. This will give me three different looks into the scene over the course of a year. If anyone has other/more ideas for when the camera should take a picture do not hesitate to comment below!

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